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.