Use of a low-dose ACTH stimulation test for diagnosis of hypoadrenocorticism in dogs.
BACKGROUND
Although definitive diagnosis of hypoadrenocorticism usually is made by an adrenocorticotrophic hormone (ACTH) stimulation test using 250 microg/dog of synthetic ACTH (cosyntropin/tetracosactrin), increased costs have prompted a search for less-expensive diagnostic methods.


OBJECTIVE
A low-dose ACTH stimulation test (5 microg/kg) will distinguish between dogs with nonadrenal illness and hypoadrenocorticism. Additionally, administration of cosyntropin will not affect the results of another ACTH stimulation test performed 24 hours later.


METHODS
Eight healthy adult dogs and 29 hospitalized dogs with suspected hypoadrenocorticism.


METHODS
In this prospective study, each healthy dog received 4 ACTH stimulation tests. Dogs received either 5 microg/kg or 250 microg/dog of cosyntropin on day 1 and the alternate dose on day 2. The opposite dosing sequence was used after a 2-week washout period (days 15 and 16). Dogs with suspected Addison's disease received 2 ACTH stimulation tests, 24 hours apart, using either a dose of 5 microg/kg cosyntropin or 250 microg/dog on the 1st day and the alternate dose on the 2nd day.


RESULTS
In healthy dogs, poststimulation cortisol concentrations on days 2 and 16 and days 1 and 15 were equivalent (90% confidence interval [CI]: 86.7-101.2%). In dogs with suspected Addison's disease, mean (+/-SD) cortisol responses to ACTH in the 5 microg/kg dose (16.2+/-7.7 microg/dL) and 250 microg/dog dose (15.9+/-6.3 microg/dL) were statistically equivalent (90% CI: 91.2-105.4%).


CONCLUSIONS
Low-dose ACTH stimulation testing distinguishes between dogs with nonadrenal illness and hypoadrenocorticism. Additionally, the administration of 2 ACTH stimulation tests on consecutive days does not affect results of the second test.
Purdue University School of Veterinary Medicine, West Lafayette, IN, USA. lathan@cvm.msstate.edu
P
P
Lathan
G E
GE
Moore
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S
Zambon
J C
JC
Scott-Moncrieff
D000309:Adrenal Insufficiency / Q000175:diagnosis / Q000662:veterinary*; D000324:Adrenocorticotropic Hormone / Q000008:administration & dosage*; D000818:Animals; D004283:Dog Diseases / Q000175:diagnosis*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005260:Female; D006728:Hormones / Q000008:administration & dosage*; D008297:Male
D006728:Hormones; D000324:Adrenocorticotropic Hormone