What Is Addison's Disease & How Does It Affect Dogs?
Addison's disease (also called canine hypoadrenocorticism) is caused by an adrenal gland hormone deficiency. It's often referred to as the great imitator by veterinarians because its clinical signs are often very vague and can mimic other conditions. But while getting to a diagnosis may be frustrating, the good news is that with lifelong treatment, most dogs with Addison's disease have an excellent prognosis and the condition shouldn't have any impact on your dog's life expectancy.
What Is Addison's Disease in Dogs?
Understanding Addison's disease begins with a quick anatomy lesson. Dogs have two small adrenal glands that are located near their kidneys, and these glands produce two important hormones:
- Cortisol: a hormone that regulates the body's response to stress.
- Aldosterone: a hormone that regulates the levels of sodium and potassium—important electrolytes that keep the body functioning properly.
When the adrenal glands don't produce enough of these hormones, that's what causes Addison's disease in dogs.
According to Corey Entriken, DVM, of Kansas City Veterinary Care, the most common cause of this deficiency is immune-mediated destruction of a particular part of the adrenal gland. In other words, the dog's immune system attacks the adrenal tissue by mistake. The Merck Veterinary Manual notes that other conditions can damage the adrenal glands as well and trigger the condition, including medications used to treat Cushing's disease (a condition caused by too much cortisol) and cancer in other parts of the body.
Although any dog can be affected by Addison's disease, it's most common in young to middle-aged female dogs. Several breeds are more prone to the condition, including standard poodles, West Highland white terriers, Great Danes, bearded collies, and Portuguese water dogs.
Signs & Symptoms of Addison’s Disease in Dogs
As mentioned earlier, the clinical signs of Addison's disease can be difficult to identify because they aren't very specific. They include:
- Repeated episodes of vomiting and diarrhea
- Loss of appetite
- Increased thirst and urination
- Weakness, lethargy
- Excessive panting
- Weight loss
Some dogs can suddenly experience what's known as an Addisonian crisis, in which the disease takes a serious turn and requires immediate medical attention. Signs of an Addisonian crisis include severe vomiting and diarrhea, shock, and collapse.
How Is Addison’s Disease Diagnosed?
Entriken says that electrolyte imbalances noticed on routine blood tests are usually the initial reason for suspecting Addison's disease, but the definitive test is called an ACTH stimulation test.
It's a multi-step process: The veterinarian first measures the amount of cortisol in the dog's blood before giving him an injection of a hormone called adrenocorticotropin. In healthy dogs, this hormone is able to stimulate the adrenal gland. Then, the veterinarian measures the level of cortisol in the dog's blood a second time. If the dog has Addison's disease, his cortisol levels will be low both times it's measured. The adrenocorticotropin will have little to no effect.
Addison's Disease in Dogs Treatment and Lifestyle Changes
According to the Merck Veterinary Manual, dogs experiencing an Addisonian crisis need immediate medical treatment with intravenous fluids. Once the patient is stable, long-term hormone replacement treatment can begin. Entriken says this usually involves either a desoxycorticosterone pivalate (DOCP) injection every three to four weeks or a dose of fludrocortisone acetate by mouth daily to correct the aldosterone deficit. A common steroid called prednisone is often prescribed to replace cortisol, and it must be given every day by mouth as well.
Treatment doesn't typically involve a change in diet, Entriken says. "Most dogs with Addison's disease do well on a normal, well-balanced canine diet," he explains.
Entriken notes that because dogs with Addison's disease don't make enough cortisol, they can have a difficult time handling stress. In fact, clinical signs can appear and worsen when stressed. "Particular attention should be paid to avoiding stressful situations," he says. As the pet owner, you are the expert on what makes your dog feel stressed, but common causes include being boarded, moving, and having house guests.
Dogs with Addison's disease will need to be treated for the rest of their lives and will require regular monitoring to make sure they're still responding well to treatment and to make adjustments, if necessary. But with therapy, most dogs have an excellent long-term prognosis and are able to live long, active lives.
If you're concerned your dog may have Addison's disease or think his current Addison's treatment needs some adjusting, don't hesitate to contact your veterinarian. A close partnership between you and your vet is the best way to keep your pet healthy.