Prolactinoma

A prolactinoma is a benign tumor of the pituitary gland that secretes excess prolactin, the hormone that normally stimulates milk production, and it is the most common type of hormone-producing pituitary tumor. Prolactinomas are classified by size as microprolactinomas, under ten millimeters across, or the less common but larger macroprolactinomas; most arise sporadically with no clear underlying cause, though a minority occur as part of an inherited cancer syndrome called multiple endocrine neoplasia type 1, and estrogen exposure appears linked to the tumor's higher frequency in women. Because prolactin's effects differ by sex, women more often notice hormonal symptoms first, including irregular or absent menstrual periods, unexpected milk production unrelated to breastfeeding, and reduced body hair, while men are more likely to be diagnosed later because of symptoms caused by the tumor's physical size, such as headaches and vision changes from pressure on nearby structures, alongside reduced fertility and sexual function in both sexes. Diagnosis begins with a blood test showing elevated prolactin, followed by an MRI of the pituitary gland with contrast to confirm the tumor's presence, size and exact location. Most prolactinomas respond well to medication: dopamine agonist drugs such as bromocriptine and cabergoline shrink the tumor and normalize prolactin levels in roughly four out of five patients, and surgery is reserved for tumors that do not respond adequately or when medication causes intolerable side effects.