Relationship between plasma prolactin and the endocrine microenvironment of the developing human antral follicle

The aim of the present study was to determine whether any obvious relationships exist between the circulating levels of prolactin at the time of ovariectomy and the endocrine microenvironment and developmental status of antral follicles. The concentrations of prolactin, follicle-stimulating hormone (FSH), and estradiol were measured in peripheral plasma and in antral fluid of follicles collected at varying stages of the menstrual cycle. In addition, the granulosa cells were recovered from each follicle (greater than or equal to 4 mm in diameter) and their numbers were quantitated. When the plasma levels of prolactin ranged from 11 to 100 ng/ml, the antral fluid levels of prolactin were uniformly low (less than 20 ng/ml) and the over-all level of intrafollicular activity remained unchanged. However, when the prolactin concentrations in plasma exceeded 100 ng/ml, the levels of prolactin in antral fluid were significantly elevated. Moreover, the high levels of intrafollicular prolactin were associated with a marked reduction in FSH accumulation and low levels of estradiol in antral fluid. Also, these follicles were severely deficient in granulosa cells. This marked reduction in intrafollicular activity was not associated with any significant changes in the mean levels of estradiol and FSH in peripheral plasma. These findings suggest that hyperprolactinemia is associated with a marked reduction in intraovarian activity and that the extent of this reduction may not be always apparent from the levels of circulating estradiol.