Hypoadrenocorticism (Addison's Disease)

What is Addison's Disease?

Addison's Disease is caused by an immune mediated destruction of the adrenal gland. The underlying cause is unknown.

The adrenal glands are responsible for the production of 2 types of hormones:

1: Glucocorticoids - which are responsible for regulation of many body functions and also include the ‘stress’ hormone cortisol.

2: Mineralocorticoids - which are responsible for mineral balance in the body.

Affected animals are normally deficient in both of the above types of hormones.

Addison's is considered rare in dogs and even more so in cats. Certain breeds are considered to be predisposed and it is generally more prevalent in females.

What are the symptoms of Addison's Disease?

Animals affected with Addison's Disease can have one of two broad clinical presentations:

1)    Acute (sudden) Addisonian crisis – animals will generally present collapsed and in ‘shock’ with a low heart rate. They may have a history of intermittent vomiting/diarrhoea/lethargy etc or may present for the first time in such a crisis. Such episodes are considered to be life threatening and aggressive emergency treatment is required.

2)    Chronic disease – animals will often have a vague history of intermittent lethargy/shaking, inappetance (decreased appetite), vomiting, diarrhoea, changes in water consumption and weight loss.

How is Addison's Disease diagnosed?

Depending upon the history your vet may have a suspicion that Addison's Disease could be responsible for the clinical signs seen in your pet. However, in chronic cases where symptoms can be very vague it is sometimes detected on routine screening tests.

There are sometimes telltale signs found on routine blood screens, such as abnormal electrolyte levels or changes in the white blood cells (cells responsible for inflammation) however changes can be varied and inconsistent.

The definitive test for Addison's Disease is called an ACTH stimulation test. If your vet has a suspicion that your pet may be affected by this disease, this test will be used to confirm it.


How is Addison's treated/managed?

Animals suffering from an acute Addisonian crisis require emergency treatment, primarily in the form of fluids and intensive nursing care, but may also need additional medications to stabilise them in the short term.

Long term treatment involves supplementation of the deficient hormones.

All animals will require lifelong supplementation of the mineralocorticoid component either using tablets or monthly injections. Most animals also need additional glucocorticoid treatment, especially at times of stress e.g. boarding, moving house etc.

In the short term affected animals will need regular appointments (every 1-2 weeks) to monitor their clinical response to treatment and also to monitor their electrolyte levels etc. Dose changes are likely in the early stages while the appropriate dose for each individual animal is found.

Once animals are stable we recommend rechecks and a blood test every 3 months.

What is the prognosis?

Assuming aggressive and early treatment is instigated (especially in the case of an Addisonian crisis) dogs will normally respond very well. The disease has a good prognosis following proper stabilisation and treatment. It is important, however, to continue to monitor animals closely as dose changes may be required and relapses can occur.