Inhibin: Differences in Bioactivity within Human Follicular Fluid in the Follicular and Luteal Stages of the Menstrual Cycle 1

Abstract

Summary

The presence of a nonsteroidal substance (inhibin) within human follicular fluid (HFF) with the ability to suppress pituitary follicle-stimulating hormone (FSH) but not luteinizing hormone (LH) secretion was determined by two methods. The first method consisted of infusion of HFF directly into the anterior pituitary gland of ovariectomized rhesus monkeys. The second employed a pituitary cell culture system. Release of LH and FSH was stimulated in HFF-treated cells by the addition of luteinizing hormone-releasing hormone (LHRH) to the tissue culture medium. In both methods, to determine the presence of inhibin, we used the criterion of a decreased release of FSH into the medium or serum that was not accompanied by an concomitant decrement in LH concentrations. Both methods detected the presence of inhibin within HFF from women during the follicular but not the luteal phase of the menstrual cycle. This finding suggests that this substance may play a role in the regulation of FSH secretion at a specific stage of the reproductive cycle in women.