Induction of luteolysis by luteinizing hormone-releasing factor (LRF) agonist: sensitivity, reproducibility, and reversibility.

The reproducibility, reversibility, and the maximal effectiveness of the luteolytic action of [D-Trp6,Pro9NEt]-LRF (luteinizing hormone-releasing factor) (LRF-agonist) were evaluated during 43 treatment cycles in 15 normal women. LRF-Ag (50 microgram) administration subcutaneously on 1 or 2 days at varying times during the luteal phase of consecutive cycles was made. Successful luteolysis was achieved in 26 of 27 cycles (96%) in which LRF-Ag was administered between 5 and 8 days after the luteinizing hormone (LH) peak. However, LRF-Ag treatment failed to induce luteolysis in 10 of 13 cycles (77%) when treatment began within 5 days of the LH peak. The luteal phase of posttreatment cycles was functionally unaffected by prior LRF-Ag treatment. The present study has thus demonstrated the reproducibility and reversibility of LRF-Ag as a potent luteolytic agent, although its action is dependent upon the timing of administration with a window of maximal effectiveness on days 5 to 8 of the luteal phase.