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What is Prolactin?

Mary McMahon
Updated May 17, 2024
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Prolactin is a hormone produced by the pituitary gland. Levels of this hormone can vary over the course of someone's life, depending on a variety of factors, including age and pregnancy. This hormone is also sometimes known as luteotropic hormone (LTH). Many medical labs can test prolactin levels in patients who have conditions which may be related to abnormal production of this hormone.

As the “lactin,” related to the Latin root for “milk,” would suggest, one of the key roles of this hormone in the body is as a stimulus to produce milk. The body starts to make this hormone in the later stages of pregnancy so that the breasts are ready when the baby is born, and prolactin will be produced throughout the nursing period. Another hormone, oxytocin, stimulates the letdown reflex, which allows the baby to access the milk.

The high levels of prolactin observed in nursing mothers also appear to be involved with the menstrual cycle. While nursing, some women experience changes in their menstrual cycles which have been linked with this hormone, and this hormone is also involved in the eventual cessation of menstruation which occurs during menopause. Like many hormones involved with the reproductive system, the hormone works with a number of other hormones and in a variety of complex ways, and researchers often discover new things about how this hormone works in the body.

This hormone also appears to be involved in sexual gratification, and in the production of progesterone by the corpus luteum. Changes in prolactin levels can result in a variety of things, including galactorrhea, in which milk is produced spontaneously and not related to a pregnancy, along with infertility, sterility, and irregularities in the menstrual cycle.

High levels can be caused by a variety of things, including pituitary gland tumors, increased exercise, and, of course, pregnancy. Hormone tests may be ordered when a doctor suspects that a patient has a problem with his or her pituitary gland, so that the doctor can review levels of several pituitary hormones, and when patients experience symptoms which may be related to excessive prolactin production.

Specialized cells known as lactotrophs in the pituitary gland are responsible for secreting this hormone. Sometimes, these cells can become cancerous, causing the levels to spike as they proliferate. In these instances, the cancerous growth may be removed, in which case it may be necessary for the patient to take supplementary drugs to ensure the hormones in the body are properly balanced.

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Mary McMahon
By Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a WiseGeek researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Discussion Comments
By ElizaBennett — On Jun 05, 2011

@rugbygirl - It's sweet of you to help your friend. What you're researching is called "induced lactation." I hadn't heard of testing one's prolactin levels for that purpose--I think prolactin tests may be more for people in whom a disease is suspected.

You can help your friend get in touch with a local La Leche League chapter; they are often knowledgeable about induced lactation. From what I heard at one of my meetings recently, some adoptive moms rent a hospital-grade breast pump a few months ahead of time, while others just wait for the baby's arrival and put baby to the breast (sometimes with an SNS, or supplemental nursing system).

Good luck and congrats to your friend!

By rugbygirl — On Jun 03, 2011

A friend of mine is adopting a baby and wants to breastfeed. I'm helping her do research. Does she need to have a prolactin blood test? Does anyone have experience in this area?

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a...

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