Chorionic gonadotropin prevents LRF-agonist-induced luteolysis in the human

The effects of exogenous and endogenous hCG on the luteolytic action of LRF-agonist, [D-Trp6, Pro9NEt]-LRF (LRF-Ag), were evaluated. In sequential studies, 4 normal cycling women treated with LRF-Ag (50 microgram S.C.) on two consecutive days had premature decline of circulating levels of progesterone (P) and estradiol (E2) with a shortened (p < 0.05) luteal phase (11.5 +/- 1.2 days) when compared to the control cycle (15 +/- 0.7 days). When intramuscular hCG was added to the LRF-Ag treatment in doses of 100 IU or 5000 IU daily for 7 days, the luteal function was prolonged (19 +/- 1.2 days, p < 0.05) with significant (p < 0.001) elevation of P and E2 levels compared with the control cycle. Four women with early pregnancy, requesting therapeutic abortion, were given LRF-Ag (50 microgram or 500 microgram S.C.) on 2 consecutive days. None of the 4 women aborted and there was no change in the levels of beta hCG, P or E2 over the course of a week. These results indicate that both exogenous or endogenous hCG can overcome the luteolytic effect of LRF-Ag within the dose and duration used. The possibility that a more prolonged administration of a larger dose of LRF-Ag may negate the luteotropic effect of hCG remains to be explored.