Gynecomastia is abnormally large breasts in males resulting from growth of excess breast tissue, rather than an increase in fat. Most cases occur temporarily to boys during adolescence, and disappear naturally after a few years. In fewer cases, the breasts grow larger with age, and can be treated through reduction surgery.
Newborn boys may experience an enlargement that usually lasts only a few weeks, but may continue until age two. The condition can affect one or both breasts, which may enlarge unevenly, and begins as a small mound under the nipple that may become sensitive.
Gynecomastia is usually benign and resolves naturally as hormone levels return to normal. In other cases, effective treatments are available.
Obesity may enlarge breasts by increasing fat tissue, a related condition called pseudogynecomastia.