Addison’s Disease in Dogs

Addison’s disease in dogs is caused by a deficiency of glucocorticoids and mineralocorticoids.  These hormones are made and released by the adrenal glands which are very small peanut shaped glands that reside next to the kidneys.  In dogs with Addison’s disease the adrenal tissue that is responsible for making these hormones becomes atrophied.  The cause of the atrophy is unknown, but it is an irreversible process.  Glucocorticoids play a significant role in many of the body’s functions, such as maintaining vascular tone, water balance, anti-inflammatory effects, maintenance of blood sugar levels, and gastrointestinal function.  Mineralocorticoids are vital in maintaining sodium, potassium, and water balances.Addison's Disease in Dogs

Clinical signs of Addison’s disease in dogs

Dogs with Addison’s disease can have acute or chronic clinical signs.  Most veterinarians at some point in their career will see a dog present to their clinic in shock from Addison’s disease.  In this situation, the diagnosis can be very easy if the appropriate labwork is performed.  The blood levels of sodium is very low and the potassium level very high. If Addison’s disease is diagnosed in time, these dogs can be treated successfully and do very well long-term.  The dogs with Addison’s disease that have chronic intermittent or progressive clinical signs can be more difficult to diagnose.  The clinical signs of being a “poor doer” or having bouts of gastrointestinal upset are not as obvious to be from Addison’s disease and sometimes get misdiagnosed.

Diagnosis of Addison’s disease in dogs

Once Addison’s disease is suspected the confirmatory test is an ACTH stimulation test.  The test requires taking a blood sample from the dog that is submitted to the lab to determine the cortisol level.  After the blood sample is taken the dog is given an injection of synthetic ACTH, which is a pituitary hormone that stimulates the adrenal glands to secret more cortisol.  An hour after the synthetic ACTH is administered another blood sample is taken for a second cortisol level to be measured.  The dog is diagnosed with Addison’s disease if the cortisol levels are both low at less then 2.0 ug/dl.

Treatment of Addison’s disease in dogs

The treatment that should be administered by a veterinarian when a dog is in an Addisonian crisis is saline intravenously, dexamethasone intravenously, and desoxycorticosterone pivalate (Percorten-V; Novartis Animal Health).  The saline is a sodium chloride fluid supplement that helps treat shock and the sodium and chloride deficiency.  The dexamethasone is a rapid-acting corticosteroid to help reverse the shock and it does not interfere with the cortisol testing to confirm Addison’s disease.  Desoxycorticosterone pivalate is a synthetic mineralocorticoid that  corrects the sodium, potassium, and water imbalance.  Chronic therapy involves either a combination of oral prednisone and intermittent injections of desoxycorticosterone, or oral prednisone and oral fludrocortisone (Florinef; E.R Squibb & Sons).  The long-term prognosis of Addison’s disease in dogs is excellent.

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