In vitro secretion of FSH by cultured clinically nonfunctioning and gonadotroph pituitary adenomas is directly correlated with locally produced levels of activin A

OBJECTIVE Expression of mRNAs encoding activin and its antagonists inhibin and follistatin has been described in human pituitary adenomas, including clinically nonfunctioning adenomas (NFAs) and gonadotroph adenomas (Gn‐omas). Since many of the NFAs and Gn‐omas secrete FSH in vitro, we hypothesized that locally produced activin may stimulate secretion of FSH in these pituitary adenomas. PATIENTS and METHODS Pituitary adenoma tissue was obtained from 38 patients diagnosed preoperatively as having NFAs (n = 17), Gn‐omas (n = 5), prolactinomas (n = 6) or growth hormone (GH)‐producing adenomas (n = 10). Actual protein levels of activin, inhibin, follistatin, FSH and LH were measured in media of these 38 cultured pituitary adenomas. In addition, we investigated correlations between concentrations of these growth factors and hormones in NFAs and Gn‐omas. RESULTS Gn‐omas were found to secrete significantly more activin A in their culture medium than PRL‐ and GH‐producing adenomas (P