Gynecomastia (also spelled gynaecomastia)[a] is the abnormal non-cancerous enlargement of one or both breasts in males due to the growth of breast tissue as a result of a hormone imbalance between estrogens and androgens.[4][5] Gynecomastia can cause significant psychological distress or unease.[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 age 50, and/or 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]

Definition[edit]

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]

Signs and symptoms[edit]

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]

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]

Causes[edit]

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[edit]

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.[28]

Newborns