[The desmopressin test in the diagnosis of Cushing's disease].

INTRODUCTION Early and precise diagnosis is necessary in successful treatment of the patients with Cushing's disease. Transsphenoidal surgery is the first line treatment option in Cushing's disease. In patients in whom magnetic resonance imaging does not visualise pituitary adenoma patient selection for surgical treatment should be based on convincing results of functional tests. OBJECTIVES The diagnostic accuracy of the desmopressin test was compared with that of the CRH test and the overnight high-dose dexamethasone suppression test in the diagnosis of Cushing's disease. DESIGN AND METHOD We studied 15 patients with pituitary-dependent Cushing's disease (10 with detected microadenoma and 5 with undetected microadenoma using magnetic resonance imaging). The diagnosis was confirmed during pituitary surgery. The control group included 15 subjects without Cushing's syndrome. Patients underwent tests with desmopressin, CRH and 8 mg overnight dexamethasone. RESULTS A false negative response to CRH was present in 1 of 15 patients, a false negative response t dexamethasone was present in 1 of 15 patients and a false negative response to desmopressin in 2 of 15 patients. In other patients positive responses to CRH, desmopressin and dexamethasone were found. A positive response to desmopressin was present in 4 of 5 patients with undetected pituitary adenoma. In the control group a positive response to CRH and dexamethazone and a negative response to desmopressin was found in all patients. CONCLUSIONS 1. The highest diagnostic accuracy in the diagnosis of some patients with Cushing's disease is achieved by using a desmopressin test with high-dose dexamethasone test and CRH-test. 2. The desmopressin test can be used to precisely identify healthy individuals.