What is gynecomastia?
Gynecomastia, often informally referred to as "man boobs," occurs when "female like" breasts form. A variety of conditions can cause male breast enlargement, but it is typically due to excessive amounts of estrogen (a female hormone) or too little testosterone (a male hormone). Gynecomastia is a benign condition and only rarely causes male breast cancer.
The imbalance between estrogen and testosterone causes the breast tissue to swell and form a breast bud. The size or severity of the overdeveloped male breast varies, but the degree of psychological impact can be quite substantial.