Addison's disease: Causes, symptoms, diagnosis and treatment

What Is Addison's disease?

Your body is a finely tuned machine. One way it keeps itself in balance is by using chemical messengers called hormones to regulate various functions. Just above each of your kidneys is a small adrenal gland. These glands make some of the hormones your body needs. When they don't make enough of these hormones, Addison's disease is the result.

Addison's disease is rare, with only 14  in 100,000 people in the UK suffering from the condition, according to the NHS. It can happen at any age to either men or women at an equal rate. People with Addison's disease can lead normal lives as long as they take their medication. President John F. Kennedy had the condition.

In Addison's disease, the adrenal glands don't make enough of a hormone called cortisol, or less often, a related hormone called aldosterone. That's why doctors sometimes call the illness chronic adrenal insufficiency, or hypocortisolism.

Cortisol's most important function is to help the body respond to stress. It also helps regulate your body's use of protein, carbohydrates, and fat; helps maintain blood pressure and cardiovascular function; and control inflammation. Aldosterone helps your kidneys regulate the amount of salt and water in your body - the main way you keep your blood pressure under control. When aldosterone levels drop too low, your kidneys cannot keep your salt and water levels in balance. This makes your blood pressure drop.

There are two forms of Addison's disease. If the problem is with the adrenal glands themselves, it's called primary adrenal insufficiency. If the adrenal glands are affected by a problem starting somewhere else - such as the pituitary gland - it's called secondary adrenal insufficiency.

What causes Addison's disease?

When Addison's disease is the result of a problem with the adrenal glands themselves, it is called primary adrenal insufficiency. About 70% of the time, this happens because the body's self-defence mechanism - the immune system - mistakenly attacks the adrenal glands. This so-called "autoimmune" attack destroys the outer layer of the glands.

Long-lasting infections - such as tuberculosis, HIV, and some fungal infections - can harm the adrenal glands. Cancer cells that spread from other parts of the body to the adrenal glands can also cause Addison's disease.

Less commonly, Addison's disease is not due to the failure of the adrenal glands themselves. This condition, secondary adrenal insufficiency, can be caused by problems with the hypothalamus or pituitary gland, located in the centre of the brain. These glands produce hormones that act as a switch and can turn on or off the production of hormones in the rest of the body. A pituitary hormone called ACTH is the switch that turns on cortisol production in the adrenal gland. If ACTH levels are too low, the adrenal glands stay in the off position.

Another cause of secondary adrenal insufficiency is prolonged or improper use of steroid hormones such as prednisolone. Less common causes include pituitary tumours and damage to the pituitary gland during surgery or radiotherapy.