Prolactin

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At a Glance

Why Get Tested?

To determine whether or not your prolactin levels are higher (or occasionally lower) than normal

When to Get Tested?

When you have symptoms of an elevated prolactin, such as galactorrhoea (milk production not during pregnancy) and/or visual disturbances and headaches; as part of investigation for female and male infertility; for follow up of low testosterone in men

Sample Required?

A blood sample taken from a vein in your arm

The Test Sample

What is being tested?

Prolactin is a hormone produced by the anterior pituitary gland, a grape-sized organ found at the base of the brain. Prolactin levels are regulated by dopamine (a brain chemical), and the hormone is normally present in low amounts in men and non-pregnant women. Its main role is to promote lactation (breast milk production).

Prolactin levels are usually high throughout pregnancy and just after childbirth. During pregnancy prolactin, oestrogen 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 soon drops back to low pre-pregnancy levels. If she does breastfeed, suckling by the infant plays an important role in the release of prolactin. When the baby feeds, this has an effect on the amount of prolactin secreted by the pituitary, and this is turn controls the amount of milk produced. Prolactin levels will continue to be high while the mother continues to breastfeed, but will eventually fall back to pre-pregnancy levels.

Besides pregnancy, the most common cause of elevated prolactin levels is a prolactinoma, a prolactin-producing tumour of the pituitary gland. Prolactinomas are the most common type of pituitary tumour and are usually benign. They develop more frequently in women but are also found in men. Problems can arise both from the unintended affects of excess prolactin, such as milk production in the non-pregnant woman (and rarely, man) and from the size and location of the tumour.

If the pituitary gland and/or the tumour 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; in men, these tumours can cause a gradual loss in sexual function and desire. If left untreated, prolactinomas may eventually damage tissues surrounding them.

How is the sample collected for testing?

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

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

The Test

Common Questions

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.