What is Addison’s Disease?
The correct medical term for this disease is Hypoadrenocorticism.
This term means that there is diminished or lowered hormone production from the outer part or cortex of the adrenal gland.
What 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 and are necessary to sustain life. The most widely known of these substances is cortisol, commonly called cortisone, produced by the outer part of the adrenal cortex. Also produced by the cortex and equally important is aldosterone which is a mineralocorticoid hormone. This hormone regulates the electrolyte and water balance of the body and is involved in the excretion of potassium and retention of sodium.
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 direct injury to the tissue due to haemorrhage, infection or certain auto immune conditions.
Thus primary hypoadenocorticoism can be immune mediated. It can also sometimes occur when treating Cushing’s Disease which can be thought of as the opposite situation (hyperadrenocorticism) where too much cortisol and aldosterone are produced.
Addisons disease can also occur if a dog has been treated with cortisone for any reason on a long term basis and this is suddenly withdrawn. Another cause can involve the pituitary gland in the brain.
What are the clinical signs?
Signs are usually vague and non-specific. They are commonly 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 are also characteristic.
These animals will often respond to non-specific medical intervention, for example the administration of fluids by injection and also administration of corticosteroids.
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 hospitalisation will be necessary for a short time.
How is it diagnosed?
Laboratory tests are necessary, often involving serial blood samples. Your dog will probably have to 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, more recently, injections. Diet and activity levels do not usually have to be materially 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 both the glucocorticoids and mineralocorticoids 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. In addition we will have to see your pet at fairly frequent intervals to check that stabilisation is satisfactory. This may involve further blood tests.
If you wish to discuss long term costs, please do not hesitate to contact us.
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.