Prolactin is a hormone produced in the pituitary gland: the name prolactin is linked to the fact that it “helps” the production of mother’s milk.

Prolactin (PRL)

During pregnancy,  prolactin plays an important role in the production of milk by the mammary glands, as its secretion serves to stimulate the development of these glands.

In the puerperium , in response to the suction of the newborn babies, it favors the production of milk (lactation) by the woman but more generally by all female mammals: through a feedback mechanism these suctions stimulate the production of prolactin and therefore also that of mother’s milk.

However, many others are the effects of this hormone on the human body. They can in fact be reflected on the reproductive system, on the metabolic system, in the regulation of fluids (osmoregulation), in the regulation of the immune system (immunoregulation), in behaviour.

The production of prolactin

The hormone prolactin is also produced by men, not just by women. As well as in other parts, in the human body it is produced in the anterior part of the pituitary gland: where there are lactotropic cells (cells that cause milk secretion) that produce this hormone, where it is stored and then released into the bloodstream.

Prolactin is also produced in the uterus of women, in immune cells, in the brain, in the breast, in the prostate of men, in the skin and in adipose tissue.

One of the main regulators of prolactin production by the pituitary gland is a hormone called  dopamine,  a hormone that is produced by the hypothalamus – the part of the brain directly above the pituitary gland.

  • Since dopamine limits the production of prolactin, the more dopamine is present, the less prolactin is released.
  • Since prolactin itself increases the secretion of dopamine, this fact produces a negative feedback loop.

Another key regulator of prolactin is estrogen  which has been shown to be effective in increasing the production and secretion of prolactin from the pituitary gland.

Several studies have highlighted the existence of small increases in prolactin in the bloodstream during phases of the reproductive cycle in women with maximum estrogen levels. This also occurs during and after pregnancy, which is explained by the fact that a higher level of circulating prolactin is required to initiate lactation.

Many other hormones, other than dopamine and estrogen, can increase and decrease the amount of prolactin released in the body: for example, thyrotropin-releasing hormone  or (TRH),  oxytocin  and  vasopressin .

Prolactin levels too high

Hyperprolactinaemia is   the condition in which the blood levels of prolactin are higher than normal. The most common causes of hyperprolactinaemia are:

  • a  pregnancy ,
  • taking drugs that reduce the action of dopamine in the body,
  • an underactive thyroid,
  • benign pituitary tumors (known as prolactinomas).

The most common symptoms of hyperprolactinaemia can consist of:

  • unwanted milk production,
  • menstrual cycle disorders,
  • problems due to  estrogen deficiency  (in women) or testosterone deficiency (in men).

One of the most frequent causes of a non-physiological elevation in prolactin levels is prolactinoma, which is a tumor of the pituitary gland.

The vast majority of people with prolactinoma can be successfully treated with drugs that mimic the action of dopamine: their active ingredient is cabergoline.

Prolactin levels too low

The condition with too little prolactin circulating in the blood is called  hypoprolactinaemia . It is very rare, and can occur in people with an underactive pituitary.

A decrease in the amount of prolactin secreted after childbirth can lead to insufficient milk production.

Most people with low prolactin levels have no specific medical problems, although some preliminary studies suggest they may have a reduced immune response to some infections.

Katherine Johnson, M.D., is a board-certified obstetrician-gynecologist with clinical expertise in general obstetrics and gynecology, family planning, women’s health, and gynecology.

She is affiliated with the Obstetrics and Gynecology division at an undisclosed healthcare institution and the online platform,

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