title: Diagnosis of Cushing's syndrome.
abstract: No single test has a 100% diagnostic accuracy, and combinations of tests are required. We routinely obtain 3 baseline IRMA-ACTH levels, followed by CRF stimulation and overnight high-dose (8 mg) dexamethasone suppression (HDS). If ACTH-independent adrenal disease is suspected, thin-section CT (with or without isotope scanning) of the adrenals is performed. In ACTH-dependent Cushing's syndrome, the clinical manifestations in conjunction with the CRF and 8 mg overnight HDS tests are used to differentiate pituitary from ectopic ACTH production. If plasma ACTH increases > 34% following CRF, and plasma cortisol decreases > 60% after HDS, pituitary MRI is the next step; if not, the ectopic ACTH syndrome is more likely and IPSS and attempts to localise the source of the ACTH production are required (see algorithmn).
authors.affiliation: Department of Endocrinology and Metabolism, University of Stellenbosch Tygerberg, W. Cape.
authors.forename: F S
authors.initials: FS
authors.lastname: Hough
mesh_terms: D000311:Adrenal Glands / Q000000981:diagnostic imaging; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000465:Algorithms; D002985:Clinical Protocols; D003346:Corticotropin-Releasing Hormone; D003480:Cushing Syndrome / Q000175:diagnosis* / Q000209:etiology; D003907:Dexamethasone; D006801:Humans; D006854:Hydrocortisone / Q000652:urine; D008279:Magnetic Resonance Imaging; D011877:Radionuclide Imaging; D014057:Tomography, X-Ray Computed
chemical_list: D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D006854:Hydrocortisone