CANINE ACTH STIMULATION TEST
An increase in cortisol levels post ACTH is expected in all dogs. In normal dogs levels will rise to less than 660 nmol/l. A post ACTH cortisol level of >660 nmol/L is POSITIVE for hyperadrenocorticism Dogs with pituitary dependant hyperadrenocorticism (PDHAC) show an exaggerated response usually greater than 660 nmol/l. In dogs with an adrenal tumour the basal cortisol is usually high with a variable response to ACTH stimulation. In cases of Addisons Disease (primary hypoadrenocorticism) or iatrogenic hyperadrenocorticism, basal cortisol values are normally low with little or no response to ACTH stimulation.
The ACTH stimulation test will identify approximately 85% of PDHAC dogs and approximately 50% of dogs with an adrenal tumour. It will not reliably distinguish between the two conditions. The dexamethasone (high dose) suppression test is recommended for distinguishing between PDHAC and an adrenal tumour following a positive ACTH stimulation test result
ACTH (SYNACTHEN) SUPPLY
Evans H and Walker M. SCL Veterinary Services Manual. 6th Edition. p.15.
Dunn, K.J., Herrtage, M.E.
and Dunn, J.K. (1995) Use of ACTH stimulation tests to monitor the treatment
of canine hyperadrenocorticism. Veterinary Record 137(7) p 161
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