What is prolactin?
Prolactin is a hormone originally named for its function of promoting milk production (lactation) in mammals in response to youth suckling after birth. It has since been shown to have more than 300 functions in the body. These can be split into several areas: reproductive, metabolic, fluid regulation (osmoregulation), immune system regulation (immunoregulation), and behavioral functions.
In humans, both in the front portion of the pituitary gland (anterior pituitary gland) and in a range of sites elsewhere in the body are produced prolactin. In the pituitary gland, the lactotroph cells produce prolactin, where they are stored and then released into the bloodstream. Human prolactin also occurs in the tissue of the uterus, immune cells, brain, breasts, prostate, skin, and adipose.
How is prolactin controlled?
One of the main regulators of pituitary gland prolactin production is the hormone called dopamine, which is produced by the hypothalamus, the part of the brain directly above the hypophyseal. Dopamine restrains the production of prolactin, thus the less prolactin is released the more dopamine there is.
Oestrogen is another key regulator of prolactin, and prolactin production and secretion from the pituitary gland have been shown to increase. Studies have shown slight increases in prolactin in women’s blood circulation during stages of their reproductive cycle where levels of estrogen are at their highest. This is also the case during and after pregnancy, which makes sense because a higher circulating level of prolactin is needed to cause lactation to begin.
Besides dopamine and estrogen, a whole range of other hormones can both increase and decrease the amount of prolactin released into the body, with some examples being a thyrotropin-releasing hormone, oxytocin, and anti-diuretic hormone.
What if I do have too much prolactin?
Hyperprolactinemia is called a condition of having too much prolactin circulating in the blood. The most common causes of hyperprolactinemia include pregnancy, drugs that reduce the action of dopamine in the body, under activity of the thyroid, and benign pituitary tumors (called prolactinomas). Symptoms may include unwanted milk production, menstrual cycle disturbances, and symptoms due to deficiency of estrogen (in women), or deficiency of testosterone (in men). The vast majority of patients with a prolactinoma may be successfully treated with drugs that mimic the dopamine action. Cabergoline is the most commonly used form.
How do you test for hyperprolactinemia?
Blood tests could measure prolactin levels. Sometimes the levels are higher if you’ve been eating recently or are under stress. After you’ve fasted and relaxed the test may be done again. Your doctor may also do a physical examination to find any obvious causes or breast discharge.
What if I do have too little prolactin?
Hyperprolactinemia is called the condition of having too little prolactin circulating in the blood. This condition is very rare and may occur in people under the activity of the pituitary.
A decrease in the amount of secreted prolactin can lead to insufficient milk after giving birth. Most people with low levels of prolactin have no specific medical problems, though preliminary evidence suggests that they may have reduced immune responses to certain infections.