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, infection or immune-mediated attack, among other things. Addison's is a potentially life-threatening but thankfully very rare disorder in cats.
How Addison's Disease Affects Cats
The clinical signs of Addison's disease can vary but almost always involve progressive loss of body condition. The signs tend to wax and wane, ranging from mild to severe, and include weakness, lethargy, anorexia, diarrhea (possibly bloody), weight loss, poor skin and coat condition, abdominal pain, dehydration, trembling and collapse. It is uncommon for cats to show signs of vomiting, regurgitation, drinking more water than normal or urinating more than normal, although dogs commonly show these additional signs. In advanced cases, the disease in cats can mimic systemic shock, with low body temperature, tremors and slow heartbeat. Some affected cats will deviate from their normal activities for no apparent reason. The signs tend to be progressively severe. Normally, by the time a cat is diagnosed with Addison's, emergency medical treatment is necessary. Once the cat has been stabilized, proper assessment can be made and proper treatment protocols can be prescribed. Addison's disease is more common in older cats, but there is no species or gender predisposition.
Causes of Addison's in Cats
The signs of Addison's are caused by an inability or insufficiency of the adrenal glands to produce the necessary amounts of mineralocorticol hormones. 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 probably is immune-mediated. Other causes of primary hypoadrenocorticism include overdoses of certain medications, metastatic tumors and granulomatous disease. Secondary Addison's can be caused by damage to the pituitary gland and, more commonly in cats, by long-term corticosteroid administration which leads to decreased secretion of ACTH and, in turn, reduced synthesis and circulation of glucocorticoid hormones.
Preventing Addison's in Cats
There is no way to "prevent" hypoadrenocorticism in our companion cats. The recommended approach for cats 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.
Addison's is very uncommon in cats, but it does occur. If not treated aggressively, 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. The prognosis for cats with Addison's disease is very good if the condition is detected early. Unfortunately, diagnosis can be difficult because the clinical signs of this disease mimic those of many more common ailments.
Hypoadrenocorticism, commonly called "Addison's disease," is a potentially life-threatening endocrine condition that is extremely rare in cats and cannot be cured but, if caught early, may be controlled. Addison's can be primary (due to damage to the adrenal glands) or secondary (from destructive lesions or congenital defects of the hypothalamus or pituitary gland). The clinical signs of Addison's are caused by an inability or insufficiency of the cat's adrenal glands to produce the necessary amounts of steroid hormones. The disease can wax and wane and normally causes progressively severe signs in cats ranging from mild gastrointestinal upset to acute collapse. Treatment protocols for cats with Addison's disease depend upon the underlying cause of the condition.
Treating Addison's Disease in Cats
The goals of treating acute Addison's episodes are to replace bodily fluid volume, correct electrolyte imbalances and provide an immediate source of rapid-acting systemic corticosteroids. These goals focus on stabilizing cortisol levels and minimizing the harmful consequences of low circulating corticosteroids, which include shock, vomiting and diarrhea, and initially requires hospitalization. Owners normally can manage their cats at home once the acute crisis has resolved.
The aggressiveness of initial treatment will depend in large part on the cat's clinical status. Acute Addisonian episodes are medical emergencies and require immediate veterinary intervention, even before diagnosis of the disease is confirmed. Waiting for the results of diagnostic tests may result in death. Emergency treatment includes placing the cat on intravenous fluids (usually normal saline) and giving injections of appropriate glucocorticoids. While dogs often show marked improvement within 24 hours of treatment, cats tend to have a slower initial response to therapy and may remain weak and listless for 3 or 5 days despite appropriate treatment. ACTH stimulation testing should be done once the cat is stabilized.
Once fluid levels are restored and hormone levels are stabilized, and after the cat has recovered from any other adverse effects of the disease, the owner can take the pet home. Chronic treatment typically will involve lifelong oral supplementation with corticosteroids, the choice of which will be made by a veterinarian based upon whether the cat's disease is primary or secondary. Addison's patients should have regular urine and blood tests to monitor their systemic cortisol and electrolyte levels. If elevated blood potassium levels persist, the cat may need additional drug therapy.
The prognosis for cats with Addison's disease is excellent as long as their owners are conscientious about daily treatments and periodic veterinary monitoring. Excellent communication between owners and their veterinarians is critical to the successful treatment of this uncommon disease in cats.