A possible role for prolactin in the control of human chorionic gonadotropin and estrogen secretion by the fetoplacental unit.

The effects of prolactin (PRL) on fetoplacental function were studied by measuring the beta subunit of human chorionic gonadotropin (hCG-beta), estradiol (E2), progesterone (P), and PRL concentrations throughout seven pregnancies in a control group (N = 6 women) and in three pregnant women with prolactinomas, who were receiving bromocriptine. In one of the latter, estriol (E3) was also assayed. Long-term suppression of PRL was associated with augmentation of hCG-beta at the first-treimester peak and in late pregnancy. Concomitant augmentation of E3 (in late gestation) and possibly E2, but not P, levels was also observed. This effect on hCG appeared dependent on PRL rather than the dopaminergic effect of bromocriptine. Short-term drug induced alterations in PRL (over 3 hours) during early pregnancy did not result in significant changes in hCG-beta or steroid concentrations. In each control pregnancy, a significant negative correlation (p less than 0.05) was observed between hCG-beta and PRL, while a significant positive correlation between the latter and E2 concentrations in these women was also demonstrated. Apart from its effect on lactation, osmoregulation, and gonadal and adrenal function, a further role for PRL during reproduction appears to be in the control of hCG and estrogen secretion in the fetoplacental unit.