Granulosa cell tumours  are  tumours  that arise from  granulosa cells . They are estrogen-secreting tumours and present as large, complex, ovarian masses. These tumours are part of the  sex cord–gonadal stromal tumour  or non-epithelial group of tumours. Although granulosa cells normally occur only in the  ovary , granulosa cell tumours occur in both ovaries and testicles (see  ovarian cancer  and  testicular cancer ). These tumours should be considered malignant and treated in the same way as other malignant tumours of ovary. The ovarian disease has two forms, juvenile and adult, both characterized by indolent growth, [ 1 ]  and therefore has high recovery rates. [ 2 ] [ 3 ]  The staging system for these tumours is the same as for epithelial tumours and most present as stage I. [ 4 ]  The peak age at which they occur is 50–55 years, but they may occur at any age.


Juvenile granulosa cell tumour  is a similar but histologically distinct rare tumour. It too occurs in both the ovary and testis. In the testis it is extremely rare, and has not been reported to be malignant. [ 5 ]  Although this tumour usually occurs in children (hence its name), it has been reported in adults. [ 6 ]


Estrogens  are produced by  functioning  tumours, and the clinical presentation depends on the patient's age and sex. [ citation needed ]


Using next generation  DNA sequencing , 97% of adult granulosa cell tumours were found to contain an identical mutation in the  FOXL2  gene  [1] . This is a somatic mutation, meaning it is not usually transmitted to descendants. Mutation c.402C>G in the sequence of FOXL2 leads to the amino acid substitution p. C134W. It is believed that this mutation may be the cause of granulosa cell tumours. [ citation needed ]


Two recent studies show that the enzyme  AKT1  is involved in juvenile granulosa cell tumours. In-frame duplications in the pleckstrin-homology domain of the protein were found in more than 60% of juvenile granulosa cell tumours occurring in girls under 15 years of age. The tumours without duplications carried point mutations affecting highly conserved residues. The mutated proteins carrying the duplications displayed a non-wild-type subcellular distribution, with a marked enrichment at the plasma membrane, leading to a strong activation of AKT1. [ 8 ]  Analysis by RNA-Seq pinpointed a series of differentially expressed genes that are involved in cytokine and hormone signaling and cell division-related processes. Further analyses pointed to a possible dedifferentiation process, and suggested that most of the transcriptomic dysregulations might be mediated by a limited set of transcription factors perturbed by AKT1 activation. These results incriminate somatic mutations of AKT1 as probable driver events in the pathogenesis of juvenile granulosa cell tumours. [ 9 ]


Tumours vary in size, from tiny spots to large masses, with an average of 10 cm in diameter. Tumours are oval and soft in consistency.
On cut-section, histology reveals reticular, trabecular areas with interstitial haemorrhage and  Call–Exner bodies -small cyst like spaces interspersed within a  Graafian follicle . [ citation needed ]


Inhibin , a hormone, has been used as biomarker for granulosa cell tumours. [ 10 ]


Juvenile granulosa cell tumors can be distinguished from adult granulosa cell tumors on  histology  by their abundant, eosinophilic cytoplasm; primitive, highly mitotic nuclei in polygonal cells; and disorganized follicles. [ 12 ] [ 13 ]


In the ovaries of aging  squirrel monkeys  (Saimiri sciureus), clusters of granulosa cells occur that resemble granulosa cell tumours in humans. [ 14 ]  These appear to be a normal change with age in this species. [ citation needed ]


Gynecomastia  (also spelled  gynaecomastia ) [ a ]  is the non-cancerous enlargement of one or both breasts in  men  due to the growth of  breast tissue  as a result of a  hormone imbalance  between  estrogens  and  androgens . [ 4 ] [ 5 ]  Physically speaking, gynecomastia is completely benign, but it is associated with significant psychological distress, social stigma, and  dysphoria . [ 6 ]


Gynecomastia can be normal in newborn male babies due to exposure to estrogen from the mother, in adolescent boys going through  puberty , in older men over the age of 50, and in  obese  men. [ 4 ]  Most occurrences of gynecomastia do not require diagnostic tests. [ 4 ] [ 5 ]  Gynecomastia may be caused by abnormal hormone changes, any condition that leads to an increase in the ratio of  estrogens / androgens  such as  liver disease ,  kidney failure ,  thyroid disease  and some non-breast  tumors .  Alcohol  and some drugs can also cause breast enlargement. [ 4 ] [ 7 ]  Other causes may include  Klinefelter syndrome ,  metabolic dysfunction , or a natural decline in  testosterone  production. [ 4 ] [ 6 ] [ 8 ]  This may occur even if the levels of estrogens and androgens are both appropriate, but the ratio is altered. [ 7 ]


Gynecomastia is the most common benign disorder of the male breast tissue and affects 35% of men, being most prevalent between the ages of 50 and 69. [ 5 ] [ 9 ]  It is normal for up to 70% of adolescent boys to develop gynecomastia to some degree. [ 6 ]  Of these, 75% resolve within two years of onset without treatment. [ 10 ]  If the condition does not resolve within 2 years, or if it causes embarrassment, pain or tenderness, treatment is warranted. [ 11 ] [ 12 ]  Medical treatment of gynecomastia that has persisted beyond two years is often ineffective. Gynecomastia is different from " pseudogynecomastia ", [ 5 ] [ 6 ]  which is commonly present in men with  obesity . [ 13 ] [ 14 ]


Medications such as  aromatase inhibitors  have been found to be effective [ 15 ]  and even in rare cases of gynecomastia from disorders such as  aromatase excess syndrome  or  Peutz–Jeghers syndrome , [ 16 ]  but surgical removal of the excess tissue can be needed to correct the condition. [ 17 ]  In 2019, 24,123 male patients underwent the procedure in the  United States , accounting for a 19% increase since 2000. [ 18 ]


Gynecomastia is the abnormal non-cancerous enlargement of one or both breasts in men due to the growth of  breast tissue  as a result of a  hormone imbalance  between  estrogen  and  androgen . [ 4 ] [ 5 ]  Gynecomastia is different from " pseudogynecomastia ", [ 5 ] [ 6 ]  which is defined as an excess of  skin  and/or  adipose tissue  in the male  breasts  without the growth of true  glandular breast tissue ; [ 19 ] [ 20 ] [ 21 ]  this is commonly associated with  obesity  and can be ruled out by physical exam. [ 13 ] [ 14 ] [ 21 ]


In gynecomastia there is always enlargement of one or both breasts, symmetrically or asymmetrically, in a man. A soft, compressible, and mobile mass of  breast tissue  is felt under the  nipple  and  its surrounding skin  in contrast to softer  fatty  tissue which is not associated with a mass. [ 9 ] [ 22 ]  It may also be accompanied by breast tenderness or nipple sensitivity, which is commonly associated with gynecomastia observed in adolescents, typically early in development. [ 21 ]  Gynecomastia that is painful, bothersome, rapidly-growing, associated with masses in other areas of the body, or persistent should be evaluated by a clinician for potential causes. [ 23 ]  Dimpling of the skin, nipple discharge, and nipple retraction are not typical features of gynecomastia and may be associated with other  disorders . [ 9 ]   Milky discharge  from the nipple is not a typical finding, but may be seen in a gynecomastic individual with a  prolactin secreting tumor . [ 7 ]  An increase in the diameter of the  areola  and asymmetry of the chest are other possible signs of gynecomastia. [ 24 ]


Much of the research on gynecomastia has focused on its causes and treatment, but little has explored its effects on mental health and overall quality of life. Gynecomastia has psychosocial implications that may be particularly challenging for adolescents who are experiencing physical maturation and self-identity formation, which includes body image disturbances, negative attitudes towards eating, self-esteem problems, social withdrawal, anxiety, and shame. [ 25 ]  Men with gynecomastia may appear anxious or stressed due to concerns about its appearance and the possibility of having  breast cancer . [ 26 ] [ 27 ]  Particular studies suggest that gynecomastia can lead to various psychological and social challenges, such as depression, anxiety and disordered eating. [ 28 ]


Gynecomastia is thought to be caused by an altered ratio of estrogens to androgens mediated by an increase in estrogen action, a decrease in androgen action, or a combination of these two factors. [ 7 ]  Estrogen and androgens have opposing actions on breast tissue: estrogens stimulate proliferation while androgens inhibit proliferation. [ 7 ] [ 26 ]  The cause of gynecomastia is unknown in around 25% of cases. [ 22 ] [ 27 ]  Known causes can be physiologic (occurring normally) or non-physiologic due to underlying pathologies such as drug use, chronic disease, tumors, or malnutrition.


Physiologic or normal gynecomastia can occur at three timepoints in life: shortly after birth in both female and male infants, during puberty in adolescent males, and in older adults over the age of 60. [ 29 ]


60-90% of male and female newborns may show breast development at birth or in the first weeks of life. [ 26 ] [ 30 ]  During pregnancy, the  placenta  converts the androgenic hormones  dehydroepiandrosterone  (DHEA) and  DHEA sulfate  to the estrogenic hormones  estrone  and  estradiol , respectively; after these estrogens are produced by the placenta, they are transferred into the  baby's  circulation, thereby leading to temporary gynecomastia in the baby. [ 26 ] [ 31 ]  In some infants, neonatal milk (also known as " witch's milk ") can leak from the nipples. [ 22 ]  The temporary gynecomastia seen in newborn babies usually resolves after two or three weeks. [ 26 ]


Hormonal imbalance (elevated ratio of estrogen to androgen) during early puberty, either due to decreased androgen production from the adrenals and/or increased conversion of androgens to estrogens, leads to transient gynecomastia in adolescent males. It can occur in up to 65% of adolescents as early as age 10 and peaks at ages 13 and 14. [ 32 ] [ 33 ]  It is self-limited in 75–90% of adolescents and usually resolves spontaneously within 1 to 3 years as pubertal progression increases testosterone levels and cause regression of breast tissue. [ 32 ] [ 26 ]  By age 17, only 10% of adolescent males have persistent gynecomastia. [ 32 ]


Declining testosterone levels and an increase in the level of subcutaneous  fatty tissue  seen as part of the normal aging process can lead to gynecomastia in older males. Increased fatty tissue, a major site of aromatase activity, leads to increased conversion of androgenic hormones such as testosterone to estrogens. [ 26 ]  Additionally, levels of  sex hormone binding globulin  (SHBG) increase with age and bind with less affinity to estrogen than androgens. [ 29 ]  Put together, the elevated ratio of estrogen to androgen leads to gynecomastia, also known as senile gynecomastia in this group. [ 26 ]  There is a 24–65% prevalence of senile gynecomastia in older males. [ 26 ]


About 10–25% of gynecomastia cases are estimated to result from the use of medications or exogenous chemicals. [ 17 ] [ 27 ]  Drugs can increase estrogen activity or increase the estrogen to androgen ratio through various mechanisms, such as binding to estrogen receptors, promoting estrogen synthesis, providing precursors that can be aromatized into estrogen, causing damage to the testes, inhibiting testosterone synthesis, inhibiting the action of androgens, or displacing estrogen from SHBG. [ 29 ]  Drugs with good evidence for association with gynecomastia include  cimetidine ,  ketoconazole ,  gonadotropin-releasing hormone analogues ,  human growth hormone ,  human chorionic gonadotropin ,  5α-reductase inhibitors  such as  finasteride  and  dutasteride , certain estrogens used for  prostate cancer , and  antiandrogens  such as  bicalutamide ,  flutamide , and  spironolactone . [ 7 ] [ 17 ] [ 37 ] [ 38 ]


