Effect of HCG on human corpus luteum of menstruation and early gestation

In order to evaluate the luteotropic effect of human chorionic gonadotropin (HCG) on the human corpus luteum, HCG was administered at the menstrual luteal phase and early gestation. Serum progesterone (P) and estradiol (E2) levels were compared after determination by radioimmunoassay. At the mid-luteal phase, although E2 secretion did not increase significantly, P secretion showed a significant increase and peaked 6-8 hr after intravenous injection of 20,000 IU HCG. Three intramuscular injections of 5,000 IU HCG were administered every other day. An increase in sex steroid production and prolongation of luteal span occurred when HCG was administered in the +7 to +11 day period (following LH peak), rather than the +3 to +7 day period. During early pregnancy (from 5 to 10 weeks' gestation) in threatened abortion cases followed by either normal continuation of pregnancy or abortion, neither a single high dosage of HCG (20,000 to 100,000 IU) nor 20,000 IU per day for 7 days produced any significant change in sex steroid secretion. From these observations, it is likely that exogenous HCG shows a luteotropic effect on the human corpus luteum during menstruation, but not during gestation.