Effect of an increase in FSH on the production of gonadotrophin-surge-attenuating factor in women.

Gonadotrophin-surge-attenuating factor (GnSAF) is a putative nonsteroidal ovarian factor that is produced by FSH and that attenuates the LH surge in superovulated women. To study further the role of FSH in the production of GnSAF, 12 normally ovulating women were divided into two groups and investigated during two cycles: a cycle treated with placebo (control) and a cycle treated with FSH. In group 1 (n = 6), placebo (2 ml 0.9% normal saline) or FSH (450 iu) was injected i.m. on day 2 of the cycle (09:00 h). In group 2 (n = 6), placebo (2 ml 0.9% normal saline) or FSH (225 iu) was injected on the day (09:00 h) on which the dominant follicle was 14-15 mm in diameter, as measured by ultrasound (i.e. after the pituitary had been primed by endogenous oestrogen for several days). The response of LH over 30 min (delta LH) to an injection of 10 micrograms LHRH i.v. (bioassay for GnSAF in vivo) was investigated once a day in group 1, and 4, 8, 12 and 24 h after the injection of placebo or FSH in group 2. In group 1, delta LH was significantly attenuated 12 h after treatment with FSH compared with the control cycles, while serum oestradiol concentrations increased 24 h after the injection of FSH. The decrease in delta LH lasted for the period when the FSH concentration was increased (3 days). A significant decrease in the basal concentration of LH was correlated with the increase in the oestradiol concentration.(ABSTRACT TRUNCATED AT 250 WORDS)