Effects of human growth hormone upon term placental hormone secretion in vitro.

The role of human growth hormone (hGH) on placental hormone secretion at term was investigated in two in vitro models: placental explants and cultured trophoblastic cells. Physiological concentrations of hGH caused a significant dose-dependent increase in placental lactogen and progesterone secretion. In the explant model it stimulated estradiol secretion. In order to determine whether this stimulatory effect on estradiol is exerted via aromatase, an isolated cell culture was utilized where androstenedione was supplied as substrate. In this model, hGH exerted a mild inhibitory effect. In conclusion, hGH at levels present in the fetal circulation exerts a significant stimulatory effect upon placental function as reflected by both peptide and steroid hormone production and secretion. The effect of estradiol secretion is the end result of an inhibitory effect on androgen aromatization and a stimulatory effect on earlier steps.