Prolactin inhibits the steroidogenesis in midfollicular phase human granulosa cells cultured in a chemically defined medium.

In vitro studies were conducted on prolactin (PRL) effects on human granulosa cell steroidogenesis. Cells derived from healthy midfollicular phase follicles were cultured in a chemically defined medium supplemented with androstenedione (delta 4 A) 10(-7) M. Cultures treated with follicle-stimulating hormone (FSH) showed a dose-dependent increase of estradiol (E2) and progesterone (P) secretion. The authors demonstrated that PRL (greater than or equal to 10 ng/ml) inhibits basal as well as FSH (10 ng/ml)-stimulated E2 and P secretion. This PRL effect was overcome only by FSH maximal stimulating doses (100 ng/ml). These results suggest a direct inhibitory effect of PRL on granulosa cell steroidogenesis acting as a negative modulator of FSH action. These effects might be related to the ovarian dysfunction observed in hyperprolactinemia.