Prolactinoma - What is a prolactinoma?

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The pituitary is a tiny gland situated at the base of the brain behind the nose and below the optic nerves.

The pituitary makes hormones which control the thyroid, ovaries, testes and adrenal glands. Another hormone made by the pituitary is PROLACTIN which stimulates the production of breast milk during pregnancy and breastfeeding. Prolactin secretion is controlled by a compound called dopamine which is made in the brain. In women, normal prolactin levels are typically less than 25 ng/ml and in men, less than 17 ng/ml. When prolactin levels are elevated in the blood, the condition is referred to as HYPERPROLACTINEMIA.

Hyper- meaning ‘increased’; Prolactin referring to the hormone;-emia meaning ‘in the blood’

Blood prolactin levels are normally elevated during pregnancy and breast feeding and may also be increased with some medications, kidney failure, and chest trauma.

A prolactinoma is an abnormal growth, or tumor, on the pituitary gland . The tumor causes the pituitary to produce too much prolactin leading to hyperprolactinemia. A prolactinoma is almost always benign, meaning it is not a cancer. About 1 in 10,000 people will develop a prolactinoma for which a clear cause is not known. Prolactinomas occur in both sexes, but are more common in women. The tumors are seldom seen in children and are rarely passed from parents to their children. Prolactinomas are usually small and rarely grow, but some (as discussed below) can become very large.

Pituitary Adenoma

Figure 1. Depiction of a pituitary adenoma (dark brown) next to normal pituitary tissue (light brown). The normal pituitary is compressed by the tumor. (reprinted with permission, from Kronenberg H, Melmed S, Polonsky K, Larsen PR (eds): Williams Textbook of Endocrinology, 11th Edition, Chapter 8, Anterior Pituitary, Melmed S and Kleinberg DL authors, Philadelphia, Penn: WB Saunders; 2008.)