Canine hypoadrenocorticism, also known as Canine Addison's Disease, is a serious illness involving the adrenal glands.

What is Addison's disease? - When the body is working properly the pituitary gland makes the hormone, adrenocorticotropic hormone (ACTH), which tells the adrenal glands to make glucocorticoid steroid (Cortisol or Cortison). The body needs Cortisol to regulate the conversion of protein and fat into glucose and Cortisol tells the body how to react to stress. In an animal with Addison's disease the body has a lack of glucocorticoid steroid and/or mineralocorticoid. The mineralocorticoid hormone is needed to regulate the body's water and electrolytes.

How did my dog get Addison's disease? - Many times Addison's disease is considered idiopathic, which means no one knows why. The doctors do know that part of the adrenal gland atrophies resulting in decreased production of the glucocorticoid and mineralcorticoid steroids. Some reported causes of Addison's disease are fungal infections, trauma, cancer, and heredity. Addison's is rare and can occur in any breed of dog.

Addison's disease symptoms - Symptoms of Addison's disease are very similar to other diseases and they seem rather vague. Symptoms may include but are not limited too; middle age female dogs, usually over 7 years of age, depression, lethargy, weakness, not eating, weight loss, vomiting and diarrhea, drinking more, urinating more, dehydration, and a fast heart rate in some patients. Many times these symptoms may go unnoticed or correctly diagnosed and the patient finally presents in a Addisonian crisis. During an Addisonian crisis the patient may present in acute collapse and in shock. This is very serious, deadly, and scary to watch. Blood work will show low sodium level, high potassium level, and high kidney enzymes. Many veterinarians will first think kidney failure, which is more common then Addison's, and will recommend IV fluids. The IV fluids will correct the electrolyte imbalance and the dog will start to feel a lot better. The veterinarian may then start to think the patient could have Addison's instead of kidney disease and recommend other tests.

Diagnosing Addison's disease - Addison's is diagnosed by a series of blood tests. A chemistry panel will show a low sodium level, a high potassium level, the resulting Na:K ratio will be low. The kidney enzymes will be high. The Adrenocorticotropic hormone (ACTH) stimulation test will give a definitive diagnosis for Addison's disease. The patient will need to be at the veterinary clinic for about 2 hours to complete the test. The test is done by drawing a sample for a baseline reading, a synthetic ACTH hormone (Cortrosyn) is given by injection, then a post blood sample is taken one hour later. Dogs with Addison's have a low cortisol concentration that will go unchanged even after the synthetic stimulation.

Treatment for Addison's disease - Treatment consists of replacing the glucocorticoid and mineralocorticoid steroids. The drugs of choice are usually Prednisone (glucocorticoid) and Percorten-V or Florinef (mineralocorticoid). The dose of Prednisone will taper over the course of a few weeks. It is very important that these drugs are given as prescribed.

Additional Information:

• Lack of mineralocorticoid steroids and glucocorticoids is life threatening. If the dog goes without treatment it will die.
• With proper treatment the dog can live a near normal life.
• The patient will need to have regular blood work done to monitor electrolytes and kidney function.
• In cases of trauma, surgery, or stressful situations alert your treating veterinarian to your dogs condition. In some stressful situations the dog may need Prednisone supplementation.
• This condition is very rare in dogs and even more rare in cats, I'm not sure there has ever been a reported case of feline Addison's disease.
• Addison's disease is the opposite of Cushing's disease.

References:

Common Diseases of Companion Animals, Alleice Summers, MS, DVM (Mosby, Inc. 2002)

Clinical Textbook for Veterinary Technicians, Dennis M. McCurnin, DVM, MS and Joanna M. Bassert, VMD (Elsevier Inc. 2006)

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