Canine Addison’s Disease (AD), also known as
hypoadrenocorticism, is similar to Addison’s Disease in humans. It is caused by faulty or malfunctioning adrenal glands that fail to produce sufficient levels of cortisol and aldosterone hormones, both of which play a critical role in canine health. Deficiencies in one or both of these hormones can affect every part of your dog’s life, all the way from immune function through energy and even behavior or mood.
Diagnosing AD in dogs isn’t easy. In fact, many pups are misdiagnosed repeatedly because the symptoms can mimic other diseases or even behavioral issues. Ironically, this is also true for AD in humans. Without blood testing and regular monitoring, it is almost impossible to be certain about diagnosis.
If you believe your dog may be affected by AD, it’s important to see your vet as soon as you can. In the meantime, the information in this post will help you understand this disease, why it occurs, and how you can help your dog once diagnosed.
What Causes Canine Addison's Disease?
As with
Addison’s Disease in humans, Canine AD is often a result of autoimmune diseases where the body attacks the adrenal glands. In rarer cases, it may also be a side effect of trauma, a side effect of certain medications, or a result of over-medicating for
Cushing’s Disease.
AD in dogs can be primary or secondary. Primary is the term we use to refer to autoimmune AD; secondary refers to AD caused by outside influences, such as medication or damage to the adrenal glands via trauma. This designation is critical because it completely changes treatment options for dogs.
Furthermore, AD may be “typical,” meaning it presents in a familiar fashion, or “atypical,” meaning it presents oddly or unusually. Atypical AD is much harder to diagnose and treat, but early intervention helps.
Sometimes, veterinarians can’t identify why a dog’s immune system chooses to attack its own adrenal glands. This is referred to as “idiopathic Addison’s Disease.” In other cases, AD may be caused by small, often benign tumors or growths on the
pituitary gland, a hormone-secreting gland in the brain that modulates adrenal tissue and adrenal hormone production. Rarely, these tumors can be malignant.
Diagnosing Canine AD
We’ve talked a little bit about why AD happens; what about how it’s diagnosed?
Every vet follows a slightly different protocol depending on how your dog presents and how severe his symptoms are. Your vet may use one or more of these methods to help get to the root of your dog’s hormone imbalance issues:
- Blood tests for kidney, liver, pancreas, and adrenal function.
- Diabetes testing to rule out excessively high or low blood sugar.
- Complete Blood Count (CBC) blood testing to rule out infections.
- Urine or blood electrolyte tests to rule out electrolyte imbalance.
- Antibody and white blood cell tests to identify hidden infections.
- T4, TSH, and T3 thyroid hormone level testing for anomalies.
- Electrocardiogram (ECG) tests to identify cardiac abnormalities.
- ACTH-stimulation tests to identify high cortisol hormone levels.
It is common for vets to find more than one issue in dogs who present with symptoms of AD. These secondary diagnoses may be a result of AD itself, or they may be the cause of AD. Regardless, extensive testing is your vet’s best method for finding out not only whether your dog has AD, but exactly why they have it.
Don’t Panic!
Canine Addison’s Disease is often very frightening for pet owners. This is mostly due to the fact that AD is misunderstood. While severe cases can occur, most dogs experience only mild to moderate AD that responds well to medication.
As a dog owner, what you need to know most about what causes AD is that the overwhelming majority of cases are caused by autoimmune disease or long-term steroid treatment. If your dog presents with autoimmune AD, you shouldn’t panic or assume it’s a death sentence – or even decide that it’s too expensive and invasive to treat. Veterinary medicine has a plethora of options available for treatment, including simple daily or monthly medications.
Regarding AD caused by medications, including steroid drugs, know that it is exceptionally rare for a dog to experience AD for this reason. Vets prescribe medications like steroids and hormone supplements only after bloodwork and only with regular monitoring to ensure issues like these don’t happen. There is no reason to assume your dog will definitely develop AD as a result. Your vet will help you make the best possible decision for you and your pup!
Treating Canine AD
Here’s the good news: dogs treated with medication for AD almost always go on to recover. As long as you continue to medicate them, levels remain on par and dogs experience virtually no need for serious lifestyle adjustments. The only thing that changes is that your dog may see the vet more often to monitor blood levels that may identify the need for medication adjustments.
Vets treat AD with a variety of medications. The approach, including which medication is best, really depends on how she presents at the clinic. Dogs who are experiencing an AD crisis – with convulsions, vomiting, diarrhea, or very high temperatures – are usually treated with a rapid IV infusion of the short-acting steroid
dexamethasone. This drug suppresses your dog’s overactive immune system, bringing levels back into check.
For dogs with chronic AD, the approach changes significantly. If medication is causing the chronic AD, your vet will re-evaluate the medication to see if a replacement exists. For chronic autoimmune AD, most vets treat with either
prednisone,
fludrocortisone, or
desoxycorticosterone pivalate. The first two are given by pill, while the last is given by injection once every three to four weeks.
Is Treatment Really Needed?
Yes. Untreated AD in dogs can cause everything from chronic pain to heart, liver, and kidney disease, especially in older, sick, or comprised dogs. Not treating AD simply isn’t an option.
It is extremely important to follow your veterinarian’s recommendations for medicating your dog. Missing even a single dose, especially after significant time in treatment, can induce a return of symptoms or even an
Addison’s crisis. Medications should be given at approximately the same time every day or on the same day of the month whenever possible.
We mentioned in a previous section that long-term steroid treatment can sometimes cause AD. This can make treating autoimmune diseases with steroids seem counterintuitive. However, most of the issues with long-term steroid treatment stem from sudden withdrawals or missed doses. Steroids change how the immune system works; when stopped all at once, the immune system tends to over-compensate by spiraling out of control and attacking the body.
Weaning protocols that reduce doses slowly over time almost entirely ameliorate this risk.
