Plasma ACTH Determinations in 58 Patients Before or After Adrenalectomy for Cushing's Syndrome

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Abstract
Results of studies carried out on 58 patients with Cushing''s syndrome either pre- or post-adrenalectomy for Cushing''s syndrome are presented. The data are consistent with the concept that Cushing''s syndrome due to adrenal hyperplasia is mediated by increased secretion of ACTH by the pituitary gland or less commonly from an ACTH-secreting nonendocrine carcinoma. The pituitary mediated form of the disease, as previously suggested, apparently can be characterized by 3 stages: 1) an initial loss of diurnal variation with little increase in plasma ACTH but increased secretion of cortical steroids by the adrenal gland presumably due to maintenance of high normal to slightly elevated ACTH throughout the 24-hr, period; 2) clearly elevated levels of ACTH which may occur coincident with elevated secretion of cortical steroids by the gland (most commonly seen following partial adrenalectomy); 3) a 3rd stage (most common after total adrenalectomy) in which plasma ACTH levels are often at extremely high levels, the patients are intensely pigmented, and the plasma ACTH is poorly suppressed by the administration of exogenous cortical steroid. This group of patients is most often found to have pituitary tumors, although such tumors have been described in the earlier stages of the disease. Patients with tumors of the adrenal gland do not have measurable plasma ACTH, but those patients with nonendocrine carcinomas associated with Cushing''s syndrome generally have elevations of this hormone. The latter finding may be useful as a diagnostic test in selected patients in differentiating between a primary tumor of the adrenal gland and a nonendocrine carcinoma producing ACTH. Patients with tumors of the pituitary gland may also have elevated plasma ACTH but appear generally to be indistinguishable from other patients with adrenal hyperplasia except in those tests which specifically demonstrate enlargement of the pituitary gland.