Clinical meaning
Galactorrhea is the spontaneous flow of milk or milky nipple discharge unrelated to breastfeeding or childbirth. It results from elevated levels of prolactin (hyperprolactinemia), a hormone produced by the anterior pituitary gland. Prolactin is normally kept in check by dopamine, which inhibits its release. When dopamine's inhibitory effect is disrupted - by pituitary tumors (prolactinomas), certain medications (antipsychotics, metoclopramide, some antidepressants), or hypothyroidism - prolactin levels rise and stimulate breast tissue to produce milk. Galactorrhea can occur in women or men, though it is more common in women. It is usually benign but requires investigation to identify and treat the underlying cause.