North American Veterinary Licensing Examination (NAVLE) Practice Test

To definitively diagnose hyperadrenocorticism (Cushing's disease) in dogs, the ACTH stimulation test is crucial. This test evaluates how well the adrenal glands respond to adrenocorticotropic hormone (ACTH). In healthy dogs, the administration of ACTH leads to a regulated increase in cortisol production from the adrenal glands. However, in dogs with hyperadrenocorticism, there is an exaggerated response or an abnormal baseline level of cortisol, indicating dysfunction in cortisol regulation.

The other tests mentioned do not specifically assess adrenal function or cortisol levels in the context of hyperadrenocorticism:

- A bile acids test evaluates liver function and can identify disorders related to hepatic function but does not specifically diagnose adrenal diseases.

- An electrocardiogram (ECG) is used to assess heart rhythm and electrical activity but does not provide information about adrenal hormone levels or functions.

- Thoracic radiographs are useful for examining the heart and lungs, but they do not provide any direct insight into adrenal gland activity or hyperadrenocorticism.

The ACTH stimulation test remains the most reliable method for diagnosing hyperadrenocorticism due to its focus on measuring adrenal response and cortisol secretion directly related to this condition.