Early follicle development alters the relationship between antral follicle counts and inhibin B and follicle-stimulating hormone levels on cycle day 3

ObjectiveTo verify whether, during the luteal–follicular transition, increased inhibin B production by abnormally large follicles modifies the expected relationship between the number of follicles and peripheral inhibin B and FSH levels.DesignProspective study.SettingTeaching hospital, France.Patient(s)A total of 192 normo-ovulatory women.Intervention(s)Serum inhibin B and FSH levels and numbers and sizes of antral follicles (3–12 mm) were measured on cycle day 3.Main Outcome Measure(s)The strength of hormonal–follicular correlations was assessed in two groups formed according to the presence (large follicle group; n = 73) or absence (small follicle group; n = 119) of one follicle measuring >7 mm.Result(s)Serum inhibin B and FSH levels were correlated with antral follicle counts (r = 0.32 and r = −0.44, respectively). These relationships were significantly weaker in the large follicle group (r = 0.24 and r = −0.28, respectively) than in the small follicle group (r = 0.51 and r = −0.55, respectively).Conclusion(s)Antral follicle size influences serum inhibin B and FSH levels and alters their expected relationship with the number of antral follicles on day 3. These results contribute to clarifying the controversial role of serum inhibin B and FSH levels in the prediction of ovarian follicular status.