High concentrations of inhibin A and inhibin B in ovarian serous cystadenoma: Relationship with oestradiol and nitric oxide metabolites

Inhibin production has been demonstrated in malignant epithelial ovarian tumours, but secretion of inhibins by benign cystadenoma has not yet been reported. The present study evaluated the concentrations of inhibin A and inhibin B and the relationship with oestradiol and nitric oxide metabolites in fluid collected from benign ovarian serous cystadenomas (n = 15). In addition, follicular fluid samples (n = 14) from women with regular ovulatory cycles undergoing ovarian stimulation for IVF were studied as a reference group. High concentrations of inhibin A (median = 89.3 ng/ml) and inhibin B (median = 116.1 ng/ml) were found in the cystic fluid of ovarian serous cystadenomas. These inhibin concentrations were even higher than in follicular fluid of stimulated follicles (inhibins A and B = 4.1.2 and 46.8 ng/ml respectively; P < 0.001), whereas oestradiol was ~18-fold lower in cystic fluid than in follicular fluid (median = 34 versus 622 pg/ml, P < 0.001). In ovarian cysts, the concentrations of inhibin A and oestradiol were inversely correlated (r = -0.678, P = 0.008). Cystic fluid samples containing the highest concentrations of NO₂^-/NO₃^- (4.5-60 μmol/l) had lower inhibin A and higher oestradiol concentrations than those samples containing lower concentrations (10-25 μmol/l) of NO₂^-/NO₃^-. It is concluded that high amounts of dimeric inhibins are present in ovarian serous cystadenoma. The source of inhibins and the determinants of the inverse association of inhibin A with oestradiol and nitric oxide remain to be determined.