Canine Addison’s disease, or hypoadrenocorticism
This happens when a dog’s adrenal glands do not produce enough corticosteroids, the hormones that allow people and dogs to adapt to stress. The adrenal glands, located near the kidneys, have a center called the medulla and an outer section called the cortex. “While both areas produce hormones, Addison’s disease concerns the hormones produced by the cortex; these hormones are called ‘corticosteroids,’” reports Mar VistaVet. The two hormones most likely to be affected by Addison’s disease are cortisol and aldosterone, according to Addisons diseaseindogs. Addison’s disease is the opposite of Cushing’s Disease, which is what occurs when the adrenal glands produce too much cortisol.
Signs of the Disease
Unfortunately, the symptoms of Addison’s are typically vague and often mimic the signs of other illnesses. Thus, it may take a while for a doctor to diagnose the disease and a diagnosis may end up being a process of elimination, instead of a straightforward process.
Furthermore, the dog’s breed, sex and age don’t typically help much in diagnosis, either. Although it very often hits females around the ages of 5 or 6, Addison’s disease can show itself in any dog.
- Weakened muscles
- Pain in hind quarters
- Reduced appetite
- Weight loss
- Darkened patches of skin
In some cases, the disease progresses to the point that dogs reach what’s called an “Addison’s crisis,” which means the dog goes into shock and collapses due to an imbalance of electrolytes and metabolism, reports Pet Education. During an Addison’s crisis, blood sugar may drop and potassium levels may soar. Approximately 30 percent of dogs suffering with Addison’s are diagnosed during a crisis, according to airportanimalemergicenter.com and Mar VistaVet.
“Dogs with Addison’s disease often have elevated blood urea nitrogen (BUN) and an elevated creatinine, as well as decreased blood glucose. The blood count may show a chronic anemia. If the blood work supports the diagnosis of Addison’s disease, then an ACTH challenge test is performed,” PetEducation writes. “In an ACTH challenge test, the dog is given an injection of the adrenal stimulating hormone ACTH. A normal dog will respond by having an increase in blood cortisol. If a dog with Addison’s disease is given ACTH, the dog will not have an increase in blood cortisol and the diagnosis of Addison’s disease is confirmed.”
During an Addison’s crisis, your veterinarian may first suspect renal failure, a diagnosis that further testing can eliminate. “The blood panel will come back showing elevations in the renal parameters (BUN and Creatinine) and thus with the elevated potassium is suggestive of acute renal failure, a condition with an extremely poor prognosis,” writes Mar VistaVet. “The veterinarian may become suspicious of another diagnosis as the patient will respond well to fluid administration and most renal failure patients do not respond well.”
What Causes Addison’s?
There doesn’t appear to be one single cause of Addison’s disease. Rather, there are several things that can cause the adrenal glands to fail. The most common cause, Pet Education says, is when the body itself attacks and kills its own tissue, known as “immune mediated destruction.” Other causes can be gland infections from “granulomatous diseases such as histoplasmosis or blastomycosis, or through other means such as infarcts, tumors, or amyloidosis of the gland. Another cause of Addison’s can be the failure of the pituitary gland to secrete ACTH, which is a hormone that stimulates the adrenal gland.”
To go along with those multiple causes, there are, in actuality, three types of the disease: primary, secondary and atypical.
This type of Addison’s disease occurs when the adrenal glands fail in producing mineralcorteroids and glucocorticoids, which requires replacing the mineralocortoids.
Secondary Addison’s happens when the “pituitary gland does not secrete ACTH, a hormone necessary to stimulate the adrenal glands,” reports dog-health-guide. This form requires “replacement therapy of glucocorticoids.”
According to Mar VistaVet, about one in 42 dogs has a special form of Addison’s, which means the problem is with the pituitary gland, located at the brain’s base, as opposed to the adrenal gland itself.
“The normal pituitary gland secretes ACTH (adrenocorticotropic hormone), which stimulates the zona fasciculate and zona reticularis (layers of the adrenal cortex) to produce glucocorticoids. Without this hormone, these two areas of the adrenal gland atrophy but the zona glomerulosa remains normal, meaning mineralocorticoid production remains intact. … It should be noted that often these patients progress to the more typical Addison’s disease, complete with electrolyte imbalance.”
Once your dog has been diagnosed with Addison’s disease, she’ll require treatment and monitoring of the disease for the rest of her life. The good news is that treating Addison’s disease is fairly straightforward and mostly consists of replacing the hormones missing from the dog’s body via oral medications.
Your vet will also likely monitor your dog’s blood sodium and potassium levels regularly at first. Once the dog’s body is regulated, she’ll probably only have to visit the vet two to three times per year to see if any medication adjustments are necessary, writes Pet Education. The prognosis for dogs with Addison’s disease is pretty positive. With proper veterinary care and medication, your dog can live a happy, healthy life.