Addison's disease (also known as primary adrenal insufficiency or hypoadrenalism) is a rare disorder of the adrenal glands, writes Fergus Bescoby.
The condition is named after Dr Thomas Addison, a renowned 19th-century English physician and scientist who first described it in 1855.
The adrenal glands are two small glands located on top of the kidneys. They produce the essential hormones cortisol and aldosterone.
Cortisol regulates the body's reaction to stressful situations and aldosterone helps with sodium and potassium regulation. The adrenal cortex also produces sex hormones (androgens).
In Addison's disease, the adrenal glands are damaged, so not enough cortisol and aldosterone are produced. Just over 8,000 people in the UK have Addison's disease at any one time.
It can affect people of any age, although it's most common between the ages of 30 and 50. It is also more common in women than men.
Types & causes
There are two major classifications for Addison's disease: primary adrenal insufficiency and secondary adrenal insufficiency.
1. Primary adrenal insufficiency
Most cases of Addison's disease result from a problem with the adrenal glands themselves. This is known as primary adrenal insufficiency. It occurs when the adrenal glands are damaged so severely they can no longer produce hormones.
This form of Addison's disease is most often caused by the immune system attacking the adrenal glands. It's otherwise known as an autoimmune disease and accounts for 70% of cases of Addison's disease. An autoimmune disease is characterised by the body's immune system mistaking any organ or area of the body for a virus, bacteria, or another outside invader. The ensuing autoimmune assault 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 and although rare, the adrenal glands can be injured as a result of a bacterial infection.
Other causes of primary adrenal insufficiency include:
- Prolonged administration of glucocorticoids (e.g. prednisone)
- Infections in the body.
- Cancer and abnormal growths.
- Certain blood thinners used to control clotting in the blood.
2. Secondary adrenal insufficiency
This is less common. It is caused by a problem with the pituitary gland or the hypothalamus, both located in the centre of the brain.
These glands produce hormones that act as a switch and can turn the production of hormones in the body on or off.
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.
Less common causes include pituitary tumours and damage to the pituitary gland during surgery or radiation.
It's also possible to develop adrenal insufficiency where those individuals prescribed corticosteroid medication fail to take it.
Corticosteroids help control chronic health conditions like asthma.
Early-stage symptoms of Addison's disease are similar to other more common health conditions, such as depression or flu. They may include the following:
- Fatigue (lack of energy or motivation).
- Muscle weakness.
- Low mood.
- Loss of appetite and unintentional weight loss.
- Increased thirst.
Over time, these problems may become more severe and further symptoms, such as dizziness, fainting, cramps and exhaustion may be experienced. Small areas of darkened skin, or darkened lips or gums may also develop.
Because symptoms of Addison's disease progress slowly, they may go unrecognised until a physically stressful event, such as another illness, surgery, or an accident worsens symptoms quickly. When this happens, it's called an Addisonian crisis.
For one in four people with Addison's disease, this is the first time they realise they are ill. An Addisonian crisis is life threatening and therefore considered a medical emergency.
Symptoms of an Addisonian crisis include:
- Shock, when the body does not get enough blood flow.
- Sudden penetrating pain in the lower back, abdomen, or legs.
- Severe vomiting and diarrhoea, followed by dehydration.
- Weakness and fatigue.
- Low blood pressure.
- Loss of consciousness.
- Multiple organ failure, including kidneys, if circulation of blood cannot be restored.
Who is at risk?
The risk of developing Addison's disease is greater for people who:
- Have cancer.
- Take anticoagulants (blood thinners).
- Have chronic infections like tuberculosis.
- Had surgery to remove any part of your adrenal gland.
- Have an autoimmune disease, like type 1 diabetes or Graves' disease
How is it diagnosed?
In its early stages, adrenal insufficiency can be difficult to diagnose. A review of a patient's medical history and symptoms may lead a doctor to suspect Addison's disease. A diagnosis is only confirmed through laboratory tests.
The aim of these tests is first to determine whether levels of cortisol are insufficient and then to establish the cause. Radiologic examinations of the adrenal and pituitary glands are also useful in helping to establish the cause.
In patients suspected of having an Addisonian crisis, health professionals must begin treatment with injections of salt, glucose-containing fluids, and glucocorticoid hormones immediately.
Although a reliable diagnosis is not possible during crisis treatment, measurement of blood ACTH and cortisol during the crisis - before glucocorticoids are given - is enough to make a preliminary diagnosis.
Low blood sodium, low blood glucose and high blood potassium are also usually present at the time of an adrenal crisis. Once the crisis is controlled, an ACTH stimulation test can be performed to obtain the specific diagnosis. More complex laboratory tests are sometimes used if the diagnosis remains unclear.
Since Addison's disease is basically caused by a lack of normal hormones, it can be treated by replacing those hormones.
This might be done with the use of hydrocortisone, a steroid hormone.
If needed, aldosterone can be replaced with a synthetic form called fludrocortisone acetate. These medications may need to be increased during times of stress or injury.
Addison's disease is still a potentially lethal condition, with excess mortality in acute adrenal failure, infection and sudden death in those patients diagnosed at young ages.
The actual prognosis for any patient with adrenal insufficiency will depend on the underlying cause. Although medication will need to be taken permanently after diagnosis, symptoms can largely be controlled.
Most people with the condition live a normal lifespan and are able to live an active life, with few limitations.
Full details will be required regarding the medical history, with reference to treatment, control and complications (if any).
- Primary adrenal insufficiency - often terms can be offered with a small loading.
- Secondary adrenal insufficiency - terms will depend on the underlying cause.
Fergus Bescoby is Distribution and Marketing Underwriting Manager, VitalityLife
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