We have compared the time courses of serum inhibin and estradiol responses to ovarian hyperstimulation in patients undergoing in vitro fertilization and embryo transfer as well as their predictive value for outcome of intermediate variables and pregnancy in in vitro fertilization and embryo transfer. Blood samples (n = 749) were collected for up to 6 days before hCG administration in 100 consecutive treatment cycles, of which 44 resulted in pregnancy, as defined by elevated luteal phase serum hCGβ levels. Inhibin and estradiol levels increased markedly in parallel during hyperstimulation and were highly correlated (r = 0.89; P < 0.001). Inhibin responses were significantly lower in women 35 yr of age or older (P < 0.001), although estradiol responses were not influenced by age. Gravidity and tubal disease also had marginal effects on the time course of inhibin responses, but not on overall mean inhibin levels or estradiol responses. The time course of hormonal responses to hyperstimulation was not influenced by any other demographic or etiological factors. Peak values of both hormones correlated with the total number of follicles (inhibin, r = 0.70; estradiol, r = 0.65; P < 0.001) and oocytes retrieved per cycle (inhibin, r = 0.49; estradiol, r = 0.39; P < 0.001). The time course and peak values of inhibin and estradiol responses to hyperstimulation did not differ significantly between conception or nonconception cycles whether judged by biochemical (luteal hCGβ) or clinical (viable ongoing pregnancy) criteria. Luteal phase serum inhibin, estradiol, progesterone, and hCG levels were significantly higher in conception than in nonconception cycles (P < 0.001). These data suggest that the rises in serum inhibin and estradiol levels during hyperstimulation have similar predictive properties for IVF-ET outcomes and could, therefore, be used interchangeably to monitor hyperstimulation regimens. The agerelated reduction in inhibin, but not estradiol, responses suggests that these two hormones reflect different granulosa cell functions and that serum inhibin responses to maximal ovarian stimulation may be a sensitive and early index of declining ovarian function with advancing age. © 1990 by The Endocrine Society.