Drugs with fair evidence for association with gynecomastia include  calcium channel blockers  such as  verapamil ,  amlodipine , and  nifedipine ;  risperidone ,  olanzapine ,  anabolic steroids , [ 17 ] [ 39 ]   alcohol ,  opioids ,  efavirenz ,  alkylating agents , and  omeprazole . [ 17 ] [ 40 ]  Certain components of personal skin care products such as  lavender [ 41 ]  or  tea tree oil  have been reported to cause prepubertal gynecomastia due to its estrogenic and anti-androgenic effects. [ 42 ] [ 43 ]  Certain dietary supplements such as  dong quai  and  Tribulus terrestris  have also been associated with gynecomastia. [ 27 ]


Malnutrition and significant loss of body fat suppress  gonadotropin  secretion, leading to  hypogonadism . This is reversible when adequate nutrition resumes, where the return of gonadotropin secretion and  gonadal  function cause a transient imbalance of estrogen and androgen that mimics puberty, resulting in transient gynecomastia. [ 44 ]  This phenomenon, also known as refeeding gynecomastia, was first observed when men returning home from prison camps during World War II developed gynecomastia after resuming a normal diet. Similar to pubertal gynecomastia, refeeding gynecomastia resolves on its own in 1–2 years. [ 44 ] [ 7 ]


Many kidney failure patients experience a hormonal imbalance due to the suppression of testosterone production and testicular damage from  high levels of urea  also known as uremia-associated hypogonadism. [ 27 ] [ 45 ]  Additionally, gynecomastia has been observed in 50% of patients with chronic kidney disease undergoing dialysis. Similar to the mechanism behind refeeding gynecomastia, dialysis allows patients with renal failure who were previously malnourished to expand their diets and regain weight. Dialysis-associated gynecomastia resolves spontaneously within 1–2 years. [ 7 ] [ 26 ]


In individuals with liver failure or cirrhosis, the liver's ability to properly metabolize hormones such as estrogen may be impaired. Additionally, those with alcoholic liver disease are further put at risk for development of gynecomastia;  ethanol  may directly disrupt the synthesis of testosterone and the presence of  phytoestrogens  in alcoholic drinks may also contribute to a higher estrogen to testosterone ratio. [ 27 ]  Conditions that can cause  malabsorption  such as  cystic fibrosis  or  ulcerative colitis  may also produce gynecomastia. [ 27 ]


A small proportion of male gynecomastia cases may be seen with rare inherited disorders such as  spinal and bulbar muscular atrophy  and the very rare  aromatase excess syndrome . [ 46 ] [ 47 ]


Gynecomastia can be caused by absolute deficiency in androgen production due to primary or secondary hypogonadism. Primary hypogonadism results when there is damage to the testes (due to radiation, chemotherapy, infections, trauma, etc), leading to impaired androgen production. [ 7 ]  It can also be caused by chromosomal abnormality seen in Klinefelter syndrome, which is associated with gynecomastia in about 80% of cases. [ 44 ] [ 26 ]  Secondary hypogonadism results when there is damage to the hypothalamus or pituitary (due to radiation, chemotherapy, infection, trauma, etc), and similarly lead to impaired androgen production. The net effect is reduced androgen production while serum estrogen levels (from peripheral aromatization of androgens) remain unaffected. [ 7 ] [ 29 ]  The lack of androgen-mediated inhibition of breast tissue proliferation combined with relative estrogen excess result in gynecomastia. [ 7 ]


Testicular tumors such as  Leydig cell tumors ,  Sertoli cell tumors [ 48 ]  (such as in  Peutz–Jeghers syndrome ) [ 10 ]  and  hCG -secreting  choriocarcinoma [ 40 ]  may result in rapid-onset gynecomastia by causing excess production of estrogen. [ 7 ]  Other tumors such as  adrenal tumors , pituitary gland tumors (such as a  prolactinoma ), or  lung cancer , can produce hormones that alter the male–female hormone balance and cause gynecomastia. [ 22 ]


Individuals with  prostate cancer  who are treated with  androgen deprivation therapy  may experience gynecomastia. [ 49 ]


The causes of common gynecomastia remain uncertain, but are thought to result from an imbalance between the actions of estrogen, which stimulates breast tissue growth, and androgens, which inhibit breast tissue growth. [ 8 ] [ 17 ]  Breast prominence can result from  enlargement  of glandular breast tissue, chest  adipose tissue  (fat) and skin, and is typically a combination. [ 40 ]  As in females, estrogen stimulates the growth of breast tissue in males. [ 7 ]  In addition to directly stimulating breast tissue growth, estrogens indirectly decrease secretion of testosterone by suppressing  luteinizing hormone  secretion, resulting in decreased testicular secretion of testosterone. [ 7 ]


One of the main mechanisms for imbalance between estrogens and androgens is the overproduction of estrogens. A possible cause may be a  neoplasm  that originates from estrogen-secreting cells. [ 50 ]  Tumors that produce  hCG  stimulate production of estradiol while reducing other testicular hormone production. [ 51 ]   Obesity  is another common cause of excess serum estrogens due to the presence of  aromatase  in peripheral tissue, which is a protein that converts androgens into estrogens. [ 51 ]   Peutz-Jeghers syndrome  is a rare cause of testicular tumors that affect aromatase expression, which results in elevated serum estrogen levels. [ 52 ]   Aromatase excess syndrome  is a rare genetic disorder that leads to increased conversion of androgens to estrogens in the body.


Primary  hypogonadism  (indicating an intrinsic problem with the  testes  in males) leads to decreased testosterone synthesis and increased  conversion of testosterone to estradiol  potentially leading to a gynecomastic appearance. [ 26 ]   Klinefelter syndrome  is a notable example of a disorder that causes hypogonadism and gynecomastia, and has a higher risk of breast cancer in males (20–50 times higher than males without the disorder). [ 53 ]   Secondary hypogonadism  (indicating a problem with the brain) leads to decreased production and release of  luteinizing hormone  (LH, a stimulatory signal for endogenous steroid hormone synthesis) which leads to decreased production of testosterone and estradiol in the testes. [ 26 ]


Estrogens can increase blood levels of the protein  sex hormone-binding globulin  (SHBG), which binds free testosterone (the active form) more strongly than estrogen, leading to decreased action of testosterone in male breast tissue. [ 7 ] [ 51 ]  Conditions such as  hyperthyroidism  and  chronic liver disease  affect levels of SHBG, leading to symptomatic gynecomastia. [ 50 ]


Dysfunction in the androgen receptor prevents the effects of testosterone from acting on its target tissues. Androgen insensitivity syndromes result from the different degrees of resistance to the effects of androgens, and can cause external  genitalia  that may not be aligned with the  genotype  of the individual's  sex chromosomes . [ 54 ]   Complete androgen insensitivity syndrome  results in the failure to develop external genitalia such as the penis and scrotum along with development of breasts in an individual with testes.  Partial androgen insensitivity syndrome  may result in a variety of presentations. Minimal androgen insensitivity syndrome may present as gynecomastia in adolescence and may additionally be associated with  infertility . [ 54 ]


Medications are known to cause gynecomastia through several different mechanisms. These mechanisms include increasing estrogen levels, mimicking estrogen, decreasing levels of testosterone or other androgens, blocking androgen receptors, increasing prolactin levels, or through unidentified means. [ 26 ]  Potential causative agents include  oral contraceptive pills ,  spironolactone , and  anabolic steroids . [ 55 ]


High levels of prolactin in the blood  (which may occur as a result of certain tumors or as a side effect of certain medications) has been associated with gynecomastia. [ 26 ]  A high level of prolactin in the blood can inhibit the release of  gonadotropin-releasing hormone  and therefore cause secondary hypogonadism. [ 7 ] [ 26 ]  Receptors for prolactin and other hormones including  insulin-like growth factor 1 ,  insulin-like growth factor 2 ,  luteinizing hormone ,  progesterone , and  human chorionic gonadotropin  have been found in male breast tissue, but the impact of these various hormones on gynecomastia development is not well understood. [ 7 ]


Individuals who have  cirrhosis  or chronic liver disease may develop gynecomastia for several reasons. Those diagnosed with cirrhosis tend to have increased secretion of the androgenic hormone  androstenedione  from the adrenal glands, increased conversion of this hormone into various types of estrogen, [ 7 ]  and increased levels of SHBG, which leads to decreased blood levels of free testosterone. [ 26 ]  Around 10–40% of males with  Graves' disease  (a common form of  hyperthyroidism ) experience gynecomastia. [ 26 ]  Increased conversion of testosterone to estrogen by increased aromatase activity, [ 7 ]  increased levels of SHBG and increased production of testosterone and estradiol by the testes due to elevated levels of LH cause the gynecomastia. Proper treatment of the hyperthyroidism can lead to the resolution of the gynecomastia. [ 26 ]


To diagnose gynecomastia, a thorough history and physical examination are obtained by a  physician . Important aspects of the physical examination include evaluation of the male breast tissue with palpation to evaluate for breast cancer and  pseudogynecomastia  (male breast tissue enlargement solely due to excess  fatty tissue ), evaluation of  penile  size and development, evaluation of  testicular  development and an assessment for masses that raise suspicion for  testicular cancer , and proper development of  secondary sex characteristics  such as the amount and distribution of  pubic  and  underarm hair . [ 7 ]  Gynecomastia usually presents with bilateral involvement of the breast tissue but may occur unilaterally as well. [ 27 ]


Diagnosis of men with breast enlargement can be evaluated using an  algorithm . A review of the medications or substances an individual takes may reveal the cause of gynecomastia. [ 27 ]  Recommended laboratory investigations to find the underlying cause of gynecomastia include tests for  aspartate transaminase  and  alanine transaminase  to rule out liver disease, serum  creatinine  to determine if kidney damage is present, and  thyroid-stimulating hormone  levels to evaluate for hyperthyroidism. If these initial laboratory tests fail to uncover the cause of gynecomastia, then additional tests to evaluate for an underlying hormonal balance due to  hypogonadism  or a testicular tumor should be checked including total and free levels of  testosterone ,  luteinizing hormone ,  follicle stimulating hormone ,  estradiol , serum beta  human chorionic gonadotropin  (β-hCG), and  prolactin . [ 27 ]


High levels of prolactin  are uncommon in people with gynecomastia. [ 27 ]  If β-hCG levels are abnormally high, then  ultrasound  of the testicles should be performed to check for signs of a hormone-secreting testicular tumor. [ 27 ]  Markers of testicular, adrenal, or other tumors such as urinary  17-ketosteroid  or serum  dehydroepiandrosterone  may also be checked if there is evidence of hormonal imbalance on physical examination. If this evaluation does not reveal the cause of gynecomastia, then it is considered to be idiopathic gynecomastia (of unclear cause). [ 27 ]


