Addison's disease, or primary hypoadrenalism, is an uncommon condition characterised by a deficiency of glucocorticoid and mineralocorticoid steroid hormones usually produced by the adrenal glands. The condition often presents between the ages of 30 and 50, and it tends to affect women more than men.
More than 90 per cent of cases are due to autoimmune disease, and there is often an association with other autoimmune conditions. TB of the adrenal gland is a rare cause, occurring in less than 10 per cent of cases.
Surgical removal of the adrenal glands also inevitably results in Addison's disease.
1. Signs and symptoms
Diagnosis of the condition can be difficult because initial symptoms are nonspecific and their onset is insidious.
Symptoms may include weight loss, loss of appetite, lethargy, weakness and depression. GI symptoms can occur such as nausea, vomiting, diarrhoea, constipation and abdominal pain. Confusion, amenorrhoea, myalgia and feeling faint on standing are all additional symptoms that may be reported.
The two most common signs are areas of pigmentation and postural hypotension. Increased pigmentation is found in more than 90 per cent of cases and is of particular significance if it occurs in a recent scar, but it can also be found on the buccal mucosa, in the palmar creases of the hands, over the flexor surfaces of joints and on the face.
Postural hypotension is present in up to 90 per cent of cases. Other signs may include weight loss, dehydration, loss of body hair and general wasting. Vitiligo and goitre may indicate the presence of other autoimmune disease processes.
2. Investigation and diagnosis
Routine testing of U&Es may occasionally be normal, but more usually reveals hyponatraemia, hyperkalaemia and raised urea. Hypercalcaemia and anaemia are also sometimes present.
More specific tests (the long and short adrenocorticotropic hormone (ACTH) or synacthen tests) are designed to demonstrate a lack of response by the adrenal glands when appropriately stimulated.
The short test is used to exclude primary adrenal failure and involves measuring plasma cortisol at the time of an injection of ACTH and then after 30 minutes. A normal test result would show a rise in cortisol of >330nmol/L or a cortisol level of >600nmol/L at 30 minutes.
If there is an absent or reduced response, the long version of the test is usually performed to exclude adrenal suppression.
This longer test involves measuring plasma cortisol at various intervals over a 24-hour period. In this situation a normal result would show a rise in cortisol of >550nmol/L and a maximum level of 1,000nmol/L.
In an emergency situation, treatment should be administered to any patient who clinically requires it, without waiting for recourse to specific investigations.
The treatment for Addison's disease involves long-term replacement of both glucocorticoid and mineralocorticoid steroid hormones. Glucocorticoid replacement is usually in the form of prednisolone or hydrocortisone, while the mineralocorticoid element is in the form of fludrocortisone.
The aim of treatment with glucocorticoids is to restore normal weight, clinical well-being and normal daily cortisol levels while on replacement.
Mineralocorticoid replacement aims to restore serum electrolyte physiology and reduce postural hypotension to a fall of <10mmHg systolic BP after two minutes of standing.
The dosages of the replacement hormones must be carefully monitored, and may need to be adjusted as necessary at times of infection, stress, illness or surgery. All these situations can result in an increased demand for circulating steroids.
4. Addisonian crisis
Addisonian crisis is a medical emergency that can be fatal if not treated immediately and appropriately. Classic symptoms of an Addisonian crisis include sudden and severe pain in the legs, back or abdomen, severe vomiting or diarrhoea, confusion, lethargy, convulsions, fever and ultimately loss of consciousness.
The major deficiencies that occur are of sodium, steroids and glucose. Emergency treatment should be in secondary care and consist of IV normal saline boluses followed by continued replacement according to the degree of dehydration.
IV dextrose is administered as required for hypoglycaemia, and hydrocortisone is given IV initially and then IM as the clinical situation dictates. Once the patient is stable, oral steroid replacement can be commenced.
Patients with Addison's disease should carry a steroid card with them at all times, as well as some form of identification with details of their condition. This data can be essential in case of emergency, accident or sudden onset of an intercurrent illness.
An in-date supply of hydrocortisone for injection should be kept at home or when travelling in case an emergency situation arises where the patient is unable to take oral steroids. Patients should also be educated in the need to titrate their medication upwards if required during times of stress or mild illness.