What is Addison's disease?

By:  Sarah J. Baker  Wednesday, 04. December 2002

Addison’s disease is a rare, chronic condition brought about by the failure of the adrenal glands. Lifelong, continuous treatment with steroid replacement therapy is required. With the right balance of daily medication, most people with the disease are able to continue life much as it was before their illness.

Adrenal function

The adrenal glands sit at the top of the kidneys, one on each side of the body and have an inner core (known as the medulla)  surrounded by the outer shell (known as the cortex). The inner medulla produces adrenaline, the “fight or flight” stress hormone. While the absence of the adrenal medulla does not cause disease, the cortex is more critical. It produces the steroid hormones that are essential for life: cortisol and aldosterone. Cortisol mobilises nutrients, it enables the body to fight inflammation, it stimulates the liver to produce blood sugar and it also helps control the amount of water in the body. Aldosterone regulates salt and water levels which affect blood volume and blood pressure. The adrenal cortex also produces sex hormones known as adrenal androgens; the most important of these is DHEA.  

The normal adrenal cortex has an enormous functional reserve. This is called upon by the body especially in times of intense stress, such as surgery, trauma or serious infection. One of the most significant consequences of Addison’s disease is, therefore, the body’s failure to adapt to such stresses and, in the absence of adequate steroid cover, this may result in a state of shock, known as an Addisonian crisis, which is a medical emergency.

Causes of adrenal failure

Thomas Addison first identified the disease in 1855 while working at Guy’s Hospital in London. At that time, the main cause of the disease was as a complication of tuberculosis. TB still remains an important cause of Addison’s in Third World countries. HIV (AIDS) is now becoming another significant infectious disease causing adrenal failure among third world population.

In more affluent countries, the most frequent cause of Addison’s disease is destructive atrophy whereby an over-active immune system starts attacking the body’s own organs; in this case, the adrenals. This accounts for around 70% of all cases and affects more women than men. In common with most other autoimmune diseases, the exact reason for the atrophy is unknown.

Other, much rarer causes of Addison’s include certain fungal infections, adrenal cancer and adrenal haemorrhage (for example, following a car accident).

Symptoms

Addison’s disease is not usually apparent until over 90% of the adrenal cortex has been destroyed, so that very little adrenal capacity is left. This can take months to years and is known as primary adrenal insufficiency. Symptoms of the disease, once advanced, can include severe fatigue and weakness, loss of weight, increased pigmentation of the skin, faintness and low blood pressure, nausea, vomiting, salt cravings and painful muscles and joints. Because of the rather non-specific nature of these symptoms and their slow progression, they are often missed or ignored until, for example, a relatively minor infection leads to an abnormally long convalescence which prompts an investigation. Frequently, it is not until a crisis is precipitated that attention is turned to the adrenals.

Secondary failure

Secondary adrenal insufficiency is sometimes described as “Addison’s”, although it has a very different cause. It mostly occurs when a pituitary tumour (such as an adenoma) forms, although autoimmune destruction of the pituitary gland is also known. In secondary adrenal insufficiency, the pituitary gland no longer triggers the adrenals to produce cortisol, and DHEA production is also believed to decline.  In most cases of secondary adrenal insufficiency, however, aldosterone is still produced, as its production is stimulated by other hormonal regulatory systems.  The pituitary hormone which triggers cortisol production is called ACTH; it is responsible for the extra pigmentation found in primary Addison’s.  People with secondary adrenal failure do not experience the extra pigmentation found in primary Addison’s, because their ACTH levels are declining.

Long term use of high doses of steroid drugs to treat other illnesses (for example high–dose prednisone for bowel disease or asthma) can also cause temporary or permanent loss of adrenal function.  This is often referred to as secondary adrenal suppression.

Until the development of steroid medication in the late 1940s, the outcome of adrenal disease was invariably fatal.  With the development of modern steroid medications, individuals with Addison’s disease can expect to have a fairly normal life span, provided they manage their daily medication sensibly.  People with Addison’s must always be aware of their own health and ready to increase their dosage if they get sick or are seriously injured.

• See section 2(a), The causes of Addison's disease and related autoimmune disease [PDF] in the Addison's Disease Owner’s Manual

or to read the complete Addison's Disease Owner’s Manual