What are the causes of Addison's disease?
Auto-immune Addison's disease
About 7 in 10 cases are due to an 'auto-immune' disease. The immune system normally makes antibodies to attack bacteria, viruses, and other 'germs'. In auto-immune diseases the immune system makes antibodies against part or patss of the body. In auto-immune Addison's disease, you make antibodies which attach to cells in the adrenal cortex. These destroy the cells which make cortisol and aldosterone. The adrenal medulla is not affected (so you still make adrenaline and noradrenaline). It is thought that something triggers the immune system to make these antibodies. The 'trigger' is not known.
If you have auto-immmune Addison's disease you have a higher than average chance of other auto-immune diseases developing such as thyroid problems, vitiligo, and pernicious anaemia.
Tuberculosis (TB)
TB is an infection which usually affects the lungs. In some cases the infection can spread to, and gradually destroy, the adrenals.
Other rare adrenal causes include:
- Other infections can sometimes affect both adrenals.
- Cancers of other parts of the body can spread and destroy the adrenals.
- Rare hereditary conditions.
'Secondary' causes of a low cortisol level
As mentioned, the amount of cortisol that you make in the adrenal glands is controlled by another hormone called ACTH. This is made in the pituitary gland. If you have low level of ACTH, your adrenals make too little cortisol. Strictly speaking, this is not a condition of the adrenals, and is not classed as Addison's disease. However, it causes similar symptoms and is called 'secondary hypoadrenalism'. Causes of a low ACTH level include:
- Some disorders and tumours of the pituitary gland which can cause a lack of ACTH (and other pituitary hormones).
- Long-term use of steroid medicines such as prednisolone. Steroid medicines are similar to cortisol. They are sometimes used to treat arthritis, cancer, and various other conditions. If you take a steroid medicine for several weeks or more, you stop making ACTH and cortisol as the steroid medicine takes over the role of cortisol. If you suddenly stop taking the steroid medicine, it takes quite some time for the pituitary and adrenal to get back into the normal making of ACTH and cortisol. Therefore, if you stop the medicine suddenly, you have no cortisol or steroid medicine equivalent. You can then quickly develop symptoms similar to an Addisonian crisis (see below).
The rest of this information only with auto-immune Addison's disease.
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