Definition of the Disease
Addison’s disease, also known as hypoadrenocorticism, is defined as diminished hormone production from the cortex of the adrenal gland. The adrenal cortex can be damaged by hemorrhage, mineralization or infection, among other things. Addison’s is a potentially life-threatening disorder of the endocrine system which cannot be cured but, if caught early, can be controlled.
How Addison’s Disease Affects Dogs
The signs of Addison’s are caused by an inability or insufficiency of the adrenal glands to produce the necessary amounts of mineralocorticol hormones. This, in turn, causes there to be abnormally low levels of sodium and chloride, and abnormally high levels of potassium, in circulation. Ultimately, this leads to low blood volume, and kidney and heart abnormalities. The signs of this condition tend wax and wane, ranging from mild to severe, and include weakness, lethargy, anorexia, vomiting, regurgitation, diarrhea (possibly bloody), weight loss, poor skin and coat condition, abdominal pain, drinking more water than normal, urinating more than normal, trembling and collapse. Some affected dogs will deviate from normal activities for no apparent reason due to the pain and muscle weakness that can accompany this disease. The signs are normally progressively frequent and increasingly severe, as the dog’s body becomes damaged from the effects of insufficient adrenocorticoid production. Normally, by the time a dog is diagnosed with Addison’s, emergency medical treatment is needed. Once the dog has been stabilized, proper assessment can be made and proper treatment protocols can be prescribed. Addison’s disease is more common in young to middle-aged female dogs, although dogs of any age or sex can be affected.
Causes of Addison’s Disease
The cause of primary Addison’s disease is not always known but is thought to be the result of atrophy of all layers of the adrenal gland, which is probably immune-mediated. Other causes are overdose of certain medication, metastatic tumors and granulomatous disease. Secondary Addison’s can be caused by injury to or disease of the pituitary gland and, more commonly in dogs, by long-term corticosteroid administration which leads to decreased secretion of ACTH and, in turn, reduced synthesis and circulation of glucocorticoid hormones.
Prevention
There is no way to actually “prevent” hypoadrenocorticism in dogs. The recommended approach for dogs with primary Addison’s disease is to continue glucocorticoid hormone replacement therapy for the lifetime of the animal, and possibly to increase the dosage of replacement hormones during periods of particular stress. Reliable tests are available to diagnose this disease, and there are good treatment protocols for managing the condition.
Special Notes
If left untreated, or if diagnosis is delayed, Addison’s can become life-threatening, primarily due to elevated potassium levels and low sodium and chloride levels which cause serious and acute dehydration, volume depletion and problems with the heart and other organs. This is called an “Addisonian crisis” and, if not treated aggressively, can be fatal. The prognosis for dogs with Addison’s is usually very good if the condition is detected early in its course. Unfortunately, diagnosis can be difficult because the clinical signs of Addison’s mimic those of many more common ailments.