Addison’s disease, also known as hypoadrenocorticism, is a chronic condition that affects your dog’s adrenal glands. It affects approximately 1 in every 250 dogs, and because its symptoms can seem to come and go and may mimic those of other diseases, it can be tricky for veterinarians to diagnose.
What Causes Addison’s Disease in Dogs?
In healthy dogs, the adrenal glands — located next to each kidney — produce hormones essential for regulating many of the body’s processes. These hormonal and endocrine functions play a crucial role in energy metabolism, blood pressure, electrolyte levels, blood sugar, immunity, and inflammation. Dogs with Addison’s disease do not produce enough of these hormones and require lifelong treatment with hormone replacement medication. Untreated Addison’s disease can be fatal.
Primary Addison’s Disease
In dogs with primary Addison’s disease — the most common form — the adrenal glands are injured or compromised by infection, cancer, or injury, or there may be no known cause. An autoimmune dysfunction, in which the immune system attacks the adrenal glands, may be to blame. Primary Addison’s disease affects the parts of the adrenal glands that produce the steroid hormones cortisol, which regulates energy metabolism, and aldosterone, which regulates blood pressure.
Secondary Addison’s Disease
In dogs with secondary Addison’s disease, the adrenal glands are not directly injured or compromised. Instead, the pituitary gland, located in the center of the brain, no longer produces ACTH, a hormone that signals the adrenal glands to produce cortisol. Secondary Addison’s disease is typically caused by a tumor or inflammation of the pituitary gland.
Which Dogs Are Most at Risk?
Addison’s disease is more common in female dogs than males and is typically diagnosed in young adult dogs around four years of age, though it can also be diagnosed in puppies and senior dogs.
Certain breeds are genetically predisposed to Addison’s disease. According to a 2017 Université de Montréal study, only about 0.38% of dogs are affected overall, yet as many as 9.73% of Great Pyrenees will develop the disease. Addison’s disease may affect nearly 5% of West Highland white terriers, while up to 2% of other at-risk breeds — including the Standard Poodle, Saint Bernard, Jack Russell Terrier, and Great Dane — are affected.
What Are the Early Symptoms of Addison’s Disease in Dogs?
Symptoms of Addison’s disease can be intermittent and tend to develop gradually. According to Dr. John August, a veterinarian at the College of Veterinary Medicine & Biomedical Sciences at Texas A&M University, symptoms may not be apparent until 90% of the adrenal gland tissue has died.
Early symptoms of Addison’s disease in dogs can include:
- Weakness and lethargy
- Vomiting and diarrhea
- Loss of appetite
- Increased thirst and urination
- Weak or irregular pulse
- Hair loss
- Shivering or shaking
Because these symptoms are nonspecific and intermittent, it is crucial to see your veterinarian as soon as possible when you notice any of the above signs. Early diagnosis is key to protecting your dog’s health.
How Is Addison’s Disease Diagnosed in Dogs?
Dogs with Addison’s disease may be diagnosed after other causes have been ruled out, or following an Addisonian crisis.
During an Addisonian crisis, the dog suddenly falls into shock and collapses. This occurs because the dog’s blood pressure becomes dangerously low due to high blood potassium and low sodium. An Addisonian crisis is a medical emergency and can be fatal.
A blood test will show electrolyte imbalances that point to Addison’s disease. The diagnosis is then confirmed with an ACTH stimulation test, during which your dog is administered ACTH, which stimulates cortisol production in healthy dogs. In dogs with Addison’s disease, the ACTH will fail to increase cortisol production.
How Is Addison’s Disease Treated in Dogs?
Addison’s disease cannot be cured, but it can be managed by replacing adrenal hormones with prescription medication.
Dogs with the more common primary form will need two medications: daily Prednisolone, given orally at home to replace cortisol, and a monthly injection to replace aldosterone. The secondary, less common form of Addison’s disease requires only cortisol replacement medication.
Aldosterone Replacement: Zycortal
Primary Addison’s disease is treated with an in-office injection of Zycortal Suspension (desoxycorticosterone pivalate injectable suspension), which replaces aldosterone.
The first dose is administered upon diagnosis. You will then bring your dog to the veterinarian for bloodwork after 10 days and again after 25 days from the first dose to determine the most effective dosage. Afterward, your dog will receive their Zycortal injection in-office every month, or as your veterinarian recommends.
Cortisol Replacement: Prednisolone
Both primary and secondary Addison’s disease require daily oral Prednisolone to replace cortisol. This dog pharmacy medication is given at home and should be administered exactly as prescribed by your veterinarian.
Prognosis for Dogs With Addison’s Disease
Dogs with Addison’s disease typically do not require any dietary changes unless needed to manage concurrent conditions. With lifelong medication and regular bloodwork, dogs have an excellent prognosis and can go on to have otherwise healthy, active lives.
