Clinical Endocrinology & Metabolism

A surgically removed pituitary adenomas, approximately 30-35% appear to be silent, unassociated with clinical or biochemical evidence of any anterior pituitary hormone excess (1, 2). However, with routine immunocytochemical staining of the pituitary tumor tissue, immunoreactive hormone material can be demonstrated in a substantial number of these seemingly nonfunctioning tumors (2). Clinically silent immunoreactive FSHand LH-containing pituitary adenomas were reported by Trouillas et al. in 1981 (3). More recently, silent pituitary adenomas secreting a-subunit have been described (4). Corticotropic pituitary adenomas without evidence of Cushing's disease have been reported by Hassoun et al. in 1979 (5) and in more detail by Horvath et al. in 1980 (2). However, secretion of biologically inactive ACTH in patients with silent corticotropic adenomas has not been described. We report here a patient with hypersecretion of immunoreactive ACTH from a clinically silent pituitary adenoma.