"Kilty” was a mischievous, five-year-old West Highland White Terrier. A credit to her thorough training as a pup, she was easy to handle. She usually “bounced” happily into the consult room and sat patiently on the table during her regular check-ups.
Today was different, "Kilty" was brought in as an emergency consult as she has been very ill overnight. She had been lethargic over the past few days and was off her food, which was very unlike her. She had no energy and seemed to be very wobbly and weak on her legs, and she had been sick and had dreadful diarrhoea. Her owner was extremely worried.
"Kilty" was admitted immediately into the clinic for hospitalisation, tests, and fluid therapy. Her tests revealed that she was suffering from a condition called Addison's disease.
Addison’s disease or hypoadrenocorticism is an uncommon disease of dogs involving the adrenal glands. This disease occurs when the adrenal glands don’t release adequate amounts of two critical corticoid substances that regulate essential body functions: Glucocorticoids and Mineralocorticoids.
The Symptoms of Addison’s Disease are: An increased thirst and urination; Vomiting; Diarrhoea; Weakness, Loss of appetite; Shivering and shaking; Abdominal pain; A weak pulse, and a notably slow heart rate.
Glucocorticoids (primarily cortisol) and mineralocorticoids are two important substances produced by the adrenal glands. Under normal conditions, the brain releases a hormone called adrenocorticotropic hormone (ACTH) that stimulates the adrenal glands to release these hormones.
Addison’s disease occurs when the brain doesn’t release adequate amounts of ACTH, or the adrenal glands are damaged and fail to release their hormones in response to the stimulating hormone ACTH.
Glucocorticoids and mineralocorticoids are essential to regulate numerous complex processes in the body and participate in critical functions such as: Maintaining the body’s fluid and electrolyte balance; Maintaining the integrity and functioning of blood vessels; Supporting heart function, blood pressure and blood flow to vital organs; Controlling blood sugar levels and carbohydrate metabolism; Helping counter the effects of stress and maintaining a functioning immune system.
In most cases, the primary cause is not determined. The disease can be caused by an immune-mediated destruction of the adrenal glands. The body’s own immune system can damage the adrenal glands’ cells so extensively that they cannot release hormones when they need to. Other less common causes include trauma, cancer, and infections.
Addison’s disease can also occur if a pet that is receiving regular steroidal medication suddenly stops getting this. The body has reduced its own cortisol production and cannot then increase it quickly enough to compensate when the steroid medication is suddenly discontinued. Therefore, any steroid medications (such as prednisone) should never be discontinued suddenly.
Addison’s disease is most diagnosed in young to middle-aged dogs, females are more commonly affected than males. The disease can affect dogs of any breed although some breeds seem to have a higher incidence, including toy and standard Poodles, Labrador Retrievers, Leonbergers, Great Danes, Rottweilers, and West Highland White terriers.
There are two types of Addison’s. The most common, or “typical”, form is due to a lack of both corticosteroids and mineralocorticoids, and this can be fatal. The less common, or “Atypical”, form, is due to a lack of corticosteroids alone. Whichever type, treatment is always needed.
To find a diagnosis of Addison’s disease may require repeated testing, but results of certain specific diagnostic tests can help support a diagnosis. Blood and Urine tests, and occasionally Abdominal imaging :X-rays and ultrasound, are required.
In dogs with typical Addison’s disease, tests may reveal Low Sodium and High Potassium electrolyte levels, an anaemia and persistent dehydration. An additional test called an ACTH stimulation test will also be done. ACTH is the hormone that the brain produces that stimulates the adrenal glands. In a dog with Addison’s disease, ACTH may be absent, or the adrenal glands may be unable to respond adequately to it. In dogs with Addison’s disease, the test does not result in any significant increase in cortisol levels and this response can be used to support a diagnosis.
Some cases of Addison’s can be seriously ill and can be brought is as emergency, collapsed cases. Usually known as an acute adrenocortical insufficiency, an “Addisonian crisis”. In such cases Low blood pressure, dehydration and impaired heart function can be fatal if not treated immediately and aggressively in hospital. In other cases, the clinical signs are less severe and can be much more subtle, and outpatient treatment and monitoring can begin.
The primary treatment for Addison’s disease consists of giving the body the adrenal hormones it has been unable to produce on its own. Cases of typical Addison’s are treated with a combination of corticosteroids (prednisolone), and mineralocorticoids available in pill and injectable formulations. The injectable mineralocorticoid fludrocortisone is usually given every 3 to 4 weeks, depending on the individual case.
Dogs who only lack the corticosteroids, “Atypical” cases, are only given prednisolone and are also monitored closely, as over time as they may need fludrocortisone too.
It is important to remember that these medications only replace missing hormones, they do not cure this disease and cases will need medication for the rest of their lives. Regular check-ups and periodic therapeutic check blood tests are needed, as sometimes dosages require adjusting. Your Vet will also discuss modifying your pet’s medication during times of any stress, when the body’s need for glucocorticoids may increase.
Fortunately, dogs that receive advised correct treatment for Addison’s disease can have normal life spans and enjoy a good quality of life.
Thankfully, lovely “Kilty” was stabilised and settled onto her advised treatment and was discharged home. She was soon happy and "bouncy" again, and her owners were delighted. She would now require regular check-ups and periodic Blood tests to make sure that she was kept stable on her treatments.
If your dog has any of the symptoms described, please arrange for a thorough check up at your Vet. The earlier that this disease is diagnosed the better.
Alison Laurie Chalmers
Senior Consultant
Crown Vets