Pituitary prolactotropic function in patients with "inactive" pituitary adenoma

Abstract

Pituitary prolactotropic function was retrospectively analyzed in 23 patients with "inactive" pituitary adenoma (8 oncocytomas and 15 zero-cell adenomas) verified by electron microscopy. Before surgery basal prolactin level, prolactin concentrations in tests with thyrotropin-releasing hormone (TRH) and Parlodel, and daily fluctuations in prolactin levels in the blood were measured in all the patients. Moderate hyperprolactinemia was detected in 11 (47.8%) patients, which was often associated with galactorrhea-amenorrhea in women and with sexual dysfunction in men and was related to disturbed hypothalamo-pituitary relationships in cases with large adenomas. Irrespective of the basal level of prolactin, its secretion in response to TRH was abnormal: the reaction was reduced, particularly in patients in whom the tumors were associated with hyperprolactinemia. Acute loading with Parlodel led to a reliable reduction of prolactin concentration in the blood both in controls and in patients with normo- and hyperprolactinemia. A reduction of prolactin level by more than half in patients with inactive pituitary adenomas and moderate hyperprolactinemia in response to Parlodel loading, similarly as in normal subjects, confirms the functional type of hyperprolactinemia in such patients. Daily fluctuations of prolactin level were revealed in patients with large or giant adenomas.