Some diseases that affect our pets are relatively easy to diagnose just based on their symptoms. For example, just as with people, diabetic animals often are drinking more water, urinating large amounts, and losing weight despite having a normal appetite. Unfortunately, life isn't always that simple. Addison's disease, which can affect both animals and people (John F. Kennedy is a famous example), is nicknamed "the great pretender" because its symptoms are very nonspecific. For example, two of the most common symptoms seen are intermittent vomiting and diarrhea. Well, there are, say, about 200 potential things that can cause those symptoms, so that is not exactly helpful!

Addison's disease is officially known as hypoadrenocorticism. It occurs when the adrenal glands, which are two small glands located just above the kidneys, stop producing their normal hormones. There are two very important hormones produced by the adrenals: cortisone, which is required for almost all of the organs in the body to function properly, and aldosterone, which controls the levels of electrolytes such as potassium in the body. This is a vital function too, because too much potassium can cause death by stopping the heart. Addison's disease is most commonly seen in middle aged dogs but it can occur at any age. The disease does occur in cats but it is extremely rare (oddly enough, I do happen to have a feline patient who is Addisonian!). No one knows what causes the adrenal glands to suddenly stop functioning; one theory is that some kind of infection damages the glands, but this has not been proven.

The good news about Addison's disease is that while it cannot be cured, it can be very successfully managed with medication and patients can go on to lead a normal, healthy life. The bad news about Addison's disease is that while there is a relatively simple test that can be used to diagnose it, it's symptoms are so vague and nonspecific that it might take some time to think that it may be the root cause of all of your patient's symptoms and that you should go ahead and run the test. There are some clues that can show up on a routine blood panel that are suggestive of Addison's disease, but unfortunately they are not always present.

As an example, our most recent Addisonian patient is a 3 year old Standard Poodle named Sultan. Sultan's main symptom was significant unexplained weight loss. He had really not had much problem with vomiting or diarrhea, and he had two blood panels run in the span of a few weeks that were both normal.

"Typical" Addisonians will have elevated blood potassium levels and decreased sodium levels on routine blood panels (because of the lack of aldosterone to regulate their electrolytes), but like I mentioned above, not all patients will have this pattern. Sultan had a full battery of tests trying to determine the cause of his weight loss that were all negative, so finally we decided to test him for Addison's disease, mostly because he is a Standard Poodle (Addison's disease is common in this breed for unknown reasons). His test for Addison's disease came up positive so we were able to start him on his medication, and he is now feeling much more like his usual cheerful self. That is one gratifying thing about Addison's disease that we can take a dog who feels miserable and make them feel much better in a short period of time. Sultan will need to be on his medication the rest of his life, but as long as he remains on his medication he should not suffer any long-term effects from his disease.