Page 894 - Small Animal Internal Medicine, 6th Edition

866 PART VI Endocrine Disorders

VetBooks.ir Additional tests for HAC
INTERPRETATION Not supportive of HAC indicated Normal Inconclusive PDH PDH PDH or ATH Suggestive † Inconclusive ‡ Normal Iatrogenic HAC PDH PDH PDH or ATH PDH PDH or ATH ATH PDH Nondiagnostic

8 hours post-dexamethasone: <1.0 µg/dL 1.0-1.4 µg/dL >1.4 µg/dL >1.4 µg/dL and <50% of pre-value >1.4 µg/dL and >50% of pre-value

Diagnostic Tests to Assess the Pituitary-Adrenocortical Axis in Dogs With Suspected Hyperadrenocorticism
4 hours post-dexamethasone: Post-ACTH cortisol concentration: Post-dexamethasone cortisol concentration: 4- or 8-hour <50% of pre-value 4- or 8-hour <1.4 µg/dL 4- and 8-hour >50% of pre-value Post-dexamethasone UCCR value: <50% of baseline value § ≥50% of baseline value Below reference range Upper half of reference range or greater than reference Lower half of reference range

RESULTS Normal Increased — — <50% of pre-value — >50% of pre-value >24 µg/dL 19-24 µg/dL 6-18 µg/dL <6 µg/dL range ACTH, Adrenocorticotropic hormone; ATH, adrenocortical tumor-dependent hyperadrenocorticism; HAC, hyperadrenocorticism; IM, intramuscular; IV, intravenous; PDH, pituitary-dependent

Urine collected at home 0.01 mg dexamethasone/kg IV; serum pre- and 4- and 8-hour post-dexamethasone 5 µg of synthetic ACTH*/kg IV; serum pre- and 1-hour 0.1 mg of dexamethasone/kg IV; serum pre- and 4- and 8-hour post-dexamethasone Urine sample for UCCR on 2 consecutive mornings, then 0.1 mg of dexamethasone/kg per os q8h for 3 treatments, then urine sample for UCCR the following morning Specific sample handling § Baseline value is th

PROTOCOL post-ACTH required

PURPOSE Rule out HAC Diagnose HAC and differentiate PDH from ATH Diagnose HAC Differentiate PDH from ATH Differentiate PDH from ATH Differentiate PDH from ATH hyperadrenocorticism; UCCR, urine cortisol/creatinine ratio. *Synthetic ACTH: Cortrosyn, Cosyntropin, Synacthen.

TABLE 50.2 creatinine ratio dexamethasone suppression test ACTH stimulation dexamethasone suppression test Oral dexamethasone suppression test Endogenous ACTH † Suggestive of hyperadrenocorticism. ‡ Inconclusive for hyperadrenocorticism.

TEST Urine cortisol/ Low-dose High-dose