Certain diseases in pets are tricksters because they can mimic other health conditions. Addison’s disease mimics so well that it’s nicknamed ‘The Great Imitator."
Addison’s disease is another name for hypoadrenocorticism, which is the decreased production of hormones in the adrenal glands. It is less common than Cushing’s Disease (hyperadrenocorticism), which is the overproduction of adrenal hormones.
The adrenal glands sit on top of the kidneys and have two major parts—the outer cortex and the inner medulla—that produce hormones. The cortex is affected by Addison’s disease. The cortex produces corticosteroids, which are categorized into glucocorticoids and mineralocorticoids. Cortisol, aka the stress hormone, is a well-known glucocorticoid that controls the ‘fight or flight’ response. Aldosterone is a mineralocorticoid that regulates the body’s sodium and potassium levels.
In most cases of Addison’s disease, the cause remains unknown. Some potential causes are listed below:
- Autoimmune disorder that destroys adrenal tissue
- Overzealous treatment of Cushing’s disease
- Tumor that has spread to the adrenal glands
Addison’s disease occurs most commonly in dogs, mainly young, middle-aged female dogs. Certain dog breeds, such as standard poodles and Great Danes, are more susceptible to the disease.
Clinical signs of Addison’s disease become apparent only when nearly all of the adrenal cortex has to be destroyed. However, these clinical signs, which are listed below, are vague and resemble clinical signs of other diseases:
- Vomiting and diarrhea
- Increased thirst and urination
- Weight loss
- Intermittent shaking
- Reduced appetite
These clinical signs can appear suddenly and wax & wane. They can worsen with stress because the adrenal glands aren’t producing enough cortisol to manage the stress.
Sometimes, the disease is severe enough to cause an Addisonian Crisis, which is a medical emergency. During an Addisonian Crisis, a dog’s body goes into shock because it cannot respond adequately to stress. Immediate hospitalization and veterinary treatment are needed if this takes place.
Because Addison’s disease is ‘The Great Imitator," clinical signs won’t be enough to make a diagnosis. A veterinarian will need to rely on the history provided by the pet parent, routine bloodwork, and a test called the ACTH Stimulation Test.
Bloodwork will show decreased sodium and increased potassium levels, which indicate an aldosterone deficiency.
The ACTH stimulation test is used to definitively diagnose Addison’s disease. To perform this test, a veterinarian will measure blood cortisol levels before and two hours after ACTH administration. ACTH is naturally produced by the pituitary gland and stimulates the adrenal glands to produce cortisol.
Cortisol levels that are low before ACTH stimulation and barely budge afterward indicate Addison’s disease. A pet in an Addisonian Crisis receives immediate treatment performed before diagnostic testing.
Severe cases of Addison’s disease require several treatments, including fluid therapy to restore normal sodium and potassium levels. Minimizing stress is another aspect of managing this disease.
Addison’s disease require lifelong replacement of glucocorticoids and mineralocorticoids in dogs. This treatment can either be done with an injectable medication every 3-4 weeks or a daily pill. Dogs with Addison’s disease do quite well and can live and happy lives, provided that their condition is well-managed.
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