Serum inhibin B levels measured early during FSH administration for IVF may be of value in predicting the number of oocytes to be retrieved in normal and low responders.

BACKGROUND: In a previous study we have found that in normal ovulatory women, serum inhibin B levels on days 4-6 of FSH administration correlated with the number of oocytes retrieved. In the current study we examined the significance of earlier inhibin B measurements in predicting the oocyte number, in both normal and low responders. METHODS: Study A consisted of 19 patients undergoing their first IVF cycle (n = 10) or had a normal response (box with v6 oocytes retrieved, n = 9), while study B consisted of 15 patients with a previous low ovarian response (less than or equal to5 oocytes retrieved). All patients had day 3 FSH levels <10 IU/l. After pituitary suppression, 300 (study A) or 600 IU (study B) of pure FSH was administered daily. Serum FSH, inhibin A, inhibin B and estradiol (E-2) were determined prior to and every 1-2 days throughout FSH treatment. RESULTS: Study A: oocyte number between 4 and 14 correlated significantly with serum inhibin B levels on all days of FSH treatment, and with inhibin A and E-2 late during treatment. No correlation was found between inhibin B and when oocyte number was >16. Study B: oocyte number correlated significantly with inhibin B and inhibin A on all days of FSH treatment, even on day 2 (r = 0.90, P < 0.001 and r = 0.65, P < 0.05 for inhibin B and A respectively). No significant correlation was found with E-2 levels. In both studies, all patients with inhibin B >100 pg/ml on treatment day 2 had >6 oocytes. CONCLUSIONS: Our data suggest that serum inhibin B measured early during FSH stimulation may indicate whether sufficient oocytes will be retrieved, in both normal and low responders. Serum inhibin B measured during early FSH treatment may be of predictive value in monitoring ovarian stimulation treatment for IVF.