What is Addison’s Disease in Dogs?

Addison’s disease is anendocrine or hormonal disorder in dogs that affects their adrenal glands. These glands are responsible for the release of important hormones like cortisol, a stress hormone, and aldosterone, a hormone that helps regulate levels of potassium and sodium in the body. 

Addison’s disease is also known as hypoadrenocorticism because the adrenals release too-low levels of these hormones. Too-high levels of cortisol and aldosterone are caused by the opposite condition – hyperadrenocorticism or Cushing’s disease.

Addison’s commonly affects young to middle-aged dogs, more females than males, and the average age of onset is four years old. Breeds like Labrador Retrievers, Standard Poodles, Bearded Collies, and Portuguese Water Dogs have a higher genetic predisposition for the disease.

Addison’s is mostly caused by an autoimmune response, which means that your dog’s immune system can attack the adrenal glands and cause disease. In some cases, infection and trauma can result in Addison’s, and adrenal gland tumors can significantly affect the way that the adrenal glands function.

Pet owners should be wary of Addison’s when it comes to certain medications. If your dog has Cushing’s disease, your vet may prescribe an oral medication known as trilostane or Vetoryl. Careful monitoring is necessary to ensure that your dog does not overdose.

If he takes too much trilostane, his adrenal glands may become suppressed which results in clinical signs for Addison’s disease. Abrupt cessation of an oral steroid like prednisone can also cause signs of Addison’s, although this condition is only temporary.

Addison’s can be tricky to diagnose because there are a wide variety of symptoms, and these signs can wax and wane over time. Lethargy, vomiting, diarrhea, increased thirst, and increased urination are the most common signs. Because of his gastrointestinal upset, your dog may have a poor appetite.

He will slowly lose weight and his muscles will start toatrophy or shrivel, resulting in an underweight body condition score. He may have a slow heart rate and a weak pulse. Addison’s patients tend to have very dry, brittle hair coats and develop moderate to severe dehydration.

If your dog has any of the above clinical signs, make sure to schedule an appointment with your veterinarian right away. She may recommend several different tests in order to rule out other underlying causes for your dog’s illness.

Routine blood work might show low amounts of sodium and high amounts of potassium because there is not enough aldosterone to prevent sodium from being excreted from the body. Blood values associated with the kidneys tend to be elevated, and white blood cells will be elevated if there is an infection. Anemia is also common, which means that the red blood cell count will be low.

With your dog’s clinical history and lab findings, your vet will recommend a special blood test known as the ACTH stimulation test. A blood sample is taken from your dog before a synthetic hormone known as adrenocorticotropic hormone (ACTH) is administered. 

About an hour later, another blood sample is taken. In a healthy dog, the administration of ACTH will cause the adrenal glands to release cortisol into the bloodstream. Dogs with Addison’s disease will have little to no response to the ACTH, and so their cortisol levels will remain low.

Imaging can also help diagnose Addison’s disease. The adrenal glands may be difficult to evaluate with x-rays because the glands are very small. Ultrasound is useful because it can locate the adrenal glands and look for the presence of tumors or overall size changes. Advanced imaging like CT and MRI can help rule out tumors in the pituitary gland at the base of the brain.

Dogs who are acutely ill may require hospital care such as intravenous fluids, antibiotics, and steroid therapy. Once confirmatory test results are received, your vet will go over long-term treatment.

Two kinds of steroids are necessary for dogs with Addison’s disease: mineralocorticoids and glucocorticoids. Aldosterone is a mineralocorticoid, and this is supplemented in the form of a long-acting injection known as desoxycorticosterone pivalate or DOCP. It is injected by your veterinarian every three to four weeks depending on your dog’s overall response to it.

Cortisol, which is a glucocorticoid, is supplemented by administering oral prednisone once a day. Because it is a low dose, your dog won’t have any of the side effects commonly associated with steroid administration such as increased thirst and urination and increased appetite.

Once treatment is initiated, your dog will need to be rechecked after the first ten days and then again one month later. His blood values will need to be checked to make sure that his sodium and potassium go back to normal. As his hormone values stabilize, your dog will gain weight, have a healthier coat, and his other clinical signs will resolve.

There is no cure for Addison’s disease, but with regular monitoring and treatment, your dog can live a normal life. Dogs who undergo treatment for Addison’s disease usually have a good to excellent prognosis. If the underlying cause is related to a tumor, your dog will require further care and may need to see a specialist for further treatment options.

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Addison’s disease is a hormonal disorder that is usually caused by autoimmune disease. It can be difficult to detect right away due to its vague clinical signs, but once testing confirms it, treatment is often highly successful.

Regular visits to your vet and routine lab work are essential for monitoring and making sure that your dog’s hormone levels are balanced. If your dog is experiencing lethargy, vomiting, diarrhea, increased thirst, and/or increased urination, be sure to make an appointment with your vet right away!    

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