Effects
Prolactin has over 300 known effects. It stimulates the mammary glands to produce milk (lactation): Increased serum concentrations of prolactin during pregnancy cause enlargement of the mammary glands of the breasts and prepare for the production of milk. Milk production normally starts when the levels of progesterone fall by the end of pregnancy and a suckling stimulus is present. Sometimes, newborn babies (males as well as females) secrete a milky substance from their nipples known as witch's milk. This is in part caused by maternal prolactin and other hormones.
Prolactin provides the body with sexual gratification after sexual acts: The hormone counteracts the effect of dopamine, which is responsible for sexual arousal. This is thought to cause the sexual refractory period. The amount of prolactin can be an indicator for the amount of sexual satisfaction and relaxation. Unusually high amounts are suspected to be responsible for impotence and loss of libido (see hyperprolactinemia symptoms).
Highly elevated levels of prolactin decrease the levels of sex hormones — estrogen in women and testosterone in men. The effects of mildly elevated levels of prolactin are much more variable, in women both substantial increase or decrease of estrogen levels may result.
Prolactin within the normal reference ranges can act as a weak gonadotropin but at the same time suppresses GnRH secretion. Physiologic levels of prolactin in males enhance luteinizing hormone-receptors in Leydig cells, resulting in testosterone secretion, which leads to spermatogenesis.
Prolactin also stimulates proliferation of oligodendrocyte precursor cells. These cells differentiate into oligodendrocytes, the cells responsible for the formation of myelin coatings on axons in the central nervous system.
Prolactin also has a number of other effects including contributing to surfactant synthesis of the fetal lungs at the end of the pregnancy and immune tolerance of the fetus by the maternal organism during pregnancy.
Prolactin delays hair regrowth in mice.
Prolactin promotes neurogenesis in maternal and foetal brains.
Read more about this topic: Prolactin
Famous quotes containing the word effects:
“The hippie is the scion of surplus value. The dropout can only claim sanctity in a society which offers something to be dropped out of—career, ambition, conspicuous consumption. The effects of hippie sanctimony can only be felt in the context of others who plunder his lifestyle for what they find good or profitable, a process known as rip-off by the hippie, who will not see how savagely he has pillaged intricate and demanding civilizations for his own parodic lifestyle.”
—Germaine Greer (b. 1939)
“Society’s double behavioral standard for women and for men is, in fact, a more effective deterrent than economic discrimination because it is more insidious, less tangible. Economic disadvantages involve ascertainable amounts, but the very nature of societal value judgments makes them harder to define, their effects harder to relate.”
—Anne Tucker (b. 1945)
“I am fearful that the paper system ... will ruin the state. Its demoralizing effects are already seen and spoken of everywhere ... I therefore protest against receiving any of that trash.”
—Andrew Jackson (1767–1845)