What causes gynecomastia?

Gynecomastia is generally caused by an imbalance between the hormones estrogen and testosterone. Estrogen controls female traits, including breast growth.

Testosterone regulates male traits, such as muscle mass and body hair. Although each of these hormones produces the usual traits seen in males and females, males produce a small amount of estrogen, and females produce a small amount of testosterone.

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Male estrogen levels that are too high or are out of balance with testosterone levels cause gynecomastia.

Gynecomastia occurs naturally at different times in a male’s life. These phases are:

  • At puberty: Hormone levels are changing during puberty (usually 12 to 14 years of age). Breast enlargement usually goes away six months to two years after the start of puberty.
  • After birth: Newborn boys are still under the effects of the estrogen they received from their mothers while developing in the womb. More than half of newborn males are born with enlarged breasts. The gynecomastia goes away within two to three weeks after birth.
  • At mid-life and beyond: Breast enlargement usually peaks in men between the ages of 50 and 80. About one in four men in this age range have breast enlargement.

Many other conditions can cause gynecomastia. These include:

  • Lack of proper nutrition
  • Kidney failure
  • Tumors in the testicles or adrenal glands
  • Liver disease
  • Hyperthyroidism
  • Hypoandrogenism
  • Obesity
  • Hypogonadism
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However, certain drugs can also cause gynecomastia, including:

  • Estrogens
  • Finasteride (Proscar, Propecia) for enlarged prostate
  • Anabolic steroids for improved athletic performance
  • Spironolactone (Aldactone), digoxin (Lanoxin), amiodarone (Cordarone), and calcium channel blockers
  • Cimetidine (Tagamet) and proton pump inhibitors for heartburn
  • Diazepam (Valium) for anxiety
  • Ketoconazole (Nizoral) for fungal infections
  • Metronidazole (Flagyl) for bacterial infections
  • Amphetamines, marijuana, heroin, methadone (“street” drugs), and alcohol
  • Human chorionic gonadotropin for fertility problems