Prolactin is a hormone that induces lactation or milk formation.
Smaller tumors, called microprolactinomas are more common in women, and larger tumors, called macroprolactinomas, are more common in men. Many of the smaller tumors do not appear to progress to larger tumors. Many women first experience symptoms while on oral contraceptives or have cessation of menses when oral contraceptives are discontinued. Prolactinomas may grow during pregnancy and may be diagnosed in the postpartum period. Sexual dysfunction occurs in many men.