In diagnosing Addison’s disease, your GP will ask about your symptoms and review your medical history.

They are also likely to ask if there is a history of conditions caused by a problem with the immune system (autoimmune disorders) in your family.

Your GP will examine your skin for any evidence of brownish discolouration (hyperpigmentation). This will be particularly noticeable where your skin creases on your palm or in your elbow, and also on any scars. However, hyperpigmentation does not occur in all cases of Addison’s disease.

You will also be tested for low blood pressure (hypotension); this will probably be measured while you are sitting down and again shortly after you stand up. This is to see whether you have postural or orthostatic hypotension (low blood pressure when you change position).

Blood tests

If Addison’s disease is suspected, blood tests will be carried out to measure the levels of sodium, potassium and the hormone cortisol in your body. A low sodium, high potassium or low cortisol level may indicate you have Addison’s disease.

You may need to see a hospital hormone specialist (endocrinologist) for your blood to be tested for the following:

• a low level of the hormone aldosterone
• a high level of adrenocorticotrophic hormone (ACTH)
• a low level of glucose (sugar used for energy)
• positive adrenal antibodies (antibodies designed to attack the adrenal gland)

Any of the above could be a sign of Addison’s disease.

Synacthen stimulation test

If cortisol in your blood is low, or your symptoms strongly suggest Addison’s disease, you will need to have a synacthen stimulation test to confirm the diagnosis.

Your GP may refer you to an endocrinology unit (a unit that specialises in the study of hormones) for the test. How urgently you are referred will depend on how severe your symptoms are.

Synacthen is a man-made (synthetic) copy of the adrenocorticotrophic hormone (ACTH). ACTH is naturally produced by the pituitary gland (a pea-sized gland below the brain) to encourage the adrenal glands to release the hormones cortisol and aldosterone. When synacthen is administered, the adrenal glands should respond in the same way as they would to ACTH, and release cortisol and other steroid hormones into the blood.

A blood sample will be taken and tested for the level of cortisol, before an injection of synacthen is given into your arm. After 30 and 60 minutes, a further blood sample will be taken for cortisol measurement.

If the ACTH level is high, but the cortisol and aldosterone levels are low, it is usually confirmation of Addison’s disease.

Thyroid function test

As well as a synacthen stimulation test, your thyroid gland may also be tested to see if it is working properly.

Your thyroid gland is found in your neck, it produces hormones that control your body's growth and metabolism (the process that turns the food you eat into energy).

People with Addison’s disease often have an underactive thyroid gland (hypothyroidism), where the thyroid gland does not produce enough hormones. By testing the levels of certain hormones in your blood, your endocrinologist (a specialist in hormone conditions) can determine whether you have hypothyroidism.

Scans

In some cases, your specialist may refer you for a scan of your adrenal gland, which could be a computerised tomography (CT) scan or a magnetic resonance imaging (MRI).

Diagnosis during an adrenal crisis

If Addison’s disease is left untreated, it will eventually lead to a situation called an adrenal crisis. This is where the symptoms of Addison’s disease appear quickly and severely.

During an adrenal crisis, there is not enough time to perform a synacthen stimulation test to confirm Addison’s disease.

If possible, blood will be taken and tested for any of the abnormalities listed above. While you are waiting for the results, treatment may be started with steroid injections, and fluids containing salt and glucose.

Read more about treating Addison’s disease.