While there can be many potential causes of male patients that present with increased breast tissue, differential diagnoses are most concerning for gynecomastia, pseudogynecomastia, and  breast cancer  (which is rare in men). Other potential causes of male breast enlargement such as  mastitis , [ 27 ] [ 56 ]   lipoma ,  sebaceous cyst ,  dermoid cyst ,  hematoma ,  metastasis ,  ductal ectasia ,  fat necrosis , or a  hamartoma  are typically excluded before making the diagnosis. [ 27 ]


Mammography  is the method of choice for  radiologic  examination of male breast tissue in the diagnosis of gynecomastia when breast cancer is suspected on physical examination. [ 7 ] [ 9 ]  If a mass/lump is felt during a physical exam some features of the lump that would point to  malignancy  would be painless, non moveable (fixed), irregularly shaped, and skin changes. Mammography is rarely indicated for men since breast cancer is an unlikely diagnosis. [ 7 ]  If mammography is performed and does not reveal findings suggestive of breast cancer, further imaging is not typically necessary. [ 9 ]  If a tumor of the  adrenal glands  or the  testes  is thought to be responsible for the gynecomastia,  ultrasound  examination of these structures may be performed. [ 7 ]


Early histological features expected to be seen on examination of gynecomastic tissue attained by  fine-needle aspiration  biopsy include the following: proliferation and lengthening of the ducts, an increase in connective tissue, an increase in inflammation, and  swelling  surrounding the ducts, and an increase in  fibroblasts  in the connective tissue. [ 26 ]  Chronic gynecomastia may show different histological features such as increased connective tissue  fibrosis , an increase in the number of ducts, less inflammation than in the acute stage of gynecomastia, increased subareolar fat, and hyalinization of the stroma. [ 24 ] [ 26 ]  When surgery is performed, the gland is routinely sent to the lab to confirm the presence of gynecomastia and to check for tumors under a microscope. The utility of pathologic examination of breast tissue removed from male adolescent gynecomastia patients has recently been questioned due to the rarity of breast cancer in this population. [ 57 ]


The spectrum of gynecomastia severity has been categorized into a grading system: [ 58 ]


If the gynecomastia doesn't resolve on its own in two years, then medical treatment is necessary. The options are medication or surgical intervention. [ 59 ]


Gynecomastia can respond well to medical treatment although it is usually only effective when done within the first two years after the start of male breast enlargement. [ 7 ]   Selective estrogen receptor modulators  (SERMs) such as  tamoxifen ,  raloxifene , and  clomifene  may be beneficial in the treatment of gynecomastia but are not approved by the  Food and Drug Administration  for use in gynecomastia. [ 7 ] [ 17 ] [ 60 ]  Clomifene seems to be less effective than tamoxifen or raloxifene. [ 60 ]  Tamoxifen may be used to treat gynecomastia in adults and of the medical treatments used,  tamoxifen  is the most effective. [ 61 ] [ 62 ]  Recent studies have shown that treatment with tamoxifen may represent a safe and effective mode of treatment in cases of cosmetically disturbing or painful gynecomastia. [ 17 ] [ 63 ]   Aromatase inhibitors  (AIs) such as  anastrozole  have been used off-label for cases of gynecomastia occurring during puberty but are less effective than SERMs. [ 16 ] [ 60 ]


A few cases of gynecomastia caused by the rare disorders  aromatase excess syndrome  and  Peutz–Jeghers syndrome  have responded to treatment with AIs such as anastrozole. [ 16 ]   Androgens / anabolic steroids  may be effective for gynecomastia. [ 60 ]   Testosterone  itself may not be suitable to treat gynecomastia as it can be  aromatized  into estradiol, but nonaromatizable androgens like  topical   androstanolone  (dihydrotestosterone) can be useful. [ 60 ]


If chronic gynecomastia does not respond to medical treatment, surgical removal of glandular breast tissue is usually required. [ 17 ]  The American Board of Cosmetic Surgery reports surgery is the "most effective known treatment for gynecomastia." [ 64 ]  Surgical treatment should be considered if the gynecomastia persists for more than 12 months, causes distress (ie physical discomfort or psychological distress), and is in the fibrotic stage. [ 65 ]  In adolescent males, it is recommended that surgery is postponed until puberty is completed (penile and testicular development should reach  Tanner scale  Stage V). [ 65 ]


Surgical approaches to the treatment of gynecomastia include  subcutaneous mastectomy ,  liposuction -assisted mastectomy, laser-assisted liposuction, and laser-lipolysis without liposuction. Complications of mastectomy may include  hematoma , surgical wound infection, breast asymmetry, changes in sensation in the breast, necrosis of the areola or nipple,  seroma , noticeable or painful scars, and contour deformities. [ 58 ]  In 2019, 24,123 male patients underwent surgical treatment for gynecomastia in the United States, accounting for a 19% increase since 2000. Thirty-five percent of those patients were between the ages of 20 and 29, and 60% were younger than age 29 at the time of the operation. At an average surgeon's fee of $4,123, gynecomastia surgery was also the 11th most costly male cosmetic surgery of 2019. [ 18 ]


Radiation therapy  and  tamoxifen  have been shown to help prevent gynecomastia and breast pain from developing in prostate cancer patients who will be receiving androgen deprivation therapy. The efficacy of these treatments is limited once gynecomastia has occurred and are therefore most effective when used prophylactically. [ 66 ]


In the United States, many insurance companies deny coverage for surgery for gynecomastia treatment or male breast reduction on the basis that it is a cosmetic procedure. [ 67 ] [ 68 ] [ 69 ] [ 70 ]


Gynecomastia itself is a benign finding. It does not confer a poor prognosis, for some patients with underlying pathologies such as  testicular cancer  the prognosis may be worse. [ 7 ]  The  glandular tissue  typically grows under the influence of hormonal stimulation and is often tender or painful. Furthermore, gynecomastia frequently presents social and psychological difficulties such as low self-esteem, depression or shame. [ 57 ] [ 58 ]


Gynecomastia is the most common  benign  disorder of the male breast tissue and affects 35 percent of men, being most prevalent between the ages of 50 and 69. [ 5 ] [ 9 ]


New cases of gynecomastia are common in three age populations: newborns, adolescents, and men older than 50 years. [ 58 ]  Newborn gynecomastia occurs in about 60–90 percent of male babies and most cases resolve on their own in about 2–3 weeks after delivery. [ 26 ] [ 27 ]  During adolescence, on average 33 percent of males are estimated to exhibit signs of gynecomastia. [ 7 ]  Gynecomastia in older men is estimated to be present in 24–65 percent of men between the ages of 50 and 80. Estimates on asymptomatic gynecomastia is about up to 70% in men aged 50 to 69 years. [ 26 ] [ 50 ]


The  prevalence  of gynecomastia in men may have increased in recent years, but the epidemiology of the disorder is not fully understood. [ 40 ]  The use of anabolic steroids and exposure to  chemicals that mimic estrogen  in cosmetic products,  organochlorine pesticides , and industrial chemicals have been suggested as possible factors driving this increase. [ 40 ] [ 70 ]  According to the  American Society of Plastic Surgeons , breast reduction surgeries to correct gynecomastia are fairly common but has been a recent decline. In 2020, there were over 18,000 procedures of this type performed in the United States which is down 11% compared to in 2019.


The term gynaecomastia was coined by  Galen . He also recognised glandular enlargement of the male breast; however, this wasn't a condition of gynaecomastia according to him. [ 71 ]  A surgical procedure for treatment of gynaecomastia was described by  Albucasis  in his second book of  Kitab al-Tasrif . [ 72 ]


Gynecomastia can result in psychological distress for those with the condition. Support groups exist to help improve the self-esteem of affected people. [ 70 ]


Moob , a  portmanteau  of  man  and  boob , is a popular term to refer to male breasts. Use of  anabolic steroids  can result in gynecomastia, and male breasts are sometimes referred to using the pejorative  bitch tits  in  bodybuilding  communities. [ 73 ]


In  Murray v.  Janssen Pharmaceuticals , Murray was a Risperidone user who was prescribed the medication at age nine and developed male breasts. A jury decided in Murray's favor in November 2015 and awarded him $1.75 million. The $1.75 million jury verdict represented damages for " disfigurement  and mental anguish," though it was later reduced to $680,000. [ 74 ]  In the second portion of the bifurcated trial, the plaintiffs sought to prove that the companies knew and deliberately disregarded evidence that Risperidone could lead to gynecomastia in young males, and nonetheless promoted the medication  off-label  and released the medication into the open market for prescription and use by patients without disclosing the side effects. [ 74 ]  The jury found for the plaintiffs in the second portion of the trial and awarded $8 billion in  punitive damages . The amount was later reduced to $6.8 million by Judge Kenneth Powell Jr. [ 75 ]


In 2019, a 12-person Philadelphia jury awarded $8 billion in punitive damages to plaintiffs tied to the use of  risperidone . Risperidone is an  atypical antipsychotic  that was originally approved to treat psychosis, but its use in children, including those with  autism ,  ADHD , and  schizophrenia  diagnoses, has grown over the last two decades. [ 76 ]


The term comes from  Greek   γυνή   gyné  (stem  gynaik- ) 'female' and  μαστός   mastós  'breast'. [ 3 ]


Pearly penile papules  (PPP; also known as  hirsutoid papillomas  or as  papillae coronae glandis , [ 4 ]   Latin  for 'papillae of the corona of the glans') are benign,  small bumps  or spots on the  human penis . [ 2 ] [ 3 ]  They vary in size from 0.5-1 mm, are pearly or flesh-colored, smooth and dome-topped or filiform, and appear in one or, several rows around the  corona , the ridge of the  head of the penis  and sometimes on the penile shaft. [ 2 ] [ 5 ]  They are painless,  non-cancerous  and not harmful. [ 2 ]  The medical condition of having such papules is called  hirsutoid papillomatosis  or  hirsuties papillaris coronae glandis  (Latin for 'papillary hirsutism of the corona of the glans').


