Abnormal enlargement of breast tissue in men. The term comes from the Greek words gyne meaning "woman" and mastos meaning "breast".
Causes may be idiopathic, familial, drugs, liver disease, hormonal problems. Klinefelter's syndrome is another cause of gynecomastia.
Under hormonal causes of gynecomastia, a raised oestrogen level, reduced androgen levels or an increased sensitivity to oestrogens can cause breast tissue enlargement in men. Liver problems and obesity can lead to gynecomastia (raised oestrogens) as can castration, prolactinomas, a pituitary tumour, adrenal insufficiency, etc.
Leprosy has also been associated with gynecomastia, possibly because leprosy can cause testicular atrophy.
Gynecomastia is correctable by surgery. Usually done for cosmetic benefit only.
Sometimes known as "bitch tits"