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00019616-199707011-00003ArticleThe EndocrinologistThe Endocrinologist© Lippincott-Raven Publishers.7January 1997 p 10S–16SCorticotropin-Releasing Hormone (CRH): Clinical Studies and UseArticle: PDF OnlyCutler, Gordon B. Jr. M.D.National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892–1862.Address correspondence to: Gordon B. Cutler, Jr., M.D., Department of Health and Human Services, National Institute of Child Health and Human Development, National Institutes of Health, Building 10, Room 10N262, 10 Center Drive MSC 1862, Bethesda, MD 20892–1862, Phone: 301–496–4686; Fax: 301–402–0574.AbstractClinical studies have suggested two areas in which corticotropin-releasing hormone (CRH) may be useful in the differential diagnosis of Cushing's syndrome. First, for patients with adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome in whom radiologic studies have failed to localize the source, CRH is useful in differentiating pituitary from ectopic sources of ACTH. Second, in patients with mild to moderate hypercortisolism, defined as urinary free cortisol excretion of 90–360 μg/day, the dexamethasone-CRH test is useful in differentiating pituitary Cushing's disease from pseudo-Cushing states. The rationale for using CRH to distinguish ectopic from pituitary sources of ACTH is that ectopic ACTH-secreting tumors, unlike pituitary ACTH-secreting tumors, do not, as a rule, express CRH receptors or respond to CRH.A simple procedure has been developed in which CRH (1 μg/kg) is given intravenously between 8 and 9 a.m. The increase in ACTH after 15 and 30 minutes is expressed as a percentage of the mean basal level, which is the average of samples taken 5 minutes and 1 minute before administration. An increase >35% in ACTH level indicates Cushing's disease. This test has a sensitivity of about 90%.The rationale for using CRH to diagnose a pseudo-Cushing state is that CRH responsiveness in these patients is blunted compared with patients with Cushing's disease. The latter hyperrespond to CRH because their endogenous CRH is suppressed and their tumors are less subject to feedback inhibition from elevated cortisol levels. By combining the low-dose dexamethasone and CRH test, a higher diagnostic accuracy can be achieved.<strong xmlns:mrws="">Corticotropin-Releasing Hormone (CRH): Clinical Studies and Use</strong>Cutler Gordon B. Jr. M.D.Article: PDF OnlyArticle: PDF Only17p 10S-16S