Mid-luteal serum inhibin-A concentration as a marker of endometrial differentiation.
Recent studies have indicated that the corpus luteum is a major source of circulating inhibin-A and serum concentrations of inhibin-A may reflect the human luteal function. The present prospective study was undertaken to determine the usefulness of mid-luteal serum concentrations of inhibin-A as markers of endometrial receptivity (as assessed by histological dating and alphavbeta3 integrin expression) and whether they are better predictors of endometrial function than serum progesterone. Consecutive infertile women (experimental group, n = 50) with regular menstrual cycles, and fertile women who were requesting contraception and had regular menstrual patterns and normal secretory endometria (control group, n = 10) were included. In all women basal body temperature, luteal serum concentrations of oestradiol, progesterone, prolactin, and inhibin-A, and endometrial biopsies were used in the same cycle to assess luteal function. Out-of-phase mid-secretory endometria were detected in 17 of the 50 infertile women. Lack of alphavbeta3 integrin expression was detected in 27 of the 50 mid-luteal endometrial biopsies. Thus, hormonal concentrations were compared in the mid-luteal phase between the following eight groups of women: group 1 (n = 10), control fertile women; group 2 (n = 50), infertile women (all); subdivided into group 3 (n = 33), with in-phase biopsies; group 4 (n = 17), with out-of-phase endometria; group 5 (n = 23), expressing alphavbeta3 integrin in endometria; group 6 (n = 27), whose endometria did not express alphavbeta3 integrin; group 7 (n = 18), with both in-phase endometrial biopsy and alphavbeta3 integrin expression; and finally group 8 (n = 12), whose endometria were out-of-phase and did not express alphavbeta3 integrin. Mid-luteal serum concentrations of oestradiol, progesterone, prolactin, and inhibin-A of the seven infertile groups were similar to those of the control group of fertile women. No statistically significant difference between the infertile groups was observed for any hormonal parameter considered. Mid-luteal serum inhibin-A determination does not accurately reflect endometrial function/maturation and it is not a better indicator of endometrial luteal phase dysfunction than mid-luteal serum progesterone.