Absent biologically relevant associations between serum inhibin B concentrations and characteristics of polycystic ovary syndrome in normogonadotrophic anovulatory infertility

BACKGROUND: Dominant follicle selection is disturbed in normogonadotrophic anovulatory infertility [World Health Organization (WHO) 2] and remaining early antral follicles are either healthy or atretic. This study was conducted to investigate whether inhibin B serum concentrations (produced by healthy small antral follicles) represent the extent of ovarian abnormalities in WHO 2 women and patients with polycystic ovarian syndrome (PCOS), constituting a subgroup of WHO 2 patients. METHODS AND RESULTS: Ultrasonographic and endocrine characteristics in 379 WHO 2 patients and 30 normo-ovulatory controls were compared. In the WHO 2 patients, the PCOS subgroup and the controls, inhibin B concentrations were similar. Inhibin B concentrations were weakly but significantly correlated with the total number of ovarian follicles (r = 0.282; P < 0.001), LH (r = 0.347; P < 0.001), and testosterone (r = 0.269; P < 0.001) but not with serum oestradiol concentrations (r = 0.057). Most (71%) patients with elevated inhibin B also presented with increased concentrations of LH and/or hyperandrogenaemia. In a subgroup of 190 subjects, classified as PCOS based on hyperandrogenaemia and polycystic ovaries, elevated inhibin B concentrations were found in 23% of cases. Aforementioned correlations were similar in PCOS as in WHO 2 patients. CONCLUSION: In conclusion, inhibin B serum concentrations are normal in WHO 2 and PCOS women, suggesting a normal number of healthy early antral follicles despite increased overall follicle numbers in PCOS.