CHANGES IN SERUM IMMUNOREACTIVE INHIBIN DURING OVULATION INDUCTION INWOMEN WITH AMENORRHEA

Changes in serum immunoreactive (IR)-inhibin were measured by RIA in t wo studies, in order to elucidate, firstly whether the pattern of IR-i nhibin secretion is similar to that of estradiol (E2), and secondly, w hether inhibin suppresses endogenous FSH release. Study 1: Purified ur inary FSH (pFSH) or human menopausal gonadotropin (hMG) were daily inj ected intramuscularly into women with hypogonadotropic amenorrhea at 1 2 to 14 week intervals. PFSH and hMG stimulated IR-inhibin release in a similar fashion in the ovulatory cycles, but the increase in estradi ol (E2) during pFSH administration was delayed and lower than that dur ing the hMG cycles. This suggests that E2 and IR-inhibin are secreted independently from the granulosa cells. Study 2: Ovulation induction w as performed in 18 cycles of 9 women with polycystic ovarian disease ( PCOD) by the step-down administration of pFSH. The serum FSH concentra tion in cycles with premature LH release increased even after the dose of pFSH was reduced, and were significantly higher than those of cycl es without premature LH release. It was also found that the serum IR-i nhibin concentration in cycles with the premature LH release was 2 to 4 times as high as in cycles without premature LH release. This sugges ts that IR-inhibin does not suppress endogenous FSH release associated with premature LH release.