Galactorrhea

Galactorrhea is milk-like nipple discharge that occurs outside expected pregnancy or breastfeeding. It is a finding, not a diagnosis. Prolactin from the anterior pituitary stimulates mammary alveolar cells to produce milk. Dopamine from the hypothalamus normally provides continuous inhibition of prolactin release—the hormonal equivalent of a brake. When dopaminergic inhibition is reduced, prolactin rises and galactorrhea may appear. A pituitary prolactinoma is one possible cause, but it is not the only one. Antipsychotics and some antiemetics can interfere with dopamine signalling. Hypothyroidism can increase hypothalamic TRH, which stimulates prolactin release. Renal failure can allow prolactin to accumulate because clearance is reduced. Repeated nipple stimulation may also sustain discharge or transiently raise the prolactin level. Hyperprolactinemia can suppress GnRH, lowering LH and FSH. The resulting pattern may include irregular or absent menstruation, infertility, reduced libido, or symptoms of low estrogen. In a male patient, sexual dysfunction or breast enlargement may accompany the discharge. These associated findings make a hormonal cause more likely than an isolated local breast problem.