Addison's disease is a hormonal disease that can make a dog become very ill due to imbalanced electrolytes. Learn about Addison's disease in dogs and find out how to treat it.
What Is Addison's Disease?
The scientific term for Addison's disease is hypoadrenocorticism, a term that generally means "low adrenal hormones." Addison's disease occurs when the adrenal glands do not produce an adequate amount of the hormones necessary to keep the body's electrolytes in balance.
The adrenals are tiny glands located near the kidneys. When a dog experiences stress, normal adrenal glands will produce extra cortisol to help the body adjust to the physiological effects of stress. However, the body cannot continue to function normally if it cannot produce enough cortisol. The water and electrolytes in the body get out of balance, leading to serious illness.
Addison’s disease is most common in young to middle-aged dogs. It is much less common than the opposite condition in dogs, Cushing’s disease, which causes an overproduction of cortisol.
Dogs with Addison's Disease may exhibit no signs at first. When signs do appear, they can vary from mild to severe. Be aware that the signs of Addison's disease may be vague and are similar to the signs of other illnesses.
If you notice these or any other signs of illness that last more than a day or two, you should see your veterinarian.
Causes of Addison's Disease in Dogs
The exact cause of primary Addison's disease is not known. It is believed to occur due to immune-mediated destruction of the adrenal tissue. Secondary Addison's occurs after some kind of damage has been done to the adrenal glands due to an outside factor. This factor may be trauma, tumor, or even medications used to treat other diseases.
Certain dog breeds may be predisposed to Addison's disease. This includes the Bearded Collie, Great Dane, Portuguese Water Dog, Standard Poodle, West Highland White Terrier, and many other breeds.
Diagnosis of Addison's in Dogs
Your veterinarian will begin by discussing your pet's medical history and current signs. Next, a physical examination will be performed. Dogs with Addison's may have dehydration, weak pulses, and/or a slow, irregular heart rate. However, lab tests will be necessary to determine the true cause of your dog's symptoms. Your vet will likely start with routine lab tests, like blood chemistry with electrolytes and a complete blood count. A urinalysis may also be necessary.
In dogs with Addison's disease, it is common for blood work to show a high potassium level and a low sodium level. This is an electrolyte imbalance. Kidney values may also be affected. The CBC and urinalysis may or may not be abnormal.
A presumptive diagnosis of Addison's disease may be made based on the initial test results, but additional testing is necessary to confirm the diagnosis. In most cases, an ACTH stimulation test is the next step. These results will confirm if Addison's disease is present.
The ACTH stimulation test is performed over a few hours in your vet's office. A preliminary blood sample is drawn to establish a baseline cortisol level. Next, an injection of ACTH (adrenocorticotropic hormone) is given to stimulate the adrenal glands to produce cortisol. A post-injection blood sample is drawn one to two hours later to measure the cortisol levels again. If the cortisol level in the blood did not rise as expected, a diagnosis of Addison's may be made.
Because other factors may affect your dog's cortisol levels, a non-definitive test result may warrant further diagnostic testing. Your vet will interpret all results and discuss the next steps for your dog.
Treatment of Addison's Disease in Dogs
A very sick dog with Addison's will typically need to be hospitalized until stabilized. This illness is called an Addisonian crisis. Dogs are often very weak and experience vomiting and/or diarrhea. The electrolyte imbalance requires careful correction with fluid therapy and medications in order to avoid further complications.
Fortunately, most cases of Addison's disease can be managed with medication once the dog's electrolytes have been regulated.
Ongoing maintenance of the Addison's dog typically involves replacement of glucocorticoids (usually prednisone), and most patients require replacement of mineralocorticoids with either desoxycorticosterone pivalate or fludrocortisone. Routine lab testing is necessary to ensure the electrolytes are in balance.
If a dog with Addison's disease becomes even slightly sick, it is essential to have that dog seen by a vet as soon as you can. An Addisonian crisis can occur at any time. The faster your dog can begin treatment, the less serious the crisis becomes.
Can Addison's Disease be Prevented?
There is no way to prevent a dog from developing primary Addison's disease. Secondary Addison's may be avoidable by making sure your dog is carefully regulated while on any medications. Routine examinations can also help your veterinarian determine risk factors for Secondary Addison's.
Early detection can make it easier to manage Addison's disease. Follow your vet's advice for routine lab work. Mild abnormalities may allow your vet to discover Addison's before your dog actually gets sick. Preventing an Addisonian crisis is the best way to keep your dog safe.
Disorders of the Adrenal Glands in Dogs. Merck Veterinary Manual
Addison's Disease. Washington State University College of Veterinary Medicine
Lathan, Patty, and Ann L Thompson. Management of hypoadrenocorticism (Addison's disease) in dogs. Veterinary medicine (Auckland, N.Z.) vol. 9 1-10. 9 Feb. 2018, doi:10.2147/VMRR.S125617