- (Fig. 1) .
- Natural cortisol levels are suppressed for >8 hours in normal animal.
- Animals with hyperadrenocorticism show breakthrough of suppression by 8 hours.
Wider range of degree and duration of suppression in cats than dogs.
- In conjunction with clinical suspicion - diagnosis of hyperadrenocorticism .
- In conjunction with discriminatory test for differentiation of adrenal and pituitary dependent disease. [High-dose dexamethasone suppression test] or ACTH assay
- Has a number of disadvantages over ACTH stimulation test
- Affected by more variables.
- Takes 8 hours to complete.
Normal (reference) values
- [Plasma cortisol] = <50% of [basal cortisol] at 2-4 hours and failure to escape suppression by 8 hours (most cases).
- Hyperadrenocorticism: [cortisol] fails to suppress or escapes suppression by 8 hours.
Errors and Artifacts
- Stress: must be minimized.
- No sedation possible.
- Recent administration of exogenous glucocorticoids may suppress the hypothalamic-pituitary axis.