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Prolactin

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Also known as: PRL
Formal name: 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.

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.

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

Common Questions

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Article Sources

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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.

Sources Used in Current Review

Gremida, A. and Lin, J. (Updated 2013 March 22). Prolactin. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/2089400-overview#showall through http://emedicine.medscape.com. Accessed October 2013.

Benson, C. (Updated 2013 March 6). Prolactin Deficiency. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/124526-overview#showall through http://emedicine.medscape.com. Accessed October 2013.

Shenenberger, D. (Updated 2013 March 21). Hyperprolactinemia. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/121784-overview through http://emedicine.medscape.com. Accessed October 2013.

Meikle, A. W. and Miller, C. (Updated 2013 July). Amenorrhea. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/Amenorrhea.html?client_ID=LTD#tabs=0 through http://www.arupconsult.com. Accessed October 2013.

Bielak, K. and Popat, V. (Updated 2012 June 5). Amenorrhea. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/252928-overview through http://emedicine.medscape.com. Accessed October 2013.

Liou, L. (Updated 2012 September 17). Prolactin. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003718.htm through http://www.nlm.nih.gov. Accessed October 2013.

(© 1995–2013). Prolactin. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/8690 through http://www.mayomedicallaboratories.com. Accessed October 2013.

Pagana, K. D. & Pagana, T. J. (© 2011). Mosby's Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 790-792.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

Merck. Anterior Pituitary Function. The Merck Manual of Diagnosis and Therapy [On-line information]. Available online at http://www.merck.com/pubs/mmanual/section2/chapter6/6c.htm through http://www.merck.com.

(2002 February 17 Updated). Prolactin. MEDLINEplus Health Information [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003718.htm.

(2002 July 24, Updated). Prolactinoma - males. MEDLINEplus Health Information [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000337.htm.

Pituitary: Overview. The Hormone Foundation [On-line information]. Available online at http://www.hormone.org/learn/pituitary_1.html through http://www.hormone.org.

Pituitary: Secretory Tumors. The Hormone Foundation [On-line information]. Available online at http://www.hormone.org/learn/pituitary_2.html through http://www.hormone.org.

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ARUP. Prolactin. ARUP's Guide to Clinical laboratory Testing [On-line information]. Available online at http://www.aruplab.com/guides/clt/tests/clt_150b.htm#1145504 through http://www.aruplab.com.

Merck. General. The Merck Manual of Diagnosis and Therapy, Section 2. Endocrine And Metabolic Disorders, Chapter 6. Hypothalamic-Pituitary Relationships [On-line information]. Available online at http://www.merck.com/pubs/mmanual/section2/chapter6/6a.htm through http://www.merck.com.

Grunebaum, A. (2001 April 23). A Tiny Gland's Big Role in Pregnancy. WebMD Health Information [On-line information]. Available online at http://my.webmd.com/content/article/3607.442 through http://my.webmd.com.

The Impotence Sourcebook (1998). Laboratory Investigations of Erectile Dysfunction. WebMD Health Information [On-line information]. Available online at http://my.webmd.com/content/article/1680.50141 through http://my.webmd.com.

Spengler, R. (2001 February 22, Updated). Prolactin. WebMD Health Information [On-line information]. vailable online at http://my.webmd.com/printing/article/4118.253 through http://my.webmd.com.

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Eckman, A. (Updated 2009 October 14). Prolactin. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003718.htm. Accessed April 2010.

Eckman, A. (Updated 2009 November 23). Prolactinoma. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000336.htm. Accessed April 2010.

(2009 May). Prolactinoma. National Endocrine and Metabolic Diseases Information Service [On-line information]. Available online at http://www.endocrine.niddk.nih.gov/pubs/prolact/prolact.htm through http://www.endocrine.niddk.nih.gov. Accessed April 2010.

Shenenberger, D. (Updated 2010 March 12). Hyperprolactinemia. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/121784-overview through http://emedicine.medscape.com. Accessed April 2010.

Mayo Clinic Staff (2010 March 6). Prolactinoma. MayoClinic.com [On-line information]. Available online at http://www.mayoclinic.com/health/prolactinoma/DS00532 through http://www.mayoclinic.com. Accessed April 2010.

Pagana, K. D. & Pagana, T. J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 767-768.

Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry: AACC Press, Washington, DC. Pp 354-355.

Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 900-901.

Fahie-Wilson, M (2003). In Hyperprolactinemia, Testing for Macroprolactin Is Essential, Clinical Chemistry. 2003;49:1434-1436. Available online at http://www.clinchem.org/cgi/content/full/49/9/1434 through http://www.clinchem.org. Accessed June 2010.

(May 2007) Fahie-Wilson M. Macroprolactin. Clinical Laboratory News Volume 33, Number 5. Available online at http://www.aacc.org/publications/cln/2007/may/Pages/series_0507.aspx through http://www.aacc.org. Accessed June 2010.

Suliman AM, Smith TP, Gibney J,McKenna T Joseph. Frequent Misdiagnosis and Mismanagement of Hyperprolactinemic Patients before the Introduction of Macroprolactin Screening: Application of a New Strict Laboratory Definition of Macroprolactinemia. Clin Chem 2003;49:1504-1509.

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