PPPs are a type of  angiofibroma . [ 3 ]  Their function is not well-understood. [ 1 ]  They are usually considered as  vestigial remnants  of  penile spines , sensitive features found in the same location in other primates. [ 6 ] [ 7 ]  They do not spread and often spontaneously regress. [ 8 ]  Along with  Fordyce glands  PPPs secrete oils to keep the skin of the  head of the penis  in good condition. [ 9 ]   Smegma  can accumulate if these oils are produced in excess or there is inadequate washing under the foreskin. [ 9 ]


Diagnosis is by visualisation. [ 3 ]  On  dermoscopy , the white-pink papules appear in a cobblestone-like pattern and contain a central dotted or comma-shaped blood vessels. There is no scale. [ 1 ]  PPPs are sometimes mistaken for  genital warts  due to a perceived similarity in appearance. [ 10 ]  They can also appear similar to  molluscum contagiosum ,  sebaceous hyperplasia  and  lichen nitidus . [ 2 ]  Histopathology shows dense  connective tissue ,  fibroblasts  and many blood vessels. [ 5 ]


Generally, reassurance is given and no treatment is needed. [ 3 ] [ 11 ]  Laser or cryotherapy may be considered for men who find PPPs distressing to look at or feel excessive embarrassment. [ 1 ]


Carbon dioxide laser  generally has good outcomes with skin healing within seven days. [ 1 ]  The procedure requires anaesthesia, may need to be performed more than once, and has a risk of bleeding, scarring and colour changes. [ 1 ]  Another procedure involves a  hyfrecator . [ 12 ]


PPPs are common and occur in 14% to 48% of young males. [ 1 ] [ 2 ]  Several studies say they are less common in  circumcised  males, [ 2 ]  occurring about half as frequently in uncircumcised men, but other studies say the opposite. [ 13 ]


Some men find PPPs distressing to look at, owing to their resemblance to some sexually transmitted infections. [ 1 ] [ 14 ]  Although it is not related to any  disease , PPPs are occasionally mistaken for  HPV warts . [ 15 ]  There are also  home remedies  for "curing" it, despite the fact that the papules are neither infectious nor detrimental to one's health and may have beneficial functions. [ 9 ] [ 14 ]  Some of the "home remedies" found on the Internet and elsewhere use mild ointments or creams to soften the papules, but others are physically dangerous techniques for papule removal which can result in irreversible damage. [ 16 ]


Since dermatologists have safe, effective ways to remove the papules if desired, home remedies involving corrosive substances or self-surgery should be avoided, as they can permanently damage sexual functioning. Removal should only be performed by a physician using proven medical techniques. [ 16 ] [ 17 ]


Human penis size  varies on a number of measures, including   length  and  circumference  when  flaccid  and  erect . Besides the natural variability of  human penises  in general, there are factors that lead to minor variations in a particular male, such as the level of  arousal , time of day, ambient temperature,  anxiety  level, physical activity, and frequency of sexual activity. Compared to other  primates , including large examples such as the gorilla, the human penis is thickest, both in absolute terms and relative to the rest of the body. Most human penis growth occurs in two stages: the first between infancy and the age of five; and then between about one year after the onset of  puberty  and, at the latest, approximately 17 years of age. [ 1 ]


Measurements vary, with studies that rely on self-measurement reporting a significantly higher average than those with a health professional measuring. As of 2015, a  systematic review  of 20 studies, of up to 15,521 men, who were measured by health professionals rather than themselves, concluded that the average length of an  erect  human penis is 13.12 cm (5.17 in), while the average circumference of an erect human penis is 11.66 cm (4.59 in). [ 2 ]  A 1996 study of flaccid length found a mean of 8.8 cm (3.5 in) when measured by staff. [ 3 ]   Flaccid penis length can sometimes be a poor predictor of erect length. An adult penis that is abnormally small but otherwise normally formed is referred to in medicine as a  micropenis .


Limited to no statistically significant correlation between penis size and the size of other body parts has been found in research. Some environmental factors in addition to genetics, such as the presence of  endocrine disruptors , can affect penis growth.


While results vary slightly across reputable studies, the consensus is that the  mean  human penis, when erect, is in the range 5–6 in (13–15 cm) in length. [ 3 ] [ 4 ] [ 5 ]


The  systematic review  by Veale et al. (2015), of 20 studies of 15,521 men, where subjects were measured by staff, rather than self measured, found the average flaccid, stretched, and erect lengths of 9.16 cm (3.61 in), 13.24 cm (5.21 in), and 13.12 cm (5.17 in), respectively, and average flaccid and erect circumferences of 9.31 cm (3.67 in) and 11.66 cm (4.59 in), respectively. Erect lengths in the included studies were measured by pushing the pre-pubic fat pad to the bone, and flaccid or erect girth (circumference) was measured at the base or mid-shaft of the penis. [ 2 ]


One study (published in 1996) found the mean flaccid penis length to be 3.5 in (8.9 cm) (measured by staff). [ 3 ]   A review of several studies found average flaccid length to be 9–10 cm (3.5–3.9 in). [ 6 ]    Length of the flaccid penis does not necessarily correspond to length of the erect penis; some smaller flaccid penises grow much longer, while some larger flaccid penises grow comparatively less. [ 7 ]


The penis and scrotum can contract involuntarily in reaction to cold temperatures, anxious or nervous level and participation in sports. [ 8 ]  This decrease of flaccid penis size is referred to by the slang term "shrinkage", due to action by the  cremaster muscle . The same phenomenon affects cyclists and exercise bike users, with prolonged pressure on the  perineum  from the  bicycle saddle  and the straining of the exercise causing the penis and scrotum to contract involuntarily. An incorrect saddle may ultimately cause  erectile dysfunction  (see  crotch pressure  for more information). Individuals with  hard flaccid syndrome  or other  pelvic floor disorders  may temporarily have an abnormally small penis.


Neither age or size of the flaccid penis accurately predicted erectile length. Stretched length has correlated with erect length in some cases. [ 3 ]   However, studies have also shown drastic differences between stretched and erect length. [ 9 ]   One study found that a minimal tension force of approximately 450 g during stretching of the penis was required to reach a full potential erection length. This study also found that tension forces exerted in this study by the urologist were shown to be significantly (P<0.01) lower than 450g. [ 10 ]   This may account for differences between stretched and erect length.


Scientific studies have been performed on the  erect  length of the adult penis. Studies that have relied on self-measurement, including those from Internet surveys, consistently reported a higher average length than those that used medical or scientific methods to obtain measurements. [ 5 ] [ 13 ]


The following staff-measured studies are composed of different subgroups of the human population (in other words, specific age range; selection of those with sexual medical concerns or  self-selection ) that could cause a  sample bias . [ 13 ] [ 14 ]


Similar results exist regarding studies of the  circumference  of the adult fully  erect  penis, with the measurement usually taken mid-shaft. [ 6 ]
As with length, studies that relied on self-measurement consistently reported a significantly higher average than those with staff measuring. In a study of penis size where measurements were taken in a laboratory setting, the average penis circumference when erect was 11.66 cm (4.59 inches). [ 2 ]


The average stretched penile length at birth is about 4 cm (1.6 in), and the length for 90% of newborn boys is between 2.4 and 5.5 cm (0.94 and 2.17 in). Limited growth of the penis occurs between birth and 5 years of age, but very little occurs between 5 years and the onset of  puberty . [ 1 ] [ 6 ]
The average size at the beginning of puberty is 6 cm (2.4 in), with adult size reached about 5 years later.


W.A. Schonfeld published a penis growth curve in 1943. [ 22 ] [ needs update ]


Age is not believed to negatively correlate with penis size. [ 6 ]


Height is correlated with flaccid stretched length and erect length. [ 2 ]


One study investigated the relationship with  digit ratio  and found that men with longer ring fingers than index fingers had slightly longer penises. [ 23 ] [ 24 ]  However, the  common misconception  that hand size predicts penis size has been widely discredited. [ 25 ] [ 26 ]


There is no correlation between  shoe size  and stretched penis size. [ 27 ] [ 28 ]


Nose size was highly related to stretched penile length in Japanese male cadavers. [ 29 ]


There may be a link between the malformation of the genitalia and the human limbs. The development of the penis in an embryo is controlled by some of the same  Hox genes  (in particular  HOXA13  and  HOXD13 ) [ 30 ]  as those that control the development of the limbs. Mutations of some Hox genes that control the growth of limbs cause malformed genitalia ( hand-foot-genital syndrome ). [ 31 ]


Alleged differences in races have led to the creation of  sexual myths . There is no scientific background to support the alleged 'oversized' penis in black people. [ 32 ]


A 2015 systematic review of 15,521 men from 20 studies found "no indications of differences in racial variability". [ 2 ]


According to Aaron Spitz, a  urologist , many websites and studies promoting variation of penis size between races use  unscientific methods  of collecting information and often ignore contradictory evidence. He concludes that "when you really take a good look at the naked data, there's not a whole lot there [showing racial variation in penis size]." [ 33 ]


A study of 253 males from  Tanzania  found that the average stretched flaccid penis length of 93 Tanzanian men is 11.5 cm (4.5 in). [ 34 ]


A 2007 study of 115 men from  Nigeria  found that the average stretched penis length of Nigerian males was 13.37 cm (5.26 in), and the median stretched penis length found was 13 cm (5.1 in). [ 35 ]


A 1990 study of 109  Chinese  men identified the average flaccid stretched penis length of 13.9 cm (5.5 in), and among 14 of the men, the average erect length found was 13.7 cm (5.4 in). [ 36 ]  Another 1993 study of 104 Chinese men found the average stretched penis length of 13.8 cm (5.4 in), and an average erect length of 13.5 cm (5.3 in). [ 37 ]
A 2014 study on 5,196 Chinese males reported an average flaccid length of 6.5 cm (2.6 in) and average stretched length of 12.9 cm (5.1 in) under the method of "gentle painless extension of the penis", which is a measurement method differing from other studies that stretch until maximal extension. A subgroup of 311 men reported an average erect circumference of 10.5 cm (4.1 in) and average erect length of 12.9 cm (5.1 in). They stated that they had "also found that penile dimensions are different in different ethnicities, but further investigations are needed to validate this". However, the 'different ethnicities' referred to in the study were ethnicities within the Chinese population. [ 38 ]


A study (published in 2021) of 14,597  Vietnamese  men identified an average flaccid penis length of 9.03 cm (3.56 in) and an average stretched penis length of 14.67 cm (5.78 in) as well as an average non-aroused circumference, at the mid-shaft, of 8.39 cm (3.30 in). [ 39 ]


A 1971 study of 702  Korean  men aged 21 to 31 found the average erect penis length to be 12.7 cm (5.0 in) and the average non-erect length 8.0 cm (3.1 in). [ 40 ]
A 1998 study of 150 Korean men found the average flaccid penis length to be 8.26 cm (3.25 in), the average flaccid girth 8.34 cm (3.28 in), the average erect length 13.42 cm (5.28 in), and the average erect girth 11.17 cm (4.40 in). [ 17 ]
In a 1998 study conducted at Seoul National University College of Medicine, which involved a sample of 287 Korean men, the average erect penis length was measured at 14.06 cm (5.54 in), and the average erect penis girth was 12.11 cm (4.77 in). [ 18 ]
A 2016 study of 248 Korean men identified the average flaccid penis length to be 7.39 cm (2.91 in) and the average erect penis length to be 13.53 cm (5.33 in). [ 19 ]


A 1999 study of 130  Colombian  men found the average erect penile length to be 13.90 cm (5.47 in). [ 41 ]


A 2014 American study by Herbenick et al. of 1,661 sexually active men involving Asian American, Black American, White American, Pacific Islander/Hawaiian, and Native American men, found average racial differences in erect penile length and circumference to be generally less than one centimeter, with averages in length being: 14.14 cm (5.57 in) for Asian Americans, 14.66 cm (5.77 in) for Black Americans, 14.88 cm (5.86 in) for Pacific Islanders/Hawaiians, 12.86 cm (5.06 in) for Native Americans, 14.18 cm (5.58 in) for White Americans, and 13.79 cm (5.43 in) for Americans reported as "Other" race; with averages in circumference being: 12.10 cm (4.76 in) for Asian Americans, 12.29 cm (4.84 in) for Black Americans, 11.88 cm (4.68 in) for Pacific Islanders/Hawaiians, 11.36 cm (4.47 in) for Native Americans, 12.25 cm (4.82 in) for White Americans, and 12.03 cm (4.74 in) for Americans reported as "Other" race. Unlike previously cited studies, findings were based on self-reported measurements with participants using paper rulers and "detailed, illustrated instructions" to measure their erect penis. [ 42 ]


Rumors about the penis size of  Congolese  men are often exaggerated and lack scientific reliability. According to research, there are significant issues with the accuracy of information disseminated on this topic. Most information sources, including radio and television broadcasts, failed to provide measurement methodologies or credible references, with 85.7% not specifying how measurements were conducted and 57.1% lacking bibliographical citations. [ 43 ]


In a 1994 cover story by  Psychology Today , [ 44 ] [ 45 ]  1,500 readers (about two-thirds women) were surveyed about male body image. Many of the women were not particularly concerned with penis size, and over 71% thought men overemphasized the importance of penis size and shape. Generally, the women polled cared more about width than men thought, and less about length than men thought, although the strength of caring for either among women showed a similar pattern.


