Updated on May 23, 2016
Addison’s Disease in Dogs
In 1855 Dr. Thomas Addison was the first person to describe a human affliction he dubbed Addison’s disease. Since that time, this disease has become a well-recognized syndrome in both people and dogs. The scientific name for Addison’s disease is hypoadrenocorticism– an insufficient production of essential hormones manufactured by the adrenal glands.
Addison’s disease can occur in any size and breed of dog. Middle-aged females are most commonly affected. A familial or inherited predisposition for the disease has been described in Standard Poodles, Bearded Collies, Great Danes, and Portuguese Water Dogs.
Normal adrenal gland function
Let the physiology lesson begin! Every dog is born with two adrenal glands located adjacent to each kidney within the abdominal cavity. These glands are responsible for producing several important hormones. Dogs with Addison’s disease lose their ability to produce two of these hormones, namely cortisol (aka, cortisone) and aldosterone. Neither man nor beast can live without adequate levels of both of them.
Cortisol is essential for normal function of virtually every organ within the body. It’s responsible for normal appetite and an overall sense of well being. Cortisol production is amped up during times of stress. Canine “stress” can stem from fear, excitement, anxiety, or significant physical exertion. Examples might include: thunderstorms, dates at the grooming parlor, a free-for-all at the dog park, running an agility course, or visiting the veterinary hospital. (Please read my thoughts on Fear-Free office visits)
Aldosterone regulates sodium and potassium levels in the body. Without aldosterone, the potassium level in the bloodstream increases and the sodium level decreases. If severe enough, these changes can be life threatening. Every once in awhile a dog develops “atypical Addison’s disease” in which there is cortisol depletion, but aldosterone production remains normal. These dogs have normal blood levels of sodium and potassium.
The cause of Addison’s disease is incompletely understood. Autoimmune destruction is suspected. This means that the individual’s own immune system is somehow triggered to attack and destroy the body’s normal tissues; in this case, cells within the adrenal glands.
Cushing’s Disease is the polar opposite first cousin of Addison’s disease. A dog with this disease develops symptoms caused by the overproduction of cortisol by the adrenal glands. Overzealous treatment to reduce the cortisol production can result in Addison’s disease.
Early on in the course of the disease Addisonian dogs may show rather vague waxing and waning symptoms. As the disease progresses, symptoms tend to become more consistent and fulminant. Not all Addisonian dogs exhibit all of the symptoms- in fact, only one or two may be observed. The most common symptoms caused by Addison’s disease include:
- diminished appetite
- increased thirst
- increased urine output
- weight loss
- hair coat changes
Addison’s disease is suspected based on symptoms. Abnormal physical examination findings may include a slowed heart rate (caused by the elevation in blood potassium), dehydration, weak pulses, thin condition, generalized weakness, and even collapse or coma.
The diagnosis of Addison’s disease begins with blood and urine testing. The urine is typically dilute rather than well concentrated. Blood test abnormalities may include increased levels of potassium, blood urea nitrogen (BUN), creatinine, and calcium along with decreased sodium and glucose levels. A chest x-ray may demonstrate decreases heart size.
Addison’s disease is definitively diagnosed by measurement of blood cortisol levels both before and after an injection of ACTH (adrenocorticotrophic hormone), a substance that stimulates the adrenal glands to release cortisol. This is known as an ACTH response test. Addisonian dogs have extremely low levels of circulating cortisol both prior to and following adrenal gland stimulation.
The great imitator
Addison’s disease is known as the “great imitator” because its symptoms are often vague and nonspecific and they may mimic those associated with a plethora of other diseases. Additionally, unless the dog is in a state of crisis, symptoms tend to be on-again, off-again. So, it’s easy to talk oneself out of a veterinary visit. And, if basic blood test abnormalities are mild, the veterinarian may not even consider Addison’s disease as a potential diagnosis.
Because of all of this, the biggest pitfall associated with Addison’s disease is its lack of recognition. The most famous Addisonian of all time, John F. Kennedy, had waxing and waning symptoms for years before his physicians finally thought about testing for Addison’s disease!
In the case of collapse or profoundly slowed heart rate, emergency therapy for the Addisonian dog may be necessary including intravenous fluid therapy, cortisone injections, and treatment for circulatory shock.
Long-term treatment for Addison’s disease involves life-long hormone replacement therapy and, in some cases, sodium supplementation- table salt added to the dog’s diet. Cortisol supplementation (prednisone is the drug most commonly used) is initiated and is ultimately weaned down to a physiologic dose or discontinued. Whether or not it is discontinued depends upon the aldosterone replacement therapy selected. A physiologic dose is intended to imitate the amount of cortisol normally released by the adrenal glands. If it is known that an Addisonian dog will be experiencing some version of stress, the dose of cortisone is increased accordingly.
Aldosterone replacement is achieved one of two ways. An injectable drug known as DOCP (desoxycorticosterone pivalate- how’s that for a mouthful!) can be administered via an injection under the skin approximately once every 25 days. Most veterinarians are willing to teach their clients how to administer this drug at home. Another injectable option is the newly released drug called Zycortal. An orally administered daily medication called Florinef is another option for aldosterone replacement.
Unfortunately, these drugs can be pretty darned pricey. Given that they are dosed based on the dog’s body weight (large breed dogs are more commonly affected) and that dogs with Addison’s disease must receive life-long medication and blood test monitoring, the cost of treatment can be enormous.
Well-managed Addisonian dogs are expected to have a normal life expectancy and an excellent quality of life. The keys to success are affordability and conscientious life-long treatment and monitoring.
Sources of support
Not all veterinarians have vast experience recognizing and/or treating dogs with Addison’s disease. Additionally, successful treatment requires considerable finesse based on lots of experience with this disease. Consider getting help from a veterinarian who specializes in internal medicine and who likely has dozens of Addisonian patients under his or her belt.
An excellent, long-running, online source of support is the forum called AddisonDogs. The site is well moderated and provides a wealth of information for those in the position of caring for an Addisonian dog.
Have you ever managed a dog with Addison’s disease? If so, what was your experience like?
Nancy Kay, DVM
Diplomate, American College of Veterinary Internal Medicine
Author of Speaking for Spot: Be the Advocate Your Dog Needs to Live a Happy, Healthy, Longer Life
Author of Your Dog’s Best Health: A Dozen Reasonable Things to Expect From Your Vet
Recipient, Leo K. Bustad Companion Animal Veterinarian of the Year Award
Recipient, American Animal Hospital Association Animal Welfare and Humane Ethics Award
Recipient, Dog Writers Association of America Award for Best Blog
Recipient, Eukanuba Canine Health Award
Recipient, AKC Club Publication Excellence Award
Become a Fan of Speaking for Spot on Facebook
Please visit http://www.speakingforspot.com to read excerpts from Speaking for Spot and Your Dog’s Best Health. There you will also find “Advocacy Aids”- helpful health forms you can download and use for your own dog, and a collection of published articles on advocating for your pet’s health. Speaking for Spot and Your Dog’s Best Health are available at www.speakingforspot.com, Amazon.com, local bookstores, and your favorite online book seller.