[Investigation of Cushing's syndrome. The diagnostic value of the dexamethasone suppression test, the metopirone test and the CRF test].

We describe thirty-one patients with Cushing's syndrome, with the object of evaluating the relative merit of the Dexamethasone suppression test, Metyrapone test and Corticotrophin Releasing Factor (CRF) test in classifying the syndrome. Bilateral adrenocortical hyperplasia (Cushing's disease) was present in sixteen patients. Three had bilateral macrodular hyperplasia of the adrenal cortex, six had adrenocortical adenoma, four had adrenocortical carcinoma, and two patients presented ectopic ACTH-syndrome. The diagnosis was surgically verified in every case. The Metyrapone test was found to give the safest classification in patients with Cushing's syndrome. The Dexamethasone test will diagnose Mb. Cushing reliably when suppression of serum cortisol is present following the large dose of Dexamethasone, but failure to suppress does not exclude the diagnosis. The CRF test is easy to perform and distinguished reliably between Mb. Cushing and other causes of the syndrome in eight out of ten patients in whom it was performed. Outpatient examination including the CRF test and CT-scanning of the pituitary and adrenal glands is advocated as a preliminary step in the classification of biochemically and clinically suspected cases of Cushing's syndrome.