Introduction Source lactotrophs in the anterior pituitary synthesize prolactin during pregnancy there is an increase in lactotrophs it is chemically similar to growth hormone Regulation prolactin secretion is regulated by chemicals that alter prolactin gene transcription stimulatory thyrotropin-related hormone (TRH) pregnancy breastfeeding suckling stimulates afferent fibers to inhibit hypothalamic dopamine secretion dopamine antagonists such as anti-psychotics sleep stress inhibitory dopamine this is a catecholamine that tonically inhibits prolactin secretion in non-pregnant and non-lactating patients dopamine mainly arises from hypothalamic dopaminergic neurons there are also dopaminergic neurons in the posterior lobe of the pituitary dopamine agonists cabergoline bromocriptine prolactin it inhibits its own secretion via upregulating hypothalamic dopamine synthesis and secretion (negative feedback) somatostatin Function milk production (lactogenesis) prolactin stimulates the production of milk components (e.g., lactose and casein) during pregnancy elevated levels of estrogen and progesterone decrease prolactin receptor numbers in the breast this is why lactation does not occur during pregnancy but at parturition recall that at parturition estrogen and progesterone levels decrease breast development stimulates the mammary ducts to proliferate and branch this is accomplished with the help of estrogen and progesterone inhibits ovulation prolactin inhibits gonadotropin-releasing hormone (GnRH) synthesis and secretion this explains why fertility is decreased during breastfeeding Clinical correlate hyperprolactinemia etiology prolactinoma antipsychotics symptoms galactorrhea infertility treatment dopamine agonists such as cabergoline bromocriptine