Prolactin synthesis and release during pregnancy and puerperium

Maternal and Fetal Prolactin

“…Women studied during the first, second, and third trimester of their pregnancy were demonstrated to release prolactin in a step-like fashion. 2 Although baseline prolactin also increases as pregnancy progresses and it is significantly greater in the third trimester, the net increase after the administration of TRH is similar to that seen in the second trimester. Thus, it can be suggested that the third trimester of pregnancy is characterized by an increased turnover with no further increase in prolactin reserve.…”

“…A similar cor-relation has been reported between serum progesterone and prolactin. [2][3][4] After this initial increase prolactin continues to rise almost in a linear fashion until the 37th week, at which time a decline until the end of pregnancy is seen. [5][6][7] The clinical significance of this decline is unclear.…”

“…9 We have reported a high correlation between serum concentration of estradiol and progesterone and prolactin throughout pregnancy. 2 It can be therefore suggested that the increase in serum estrogen, which begins early in human gestation, causes the elevated serum prolactin levels. Although it is possible that estrogen enhances the prolactin release by suppressing dopamine or by stimulating the release of a prolactin-releasing factor, a direct estrogenic stimulatory effect on the lactotrophs resulting in hyperplasia and hypertrophy seems to be the main mechanism.…”

“…After delivery the secretion of prolactin is quickly reduced and 10 days later the circulating levels have been reduced threefold. 2 This decrease follows the sudden removal of the placenta, which eliminates the source of estrogen and progesterone stimulation, and therefore a reverse process begins to restore the pituitary to its original size. Facilitated by the absence of the estrogen blocking effect on breast prolactin receptors, the prolactin stored in the pituitary during pregnancy initiates lactation.…”

Production and localization of human prolactin in the placental and decidual tissue at term.

“…Kletzky et al reported that increased synthesis of PRL with increasing gestation was thought to be due to the stimulatory effects of E2 and progesterone, resulting in hyperplasia of lactotrophs (6). Rigg et al reported that in human gestation the increase in PRL secretion was related to supramaximal reflection of hypertrophy and hyperplasia of pituitary lactotrophs (11).…”