Addisonian Disease in Animals
March 21, 2011
This disease is most correctly termed hypoadrenocorticism in animals—a complex word for an equally complex disease!
Addisonian Disease is a hormonal deficiency that results from the reduced production of certain hormones released from the adrenal glands, a pair of small but very important structures that are located at the tip of each kidney. There are two major classes of hormones that can be affected, the glucocorticoid (cortisol) and the mineralocorticoid (aldosterone) hormones. The signs of this condition in dogs and cats vary considerably depending on how much of each hormone is missing. Certain dog breeds such as Standard Poodles, Rottweilers, Westies and Great Danes appear to have increased risk of developing this condition. This is a fairly uncommon condition in dogs, and is very rare in cats.
Common symptoms of this disease include vomiting, loss of appetite, lethargy, weight loss and increased thirst and urination (PU/PD). In dogs, bloody diarrhea sometimes occurs. In a severe crisis, the animal may collapse, have a low body temperature, a weak pulse, and dehydration. The blood electrolytes such as sodium, potassium and chloride are often out of balance as well. Blood sugar levels may also be reduced and nitrogen wastes may accumulate in the bloodstream.
The reduced hormone production may result from adrenal gland malfunction (termed Addison's disease in humans) or from low stimulation hormone production in the pituitary gland of the brain, which is the master controller gland for the adrenals. That brain hormone, adrenocorticotrophic hormone (ACTH) stimulates adrenal gland hormone release after it travels through the bloodstream.
The history and the physical examination are helpful for identifying the effects of hypoadrenocorticism, but the diagnosis is confirmed by examining blood counts, blood chemistry and electrolyte levels, and performing an ACTH stimulation test. In healthy pets, ACTH administration causes increased blood cortisol hormone levels. In afflicted pets, there will be reduced levels before and after the ACTH test. Sometimes X-rays are also helpful to check for reduced heart size, another potential effect of the hormone deficiency.
Your veterinarian will design a treatment program based on the severity of the signs and the source of the problem (pituitary or adrenal gland). Therapy consists of supportive care in a very ill patient and replacement hormone therapy for life. These prescribed hormones must often be increased if the pet is stressed. It is very important that changes in dosages are prescribed and overseen by your veterinarian. Follow up monitoring is essential and all prescriptions should be carefully adhered to. Many pets carry on with a normal life once this condition is stabilized.