In a small study conducted by  University of Texas–Pan American  and published in 2001 in  BMC Women's Health , 50 undergraduate women were surveyed by two popular male athletes on campus about their perceptions of sexual satisfaction; it was concluded that the width of a penis feels better than the length of a penis, when subjects are asked to choose between the two (size was left unspecified). It was also concluded that this may show that penis size overall affects sexual satisfaction, since women chose between the two options they were given. [ 46 ]


A study published in 2002, conducted at  Groningen University Hospital , asked 375 sexually active women (who had recently given birth) the importance of penis size. The results showed that 21% of women felt length was important and 32% felt that girth was important. [ 47 ]


A study conducted at the  Australian National University , published in early 2013, showed that penis size influences a man's sex appeal, and the taller the man, the bigger the effect. [ 48 ]  The study showed life-sized 3D computer-generated images, altering the height and other physical attributes, with women typically registering preferences in under 3 seconds. A preference for taller men's larger penis size was indicated.


A US study published in 2015 of the stated preferences of a panel of 75 women using  3D-printed  models as scale references showed a preferred penis length of 16 cm (6.3 in) and a preferred circumference of 12.2 cm (4.8 in) for long-term sexual partners, with slightly larger preferred sizes of a length of 16.3 cm (6.4 in) and circumference of 12.7 cm (5.0 in) for one-time sexual encounters. [ 49 ]


According to the study, however, when asked to estimate the length of their partner's penis, most women would say a size significantly smaller than what their partner was recorded to be. This suggests that perception of size is not entirely accurate. [ 49 ]  The visual impression of the size is not necessarily in correlation with the feeling in the vulva and vagina. A very long penis can cause  dyspareunia , if the man doesn't understand how to use it carefully.


One Australian study of 184 men looked at penis length and circumference in relationship to condom breakage or slippage. 3,658 condoms were used. The study found that when used correctly, condoms had a breakage rate of 1.34% and a slippage rate of 2.05%, for a total failure rate of 3.39%. Penile dimensions did not influence slippage, although penis circumference and broken condoms were strongly correlated, with larger sizes increasing the rate of breakage. [ 50 ]


Androgens  like  testosterone  are responsible for penis enlargement and elongation during puberty. [ 51 ]  Penis size is positively correlated with increasing testosterone levels during puberty. [ 52 ]  But after puberty, administration of testosterone does not affect penis size, and androgen deficiency in adult men only results in a small decrease in size. [ 52 ]   Growth hormone  (GH) and  insulin-like growth factor 1  (IGF-1) are also involved in penis size, with deficiency (such as that observed in  growth hormone deficiency  or  Laron syndrome ) at critical developmental stages having the potential to result in  micropenis . [ 53 ]


There are certain genes, like  homeobox  (Hox A and D) genes, which may have a role in regulating penis size. In humans, the  AR gene , located on the  X chromosome  at Xq11-12, may affect penis size. The  SRY gene  located on the  Y chromosome  may have a role to play. Variance in size can often be attributed to  de novo  mutations . Deficiency of  pituitary growth hormone  or  gonadotropins  or mild degrees of androgen insensitivity can cause small penis size in males and can be addressed with growth hormone or testosterone treatment in early childhood. [ citation needed ]


An adult penis with an erect length of 2.5  SD  below the average but otherwise formed normally is referred to in a medical context as having the  micropenis  condition. [ 54 ]  The condition affects 0.6% of men. [ 7 ]  Some of the identifiable causes are  deficiency of pituitary growth hormone  or  gonadotropins , mild degrees of  androgen insensitivity , a variety of genetic syndromes and variations in certain  homeobox  genes. Some types of micropenis can be addressed with growth hormone or  testosterone  treatment in early childhood. Operations are also available to increase penis size in cases of micropenis in adults. [ 55 ]


It has been suggested that differences in penis size between individuals are caused not only by  genetics , but also by environmental factors such as  culture ,  diet  and chemical or pollution exposure. [ 56 ] [ 57 ] [ 58 ] [ 59 ]   Endocrine disruption  resulting from chemical exposure has been linked to genital deformation in both sexes (among many other problems). Chemicals from both synthetic (e.g., pesticides, anti-bacterial  triclosan ,  plasticizers  for plastics) and natural (e.g., chemicals found in  tea tree oil  and lavender oil) [ 60 ] [ 61 ]  sources have been linked to various degrees of endocrine disruption.


Both  PCBs  and the plasticizer  DEHP  have been associated with smaller penis size. [ 62 ]  DEHP metabolites measured from the urine of pregnant women have been significantly associated with the decreased penis width, shorter  anogenital distance  and the incomplete descent of  testicles  of their newborn sons, replicating effects identified in animals. [ 63 ]  According to a 2008 study published by the US  National Library of Medicine , approximately 25% of US women have  phthalate  levels similar to those observed in animals. [ 63 ]


A 2007 study by the  University of Ankara , Faculty of Medicine, found that penile size may decrease as a result of some  hormonal therapy  combined with external beam  radiation therapy . [ 64 ]  In addition, some estrogen-based  fertility drugs  like  diethylstilbestrol  (DES) have been linked to genital abnormalities or a smaller than normal penis (microphallus). [ 65 ]


Perceptions of penis size are culture-specific. [ 66 ]  Some prehistoric sculptures and  petroglyphs  depict male figures with exaggerated erect penises. [ 67 ]   Ancient Egyptian  cultural and artistic conventions generally prevented large penises from being shown in art, as they were considered obscene, [ 68 ]  but the scruffy, balding male figures in the  Turin Erotic Papyrus  are shown with exaggeratedly large genitals. [ 68 ] [ 69 ]  The Egyptian god  Geb  is sometimes shown with a massive erect penis and the god  Min  is almost always shown with an erection. [ 67 ]


The males of  ancient Greece  believed that small penises were ideal. [ 66 ]
Scholars believe that most ancient Greeks probably had roughly the same size penises as most other Europeans, [ 66 ]  but Greek artistic portrayals of handsome youths show them with inordinately small, uncircumcised penises with disproportionately large  foreskins , [ 66 ]  indicating that these were seen as ideal. [ 66 ]  Large penises in  Greek art  are reserved exclusively for comically grotesque figures, [ 66 ] [ 67 ]  such as  satyrs , a class of hideous, horse-like woodland spirits, who are shown in Greek art with absurdly massive penises. [ 66 ]
 Actors  portraying male characters in  ancient Greek comedy  wore enormous, fake, red penises, which dangled underneath their costumes; [ 71 ]


In  Aristophanes 's comedy  The Clouds , "Mr. Good Reason" gives the character Pheidippides a description of the ideal youth: "A glistening chest and glowing skin / Broad shoulders, a small tongue /A mighty bottom and a tiny prong." [ 72 ]
In  Greek mythology ,  Priapus , the god of fertility, had an impossibly large penis that was always  permanently erect . [ 73 ] [ 67 ]  Priapus was widely seen as hideous and unattractive. [ 73 ]  A  scholion  on  Apollonius of Rhodes 's  Argonautica  states that, when Priapus's mother  Aphrodite , the goddess of love and beauty, gave birth to him, she was so horrified by the size of his penis, his massive  potbelly , and his huge tongue that she  abandoned him to die  in the wilderness. [ 73 ]  A herdsman found him and raised him as his son, [ 73 ]  later discovering that Priapus could use his massive penis to aid in the growth of plants. [ 73 ]


Nonetheless, there are indications that the Greeks had an open mind about large penises. [ 67 ]  A statue of the god  Hermes  with an exaggerated penis stood outside the main gate of  Athens [ 67 ]  and in  Alexandria  in 275 BC, a procession in honor of  Dionysus  hauled a 180-foot phallus through the city and people venerated it by singing hymns and reciting poems. [ 67 ]  The Romans, in contrast to the Greeks, seem to have admired large penises [ 67 ] [ 70 ]  and large numbers of large phalli have been recovered from the ruins of  Pompeii . [ 67 ]  Depictions of Priapus were very popular in Roman erotic art and literature. [ 67 ] [ 70 ]  Over  eighty obscene poems dedicated to him  have survived. [ 67 ]


Penis size is alluded to in the  Bible : [ 67 ]


18  And she revealed her whorings, and she revealed her nakedness, and so I turned from her  just as  I turned from her sister.   19  Yet she increased her whorings,  recalling  the days of her childhood when she was prostituted in the land of Egypt.   20  And she lusted after her male lovers whose genitalia  were the  genitalia of male donkeys and  their  seminal emission  was the  seminal emission of horses.  Ezekiel 23:18–20 Lexham English Bible


Ancient Chinese legend holds that a man named  Lao Ai  had the largest penis in history and that he had an affair with  Queen Dowager Zhao  ( c.  280–228 BC), the mother of  Qin Shi Huang , by pretending to be a  eunuch . [ 67 ]   Ancient Koreans  admired large penises and  King Jijeung  (437–514 AD) of the  Silla  Dynasty is said to have had a forty-five-centimeter penis that was so large his subordinates had to search for a woman that fit him. [ 67 ]  Traditional  Japanese  erotic paintings usually show genitals as exaggeratedly large. [ 67 ]  The oldest known painting of this type, found in the  Hōryū-ji  Temple in  Ikaruga , dates to the eighth century AD and depicts a fairly large penis. [ 67 ]


The ancient Indian sexual treatise  Kama Sutra , originally written in  Sanskrit , probably between the second and fourth centuries AD, divides men into three classes based on penis size: "hare" size (about 5–7 cm, or 2–3 inches, when erect), "bull" size (10–15 cm, or 4–6 inches), and "horse" size (18–20 cm, or 7–8 inches). [ 67 ]  The treatise also divides women's vaginas into three sizes ("deer", "mare", and "elephant") [ 67 ]  and advises that a man match the size of the vagina of the woman he is having sex with to the size of his own penis. [ 67 ]  It also gives medically dubious advice on how to enlarge one's penis using  wasp stings . [ 67 ]


In medieval  Arabic literature , a longer penis was preferred, as described in an  Arabian Nights  tale called "Ali with the Large Member". As a witty  satire  of this fantasy, the 9th-century  Afro-Arab  author  Al-Jahiz  wrote: "If the length of the penis were a sign of honor, then the  mule  would belong to the  Quraysh " (the tribe to which  Muhammad  belonged and from which he descended). [ 74 ] [ 67 ]


