Pituitary gland
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 functioning pituitary tumor. Prolactinomas are, the majority of times, 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, irregular periods, sexual dysfunction, and infertility. Many things may cause an increase in prolactin production, with the most common cause being a prolactinoma. Prolactinoma is diagnosed most often in women, although it occurs in men as well. (See Diagnosing and Treating Prolactinoma.)

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

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Our Care Team

  • Vice Chair for Clinical Research
  • David and Ursel Barnes Professor of Minimally Invasive Brain Surgery
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Reviewed by: Georgiana Dobri, M.D.
Last reviewed/last updated: September 2023
Illustration by Thom Graves, CMI

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