Addison’s Disease in Dogs: Symptoms, Diagnosis, Treatment

What is Addison’s Disease?

The most common form of Addison’s disease is an auto-immune disease, meaning the dog’s body attacks and destroys its own adrenal glands. The vital hormones the adrenal glands make are necessary to live, and if dogs do not have enough of them, it can cause severe illness.

Any dog breed can get Addison’s disease, but it usually occurs in young to middle-aged female dogs. The most commonly affected breeds are Westies, Great Danes, all types of poodles, Portuguese water dogs, bearded collies, and basset hounds. 

Symptoms of Addison’s Disease in Dogs

Addison’s disease has a reputation as being a “great pretender” of other diseases. Meaning the symptoms are vague and often mimic other illnesses. Some dogs start showing signs of Addison’s disease within days to a couple of weeks. 

Other dogs have symptoms that gradually worsen over multiple months or even come and go over time. This variation in the onset of symptoms and the variety of symptoms can lead to underdiagnosis. 

The most common signs of Addison’s disease include: 

• Decreased appetite
• Depressed attitude and lethargy
• General weakness
• Weight loss 
• Vomiting
• Diarrhea
• Increased thirst and urinating more frequently and in larger amounts
• Shaking or full body tremors
• Collapse 

Dogs with Addison’s disease can have a sudden onset of symptoms called an “Addisonian crisis.” This is a medical emergency and can be life-threatening. Dogs having an Addisonian crisis are weak and often collapse after a few days of poor appetite. 

What Causes Addison’s Disease in Dogs?

Addison’s disease occurs when there are not enough of two specific hormones in the body: aldosterone (a mineralocorticoid) and cortisol (a glucocorticoid). Aldosterone and cortisol regulate many vital processes in the body, including water retention, blood pressure, and nutrient metabolism. Without these essential hormones, dogs and humans cannot live. 

• The most common cause of Addison’s disease is the destruction of the organ that makes aldosterone and cortisol, called the adrenal glands. This is a form of autoimmune disease because the dog’s own body attacks and destroys the adrenal glands until they can no longer function. 
• About 30% of dogs have a slightly different form of Addison’s called atypical Addison’s disease. Symptoms of atypical Addison’s disease are usually milder compared to the common form of the disease. Dogs with atypical Addison’s disease still have enough aldosterone (mineralocorticoid) but not enough cortisol (glucocorticoid). 
• An overdose of medications used to treat Cushing’s disease (hyperadrenocorticism), such as trilostane and mitotane, can also lead to Addison’s disease. 

How is Addison’s Disease Diagnosed?

An ACTH stimulation test is the most common test used to diagnose Addison’s disease in dogs. The test is conducted over a couple of hours and starts by obtaining a blood sample. Then, a hormone medication called ACTH is administered to increase cortisol in the body. Another blood sample is then taken two hours later. Blood sample results measuring cortisol are compared before and after the ACTH is given. Dogs with Addison’s disease will have deficient cortisol levels on the ACTH stimulation test. 

Veterinarians will also use a combination of the following when diagnosing Addison’s disease: 

• Physical examination and history you provide them
• Labwork – a common finding in dogs with Addison’s disease is too high potassium and too low sodium and chloride in the blood
• Urinalysis
• X-rays to exclude other reasons for your dog’s symptoms 
• Abdominal ultrasound
• Electrocardiogram (EKG) 
• Resting cortisol levels- a blood test usually used in emergencies to exclude the possibility of Addison’s disease

Treatment for Addison’s Disease in Dogs

The treatment for Addison’s disease in dogs is to replace the aldosterone (mineralocorticoid) and cortisol (glucocorticoid) the body lacks. Treatment is lifelong, and the most common medications used for this are:

• DOCP (Percorten, Zycortal) – a mineralocorticoid used to replace aldosterone. It is given every 25-28 days by injection under the skin. Labwork to monitor electrolyte values is needed every few weeks when starting this medication. Once the appropriate dose is determined, labwork is recommended twice a year to ensure the dose is still adequate. 
• Prednisone – a glucocorticoid to replace cortisol. Most dogs on DOCP need a low dose of oral prednisone daily.

A less commonly used alternative to DOCP is fludrocortisone acetate (Florinef). It is an oral medication given twice daily but can be costly in larger dogs.