Evidence for the release of a novel pituitary polypeptide (7B2) from the growth hormone-producing pituitary adenoma of patients with acromegaly.

We studied the release of the pituitary polypep-tide 7B2 in normal subjects and patients with acromegaly. Plasma 7B2 concentrations did not increase in response to human GHRH and TRH in normal subjects. Plasma 7B2 concentrations significantly increased from 124.4 ± 39.9 (mean ± se) to 206.9 ± 55.9 ng/L (180.8 ± 17.9% of the basal value; P < 0.01) 15 min after iv administration of GHRH in eight acrome-galic patients, but they did not increase in nine other acromegalic patients. Mean plasma 7B2 levels increased from 68.8 ± 17.9 to 168.7 ± 53.5 ng/L (241.8 ± 34.2% of the basal value; P < 0.005) 30 min after iv administration of TRH in four acromegalic patients, but the two other patients tested had no response. No elevations of plasma 7B2 were found after iv administration of ovine CRH in six patients with Cushing's disease and after iv administration of TRH and/or oral administration of bromo-criptine in six prolactinoma patients. In experiments using cultured human somatotroph adenoma cells, high K+ induce...