DIAGNOSIS OF CUSHING'S SYNDROME

Abstract

ABSTRACT Adrenal function tests were performed in 9 patients with Cushing's syndrome (6 with adrenal hyperplasia and 3 with adrenal adenoma) in order to study the hypothalamus-pituitary-adrenal system. These tests involved the determination of a) diurnal rhythm of plasma corticosteroids (11-OHCS) and the effect of corticotrophin (ACTH) and dexamethasone administration, b) urinary corticosteroid excretion (17-OHCS), basal and after ACTH, dexamethasone and metapyrapone treatment and c) cortisol production rate. In addition the patients were submitted to insulin-induced hypoglycaemia and intravenous infusion of synthetic lysine-vasopressin and the plasma corticosteroids were determined. All 9 patients regardless of the nature of adrenal pathology responded to insulin-induced hypoglycaemia in the same manner and failed to show the normal increase of 11-OHCS. During lysine-vasopressin infusion an opposite effect was observed: all 6 patients with hyperplasia showed a distinct rise in plasma corticosteroids in contrast to the 3 patients with adenoma who did not respond at all. These findings show that the lysine-vasopressin test may be very useful in differentiating between adrenal hyperplasia and adrenal adenoma. This procedure is recommended as a screening test because of its simplicity and high degree of diagnostic accuracy. Results are discussed with regard to the different pathogenesis of the two forms of Cushing's syndrome.