Gynecomastia is a condition of overdevelopment or enlargement of the breast tissue in men or boys. The breasts become larger. They may grow unevenly.
Gynecomastia often happens when a preteen or teenage boy is going through the hormonal changes of puberty. But it can also happen to newborn babies and to men as they age.
Gynecomastia is usually a benign (noncancerous) condition. It may be linked to many different causes of hormone changes. In many cases, the cause isn’t known.
Gynecomastia is often caused by changes in levels of the female hormone (estrogen) and the male hormone (testosterone). But it can be caused by other things as well.
Gynecomastia can be a side effect of certain medicines, such as antidepressants, antibiotics, chemotherapy, prostate cancer medicines, ulcer or cardiovascular medicines. Illegal drugs, such as anabolic steroids, heroin, or marijuana can also cause gynecomastia.