Differentiate between Cushing’s disease and pseudocushing’s.
Measure plasma ACTH at baseline, 10 min, 20 min, and 30 min after administration of ddAVP 10 μg intravenously.
ACTH increase over baseline by ≥ 6 pmol/L after ddAVP indicates Cushing’s disease (Sn 81·5%, Sp 90%). [Giraldi 2007]
The utility of the test has not been validated in a large population of patients with all causes of Cushing’s syndrome. [Nieman 2008]
Pecori Giraldi F, Pivonello R, Ambrogio AG, De Martino MC, De Martin M, Scacchi M, Colao A, Toja PM, Lombardi G, Cavagnini F. The dexamethasone-suppressed corticotropin-releasing hormone stimulation test and the desmopressin test to distinguish Cushing’s syndrome from pseudo-Cushing’s states. Clin Endocrinol (Oxf). 2007 Feb;66(2):251-7.
Lynnette K. Nieman, Beverly M. K. Biller, James W. Findling, John Newell-Price, Martin O. Savage, Paul M. Stewart, Victor M. Montori. The Diagnosis of Cushing’s Syndrome: An Endocrine Society Clinical Practice Guideline. JCEM, Volume 93, Issue 5, 1 May 2008, Pages 1526–1540.