Hypoadrenocorticism (Addison's Disease)
Addison's Disease
Hypoadrenocorticism (Addison's) was first discovered in 1855 in human patients by a physician named Thomas Addison for whom the disease is also named. It refers to a condition where there is insufficient production of specific hormones from the adrenal gland.
What are adrenal glands?
The adrenal glands are 2 small glands that sit above each kidney. They are responsible for secreting various hormones. There are 2 classes of hormones that are specifically affected in patients that have Addison’s – mineralocorticoids and glucocorticoids (cortisol). Some patients have deficiencies in both hormones while others may only be glucocorticoid deficient. Glucocorticoids such as cortisol are critical in maintaining normal sugar, fat and protein metabolism in the body. They are also important in maintaining normal physiologic function in times of stress. Release of glucocorticoids from the adrenal glands is controlled by a hormone called adrenocorticotropic hormone (ACTH) from the pituitary gland.Mineralocorticoids are the hormones responsible for maintaining normal electrolyte and water balance in the body. Both of these hormones play an important role in helping the body adapt to stressful situations and without them the body fails to function correctly.
What are the signs of Addison's disease?
Unfortunately the signs of hypoadrenocorticism can be very vague. They can range from malaise, lethargy and poor appetite to collapse and shock. The variability of symptoms can mimic a wide range of other illnesses such as kidney disease, neurologic diseases or gastrointestinal disease. How is Addison’s diagnosed? In addition to clinical signs and history, there may be clues in the routine blood tests that can sometimes be suggestive of this disease. Some of the more salient changes are low blood sugar, high calcium, low sodium and elevated potassium levels. Patients with Addison’s don’t necessarily have to have all of these changes and the abnormalities may be subtle. If your veterinarian suspects Addison’s disease based on your pets signs or lab data, the most definitive test is an ACTH stimulation test. For this test a blood sample is drawn, a synthetic version of the adrenocorticotropic hormone secreted from the pituitary gland is given, and a second blood sample is drawn an hour later. These blood samples are then sent to a lab to measure cortisol (steroid) levels. In normal dogs, there should be a rise in the cortisol level between the first and second sample. In Addisonian dogs, the cortisol level starts low and stays low despite the ACTH.
How is Addison's disease treated?
The main goal of therapy in these patients is providing them with a source of the hormones they are deficient in. Fludrocortisone (Florinef) is one of the drugs that your veterinarian may use. It is primarily a mineralocorticoid but also has some glucocorticoid activity. It comes in pill form and must be given daily. Desoxycortisone pivalate (DOCP) is an injectable mineralocorticoid that is given approximately every 25 days. Because this medication has no glucocorticoid activity however, daily cortisol supplementation such as prednisone will also be needed. Some dogs respond better to DOCP while others do well with Florinef so you and your veterinarian will decide which is the best medication for your pet. Since patients with Addison’s cannot produce enough cortisol on their own, it is necessary to provide extra supplementation during stressful events such as boarding, grooming, travel, etc. Your veterinarian will give you guidelines about this as well.
What about monitoring and follow-up care?
Once your pet has been diagnosed with Addison’s disease it will be important to see your veterinarian periodically to evaluate the electrolyte levels and kidney function. Keeping an eye on how they are doing at home is also important – are they eating well? any vomiting or diarrhea? Lethargy? Any sign of illness should prompt a phone call or a visit to your veterinarian. In the event that your pet is feeling ill and may be experiencing a relapse of their Addison’s disease, your veterinarian may also instruct you to give an extra dose of prednisone when you start to see any problems.
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