Selective inhibition of follicle-stimulating hormone by porcine follicular fluid extracts in the monkey: effects on midcycle surges and pulsatile secretion.

Nonsteroidal factor(s) in porcine follicular fluid (pFF) can selectively suppress tonic follicle-stimulating hormone (FSH) concentrations when administered in the follicular phase to monkeys. Here it is demonstrated that when administered in either the early follicular phase or in the midst of the spontaneous preovulatory estradiol (E2) surge (E2 greater than or equal to 200 pg/ml), pFF preferentially inhibits FSH or blocks the FSH surge, respectively, whereas immunoassayable and bioassayable luteinizing hormone (LH) surges persist. Delay in the timing of ovulation uniformly follows follicular phase pFF administration, and corpus luteal insufficiency is often seen. The inhibitions of FSH in circulation were achieved by a decrease in amplitude and frequency of FSH pulses. No discernible effect on LH pulsatility was observed.