The life expectancy of Addison's disease in dogs depends on several factors. The biggest factor appears to ultimately be owner compliance in following the recommended treatment plan. In order to better understand the impact Addison disease has on the dog's body, it helps to better understand the disease, its causes, symptoms and what treatment options are available out there. Once all this factors are considered, it is possible to draw a rough estimate on the life expectancy of Addison's disease in dogs by looking at what vets have to say.
A Shortage of Hormones
A dog's endocrine system is a marvelous machine composed by several glands whose main purpose is to produce hormones. Hormones are special chemical messengers of the body that are created in the endocrine glands and which are responsible for several important tasks.
When everything is working well, hormones are effectively delivered through the bloodstream reaching cells and organs responsible for important bodily functions. When there is a system failure though affecting some of the mechanisms of the endocrine machine, important functions are interrupted, producing a variety of disorders. One cause of such disrupted functionality is Addison's disease.
Addison's disease, also medically referred to as hypoadrenocorticism, is an endocrine disorder affecting dogs which derives from a shortage in the production of corticosteroids from the adrenal glands. The adrenal glands, one found on each kidney, commonly secrete several substances known as glucocorticoids and mineralocorticoids which help regulate various important bodily functions.
Cortisol, for instance, is an important glucocorticoid secreted by the outer layer of the adrenal glands. It is responsible for eliciting a fight or flight response under stressful situations and ensuring a correct level of blood sugar, fat, and protein metabolism. Whereas, aldosterone, another mineralocorticoid secreted by the adrenal glands, plays an important role in balancing the minerals sodium and potassium, important electrolytes found in the dog's body.
When such substances are not produced sufficiently enough, the electrolyte balance is thrown off the charts, creating the ideal grounds for a series of malfunctions and complications characteristic of Addison disease.
Addison's disease affects in 75 to 80 percent of cases, mostly young to middle-aged female dogs around 4 years old. Dog breeds predisposed to Addison's disease include Portuguese water dogs, bearded collies, standard poodles, great danes, soft coated wheaten terriers, Airedale terriers, basset hounds, springer spaniels, West Highland white terriers, Leonbergers, Labrador retrievers, Rottweilers, Saint Bernards, Nova Scotia duck tolling retrievers, German Shepherds and German Shorthaired Pointers.
"Adrenal glands suffer from two opposing pathologies, hyper-function (Cushing’s disease) and hypo-function (Addison’s disease)."~Dr. Peter Tobias
Symptoms of Addison's Disease in Dogs
Common symptoms suggesting Addison's disease in dogs are often quite vague and consist of the following: lethargy, loss of appetite, vomiting, diarrhea, abdominal pain, hind-end pain, muscle weakness, reduced appetite, confused mental state, and tremors. Increased drinking and increased urination may also take place.
Dogs often present to the vet mostly as weak and dehydrated. The vet typically detects weak pulses along with a slow, irregular heart rate. Because such symptoms of Addison's disease in dogs tend to come and go and because they may mimic several other disorders (not coincidentally, Addison disease is often nicknamed ''the great imitator''), affected dogs may not be diagnosed promptly.
Dogs may be mistakenly diagnosed with other disorders such as as inflammatory bowel disease (IBD), infections, pancreatitis, acute kidney failure, cancer of the gastrointestinal tract, or poisoning.
Left untreated, however, Addison's disease will progress. The electrolyte imbalance seen in this disease may lead to acute renal failure, heart arrhythmias, decreased volume of circulating blood which may lead to what's known as an Addisonian crisis. This potentially fatal condition will not go unnoticed, since in this scenario the dog will literally collapse. It is estimated that around 30 to 35 percent of dogs affected by Addison’s disease are diagnosed during a crisis.
Causes of Addison's Disease in Dogs
There may be several causes as to why the adrenal glands may fail causing adrenal insufficiency. A main cause is an immune-mediated destruction, where the immune system may erroneously destroy its own tissues, by marking them as ''foreign."
Other possible causes of adrenal insufficiency may be failure of the pituitary gland from secreting ACTH, a hormone responsible for stimulating the adrenal glands or failure of the hypothalamus from producing CRH, a hormone that controls the adrenal glands. The pituitary gland may also stop working because of the presence of inflammation, infection or a tumor.
Addison's disease at times may also derive from an abrupt discontinuation of steroid medications. Normally, steroid medications should be weaned gradually as per the veterinarian's instructions. When the administration of steroids is halted too abruptly, the dog's system may crash causing an Addisonian crisis, a potentially fatal disorder if left untreated.
In some cases, Addison's disease may stem from cancer, as a surgical complication or from a fungal infection. A stressful event is often a main culprit in causing a dog to show clinical signs of illness.
At the Vet's Office
This condition may be diagnosed casually when a dog is hospitalized for an episode of gastroenteritis that is responsive to intravenous fluid therapy. Then, once the dog is discharged from the hospital, the condition returns.
This condition may be suspected upon detecting complete blood count and biochemistry profile abnormalities. Also, the urine's specific gravity may be abnormal as the urine isn't concentrated as it should. An ultrasound may too be insightful considering that dogs with Addison's usually have a small adrenal gland. An ultrasound may also be helpful in ruling out other disorders.
The definitive test though required to diagnose Addison's disease is called the ACTH test for dogs. In this test, the dog is given ACTH which is normally produced by the pituitary gland and should stimulate the adrenal glands to produce cortisol. If the dog's body does not respond by secreting cortisol, then a diagnosis of Addison disease can be made.
Currently there are two promising medications prescribed to dogs affected by Addison's disease, Florinef (fludrocortisone acetate) and an injectable drug called DOCP or Percorten-V. Corticosteroid and mineralocorticoid replacement therapy is administered for life.
Life Expectancy of Addison's Disease in Dogs
What's the life expectancy of Addison's disease in dogs? While Addison's disease may appear as a debilitating disease, truth is, most dogs will still be able to lead happy lives as long as they always undergo routine monitoring and the medications are given as prescribed. Dog owner compliance therefore plays a main role in the life expectancy of Addison's disease in dogs, granting a good to excellent prognosis and therefore great outlook.
According to a study on the life expectancy of Addison's disease in dogs, the long-term treatment of 225 dogs with suffering from Addison's disease was evaluated and it was found that a good to excellent response to treatment was seen in more than 80 percent of the dogs, while a fair response to treatment was seen in 12.5 percent. The median survival times was found to be 4.7 years with many dogs still alive a the end of the study.
No significant difference in life expectancy of Addison's disease in dogs was observed when comparing dogs treated with fludrocortisone versus DOCP. Out of the 124 dogs who perished, the cause of death was not related to Addison's disease.
- Kintzer PP, Peterson ME. Treatment and long-term follow-up of 205 dogs with hypoadrenocorticism. J Vet Int Med. 1997;11:43–49.