ECTOPIC ACTH SYNDROME AND MEDULLARY THYROID CARCINOMA

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Abstract
A 40 yr old patient with medullary thyroid carcinoma subsequently developed Cushing''s syndrome with presumably ectopic ACTH formation. The immunoreactive calcitonin in the plasma was greatly and ACTH slightly increased. Despite the excessively high calcitonin concentration the patient developed serious osteoporosis which presumably resulted from Cushing''s syndrome. A raised endogenous plasma calcitonin level did not prevent osteoporosis caused by hypercortisolism. Autopsy revealed bilateral hyperplasia of the adrenal cortex and a normal pituitary gland suggesting that Cushing''s syndrome was probably caused by an ectopic ACTH source. Additional cases (22) of medullary thyroid carcinoma with Cushing''s syndrome reported in the literature were reviewed. Eighteen of 23 patients were alkalotic which is typical of ectopic ACTH production. In these patients the characteristic clinical signs of hypercortisolism were as frequently observed (70%) as in patients with nonectopic Cushing''s syndrome (91%). Ectopic Cushing''s syndrome occurs only in 2-4% of advanced cases of medullary thyroid carcinoma and is a serious complication. Among the 23 patients, 18 died, with an average survival time of only 4.5 mo. after the diagnosis of Cushing''s syndrome was established.

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