Addison's Disease in Dogs (Hypoadrenalcorticism)
Addison's disease is a condition in which the adrenal glands are not functioning properly. There is one adrenal gland located near each kidney (two glands total). An adrenal gland's job is to secrete hormones called cortisol and aldosterone which help the body deal with stress, maintain normal body functions, and regulate hydration and electrolytes. When there is a deficiency in these hormones, the disease is called Addison's disease or hypoadrenalcorticism.
Addison's disease may be caused by an autoimmune disorder, tumor, or quick withdrawal of steroid medication. Addison's disease can happen to any dog, but most cases are young adult females.
Clinical signs of Addison's disease initially can be very vague. Unfortunately, most pets are not diagnosed until they are acutely and severely ill (this is term an "Addisonian crisis"). Symptoms may include: lethargy, weakness, collapse, loss of appetite, excessive drinking and urinating, diarrhea, and vomiting.
Addison's disease is diagnosed by doing a physical exam and bloodwork. Standard bloodwork will help your veterinarian assess your dog's sodium and potassium levels and rule out other causes of illness. If Addison's disease is suspected based on this initial test, then an ACTH stimulation test is performed. An ACTH stimulation test is a means of measuring your pet's baseline cortisol level and how your pet's adrenal glands respond to stimulation. A blood sample is drawn first, then your pet is given an injection of medication that simulates your dog's natural ACTH hormone. Under normal conditions, ACTH signals the adrenal glands to produce cortisol when your dog's body requires it. Two hours after the injection, your dog's blood will be sampled again and compared to the first sample to see if the adrenal glands are functioning.
Dogs in Addisonian crisis will need immediate hospitalization and aggressive treatment to provide electrolytes, fluids, and other supportive measures. If the dog stabilizes, then life long medications are required. Periodic bloodwork is also necessary as medication doses and needs will change over time.