Cortisol and Adrenal Function Testing

Cortisol is the body's natural steroid and is normally present at some level in your pet's blood stream. Cortisol along with the other important steroids is produced in the body's adrenal glands.

There are several important disorders in which the levels of cortisol may be abnormally high or low. Animals with an abnormally high level of cortisol may have what is called Cushing's syndrome, or hyperadronocorticism. Symptoms your pet may exhibit include abnormal weight gain, pot bellied appearance, symmetrical hair loss, increased thirst and urination, panting, among others. There are also important changes which may be noted on a serum chemistry profile.

If history, physical examination findings or blood test results are supportive of Cushing's syndrome, additional screening and diagnostic tests may be recommended. A screening test for Cushing's syndrome is the urine cortisol: creatinine ratio in which a urine sample collected at home is tested for abnormal cortisol levels. If this test is positive, a series of in hospital day long blood tests may be recommended for your pet.

These tests include the ACTH stimulation test in which cortisol levels are measured before and one hour after injection of a synthetic adrenal stimulating hormone. Another test is the dexamethasone suppression test in which cortisol levels are measured before, and four and eight hours after injection of a synthetic cortisol. Results of these tests will definitively diagnose if your pet has Cushing's disease, may indicate which of the two major types is more likely, and help dosing of appropriate medication. Periodic testing with the ACTH stimulation will also be needed to monitor your pet's disease and whether dosing of the medication needs adjustment.

Another important disorder is Addison's disease, or hypoadrenocorticism, in which the adrenal glands are underproducing the body's cortisol and other steroids. The signs of this disease are less easily recognized, but may include serious illnesses after stressful events, unexplained episodes of collapse or severe weakness, and recurring infections. Electrolyte and white blood cell changes may be noted on complete blood count and serum chemistry profile. Diagnostic testing will include the ACTH stimulation test. ACTH stimulation testing will be periodically needed to monitor your pet's disease and adjustment of medication as needed.

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