Addison's disease

 

What is Addison's Disease?

Addison's disease is the name given to a rare illness that affects the adrenal glands. These two glands are about the size of a walnut and are positioned just above the kidneys at the top of the abdomen near the back. The middle of each gland produces the hormone adrenaline, which is responsible for what is commonly called the "fight and flight" response to excitement or stress.

However it is the outer covering or "cortex" that is affected by Addison's disease. This part of the gland produces three types of hormone:

  • Androgens: This is a type of male hormone, which exists even in women.
  • Cortisol: This is a type of steroid essential for the general running of the body's metabolism especially at times of stress or during illness.
  • Aldosterone: This keeps the body's salt content at the correct level and this also helps to maintain the blood pressure.

In the 1850's a physician called Thomas Addison described a condition resulting from the failure of the cortex of the adrenal glands to work properly and the subsequent lack of the three hormones mentioned above. As a result the disease was named after him and is used to describe the illness suffered by approximately 4.7 - 6.2 per 1,000,000 people in the UK.

 

What causes it?

The most common cause of Addison's disease is something called auto-immune adrenal destruction. This accounts for about 90% of cases in the UK. It results from the body's immune system attacking it's own tissue, in this case the tissue forming the cortex of the adrenal glands. This causes the adrenal tissue to shrink and fail to produce the essential hormones described above. Some infections, eg Tuberculosis (TB) or some types of fungal infections and viruses, can also cause destruction of the adrenal glands, as can certain types of secondary tumours (eg as the breast).

Rare causes include haemorrhage (bleeding) into the adrenal glands as a result of septicaemia such as that associated with meningitis and rare inherited disorders. Also, as the adrenal glands are stimulated to produce their hormones by the pituitary gland (which lies at the base of the brain), surgical removal or tumours of the pituitary gland can have a knock-on effect and produce under-functioning of the adrenal glands. This is called secondary adrenal failure since the failure of the adrenal glands is secondary to a problem elsewhere (in this case the pituitary gland).

 

What symptoms does it cause?

Addison's disease causes a number of symptoms all of which result from the lack of the important hormones which it produces. However, on the one hand it can develop very rapidly producing a sudden drop in blood pressure, salt imbalance and low blood pressure enough to result in sudden severe illness. On the other hand it can develop slowly. When it arises slowly it tends to result in the following symptoms:

  • Tiredness.
  • Weakness.
  • Loss of appetite.
  • Odd pigmentation such as darkening of the creases of the hand, old scars or gums, knuckles, elbows and knees.
  • Abdominal pains.
  • Muscle pains.
  • Fainting (mainly due to a lowering of normal blood pressure).
  • Disturbance of the normal menstrual cycle.
  • Salt craving.
  • Hair loss.
 

How is it diagnosed?

Addison's disease can be difficult to diagnose partly because it is a relatively rare condition and partly because the symptoms it causes are very non-specific i.e. they can be caused by many types of illness.

If the disease comes on suddenly (Addisonian crisis, also known as "acute adrenal insufficiency"), the patient will usually need admission to hospital with diarrhoea, vomiting and "collapse". In hospital the diagnosis will usually be considered following initial blood tests showing an abnormality of the chemicals in the blood and frequently a low blood sugar. Following urgent treatment, the diagnosis is then confirmed by measuring the person's cortisol levels in their blood and performing a special test called a Synacthen test. This involves giving the individual an injection of a hormone to stimulate the adrenal glands and then measuring the levels of certain hormones in the blood at intervals after the injection.

This enables the doctors to tell whether or not the adrenal glands are working properly.

If the disease comes on more gradually the doctor may suspect the diagnosis from the symptoms mentioned above and then order some routine blood tests. The GP may then refer the patient to a specialist for further tests including the Synacthen test.

In either case more tests such as CT or MRI scans of the adrenal or pituitary glands may be done to try to find the particular cause for the Addison's disease.

 

How is Addison's disease treated?

As discussed above sometimes emergency treatment is required for those cases of Addison's disease where the illness comes on very quickly. In these situations hospital admission is usually required for fluid replacement (often through a "drip") and correction of the abnormalities in the body's minerals and metabolism before going on to give the specific long term treatment.

The long term treatment consists of replacing those hormones that the adrenal glands themselves are no longer producing. This means giving cortisone, usually in the form of Hydrocortisone, to replace the cortisol no longer produced by the adrenals. A drug called Fludrocortisone replaces the aldosterone no longer being made. The third type of hormone, androgen, is rarely replaced because in women it is not essential and in men it is also produced by the testicles. The medication is usually given in tablet form on a daily basis for the rest of the person's life as to stop it would mean the return of the illness. The patient's specialist will decide the dose of each drug.

The individual will also be given instructions about certain special situations such as those times when they cannot absorb their treatment due to vomiting. In this case they would need to have their medication in injection form. Also, since the body usually releases more cortisol at certain times such as illness or after an operation, someone with Addison's disease will be advised to take additional hydrocortisone in these situations to mimic what the body would have done. This helps the body to cope with these situations; without the extra hydrocortisone the person's metabolism could have difficulty dealing with these circumstances. It is also usually suggested that people with Addison's disease wear a Medic-Alert bracelet or similar so that if they are involved in an accident doctors treating them will be aware of their special requirements.

Once treatment has been established most individuals with Addison's disease feel back to normal and, apart from the precautions mentioned above, can resume an entirely normal life although they may be asked to attend occasional specialist outpatient appointments for monitoring of their treatment.

 

Where can I get further information?

Apart from contacting your GP, the following organisations may be of further help:

Addison Disease Self Help Group
PO Box 1083
Guildford
Surrey
GU1 9HX
Website: www.addisons.org.uk/comms/contact

MedicAlert Foundation
1 Bridge Wharf
156 Caledonian Road
London
N1 9UU
Phone: 0207 833 3034
Website: www.medicalert.org.uk