Inhibin-B: The physiologic basis of the clomiphene citrate challenge test for ovarian reserve screening

Objective: To determine inhibin-B concentrations during ovarian reserve screening in women with normal and diminished ovarian reserve as determined by the clomiphene citrate challenge test. Design: Retrospective. Setting: Tertiary fertility center. Patient(s): Women undergoing ovarian reserve screening for a routine fertility evaluation. Intervention(s): Clomiphene citrate challenge test. Main Outcome Measure(s): Inhibin-B concentrations on menstrual days 3 and 10. Result(s): Nineteen patients with normal ovarian reserve and 15 with diminished ovarian reserve had serum inhibin-B concentrations determined during ovarian reserve screening. For all patients, day 10 inhibin-B concentrations were higher than day 3. Women with normal ovarian reserve had higher inhibin-B concentrations on both days 3 and 10 than women with diminished ovarian reserve. Inhibin-B concentrations demonstrated a negative correlation with FSH levels on both cycle days 3 and 10 and a positive correlation with E₂ on cycle day 10. Conclusion(s): Women with diminished ovarian reserve during ovarian reserve screening had reduced granulosa cell inhibin-B production compared with women with normal ovarian reserve. The lower inhibin-B concentrations may be responsible for the elevated FSH concentrations and may be indicative of the aging follicular apparatus.