CLINICAL AND PATHOPHYSIOLOGICAL ASPECTS OF INHIBIN

Inhibin is a peptide hormone normally produced by the ovary. We have previously reported that serum inhibin concentrations are elevated in patients with granulosa cell tumours of the ovary. The aim of this study was to measure serum inhibin in a prospective, consecutive series of 200 patients admitted for suspected ovarian cancer. The serum inhibin radioimmunoassay had a sensitivity of 77 mu/l. The median effective dose was 640 mu/l, while within- and between-assay coefficients of variation in the region of maximal assay precision were 4.3% and 4.3%, respectively. The average effective doses (10 and 90%) in 35 consecutive assays were 211 and 1908 mu/l, respectively. We designated a serum inhibin concentration of greater-than-or-equal-to 130 mu/l as pathological in castrate or functionally agonadal women. Serum inhibin concentrations were elevated in 12 of 13 post-menopausal patients with mucinous cystadenocarcinoma of the ovary. By contrast, elevated serum inhibin values were found in only nine of 65 women with non-mucinous epithelial ovarian cancers. All patients showed a fall in serum inhibin levels to below 130 mu/l by 1 week after surgery. In post-menopausal women (n = 54) with proven ovarian cancer, serum inhibin concentrations correlated negatively with serum FSH and the clinical stage of their disease (P < 0.05). By contrast, serum inhibin correlated positively with serum oestradiol and progesterone (P < 0.001) but there was no correlation between serum inhibin and serum CA-125 values. We conclude that serum inhibin concentrations are typically elevated in patients proven to have mucinous cystadenocarcinoma of the ovary. Serum inhibin values fall after cytoreductive surgery in malignant, borderline and benign ovarian neoplasms. Serum inhibin appears to be a useful tumour marker of mucinous cystadeno-carcinoma of the ovary.