Prolactin Health Dictionary

A hormone produced by the pituitary gland. Prolactin helps to stimulate the development of the mammary glands (see breast), and to initiate and maintain milk production for breastfeeding. (See also prolactinoma.)

Prolactin is the pituitary hormone (see PITUITARY GLAND) which initiates lactation. The development of the breasts during pregnancy is ascribed to the action of OESTROGENS; prolactin starts them secreting. If lactation does not occur or fails, it may be started by injection of prolactin.

The secretion of prolactin is normally kept under tonic inhibition by the secretion of DOPAMINE which inhibits prolactin. This is formed in the HYPOTHALAMUS and secreted into the portal capillaries of the pituitary stalk to reach the anterior pituitary cells. Drugs that deplete the brain stores of dopamine or antagonise dopamine at receptor level will cause HYPERPROLACTINAEMIA and hence the secretion of milk from the breast and AMENORRHOEA. METHYLDOPA and RESERPINE deplete brain stores of dopamine and the PHENOTHIAZINES act as dopamine antagonists at receptor level. Other causes of excess secretion of prolactin are pituitary tumours, which may be minute and are then called microadenomas, or may actually enlarge the pituitary fossa and are then called macroadenomas. The most common cause of hyperprolactinaemia is a pituitary tumour. The patient may present with infertility – because patients with hyperprolactinaemia do not ovulate – or with amenorrhea and even GALACTORRHOEA.

BROMOCRIPTINE is a dopamine agonist. Treatment with bromocriptine will therefore control hyperprolactinaemia, restoring normal menstruation and ovulation and suppressing galactorrhoea. If the cause of hyperprolactinaemia is an adenomatous growth in the pituitary gland, surgical treatment should be considered.

(lactogenic hormone, luteotrophic hormone, luteotrophin) n. a hormone, synthesized and stored in the anterior pituitary gland, that stimulates milk production after childbirth and also stimulates production of *progesterone by the *corpus luteum in the ovary. Excessive secretion of prolactin, resulting in raised serum levels of the hormone (hyperprolactinaemia), is usually due to the presence of a pituitary adenoma (see prolactinoma); other causes include *dopamine receptor antagonists (e.g. antipsychotic drugs) and chronic renal failure.