A Cyproheptadine-Reversible Defect in ACTH Control Persisting after Removal of the Pituitary Tumor in Cushing's Disease

We studied two phases of cortisol feedback suppression of ACTH in nine patients who had had adrenalectomy for Cushing's disease. Four had been treated by adrenalectomy alone and presumably had ACTH-secreting pituitary tumors. Five others were studied two or more years after transsphenoidal removal of an ACTH-secreting microadenoma. In both groups, cortisol-ACTH feedback during the first 30 minutes of cortisol infusion was abnormal; plasma ACTH fell only 2.7±2.6 per cent (mean ±S.E.), as compared with 28.0±10.1 per cent in five hypoadrenal controls (P