Addison’s disease, medically called hypoadrenocorticisim, is a condition that occurs when one or both of a cat’s adrenal glands aren’t functioning properly and don’t produce enough of several essential adrenal hormones. Cats with Addison’s disease become weak and relatively inactive, especially when they are going through periods of stress. They develop stomach-aches, nausea, vomiting, diarrhea, weight loss, depression and other unpleasant symptoms, which typically come and go in waves. Some cats with Addison’s disease collapse without warning. Their levels of circulating electrolytes, such as glucose, potassium, sodium and chloride, become imbalanced, which can lead to dehydration and other severe problems. Owners who notice that their cat isn’t feeling well for no apparent reason should consult with a veterinarian. A simple blood test can confirm whether or not a kitty has Addison’s disease. Fortunately, this disorder is manageable through the use of hormone replacement therapy.
Symptoms of Addison’s Disease - What the Owner Sees
Cats with Addison’s disease may or may not show any observable signs of illness. When they do, their symptoms are notoriously non-specific and often come and go for no apparent reason. They can include:
- Inactivity; lack of energy
- Lack of appetite (inappetance, anorexia)
- Vomiting (uncommon but can occur))
- Increased thirst and consumption of water (polydipsia; uncommon but can occur)
- Increased production and output of urine (polyuria; uncommon but can occur)
- Sudden collapse (fairly common)
These vague symptoms can be caused by any number of things other than Addison’s disease. However, even though it isn’t common in cats, Addison’s should be on the list of differentials for a feline pal that just isn’t acting like its normal bouncy self. The good news is that feline Addison’s disease is fairly easy to diagnose by a series of simple blood tests. It also is relatively easy to treat, or at least to manage, by adrenal hormone replacement therapy.
Causes of Addison’s Disease in Cats
Addison’s disease is the common name for what medically is known as hypoadrenocorticism. It occurs when one or both of a cat’s paired adrenal glands, which sit just above each kidney, do not make and secrete enough essential adrenal hormones into the cat’s bloodstream. The adrenal glands primarily produce steroid hormones. Addison’s is uncommon in companion cats. When it does occur, it usually is caused by atrophy, or wasting, of the adrenal gland or glands due to something wrong with the cat’s immune system. In other words, something stimulates the cat’s immune system to start attacking its own tissues. Why this happens is still a medical mystery. Some authorities suggest that overdoses of corticosteroid drugs, cancer (neoplasia), physical trauma to the pituitary gland, mineralization of the pituitary gland, abnormal internal bleeding (hemorrhage), infection and/or granulomatous disease all may contribute to feline Addison’s disease. Granulomatous diseases are those that involve the formation of granulomas, which are actively growing tumor-like masses or nodules that develop when wounded tissue is healing.
Diagnosing Addison’s Disease in Cats
After taking a history and performing a physical examination, most veterinarians presented with a kitty that “just ain’t doing right” will recommend taking a blood sample and submitting it for routine blood work, which is referred to as a complete blood count (CBC) and serum chemistry profile (chem panel). They probably will also recommend taking a urine sample and performing a urinalysis. Routine blood and urine test results can show a great deal about the function of a cat’s vital organs, but typically will not be completely diagnostic of Addison’s disease. Based on the results of those tests, the veterinarian may suggest chest X-rays (radiographs), an abdominal ultrasound and/or other tests. The most reliable way to diagnose Addison’s disease is by conducting an ACTH stimulation test. This involves taking an initial blood sample and having a laboratory assess the levels of a hormone called cortisol in the cat’s blood. Then, a different hormone that normally is made by the pituitary gland, called ACTH, is administered to the cat by intravenous or intramuscular injection (by “giving the cat a shot”). Finally, the vet will take 2 more blood samples, approximately 30 and 60 minutes after giving the ACTH injection. The lab will evaluate those samples for the levels of post-ACTH-administration cortisol in the cat’s blood. Cats with Addison’s disease will have little if any increase in their circulating blood cortisol levels, while cats that don’t have Addison’s disease should have significantly elevated cortisol levels.
How aggressively a veterinarian and owner will treat cats with Addison’s disease will depend in large part on the individual cat’s clinical status. Acute Addisonian episodes are true medical emergencies and require immediate veterinary intervention, even before diagnosis of the disease is confirmed. Waiting for a definitive diagnosis may result in death. Emergency treatment includes placing the cat on intravenous fluids (usually normal saline) and giving injections of corticosteroids. While dogs often show marked improvement within 24 hours of treatment, cats tend to have a much slower response to therapy and may remain weak and listless for 3 to 5 days or more, despite appropriate stabilization and treatment. ACTH stimulation testing should then be done. This involves a simple series of blood tests and injection of a hormone that normally stimulates production of adrenal hormones. Cats with Addison’s disease won’t respond normally to injection of ACTH. Once the cat’s fluid levels are restored and its hormone levels are stabilized, and after it has recovered from any other adverse effects of the disease, the owner can take their kitty home. Long-term treatment of Addison’s disease typically involves life-long oral supplementation with adrenal corticosteroid hormones, 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 the level of adrenal hormones and other substances circulating in their blood. If elevated potassium levels persist, the cat may need additional drug therapy.
Prognosis and Outcome for Cat’s with Addison’s Disease
The prognosis for cats with Addison’s is excellent, as long as their owners are conscientious about daily treatments and take them to the veterinarian for regular periodic monitoring. Good communication between owners and their veterinarians is essential to successful treatment of this uncommon feline disease.