The limited value of the desmopressin test in the diagnostic approach to Cushing's syndrome

Abstract

The present data suggest that the CRH test is more reliable than the desmopressin test in determining the aetiology of Cushing's syndrome. The desmopressin test resulted in a high frequency of false positive results in patients with ectopic ACTH secondary to carcinoid tumours. This finding may be due to the capability of these tumours to express the V3 vasopressin receptor through which desmopressin acts. However, the clinical endocrinologist may be confronted with some disturbing cases which are misdiagnosed because it is almost impossible to set a diagnostic criterion providing complete specificity in the differentiation of (occult) ectopic Cushing's syndrome using either CRH or desmopressin tests.