CHANGES IN PITUITARY-RESPONSE TO GONADOTROPIN-RELEASING-HORMONE FOLLOWING BILATERAL OVARIECTOMY IN WOMEN TREATED WITH FOLLICLE-STIMULATING-HORMONE

Superovulation induction in women attenuates the Pituitary response to gonadotropin-releasing hormone (GnRH). The aim of this study was to a ssess the duration of the suppressing activity of the ovaries on the p ituitary. Eighteen normally ovulating women received treatment with fo llicle-stimulating-hormone (FSH, 225 IU/day) on cycle days 2, 3 and 4. On cycle day 4, six women underwent hysterectomy plus bilateral ovari ectomy (group A), another six women underwent hysterectomy without ova riectomy (group B) and the remaining six women underwent no operation (group C). The women of group C were also investigated during a preced ing untreated spontaneous cycle (group D). The response of luteinizing hormone (LH) to an intravenous injection of 10 mu g GnRH was investig ated on cycle days 2, 3, 4 (2 and 12 h after clamping of the infundibu lopelvic and/or round ligaments), 5, 6 and 7 in all four groups The re sponse of LH to GnRH at 30 min (Delta LH) was significantly attenuated as early as 12 h from the onset of FSH treatment (group A, B and C), while estradiol and inhibin concentrations started to increase later ( group C). In group C (no operation), the attenuation of Delta LH value s continued throughout the study period, while in groups A and B tile initial attention was followed by a marked increase in Delta LH values within 2 h from the operation. The increase in group A was twice the value in group B. Following this, Delta LH values in group B were atte nuated again within the next 24 h, while in group A they remained for tile rest of tile postoperative period significantly higher than in gr oup B. In conclusion, it was found that the factor that mediates the s uppressing superovulated ovaries on tile pituitary has a short-lasting (< 2 h) attenuating activity in the circulation.