Clinical experience with a simple screening test for Cushing's syndrome combining the determination of plasma cortisol circadian rhythm with the overnight dexamethasone suppression test.
In 17 normal subjects and 126 patients with various endocrine disorders, including 13 patients with Cushing's syndrome, plasma levels of fluorogenic corticosteroid were measured at 9 AM and midnight, and again at 9 AM the following morning, after the patient had received 1 mg of dexamethasone by mouth immediately after the midnight sampling. Basal morning levels of plasma corticosteroids were of little diagnostic value in differentiating between Cushing's syndrome and non-Cushing's states because of the wide overlap of values observed. At midnight the overlap almost completely disappeared. After overnight suppression, only one patient with a mild form of Cushing's disease had normal (false-negative) results in two of four instances. There were virtually no false-positive results, except for two patients with anorexia nervosa showing minor abnormalities of the test. The results were in general agreement with those of the classic Liddle test. However, one patient with Cushing's disease had repeatedly abnormal responses to overnight suppression and normal responses to the Liddle test. When the inhibitory tests gave equivocal results in the differential diagnosis between exogenous obesity and Cushing's disease due to adrenal hyperplasia, the response of plasma corticosteroids to hypoglycemia, normal in obesity and absent in Cushing's disease, proved to be an excellent ancillary test in differentiating between the two conditions.
D000305:Adrenal Cortex Hormones / Q000097:blood; D000328:Adult; D002940:Circadian Rhythm; D003480:Cushing Syndrome / Q000175:diagnosis*; D003907:Dexamethasone; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D006889:Hydroxycorticosteroids / Q000097:blood; D008297:Male; D010912:Pituitary-Adrenal Function Tests
D000305:Adrenal Cortex Hormones; D006889:Hydroxycorticosteroids; D003907:Dexamethasone; D006854:Hydrocortisone