Evaluation of a low-dose synthetic adrenocorticotropic hormone stimulation test in clinically normal dogs and dogs with naturally developing hyperadrenocorticism.
OBJECTIVE
To determine whether low doses of synthetic ACTH could induce a maximal cortisol response in clinically normal dogs and to compare a low-dose ACTH stimulation protocol to a standard high-dose ACTH stimulation protocol in dogs with hyperadrenocorticism.


METHODS
Cohort study.


METHODS
6 clinically normal dogs and 7 dogs with hyperadrenocorticism.


METHODS
Each clinically normal dog was given 1 of 3 doses of cosyntropin (1, 5, or 10 micrograms/kg [0.45, 2.3, or 4.5 micrograms/lb] of body weight, i.v.) in random order at 2-week intervals. Samples for determination of plasma cortisol and ACTH concentrations were obtained before and 30, 60, 90, and 120 minutes after ACTH administration. Each dog with hyperadrenocorticism was given 2 doses of cosyntropin (5 micrograms/kg or 250 micrograms/dog) in random order at 2-week intervals. In these dogs, samples for determination of plasma cortisol concentrations were obtained before and 60 minutes after ACTH administration.


RESULTS
In the clinically normal dogs, peak cortisol concentration and area under the plasma cortisol response curve did not differ significantly among the 3 doses. However, mean plasma cortisol concentration in dogs given 1 microgram/kg peaked at 60 minutes, whereas dogs given doses of 5 or 10 micrograms/kg had peak cortisol values at 90 minutes. In dogs with hyperadrenocorticism, significant differences were not detected between cortisol concentrations after administration of the low or high dose of cosyntropin.


CONCLUSIONS
Administration of cosyntropin at a rate of 5 micrograms/kg resulted in maximal stimulation of the adrenal cortex in clinically normal dogs and dogs with hyperadrenocorticism.
Kerl
M E
ME
Department of Medicine, Animal Medical Center, New York, NY 10021, USA.
Peterson
M E
ME
Wallace
M S
MS
Melián
C
C
Kemppainen
R J
RJ
D000304:Adrenal Cortex Function Tests / Q000662:veterinary*; D000308:Adrenocortical Hyperfunction / Q000175:diagnosis / Q000662:veterinary*; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D015331:Cohort Studies; D003366:Cosyntropin; D004283:Dog Diseases / Q000175:diagnosis*; D004285:Dogs / Q000097:blood / Q000502:physiology*; D005069:Evaluation Studies as Topic; D005260:Female; D006854:Hydrocortisone / Q000097:blood; D008297:Male
D003366:Cosyntropin; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone