Ron Hines DVM PhD 4/24/06

I will try to tell you some things about hypoadrenocorticism -- a long word for a comparatively simple, if serious, disease also known as Addison's disease. Both you and your dog have two, lima bean shaped organs that lie just ahead of your kidneys. These are called the adrenal glands. Although they are small, they are very important organs that you cannot live without. They are a creamy strawberry pink in color. The outer layer of these glands is called the cortex. It is responsible for producing cortisol (glucocorticoids), hormones that helps your body deal with stres and mineralcorticoids that regulate the quantity of potassium and sodium in the bloodstream. Cortisones decrease inflammation, suppress the immune system, increase the production of fat and decrease the number of certain white blood cells called lymphocytes. The inner portion of the gland or medulla produces a hormone called epinephrine “the fight or flight” hormone. This hormone is secreted in stressful situations to increase your heart rate, blood sugar and to speed blood clotting. It increases blood flow to muscles of the legs and arms but decreases blood flow to other organs – all these changes occur so you can fight or run away.

I am going to call hypoadrenocorticism Addison’s disease because it is easier to write and say. It is not a common disease but when it does occur it is primarily in young or middle-aged female dogs. Usually, it is only the outer portion of the adrenal glands that are effected. In most cases the problem is within the adrenal glands themselves (primary Addison’s disease). Less frequently, a messenger hormone (ACTH) from the brain cease to flow adequately to the adrenal glands to activate them. We think that primary cases are a form of autoimmune disease in which the body mistakenly attacks its own tissues. Autoimmune disease may appear spontaneously or be triggered by something as innocuous as a vaccination. Secondary Addison's disease can occur in dogs that were receiving cortisol replacements (prednisone, prednisolone) that were suddenly discontinued.

Signs of Addison’s Disease in Dogs:
Generally, the disease begins very gradually and it is very easily missed in its early stages. Because of this, it is quite rare for me to make this diagnosis on my first examination of the dog. Case histories of Addison’s disease are signs that could have numerous other causes. These signs include failure to eat (anorexia), vomiting, weakness, hair loss, painful tummy, bloody stools, slow heart rate, trembling, low body temperature, collapse, diarrhea, dehydration, and depression that come and go. Many pets have heart irregularities and low blood pressure. Frustratingly, most of these dogs with mild signs improve with almost any treatment as long as the stressful situation passes. However, sooner or later the dogs are presented to me with similar signs that have reoccurred. When I am lucky, owners associate these signs with a distressful event in the dog’s life – such as a party, a trip or being boarded or groomed.
Blood results from pets with this condition often show dehydration, an increase in kidney waste products (azotemia, uremia), metabolic acidosis (too acidic a body) elevated blood potassium (hyperkalemia in 95% of cases), low blood sodium (hyponatremia) and occasionally elevated blood calcium. Urine specific gravity is low in seventy-five percent of the cases.

Diagnosing Addison’s Disease:

Blood drawn from dogs with Addison’s disease is deficient in cortisol. Most cases I have seen were primary adrenal gland disease. In these cases, when a brain chemical (ACTH) that stimulates the adrenal gland is given by injection, serum cortisol does not rise. This is called an ACTH stimulation test. In cases where the root problem is the brain, ACTH blood levels are elevated (secondary Addison’s disease). A screening test for hypoadrenocorticism, the urinary cortisol/creatinine ration, can also be helpful in diagnosing the disease.

Treatment of Addison’s Disease:

A full-blown case of Addison’s collapse is frightening and can be life threatening. It must be treated immediately with large amounts of intravenous saline (salt) solution and injectable synthetic cortisol (dexamethasone 1-3mg/lb, prednisolone 8-15 mg/lb). These dogs are often presented to me in a coma. Once we have gotten them over their acute episode, they can often be maintained on only 0.1mg/lb/24-48 hours of prednisolone or prednisone. This can be given orally as soon as the pet is no longer vomiting and having diarrhea. When dogs are stressed, the dose needs to be increased two to ten times the normal amount. When blood potassium is significantly elevated we also supplement these pets with fludrocortisone acetate (Florinef, Squibb) at about 1 microgram/pound given orally every day to keep serum salts in balance. Another drug that accomplishes the same thing is deoxycorticosterone pivilade (Percorten V). It has the advantage of only having to be injected every month at the same dose.

Some dogs also need to receive bicarbonate of soda by injection or orally to nutrilize acid. Addison's disease is treatable but not curable. Some breeds develop this disease more commonly than others. We call this predisposition. These breeds include Portuguese Water Spaniels, Great Danes, West Highland White Terriers, Rottweilers, Standard Poodles, and Wheaten Terriers. Please do not breed dogs that have a tendency to this condition.

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