Injections of exogenous (synthetic) ACTH (Cosyntropin; Cortrosyn) usually result in increased levels of endogenous cortisol, and a lack of response usually indicated adrenal non-responsiveness as a result of underlying adrenal tumors.
Synthetic ACTH is injected either intravenously or intramuscularly at a dose of 5 μg/kg and cortisol levels in normal dogs would subsequently rise to 1.4 µg/dL after eight hours.
A four-hour post-injection sample with cortisol < 1.4 µg/dL or 50 percent lower than the baseline or eight-hour value is consistent with pituitary-dependent hyperadrenocorticism.
A low-dose dexamethasone suppression test and urine cortisol:creatinine ratio are usually simultaneously performed.
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