With hyperprolactinemia, hyper- means above, -prolactin refers to the hormone produced by the pituitary gland, and -emia refers to the blood, so hyperprolactinemia means higher than normal prolactin levels in the blood.
Normally, at the base of the brain, there’s a small pea-sized gland called the pituitary gland.
The anterior pituitary - the front of the pituitary gland - has a number of different cells, each of which secretes a different hormone.
One group, the lactotroph cells, secrete prolactin. In men, excess prolactin decreases testosterone production.
In women, during pregnancy, elevated levels of estrogen stimulate the lactotrophs to produce large amounts of prolactin which stimulates alveolar cells in the breasts.
In response to prolactin, the alveolar cells divide and enlarge - and once a baby is born, lactogenesis begins - which means that milk is produced.
Apart from milk production, high levels of prolactin also inhibit the release of gonadotropin releasing hormone from the hypothalamus, which results in decreased luteinizing and follicle stimulating hormone levels, which in turn, decreases estrogen levels.
In women, this can stop ovulation and menstruation, which is why women typically don’t have a menstrual period while breastfeeding. In women that are not pregnant or breastfeeding, and in men, prolactin levels are usually kept in check by the hypothalamus in two ways.
