Addison's disease - Hypoadrenocorticism
What is Addison’s disease?
Addison’s disease is the common name for hypoadrenocorticism, caused by decreased hormone production from the outer part or cortex of the adrenal gland.
What are the adrenal glands and what do they do?
The adrenal glands are small, paired glands located near the kidneys. Each glandconsists of an outer cortex and an inner medulla. The glands produce two important hormones that regulate a variety of body functions and are necessary to sustain life. The two hormones are cortisol, a stress hormone, and aldosterone, a hormone that regulates the body’s levels of the minerals sodium and potassium. Sodium and potassium regulation is vital for maintaining the body’s fluid balance.
What causes Addison’s disease?
Addison’s disease in dogs is usually caused by an immune–mediated destruction of adrenal tissue (the body attacks the adrenals for unknown reasons). Less commonly, the adrenal glands may be damaged by trauma, infection, or cancer. Addison’s disease can also occur following treatment of Cushing’s disease (hyperadrenocorticism).
A secondary form of Addison’s disease can result from a tumour or defect in the pituitary gland, which is an important hormonal regulator located in the brain. Secondary Addison’s disease can also develop if a dog
has been treated with long- term steroids for any reason and the medication is abruptly stopped. This last condition is known as iatrogenic hypoadrenocorticism and is generally temporary.
Certain breeds seem to be at increased risk for developing Addison’s disease. These include, but are not limited to: Portuguese Water Dogs, Bearded Collies, Standard Poodles, Great Danes, and Labrador Retrievers.
What are the clinical signs of hypoadrenocorticism?
Clinical signs of Addison’s disease are usually vague and non-specific, meaning there are no particular signs
that indicate a diagnosis of the disease. Addisonian patients may present with lethargy, diarrhoea, vomiting, increased thirst, increased urination, and unplanned weight loss. Intermittent shaking episodes are sometimes seen. The signs may be intermittent.
Non-specific medical treatment like the administration of fluids or corticosteroids appears to help temporarily, but the signs soon return. If a pet experiences recurrent bouts the above illnesses, your vet may talk to you about testing for Addisons disease.
What is an Addisonian crisis?
Sometimes this condition takes on a much more serious presentation resulting in sudden weakness, with severe vomiting and diarrhoea, and sometimes collapse. This is an Addisonian crisis and is considered a medical emergency. Immediate hospitalization and supportive treatment are needed.
How is Addison’s disease diagnosed?
Diagnosis is based on your pet’s medical history, including any medications, clinical signs, and the results of blood and urine tests, most notably electrolyte imbalances. The most definitive diagnostic test for Addison’s disease is the ACTH- stimulation test. In this test, cortisol levels are measured before and after injection of a synthetic form of ACTH. These tests are quite expensive as the ACTH is an expensive product and lab fees are also charged. Additional tests may also be required.
How is Addison’s disease treated?
Once diagnosed, most dogs with Addison’s disease can be successfully treated.
Most Addison’s patients do best on oral medications that replace both the mineralocorticoid and the glucocorticoid such as fludrocortisone (brand name Florinef®). There is a monthly injection available but this seems to sting, so we rarely use this.
Your dog’s diet and activity levels don’t generally change long term. Most dogs resume normal lives, even after an Addisonian crisis.
What is the prognosis for a dog diagnosed with Addison’s disease?
Most patients with Addison’s disease have a good to excellent prognosis once the diagnosis is made and they have been stabilized with the appropriate medications. Your veterinarian will provide you with information on the long-term prognosis for your pet.