The medieval  Norsemen  considered the size of a man's penis as the measure of his manliness, [ 75 ]  and a thirteenth-century Norse magic  talisman  from  Bergen , a  wooden stave  inscribed with writing in  runic script , promises its wearer: "You will fuck Rannveig the Red. It will be bigger than a man's prick and smaller than a horse's prick." [ 75 ]  A late fourteenth century account of the life of  Saint Óláfr  from the  Flateyjarbók  describes a pagan ritual which centered around a preserved horse's penis used as a cult artifact [ 75 ]  which members of the cult would pass around in a circle, [ 75 ]  making up verses in praise of it, [ 75 ]  encouraging it and the other members of the group to behave in sexually suggestive ways. [ 75 ]


During the  Renaissance , some men in Europe began to wear  codpieces , which accentuated their genitals. [ 67 ]  There is no direct evidence that it was necessarily worn to enhance the apparent size of the wearer's penis, [ 67 ]  but larger codpieces were seen as more fashionable. [ 67 ]


Males may quite easily underestimate the size of their own penis relative to those of others. A survey by  sexologists  showed that many men who believed that their penis was of inadequate size had average-sized penises. [ 76 ]  Another study found sex education of standard penile measurements to be helpful and relieving for patients concerned about small penis size, most of whom had incorrect beliefs of what is considered medically normal. [ 77 ]  The study found that almost all of their patients that were concerned about their penis size overestimated the average penis size. The perception of having a large penis is often linked to higher self-esteem. [ 78 ]  Fears of shrinking of the penis in folklore have led to a type of  mass hysteria  called  penis panic , though the penis legitimately can shrink in size due to scar tissue formation in the penis from a medical condition called  Peyronie's disease . [ 79 ] [ 80 ]  Marketers of  penis enlargement  products exploit fears of inadequacy, but there is no consensus in the scientific community of any non-surgical technique that permanently increases either the thickness or length of the erect penis that already falls into the normal range.


Small penis syndrome (SPS), a term sometimes used in medical literature, is characterized by an obsessive concern that the penis is smaller than average, often despite normal measurements. It has been associated with wider psychological disorders, including  anxiety  and body  dysmorphic  disorder. Assessment focuses on confirming normality and addressing underlying psychological factors. [ 81 ] [ 82 ]


Widespread private concerns related to penis size have led to a number of  folklore  sayings and  popular culture  reflections related to penis size. Penis panic is a form of mass hysteria involving the believed removal or shrinking of the penis, known as  genital retraction syndrome . The penis can significantly shrink due to scar tissue formation from a condition called Peyronie's disease which affects up to 10% of men. [ 83 ]  Products such as penis pumps, pills, and other dubious means of penis enlargement are some of the most marketed products in  email spam . At present there is no consensus in the scientific community of any non-surgical technique that permanently increases either the thickness or length of the erect penis that already falls into the normal range (4.5" to 7").


A study undertaken at  Utrecht University  found that the majority of  gay men  in the study regarded a large penis as ideal, and having one was linked to self-esteem. [ 84 ]  One study analysing the self-reported  Kinsey  data set found that the average penis of a homosexual man was larger than the average penis of their heterosexual counterparts (6.32 inches [16.05 cm] in length amongst gay men versus 5.99 in [15.21 cm] in heterosexuals, and 4.95 inches [12.57 cm] circumference amongst gay men versus 4.80 in [12.19 cm] in heterosexual men). [ 85 ]


While more than 46% of people have watched  pornography , with 30%–90% of women and 60%–98% of men having watched it at some point in their lifespan, between 1973 and 2016, among and in comparison to other racial groups,  Black women  and Black men were reported to have watched the most porn. [ 86 ]  Pornography tends to depict  Black people  through  racist  and  sexist   stereotypes , such as Black people being hypersexual and animalistic, and  sexually objectifies  Black people through its emphasis and focus on sexual vigor and genitalia; this is socially generated and reinforced through production and supply of porn, such as  Black porn  and  interracial porn  that initially debuted in 1982 and big Black cock ( BBC ) porn, which then meets the demand from porn consumers, such as White men with  fantasies  about the  sexuality of Black people  in 1982 and porn consumers on  Pornhub  whose top search terms in 2022 were: "Black", the 13th most searched term, "BBC", the 9th most searched term, and "Ebony", the 3rd most searched term and the most searched category of 2022. [ 86 ]  Cosmetic changes and digital changes to genitalia can occur in porn, with the  Labia minora  of women being portrayed as smaller than the average size and the penis of men being portrayed as larger than the average size. [ 86 ]  Genital self-image is affected by the consumption of pornography as the primary focus of pornography is on genitalia and  sexual acts . [ 86 ]  The genital  self-image  and focus for Black women were genital odor and appearance, and the genital self-image and focus for Black men were penis size; racially diverse study sample sizes indicate that, in contrast to women who tend to have a less positive genital self-image, men tend to have a more positive genital self-image. [ 86 ]


The human penis is thicker than that of any other primate, both in absolute terms and relative to the rest of the body. [ 87 ]  Early research, based on inaccurate measurements, concluded that the human penis was also longer. In fact, the penis of the  common chimpanzee  is no shorter than in humans, averaging 14.4 cm (5.7 inches), and some other primates have comparable penis sizes relative to their body weight. [ 88 ]


The evolutionary reasons for the increased thickness have not been established. [ 89 ] [ needs update ]  One explanation is that thicker penises are an  adaptation  to a corresponding increase in  vaginal size . The vaginal canal is believed to have expanded in humans to accommodate the larger size of a newborn's  skull . Women may then have  sexually selected  men with penises large enough to fit their vagina, to provide  sexual stimulation  and ensure  ejaculation . [ 89 ]


Other evolutionary hypotheses to explain humans' relatively large penis length and girth include a sperm competition hypothesis and a mate competition hypothesis. The sperm competition hypothesis does not have much support as in other mammals where sperm competition is present, larger testes evolve, not larger penises. The mate competition hypothesis involves the prediction that a human with a larger penis would be able to displace the sperm of another. Studies have found that larger penises do not displace other sperm more effectively than smaller penises, but rather longer penises may ejaculate sperm inside the vagina in places that would be harder for a following penis to displace. The depth of pelvic thrusting was correlated to the displacement of competing sperm. [ 90 ]


Hyperactivation  is a type of  sperm   motility .  Hyperactivated sperm motility is characterised by a high amplitude, asymmetrical beating pattern of the sperm tail ( flagellum ).  This type of motility may aid in sperm penetration of the  zona pellucida , which encloses the  ovum . [ 1 ]


Hyperactivation could then be followed by the  acrosome reaction  where the cap-like structure on the head of the cell releases the enzymes it contains.  This facilitates the penetration of the ovum and fertilisation.


Some definitions consider  sperm activation  to consist of these two processes of  hyperactivation  and the  acrosome reaction .


Hyperactivation is a term also used to express an X chromosome gene dosage compensation mechanism and is seen in Drosophila. Here, a complex of proteins bind to the X-linked genes to effectively double their genetic activity. This allows males (XY) to have equal genetic activity as females (XX), whose X's are not hyperactivated.


Mammalian sperm cells become more active when they approach an egg cell in a process called  sperm activation . Sperm activation has been shown to be caused by  calcium   ionophores   in vitro ,  progesterone [ 2 ]  released by nearby  cumulus cells  and binding to  ZP3  of the zona pellucida.


The initial change is called "hyperactivation", which causes a change in spermatozoa motility. They swim faster and their tail movements become more forceful and erratic.


A recent discovery links hyperactivation to a sudden influx of calcium ion into the tails.  The whip-like tail (flagellum) of the sperm is studded with  ion channels  formed by proteins called  CatSper . [ 3 ]   These channels are selective, allowing only calcium ion to pass.  The opening of CatSper channels is responsible for the influx of calcium.  The sudden rise in calcium levels causes the flagellum to form deeper bends, propelling the sperm more forcefully through the viscous environment.  Sperm hyperactivity is necessary for breaking through two physical barriers that protect the egg from fertilization.


Hyperactivation has also shown to serve as a feature of the human sperm  chemotaxis . When the sperm is exposed to chemo-attractant, especially progesterone; the sperm will exhibit sudden flagellar arrest, followed by sharp turn and hyperactivation. This response suggests that hyperactivation serves as method to quickly guide sperm through chemo-attractant gradient. [ 4 ]


Before reaching the egg, the sperm are often trapped in  epithelial cells  in a  fallopian tube , meaning they are rendered inert unless they undergo hyperactivation. The change in motion and force of the tail movements enable the sperm to escape from the epithelium.  Thus, only those sperm which have undergone hyperactivation have the ability to fertilize the egg. [ 5 ]


The  Icelandic Phallological Museum  ( Icelandic :  Hið íslenzka reðasafn   [ˈhɪːð   ˈistlɛnska   ˈrɛːðaˌsapn̥] ), located in  Reykjavík , Iceland, houses the world's largest display of  penises  and penile parts. As of early 2020 the museum moved to a new location in Hafnartorg, three times the size of the previous one, and the collection holds well over 300 penises from more than 100 species of mammal. The museum also holds 22 imagined penises from creatures and peoples of Icelandic folklore.


In July 2011, the museum obtained its first  human penis , one of many promised by would-be donors. Its detachment from the donor's body did not go according to plan and it was reduced to a greyish-brown shriveled mass that was pickled in a jar of  formalin . The museum continues to search for "a younger and a bigger and better one." [ 2 ]  In the meantime, they have begun exhibiting a cast of Matt Barr of Great Britain who has "the longest urinary measurement ever recorded and...the longest and girthiest phallus, of any man alive today." [ 3 ]


Founded in 1997 by since-then retired teacher Sigurður Hjartarson and now run by his son Hjörtur Gísli Sigurðsson, the museum grew out of an interest in penises that began during Sigurður's childhood when he was given a cattle whip made from a bull's penis. He obtained the organs of Icelandic animals from sources around the country, with acquisitions ranging from the 170 cm (67 in) front tip of a  blue whale penis  to the 2 mm (0.08 in)  baculum  of a  hamster , which can only be seen with a magnifying glass. The museum claims that its collection includes the penises of elves and trolls, though, as  Icelandic folklore  portrays such creatures as being invisible, they cannot be seen. The collection also features phallic art and crafts such as lampshades made from the scrotums of bulls.


