gynecomastia
n. abnormal development of breast tissue in males. In young men, the condition usually occurs on both sides, whereas in men over age 50, gynecomastia tends to be unilateral. It may occur as a result of a hormonal imbalance related to a tumor or as a side effect of therapy with antiandrogens or with dopamine-receptor antagonists, which include many antipsychotic drugs. Dopamine inhibits the release from the anterior pituitary of the hormone prolactin; therefore, inhibition of dopaminergic activity may result in excess secretion of prolactin, leading to engorgement of breast tissue and possibly expression of breast milk (see galactorrhea). Gynecomastia may also be observed (though rarely) with administration of SSRIs.