Small Animal Referral Hospital Hypoadrenocorticism (Addison’s Disease)

• Hypoadrenocorticism is steroid hormone deficiency - dogs may be deficient in one or more steroid hormones
• Treatment with steroid hormone replacement is needed lifelong
• The prognosis is usually excellent so long as appropriate treatment and monitoring are maintained

Hypoadrenocorticism is a disease of steroid hormone deficiency.

In health, steroid hormones are made in the adrenal glands (near the kidneys in the abdomen). Important steroid hormones include:

• Cortisol - this has important roles in most cells in the body, including maintaining appetite, gastrointestinal health, nerve and muscle function and blood cell production. Cortisol deficiency commonly causes lethargy, inappetence, vomiting, diarrhoea, weight loss and weakness.
• Aldosterone - maintains normal blood electrolyte (sodium and potassium) levels and normal blood volume. Aldosterone deficiency results in poor circulation and high levels of blood potassium which can cause a slow heart rate and risk of heart rhythm disturbance, resulting in lethargy, weakness and collapse.

Hypoadrenocorticism most commonly occurs due to immune-mediated destruction of the adrenal glands, which results in deficiency of cortisol and/or aldosterone.

Clinical signs in patients with hypoadrenocorticism can be highly variable and include intermittent inappetence, regurgitation or vomiting, diarrhoea, weight loss, exercise intolerance, lethargy and episodes of collapse.

Treatment is lifelong and requires replacement of the hormone deficiencies.

Aldosterone is replaced with desoxycortone pivalate (DOCP) - this is given as a subcutaneous (under the skin) injection on a regular basis. The dose needed is variable between different dogs - fairly regular (every 2 weeks or so) blood tests are required for the first 2-6 months’ of treatment to establish the correct dose and interval of DOCP injections. On average the injection lasts approximately 4-6 weeks. Once the dose is established, monitoring blood tests are reduced to every 3-6 months’, although regular veterinary appointments are needed for the DOCP injections.

Cortisol is usually replaced with prednisolone tablets - these are usually started at a moderate dose, which is reduced over the first few weeks of treatment to a longer term daily maintenance dose. The most common side effects of prednisolone are increased appetite, drinking, urination and lethargy - these should not occur at the doses needed to treat hypoadrenocorticism. If these occur, the dose is too high - please liaise with your veterinary surgeon for a more suitable dose.

During times of stress the body usually makes cortisol. Dogs with cortisol deficiency cannot do this. In order to compensate for stressful events, the prednisolone dose should be doubled on anticipated stressful days - examples include time in kennels or during other illness.

The prognosis for dogs with Addison’s disease is excellent, with many dogs experiencing a normal quality and longevity of life, so long as they receive their medication and are monitored appropriately.

Dogs may be deficient in one (usually cortisol) or both hormones at the time of diagnosis. Some dogs who only have one hormone deficiency will develop deficiency in the other hormone in the future – there is no test that can predict this, but if your dog develops any clinical illness (particularly inappetence, vomiting, diarrhoea, lethargy, weakness, collapse) then immediate veterinary attention to test for the other hormone deficiency is required.