The museum has become a popular tourist attraction with thousands of visitors a year and has received international media attention, including a Canadian documentary film called  The Final Member , which covers the museum's quest to obtain a human penis. According to its mission statement, the museum aims to enable "individuals to undertake serious study into the field of phallology in an organized, scientific fashion." [ 4 ]


The museum's founder Sigurður Hjartarson worked as a teacher and principal for 37 years, teaching history and Spanish at Reykjavík's  Hamrahlid College  for the last 26 years before his retirement. [ 5 ]  As a child, he owned a bull's  pizzle , which was given to him to use as a cattle whip. He began collecting penises after a friend heard the story of the bull's penis in 1974 and gave him four new ones, three of which Sigurður gave to friends. Acquaintances at whaling stations began bringing him  whale penises  as well, and the collection grew from there, expanding through donations and acquisitions from various sources around Iceland. [ 6 ]


The organs of farm animals came from  slaughterhouses , while fishermen supplied those of  pinnipeds  and the smaller whales. The penises of larger whales came from  commercial whaling stations , although this source dried up after the  International Whaling Commission  implemented a global ban on commercial whaling in 1986. Sigurður was able to continue to collect whale penises by harvesting them from the 12–16 whales that fall victim to stranding on the Icelandic coast each year. [ 6 ]  He also obtained the penis of a  polar bear  shot by fishermen who found the animal drifting on  drift ice  off the  Westfjords . [ 2 ]


Sigurður was assisted by his family, though not without some occasional embarrassment. His daughter Þorgerður recalls that she was once sent to a slaughterhouse to collect a specimen but arrived just as the workers were taking a lunch break: "Someone asked, 'What's in the basket?' I had to say, 'I'm collecting a frozen goat penis.' After that I said, 'I will never collect for you again.'" [ 7 ]  According to Sigurður, "Collecting penises is like collecting anything. You can never stop, you can never catch up, you can always get a new one, a better one." [ 8 ]


The collection was at first housed in Sigurður's office at the college until he retired from his teaching job. He decided, more as a hobby than a job, to put it on public display in Reykjavík and was awarded a grant from the city council of  ISK  200,000 to support the opening of a museum in August 1997. [ 9 ]  By 2003, it was attracting 5,200 visitors a year, of which 4,200 were from abroad. He put the museum up for sale in 2003, but also offered it to the city of Reykjavík as a gift. [ 10 ]  However, he was unsuccessful in obtaining financial support from the state or city. When he retired in 2004, he could no longer afford the rent on the museum's premises. [ 11 ]


After his retirement, he moved along with his collection to  Húsavík , a fishing village with a population of about 2,200 people located 298 miles (480 km) northeast of the capital. The museum was housed in a small building, formerly a restaurant, [ 11 ]  that was marked with a giant wooden penis and a stone phallus standing outside on the street. The village's inhabitants were at first skeptical of the new arrival, but came to accept it when they were persuaded that there was nothing pornographic about the museum. [ 2 ]


In 2012 he handed over the collection to his son, Hjörtur Gísli Sigurðsson (described by  Slate  as "the world's only hereditary penis-museum operator" [ 7 ] ). It was relocated from Húsavík to Reykjavík's main shopping street at  Laugavegur  116. [ 12 ]  Its former location in Húsavík is now home to  The Exploration Museum . [ 13 ]  An offer from a wealthy German to buy the museum for ISK 30 million (US $232,000 / €186,000) and a proposal to move it to the United Kingdom were both turned down, as Hjörtur insists that "the museum has to be in Iceland." [ 14 ]  He intends to continue acquiring new penises because you can "always get a better, newer one ... a bigger size or better shape, you know?" [ 15 ]


According to  University of Iceland   anthropologist  Sigurjón Baldur Hafsteinsson, Icelanders' tolerance of the museum is an indicator of how Icelandic society has changed since the 1990s, when a newly elected  neoliberal  government fostered a more open outlook on entertainment, creativity and tourism that has "enabled new ideas to emerge publicly". [ 8 ]  He has documented the significance of the museum's role in Icelandic culture in a book,  Phallological museum . [ 16 ] [ 17 ]


According to the museum's website, the collection comprises 280 specimens from 93 species of animals. They range from some of the largest to some of the smallest penises in the animal world. Its largest exhibit is a portion of a blue whale's penis measuring 170 cm (67 in) long and weighing 70 kilograms (150 lb), [ 18 ]  which  Iceland Review  has dubbed "a real Moby Dick". [ 19 ]  The specimen is just the tip, as the entire organ, when intact, would have been about 5 m (16 ft) long and weighed about 350–450 kilograms (770–990 lb). The baculum of a hamster, only 2 mm (0.08 in) long, is the smallest item in the collection and needs a magnifying glass to be viewed. [ 18 ]  Sigurður has described the collection as the product of "37 years of collecting penises. Somebody had to do it." [ 8 ]


The museum also has a "folklore section" exhibiting mythological penises; its online catalogue lists specimens reportedly taken from elves, trolls,  kelpies , and "The Nasty Ghost of  Snæfell ". [ 20 ]  Sigurður says that the elf's penis, which the museum's catalogue describes as "unusually big and old", is among his favourites. It cannot be seen, as Icelandic folklore holds that elves and trolls are invisible. [ 11 ]  The folkloric penises also include those of a  merman , a one-legged, one-armed and one-eyed monster called a Beach-Murmurer, an Enriching Beach Mouse (said to draw "money from the sea to enrich her owner"), and an  Icelandic Christmas Lad  reportedly found dead at the foot of a mountain in 1985 and whose penis was presented to the museum by a former mayor of Reykjavík. [ 20 ]


The museum's website states that it enables "individuals to undertake serious study into the field of phallology in an organized, scientific fashion", giving due prominence to a field that until now has only been "a borderline field of study in other academic disciplines such as history, art, psychology, literature and other artistic fields like music and ballet." [ 21 ]  The museum aims to collect penis specimens from every  mammal in Iceland . It also exhibits phallic artwork and penis-related objects or "phallobilia" such as lampshades made from the  scrotums  of bulls. [ 4 ]  Other exhibits range "from an 18th-century engraving depicting the circumcision of Christ to a 20th-century plastic penis pacifier." [ 19 ]  Most of the collection has been donated, and the only purchase to date has been an  elephant's penis  measuring nearly 1 m (3.3 ft) long. The penises are either preserved in  formaldehyde  and displayed in jars or are dried and hung or mounted on the walls of the museum. [ 18 ]


Sigurður has used a variety of techniques to preserve the penises, including preservation in formaldehyde, pickling, drying, stuffing and salting. [ 22 ]  One particularly large penis taken from a bull has been converted into a walking stick. [ 8 ]  Many of the museum's exhibits are illuminated by lamps made by Sigurður from rams' testicles. [ 22 ]  Sigurður has also carved wooden phalluses, which can be found adorning various objects around the museum, [ 2 ]  and has a bow tie decorated with images of phalluses that he wears on special occasions. [ 11 ]


Josh Schonwald of  Salon  described his impressions of the museum when he visited in 1998:


They were hanging on the walls, stuffed in jars, displayed with curatorial love – dried penises, penises embalmed in formaldehyde, massive penises displayed like hunting trophies. A tanned  bull's penis , a smoked  horse's penis . There were runty, shriveled  penises of reindeer ,  foxes , minks and rats. There were seal and walrus penises with stiff  penis bones  – ensuring a perpetually erect state. There was the Big Penis – a 3-foot-long blue whale penis (which could have been an oar for a canoe). [ 6 ]


The museum is open every day [ 23 ]  and by July 2011 was attracting up to 11,000 visitors annually. [ 2 ]  Sixty percent of the museum's visitors are reported to be women, [ 18 ]  though according to the authors of the  Rough Guide to Iceland , mentioning the museum "causes the staff at the tourist office to blush with embarrassment." [ 24 ]  The museum's guest book includes comments such as, "I've never seen so many penises–and I went to boarding school!" (from a New Zealand visitor), "They're bigger in the USA," (from someone from Wisconsin) and "Is there a vagina museum?" [ 7 ]  On this point, Sigurður has said, "I'm only collecting the male organ. Somebody else has to do the other job. I'd be interested in how they would preserve it. I think vaginas are better alive." [ 25 ]  (There used to be a pop-up museum called "Museum of Vaginal Imagination" in Rotterdam in the Netherlands [ 26 ]  and a  Vagina Museum [ 27 ]  opened in London in 2017.)


For many years, the museum sought to obtain a human penis. Sigurður was able to obtain human  testicles  and a  foreskin  from two separate donors; [ 28 ]  the foreskin was donated by Iceland's National Hospital after an emergency  circumcision  operation. [ 24 ]  The museum also contains sculptures of 15 penises based on the  Iceland men's national handball team . As the team had  won the silver medal at the 2008 Beijing Olympic Games , the penises were made from a silvered material. According to Sigurður, they are not displayed in the same order as the individuals shown in the photograph that accompanies them. In an interview Hjartason suggested that "their wives would recognise them." [ 2 ]  According to  Slate , these sculptures were created by Sigurður's daughter, Þorgerður Sigurðardóttir, and were based on her own experience rather than any knowledge of the team. The team's goalkeeper denies that the sculptures are casts. [ 7 ]


The museum has so far received pledges from four men—an Icelander, a German, an American and a Briton—to donate their penises. Canadian film-maker Zach Math comments that the American, Tom Mitchell, "is an ordinary guy but he has this quirk where he thinks of his penis as a separate entity from his body—Elmo. He has this dream that he wants it to be the most famous penis in the world." [ 29 ]  According to Sigurður, Mitchell "wanted to have his penis cut off even during his lifetime and then visit the museum." [ 11 ]  Mitchell sent a cast of his penis to serve as a substitute in the meantime, [ 18 ]  along with photographs of it dressed up as  Santa Claus  and  Abraham Lincoln . [ 30 ]  The donor also tattooed his penis with the  Stars and Stripes  to make it look more appealing. [ 29 ]  He says that "I've always thought it'd be really cool for my penis to be the first true penis celebrity" and has made it the star of its own comic book,  Elmo: Adventures of a Superhero Penis . [ 31 ]


The Icelandic donor was a 95-year-old man from nearby  Akureyri  who was said to have been a womaniser in his youth and wanted to donate his penis to the museum to ensure his "eternal fame". [ 18 ]  Sigurður said that, even at the age of 95, the donor remained active, "both vertically and horizontally". [ 6 ]  However, the donor was said to be concerned that "his penis is shrinking as he gets older and he is worried it might not make a proper exhibit." [ 18 ]


His penis was given priority over those of the non-Icelandic donors in accordance with the museum's mission to display the organs of  Icelandic mammals . Removing and preserving it was not an easy proposition, as Sigurður explained: "The donor and the doctors are in agreement, it must be taken while the body is warm. Then bleed it and pump it up. If it cools you can't do anything, so [the donor] is eager to have it taken warm and treated to be preserved with dignity." [ 22 ]


In January 2011, the Icelandic donor died and his penis was surgically removed so that it could be added to the museum's collection. The  penectomy  was not entirely successful and left the penis "a greyish-brown, shrivelled mass". According to Sigurður, "I should have stretched it and sewn it at the back to keep it in more or less a normal position". Instead, it "went directly into the formaldehyde". Although disappointed with the results, Sigurður expressed confidence that "I will get a younger and a bigger and better one soon." [ 2 ]


Visitors' most common reaction to the preserved human penis is "that it's very old, you know, a bit shrunken, and the male members [ sic ] say 'oh, I hope mine will not look like this when I get old. ' " [ 15 ]  Sigurður has considered donating his own penis to the museum when he dies but said that it depends on his wife: "If she dies first, my specimen would go in here. If I die first, well I can't say. She might say no." [ 2 ]


American writer and actor  Jonah Falcon , known for his claim to an impressively sized penis, was invited by the museum via  The Huffington Post  to donate his member after his death. It was announced in May 2014 that Falcon had accepted the proposal, suggesting a display alongside a sperm whale to be called " Jonah and the whale ", after the biblical story. [ 32 ]


In May 2022, the museum announced that it would display a plaster cast of  Jimi Hendrix 's erect penis, created in 1968 in Chicago by  Cynthia Plaster Caster . The famous  groupie , whose real name was Cynthia Albritton, donated the item to the museum in April 2022, shortly before her death. [ 33 ]


In December 2024, the museum began displaying a confirmed erect plaster cast of Matt Barr, measuring over 36cm, the largest ever verified cast of a human penis. [ 34 ]


The museum is the subject of  The Final Member , a film by Canadian documentarians Zach Math and Jonah Bekhor. It profiles Sigurður and his quest to obtain a human penis for the museum, telling the story of the American and Icelandic donors and examining the quasi-taboo nature of the museum's collection. Bekhor says: "I wouldn't say it's a  Rorschach test , but depending on how you react to it really says a lot about what your relationship is with that element of the human anatomy. It's a really interesting phenomenon and we're really curious to see how audiences respond." The film premiered on 1 May 2012 at the  Hot Docs Canadian International Documentary Festival . [ 35 ]


The  International Prostate Symptom Score (IPSS)  is an eight-question written  screening  tool used to screen for, rapidly diagnose, track the symptoms of, and suggest management of the  lower urinary tract symptoms  of  benign prostatic hyperplasia  (BPH).


