By Dr Ananya Mandal, MD
Addison’s disease is seen in humans but has been seen in some breeds of dogs and cats as well. This condition is relatively uncommon in dogs and is considered rare in cats.
Female dogs that are young to middle-aged are more likely to present with this uncommon condition. However all ages, both genders of dogs as well as cats have been diagnosed with Addison’s disease. Both intact and neutered animals have been detected with this condition.
Some breeds of dogs that are more likely to get Addison’s disease include the Portuguese water dog, standard poodle and the bearded collie. All breeds including mixed breeds may be diagnosed with this condition.
What causes Addison’s disease in animals?
In dogs when the cortex of the adrenal gland fails to produce steroid hormones like cortisol and aldosterone, a primary adrenal insufficiency develops. This is called Addison’s disease and is named after a 19th Century physician who first described the condition in humans.
In normal animals these hormones are produced by the adrenal glands that are which are located just in front of the kidneys. Cortisol is vital for the functioning of the body as it regulates several actions.
Cortisol production is regulated by hormones produced in the brain from the pituitary gland. These hormones stimulate the adrenal glands. When the adrenal glands receive the signal from the pituitary they produce cortisol. Cortisol gears up the body for stress.
Aldosterone helps in maintaining the salt and water balance in the body and regulates the blood pressure. Aldosterone signals the kidneys to keep the sodium and excrete potassium. When aldosterone production declines the blood pressure and blood volumes drop drastically.
Causes of Addison’s disease in animals
Addison's disease results from damage to the adrenal glands. The destruction takes place in the outer layer of the adrenal glands called the cortex. The body’s own immune system may fail to recognize the cortical cells and attack them. This is called an autoimmune disease.
Symptoms of Addison’s disease in animals
Early symptoms are usually difficult to detect and may go unnoticed. This condition usually affects younger dogs and females are more at risk than males. Repeated bouts of vomiting and diarrhea in the pet are an early indication of the condition in some dogs.
There is a long term fatigue and muscle weakness along with loss of appetite and weight loss. The animal appears lethargic, drowsy and confused. There may be symptoms of increased thirst and increased urination especially at night. In some young dogs and toy breeds there may be an added problem of low blood sugar. Females usually miss their season.
If untreated and undetected an Addisonian crisis may occur. There is severe vomiting or diarrhea following which there is a circulatory collapse.
Addison's disease is treated using cortisol and aldosterone replacements. Oral steroid tablets (prednisone, prednisolone, dexamethasone) are prescribed to replace cortisol.
For aldosterone replacement DOCF injections or ludrocortisone acetate tablets may be prescribed.
For treatment of an Addisonian crisis admission and supportive management on an urgent basis is warranted. Immediate intravenous injections of hydrocortisone and a saline drip is indicated.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)