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The pituitary gland is responsible for producing the hormone prolactin, which regulates milk production in breast-feeding women. A hormone-producing tumor called a prolactinoma increases prolactin levels and can cause unexpected lactation and other symptoms.

A prolactinoma, a hormone-producing tumor that generates excess levels of the hormone prolactin, is the most common type of pituitary tumor. Prolactinomas are benign (non-cancerous) tumors, but they do require treatment to alleviate symptoms.

Prolactin is a hormone produced by the pituitary gland, and like most hormones its role in the body is complex. Its most familiar job, however, is to stimulate lactation in breast-feeding women. (Both men and women produce prolactin, although its role in men’s health is not completely understood.) Prolactin levels rise during pregnancy to prepare for breast-feeding. In new mothers, prolactin levels rise when the baby nurses, and the elevated hormone level causes increased milk production. When a new mother does not breast-feed, her prolactin levels fall back to normal, pre-pregnancy levels.

High levels of prolactin in individuals who are neither pregnant nor breast-feeding, however, can lead to unexpected milk production, sexual dysfunction, and other symptoms. Although several things may cause an increase in prolactin production, the cause of most cases of elevated prolactin is a prolactinoma. Prolactinoma is diagnosed most often in women, although it can occur in men as well. (See Diagnosing and Treating Prolactinoma.)

What Causes Prolactinoma?
Prolactinomas do not appear to have a genetic connection, and it is unknown what causes them.

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Reviewed by: Theodore Schwartz, M.D.
Last reviewed/last updated: January 2015
Illustration by Thom Graves, CMI