Back Blood-tests Explained


Prolactin


At a Glance

Why Get Tested?

To help investigate unexplained flow of breast milk (galactorrhea), abnormal nipple discharge, absence of menstrual periods, and/or infertility in women; in men, to help diagnose the cause of decreased libido and/or erectile dysfunction; to detect and monitor a prolactin-producing pituitary tumor (prolactinoma)

When to Get Tested?

When you have symptoms of elevated prolactin, such as galactorrhea and/or visual disturbances and headaches; during a workup for infertility; for follow-up of low testosterone in men; periodically to monitor for recurrence of a prolactinoma

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None; however, the sample should be collected 3 to 4 hours after waking.

The Test Sample

What is being tested?

Prolactin is a hormone produced by the anterior portion of the pituitary gland, a grape-sized organ found at the base of the brain. Normally present in low amounts in men and non-pregnant women, prolactin's primary role is to promote lactation (breast milk production). This test measures the amount of prolactin in the blood.

Prolactin secretion is regulated and inhibited by the brain chemical dopamine. The prolactin level is usually high throughout pregnancy and just after childbirth.During pregnancy, the hormones prolactin, estrogen, and progesterone stimulate breast milk development. Following childbirth, prolactin helps initiate and maintain the breast milk supply.If a woman does not breastfeed, her prolactin level soon drops back to pre-pregnancy levels. If she does nurse, suckling by the infant plays an important role in the release of prolactin. There is a feedback mechanism between how often the baby nurses and the amount of prolactin secreted by the pituitary as well as the amount of milk produced.

A common cause of an abnormally elevated prolactin level is a prolactinoma, a tumor of the pituitary gland that causes excess production of prolactin. Prolactinoma is the most common type of pituitary tumor and is usually benign. They develop more frequently in women but are also found in men. Problems resulting from them can arise both from the unintended effects of excess prolactin, such as milk production in a woman who is not pregnant or nursing and, rarely, in a man (galactorrhea) and from the size and location of the tumor.

If the anterior pituitary gland and/or the tumor enlarge significantly, it can put pressure on the optic nerve, causing headaches and visual disturbances, and it can interfere with the other hormones that the pituitary gland produces. In women, prolactinomas can cause infertility and irregularities in menstruation while in men, these tumors can cause a gradual loss in sexual function and libido. If left untreated, prolactinomas may eventually damage the surrounding tissues.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed, but the sample is typically collected 3 to 4 hours after waking.

The Test



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