Canine Hypoadrenocorticism (more commonly known as Addison's disease) is the medical dysfunction of the adrenal gland whereby it does not produce enough of a steroid hormone, namely 'aldosterone' or 'cortisol'. The lack of this hormone means that the levels of the potassium and sodium in the blood are not balanced correctly and as a result can cause serious health complications for a dog.

The most frequently occurring reason for the development of Addison's disease is when a dog's immune system damages the adrenal gland tissue; unfortunately there has been no medical evidence to date to suggest why this happens.

Dogs that cannot produce the adrenocorticotrophic hormone (ACTH) will also suffer from Addison's disease. This is because ACTH stimulates the adrenal gland which in turn produces cortisol.

Another cause of this disease can be related to medication. If a dog is put on medication containing steroids then its adrenal gland will stop its natural production of aldosterone or cortisol. Once the course of steroids stops, it can take up to several weeks for the dog's adrenal gland to start naturally producing steroid hormones again. As a result, the dog may develop Addison's disease for a period of time. This is why it is imperative to gradually decrease the dosage rather than to just abruptly stop the course of steroids altogether.

This disease generally occurs in young to middle-aged canines with 70% of cases being female. It can affect any kind of dog but there are certain breeds in which it is found in more than others. These include Poodles, Great Danes, Bearded Collies, Portuguese Water Dogs and Soft Coated Wheaten Terriers.

Most of the symptoms of this disease are considerably vague as they tend to indicate other diseases or illnesses may be present. Such symptoms include vomiting, sickness, lethargy, a loss of appetite, increased thirst, muscle weakness/tremors, trembling and shivering. These symptoms may not occur that frequently and so it can be hard to trace them to Addison's disease.

However, in some cases a dog suffering from Addison's disease may experience what is known as an Addisonian crisis. This occurs when there are extremely high levels of potassium in the blood which disrupts the normal functions of the heart. As a result, the dog will collapse and remain unable to respond or get up even though it is conscious. Bouts of diarrhoea and sickness may occur whilst the dog's pulse will be light and its heart rate slow. If this happens then it should be treated as a medical emergency and the dog should be taken to the nearest vet immediately.

As so many of the symptoms can indicate another illness other than Addison's disease, there are various tests that have to be completed to eliminate the possibility of any such illness. Initially, the complete medical history of the dog will be looked at. Then a urine test will be undertaken to check that there is no glucose present (if there was then it would indicate that the dog has diabetes).

A complete bloodworks profile will be implemented; particularly looking at the levels of sodium and potassium and kidney functions. If the sodium levels are low, the potassium levels are high and the ratio (this worked out by dividing the potassium levels into the sodium levels) between the two is low (lower than 27), then it usually indicates that Addison's disease is present in the subject.

Once the urinalysis (urine test), blood count and biochemistry tests have been completed and all other possible causes of the dog's illness have been eliminated, an ACTH stimulation test will be performed. The dog's cortisol levels are measured. Then the dog is injected with a synthetically produced ACTH to make the adrenal gland produce cortisol. An hour later the cortisol levels are checked again. If there is no rise, or a minimal rise of the level of cortisol in the blood, then it concurs that Addison's disease is present.

There are two types of treatment for the effect that Addison's disease can have on a dog, Firstly, if a dog is taken to the vet as a result of an Addisonian crisis then the dog will be put on an IV of saline (salty water) to improve circulation and rehydrate the canine. This a short-term treatment to get the dog back to health quickly.

Once the dog has been diagnosed with Addison's disease the long-term treatment comes in the form of medication that shares the same properties as aldosterone, such as 'fludrocortisone acetate'. The dog's sodium and potassium levels will be tested a week after the initial dosage has been taken. This is to check what affect the medication is having on the dog and the dosage may be altered. Tests will continue to be taken for the next few weeks until the right dosage is found.

A positive to be taken from this disease is that with most cases the dog has returned to normal with treatment and even those that have not gone back to normal have had a high quality standard of life.

Please be aware that this post is for advice purposes only and should not be read as a medical document. If you are worried about your pet then please contact your local veterinarian.