Corticotropin-releasing hormone (CRH) is a 41-amino acid peptide that is the major physiologic adrenocorticotropic hormone (ACTH) secretagogue . There is considerable sequence homology of CRH among species, particularly in the amino-terminal region, which is required for biologic activity. As a result, both ovine and human sequences are used in endocrine testing to:
●Evaluate the cause of ACTH-dependent Cushing's syndrome (with or without vasopressin analogs).
●Discriminate between pseudo-Cushing's and Cushing's syndrome.
●Discriminate between pituitary or hypothalamic localization of central adrenal insufficiency.
●To assess ACTH suppression in patients suspected of primary adrenal mild Cushing's syndrome when basal ACTH levels are incompletely suppressed between 5 and 15 pg/mL [1.1 to 3.3 pmol/L]. (See "Cushing's syndrome due to ACTH-independent macronodular adrenal hyperplasia".)