Causes, Incidence and Risk Factors 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.
Prolactinomas occur most commonly in those under 40 years old. The incidence is 3 out of 10,000 men and 1 out of 1,000 women. The symptoms of infertility , irregular menses, decreased sexual interest , and milk flow not related to childbirth or nursing can be improved with treatment. Men should also be treated when decreased sexual drive, infertility, or impotence are present. Larger tumors or those resistant to bromocriptine may respond to surgical resection, radiation therapy , or a combination of treatments.