Gynecomastia
Gynecomastia is the growth of abnormally large breasts in males. It is due to the excess growth of breast tissue, not excess fat tissue.
The condition may occur in one or both breasts and begins as a small lump beneath the nipple, which may be tender. The breasts often enlarge unevenly. Gynecomastia during puberty is not uncommon and usually goes away over a period of months.
In newborns, breast development may be associated with milk flow (galactorrhea). This condition usually lasts for a couple of weeks, but in rare cases may last until the child is 2 years old.
Androgens are hormones that create male characteristics, such as hair growth, muscle size, and a deep voice. Estrogens are hormones that create female characteristics. All men have both androgens and estrogens.
Changes in the levels of these hormones, or in how the body uses or responds to these hormones can cause enlarged breasts in men.
More than half of boys develop gynecomastia during puberty.
Other causes include:
Aging
Cancer chemotherapy
Chronic liver disease
Exposure to anabolic steroid hormones
Exposure to estrogen hormone
Kidney failure and dialysis
Lack (deficiency) of testosterone (male hormone)
Marijuana use
Hormone treatment for prostate cancer
Radiation treatment of the testicles
Side effects of some medications (ketoconazole, spironolactone, metronidazole, cimetidine (Tagamet))
Rare causes include:
Genetic defects
Overactive thyroid
Tumors
Breast cancer in men is rare. Signs that may suggest breast cancer include:
One-sided breast growth
Firm or hard breast lump that feels like it is attached to the tissue
Skin sore over the breast
Bloody discharge from the nipple
