Atypical Addison's Disease in Dogs

Atypical Addison’s disease can be difficult to diagnose because the symptoms are so vague and even if your veterinarian suspects your dog has Addison’s, his electrolytes will be normal so it may go unnoticed. Even though atypical Addison’s disease only affects the cortisol, this hormone affects many important functions in your dog’s body such as regulating certain white blood cells, decreasing inflammation, keeping glucose levels stable, and monitoring fat production.

If you believe your dog has atypical Addison’s disease, insist that your veterinarian do an ACTH stimulation test to be sure. With the ACTH stimulation test, the veterinarian should be able to see a decreased level of cortisol both before and after the injection of synthetic ACTH.

Addison’s disease in dogs is a regulatory process malfunction in the corticosteroid secretion from the adrenal glands. The adrenal glands are the small hormone-producing glands on top of the kidneys. In atypical Addison’s disease, only certain layers of the adrenal cortex are affected rather than the entire adrenal gland. The top layer (zona glomerulosa) still functions in atypical Addison’s disease, which is the part that makes the aldosterone. This is what controls the sodium and potassium levels so your dog’s electrolytes are not usually affected like they are with primary and secondary Addison’s disease.

The signs of atypical Addison’s disease are often vague and may be overlooked. Many times, the signs mimic other illnesses so your dog may get misdiagnosed several times before getting the right diagnosis. Some of the common signs of atypical Addison’s disease are:

• Increased thirst and urination
• Slow heart rate
• Weak pulse
• Diarrhea
• Vomiting
• Weakness
• Sleepiness or lethargy
• Loss of appetite
• Weight loss
• Abdominal pain
• Shivering or shaking
• Dehydration
• Shock (low blood pressure, cold extremities, extreme lethargy, and collapse)

Types

There are three types of Addison’s disease, which include:

• Atypical Addison’s disease only some parts of the body are affected so you may not see as many symptoms
• Primary Addison’s disease is the most common form of Addison’s and is due to an abnormal decrease of hormones from the adrenal glands
• Secondary Addison’s disease is caused by a lack of pituitary gland function

Although the cause of atypical Addison’s disease is not completely understood, many veterinary care providers believe damage to the adrenal gland is the issue. They believe it may be from destruction of the adrenal gland by using an adrenal enzyme inhibitor (trilostane), adrenolytic agent (mitotane), infarction, hemorrhages, metastatic tumors, or a granulomatous disease. Certain breeds of dogs are more susceptible than others such as:

• West Highland White Terriers
• Great Danes
• Wheaten Terriers
• Standard Poodles
• Retrievers
• Portuguese Water Dogs

A physical examination will be done first, after getting your dog’s medical history and shot records. The veterinarian will check your dog’s vital signs, overall condition, and perform a palpation and auscultation analysis. Diagnostic testing is done next, which includes laboratory tests and imaging.

The most important tests your veterinarian will do are an ACTH-stimulation test to check cortisol levels, thyroid test to check thyroid function, and EKG to check the heart rhythm. Chemical blood tests to evaluate the function of the pancreas, liver, and kidneys, glucose (sugar) levels, blood count, antibody tests to check for infection, urinalysis, electrolyte tests, x-rays, ultrasound, and possibly a CT scan or MRI may be suggested.

If your dog is in shock, the veterinarian will most likely give him dexamethasone intravenously. If not, the veterinarian will give your dog an injection of prednisolone or another drug and treat him with fluid therapy as well as other miscellaneous treatments that are needed.

Medications

Besides the prednisolone injection, the veterinarian may also administer desoxycorticosterone pivalate (DOCP), which only needs to be injected once a month. The veterinarian will give your dog the lowest dose possible to treat the clinical symptoms to reduce chances of side effects such as Cushing’s disease.

Fluid Therapy

To prevent dehydration, fluids and electrolytes will be given intravenously. This will also regulate your dog’s electrolyte levels, if needed, and increase circulation.

The majority of dogs with atypical Addison’s disease can resume their normal lives with treatment. You may need to give your dog cortisol or DOCP on a regular basis for the remainder of his life.

There will also be situations in which your dog may need to have increased doses of medication such as stressful times like surgery, boarding, and traveling. Of course, you should never increase your dog’s medication without approval from the veterinarian. In addition, your dog will need to see the veterinarian on a regular basis for laboratory tests and a physical examination. Call your veterinarian if you have any questions or concerns.