title: Extended low-dose dexamethasone suppression test for diagnosis of atypical Cushing's syndrome in dogs.
abstract: The purpose of this study was to evaluate extension of the low-dose dexamethasone suppression (LDDS) test from 8 h to 12 h to detect possible hypercortisolemia associated with atypical hyperadrenocorticism (AHAC). Twelve client-owned dogs were enrolled in the study: 6 healthy dogs (group 1) and 6 dogs with suspected AHAC (group 2). Baseline EDTA plasma samples were collected for endogenous ACTH determination using an immunoradiometric assay. Serum samples were collected before and at 4, 8, 10, and 12 h post-administration of 0.01 mg/kg dexamethasone IV for cortisol concentration determination via chemiluminescent assay. Mean endogenous ACTH concentration did not differ between groups (group 1: 22.4 pg/mL, group 2: 20.0 pg/mL; P > 0.2). Mean baseline cortisol concentration also did not differ significantly between groups (group 1: 3.03 μg/dL, group 2: 4.95 μg/dL; P > 0.2) nor was there any difference in mean cortisol concentration between the groups at any other time point (P > 0.2). The cortisol concentration from 1 dog in group 2 suppressed to 0.7 μg/dL at 8 h but increased to 1.5 μg/dL at 10 h and 3.7 μg/dL at 12 h post-dexamethasone. Based on results of this study, use of an extended LDDS test could not differentiate between healthy dogs and dogs with AHAC. Diagnosis of AHAC should continue to be based on prior established criteria until new testing has been identified.
authors.affiliation: Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, 2407 River Drive, Knoxville, TN 37996, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Fowler
authors.affiliation: Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, 2407 River Drive, Knoxville, TN 37996, USA. Electronic address: Lfrank@utk.edu.
authors.forename: L A
authors.initials: LA
authors.lastname: Frank
authors.affiliation: Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, 2407 River Drive, Knoxville, TN 37996, USA.
authors.forename: F
authors.initials: F
authors.lastname: Morandi
authors.affiliation: Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, 2407 River Drive, Knoxville, TN 37996, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Whittemore
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D003907:Dexamethasone / Q000008:administration & dosage* / Q000494:pharmacology; D004283:Dog Diseases / Q000175:diagnosis*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D005938:Glucocorticoids / Q000008:administration & dosage* / Q000494:pharmacology; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D047748:Pituitary ACTH Hypersecretion / Q000175:diagnosis / Q000662:veterinary*
chemical_list: D005938:Glucocorticoids; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone
keywords: Atypical hyperadrenocorticism; Dog; Low-dose dexamethasone suppression test; Occult hyperadrenocorticism