It contains seven questions related to symptoms related to BPH and one question related to the patient's perceived  quality of life . Created in 1992 by the  American Urological Association , it originally lacked the eighth quality of life question, hence its original name: the American Urological Association symptom score (AUA-7). [ 1 ]  World Health Organization International Consultation on BPH adopted the "eight question" index and labeled it the IPSS. [ 2 ]


The seven questions relating to symptoms experienced in the last month include  feeling of incomplete bladder emptying ,  frequency of urination ,  intermittency of urine stream ,  urgency of urination , weak stream, straining and  waking at night to urinate . [ 1 ]


The IPSS was designed to be self-administered by the patient, with speed and ease in mind. Hence, it can be used in both urology clinics as well as the clinics of primary care physicians (i.e. by general practitioners) for the screening and diagnosis of BPH. [ 1 ]


Additionally, the IPSS can be performed multiple times to compare the progression of symptoms and their severity over months and years. [ 1 ]


In addition to diagnosis and charting disease progression, the IPSS is effective in helping to determine treatment for patients. [ 1 ]


The symptoms must have been experienced in the last month and each answer is scored from 0 to 5 for a maximum score of 35 points. [ 1 ]


The first six questions are scored based on the following: [ 1 ]


The seventh question, relating to nocturia, is scored from 0 to 5 based on how many times the patient gets up at night to urinate (viz. 1 is scored for one time per night and 5 for five times per night). [ 1 ]


The eighth, and final question (not included in the main IPSS score), relating to the patient's perceived  quality of life , is assigned a score of 0 (delighted) to 6 (terrible). [ 3 ]


The  mnemonic  "FUN WISE" can be used to remember the seven questions relating to symptoms of BPH. They are as follows:


In research, the IPSS is used to standardise patients' complaints and symptoms. However, a meta-analysis on the subject of the influence of position (whether standing or sitting) on  urodynamics  (that is, on tests of how completely the bladder, sphincter and urethra store and release urine) noted that, in most cases, physicians either did not use the IPSS, or did not use it adequately. [ 4 ]


Koro  is a  culture bound  delusional disorder in which individuals have an overpowering belief that their  sex organs  are retracting and will disappear, despite the lack of any true longstanding changes to the genitals. [ 1 ] [ 2 ]   Koro is also known as  shrinking penis , and was listed in the  Diagnostic and Statistical Manual of Mental Disorders .


The syndrome occurs worldwide, and  mass hysteria  of genital-shrinkage anxiety has a history in  Africa ,  Asia  and  Europe . [ 3 ]  In the  United States  and Europe, the syndrome is commonly known as  genital retraction syndrome . [ 4 ]


The condition can be diagnosed through psychological assessment along with physical examination to rule out genuine disorders of the genitalia that could be causing true retraction. [ 5 ] [ 6 ]


The word was borrowed from  Malay  and means the  head of a turtle  (or  tortoise ), referring to how it looks when they retract their heads into their shells. [ 7 ] [ 8 ]


Most patients report acute anxiety attacks due to perceived genital retraction and/or genital shrinkage, despite a lack of any objectively visible biological changes in the genitalia that are longstanding. "Longstanding" refers to changes that are sustained over a significant [ specify ]  period and do not appear reversible, unlike the effect of cold temperatures on some genital regions that cause retraction. These changes may trigger a koro attack when observed, although the effects of cold temperatures are objectively reversible. [ 9 ]  According to literature, episodes usually last several hours, though the duration may be as long as two days. [ 7 ]  There are cases in which koro symptoms persist for years in a chronic state, indicating a potential co-morbidity with  body dysmorphic disorder . [ 5 ] [ 10 ]  In addition to retraction, other symptoms include a perception of alteration of penis shape and loss of penile muscle tone. In cases when patients  have no perception of retraction, some patients may complain of genital  paraesthesia  or genital shortening. [ 11 ]  Among females, the cardinal symptom is nipple retraction in the breast, generally into the breast as a whole. [ 5 ]


Psychological components of koro  anxiety  include fear of impending death, penile dissolution and loss of sexual power. [ 5 ] [ 3 ]  Feelings of impending death along with retraction and perceived  spermatorrhea  has a strong cultural link with Chinese traditional beliefs. This is demonstrated by the fact that Asians generally believe koro symptoms are fatal, unlike most patients in the West. [ 5 ] [ 12 ]  Other ideational themes are intra-abdominal organ shrinkage, sex-change to female or  eunuch , non-specific physical danger,  urinary obstruction ,  sterility , impending madness, spirit possession and a feeling of being bewitched. [ 5 ]


Individuals with extreme anxiety and their family members may resort to physical methods to prevent the believed retraction of the penis. A man may perform manual or mechanical penile traction, or "anchoring" by a loop of string or some clamping device. [ 13 ]  Similarly, a woman may be seen grabbing her own breast, pulling her nipple, or even having iron pins inserted into the nipple. [ 12 ]  Physical injury may occur from these attempts. [ 5 ]  These forceful attempts often lead to injuries, sometimes death. [ 14 ]


Psychosexual conflicts, personality factors, and cultural beliefs are considered as being of  etiological
significance to koro. [ 15 ]  Sexual adjustment histories of non-Chinese individuals are often significant, such as  premorbid  sex inadequacy,  sexual promiscuity , guilt over  masturbation , and  impotence . [ 16 ]


Several criteria are typically used to make a diagnosis of koro.  The primary criterion is a patient's report of genital (typically penile or female nipple) retraction despite a lack of objective physical evidence demonstrating retraction.  This is accompanied by severe anxiety related to the retraction, fear of death as a result of retraction, and use of mechanical means to prevent retraction. [ 17 ]  Cases that do not meet all the requirements are generally classified as koro-like symptoms or given a diagnosis of partial koro syndrome. [ 17 ]  It has been argued that the criteria are sufficient but not necessary to make a diagnosis of koro. [ 5 ]   Researchers have identified koro as a possible "cultural relative" of  body dysmorphic disorder .   DSM-IV  explains the process of  differential diagnosis  between these two disorders. [ 10 ]


A medical, psychosexual and psychiatric history should be documented. The physician should explore the patient's concerns about appearance and body image (ruling out  body dysmorphic disorder ).  Additionally, the physician should inquire about overall beliefs, personal values, and assumptions that the patient is making about his or her genitals.  Given that koro is often an “attack” with a great deal of associated anxiety, the physician should ascertain the patient's emotional state along with the timeline from onset to the presentation at the examination. [ 18 ] [ 19 ] [ 20 ]


A physical examination should involve an assessment of overall health along with a detailed genital examination.  In men, genital examination should be performed immediately after penile exposure, to avoid changes due to external temperature.  The primary intent of the male exam is to exclude genuine penile anomalies such as  hypospadias ,  epispadias  and  Peyronie's disease . [ 5 ] [ 19 ]  The presence of a significant suprapubic fat pad should be noted as well. [ 21 ]  Careful measurements of flaccid length, stretched length and flaccid girth will also be useful. If male patients insist that their penis is shrinking and disappearing, [ 5 ]  measurements after intracavernosal  alprostadil  may be used in the office to determine the true erect length and to diagnose any penile abnormalities in the erect state. [ 19 ]   A physical examination should note any injuries inflicted by the patient in an effort to "prevent" retraction as further confirmation of koro. [ 5 ]


In  DSM-IV-TR , koro is listed as one of the entries in the Glossary of Culture-Bound Syndromes of Appendix I. The manual gives koro's definition as "a term, probably of Malaysian origin, that refers to an episode of sudden and intense anxiety that the  penis  (or, in females, the  vulva  and  nipples ) will recede into the body and possibly cause death." [ 1 ]  Attempts have been made by numerous authors to place koro into different classes.  For example, koro may fit into the group of "specific culture-imposed  nosophobia " (classification with cardinal sign), [ 22 ]  "the genital retraction taxon" (classification with common factors between syndromes), [ 23 ]  and the group with "culture-related beliefs as causes for the occurrence" (classification according to how the syndromes might be affected by cultural factors). [ 24 ]


Various authors have attempted to distinguish between complete and incomplete forms of koro, along with cultural and non-cultural forms. [ 15 ]  Cultural forms are said to involve a cultural belief or myth which plays a role in the genesis and spread of the disease in the community.  These are regarded as complete forms of koro, matching all the symptoms required for diagnosis without significant co-morbidity. [ 15 ] [ 5 ]  Differentiation into primary koro, a culture-bound expression, and secondary koro.  Secondary koro is proposed to have co-morbidity with a  CNS disorder , another  psychiatric disorder , or possible drug use. [ 5 ]


Traditional Chinese medicine  recognises koro as a sexual disease and classifies it into two categories, namely "cold conglomeration in  liver " and "depletion of  kidney 's  yang ". [ 25 ]


Men who present with this complaint may have koro, but they may also be misinformed about normal genital size. [ 6 ]   Additionally, they may have penile  dysmorphophobia . [ 26 ]   Penile dysmorphophobia is related to  body dysmorphic disorder  (BDD), defined by the Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition (Text Revision) ( DSM-IV -TR) as a condition marked by excessive preoccupation with an imaginary or minor defect in a facial feature or localized part of the body.  BDD is different from koro.  In koro, a patient is overcome with the belief that his penis is actively shrinking, and it may be in imminent danger of disappearing. [ 27 ]  Clinical literature indicates that these two psychological conditions should be separated during  differential diagnosis . [ 6 ]


In addition to differentiating koro from  body dysmorphic disorder , physicians also recommend that  differential diagnosis  separates koro from physical urological abnormalities. [ 5 ] [ 6 ] [ 28 ]  For example, one physical disorder that causes loss of penile size is  Peyronie's disease , where the  tunica albuginea  develops scar tissue that prevents the full expansion of an erection and causes flaccid penis retraction. [ 29 ] [ 30 ]   Additionally, a  buried penis  is a normally developed penis, partially covered by the suprapubic fat which can be surgically removed. [ 6 ] [ 21 ]