Pet Health Articles

Addison's Disease

diagram of a dog with addison's diseaseWhat is Addison’s disease?

The medical term is hypoadrenocorticism. The term indicates diminished or lowered hormone production from the outer part (cortex) of the adrenal gland.

What and where are the adrenal glands?

The adrenal glands are paired glands situated adjacent to the kidneys. Each gland essentially consists of an outer cortex and an inner medulla. The glands produce several vital substances which regulate a variety of body functions that are necessary to sustain life. Cortisol, commonly called cortisone, produced by the adrenal cortex, is probably the best known adrenal hormone. Also produced by the cortex and equally important is aldosterone. This hormone regulates the electrolyte and water balance of the body and is involved in the excretion of potassium and retention of sodium by the body.

Deficiency of this hormone together with cortisol is referred to as Addison's disease.

What causes the disease?

In the dog the main causes are usually the result of injury to the adrenal gland. This can be due to haemorrhage, infection or auto immune conditions.

"In the dog the main causes are usually the result of injury to the adrenal gland. This can be due to haemorrhage, infection or auto immune conditions."

Addison’s disease can also sometimes occur when treating Cushing’s disease. This can be thought of as the opposite of Addison’s disease. With Cushing’s disease (hyperadrenocorticism) too much cortisol and aldosterone are produced. 

Addisons disease can also occur if a dog has been treated long term with cortisone and this is suddenly withdrawn. Another cause can be dysfunction of the pituitary gland in the brain.

What are the signs of Addison’s disease?  

These signs are usually vague and non-specific. Signs are often seen in animals with more common medical disorders, for example, chronic gastroenteritis or renal diseases. There may be vomiting and weight loss. A waxing and waning course with diarrhoea, sometimes increased thirst and urination is not unusual. Intermittent shaking episodes also occur.

Patients will often respond to non-specific medical intervention, e.g. the administration of fluids by injection or corticosteroids.

Addisonian crisis

Sometimes the condition takes on a much more acute form. There is sudden weakness, vomiting and diarrhoea, sometimes with collapse. This is an Addisonian crisis. Under these circumstances urgent veterinary attention and hospitalisation may be necessary.

How is it diagnosed?  

Laboratory tests are necessary, often involving serial blood samples. Your dog will probably have to be admitted for the day for the necessary tests. 

What does treatment involve? 

Once diagnosis has been positively established most dogs can be successfully stabilised with oral treatment usually in the form of tablets or a combination of injections and tablets.

Diet and activity levels do not usually have to be altered.

In the majority of cases even following an Addisonian crisis the condition can be stabilised.

It will be necessary to monitor progress carefully, particularly at the start of treatment and this may involve occasionally staying with us for the day. 

It must be emphasised that lifelong replacement of the deficient hormones may be necessary. Some of these tablets may have to be increased during periods of stress, such as when travelling or if the dog is kennelled or has to undergo surgery. We will have to see your pet at fairly frequent intervals to check stabilisation is satisfactory. This may involve further blood tests.

Prognosis

The vast majority of patients with Addison’s disease have a good to excellent prognosis once the diagnosis has been established and they have been stabilised with the appropriate drugs. Please do not hesitate to contact us if you have any questions or concerns.

Trevor Turner, BVetMed, MRCVS, FRSH, MCIArb, MAE. Adapted by Philip H Brain, BVSc, CMAVA, FACVSc (small animal medicine), FAVA
© Copyright 2016 LifeLearn Inc. Used and/or modified with permission under license.