Short Synacthen test

A short Synacthen test is done to assess how well your adrenal glands are working. It's used to check if your adrenal glands are producing enough of the steroid hormone called cortisol.

The test is named 'short Synacthen test' because the test only takes a few minutes. During the test you will be given a medicine called Synacthen (also known as tetracosactide) which stimulates your adrenal glands to produce cortisol.

A blood sample is taken to test your cortisol levels, you then have the Synacthen injection and 30 minutes later another blood sample is taken to test your cortisol levels again. Read more about how the test is done below. 

Note: Although the test only takes a few minutes, you will need to have an appointment for up to an hour because the test involves blood tests before and after having Synacthen.

What is cortisol?

• Cortisol is a hormone produced by the adrenal glands. The adrenal glands are found on top of each kidney. The adrenal glands produce cortisol in response to adrenocorticotrophic hormone (ACTH), which is a hormone produced by the pituitary gland. The pituitary gland is a small, pea-sized gland just below the brain. 
• Cortisol is important for your body's response during illness and stress. It helps to regulate your blood pressure, blood glucose and your immune system. Greater amounts of cortisol are produced by your body in times of illness and as a response to stress. If your body is unable to produce enough cortisol you may not be able to cope with illness and could become very unwell. 
  
  

Image credit: Healthify He Puna Waiora

The short Synacthen test is done to help diagnose problems with your adrenal glands, mainly primary adrenal insufficiency (also known as Addison's disease). This condition occurs when your adrenal glands are damaged from infection, injury or autoimmune problems and can't produce enough cortisol. Read more about adrenal insufficiency.

Timing

The test can be done at any time of day but preferably in the morning.

You can eat and drink as normal before the test. It's not necessary to fast.

Taking steroid medicines will affect the results of your test

• Steroid tablets: If you're taking prednisone or prednisolone tablets don't take these tablets for 24 hours before the test.
• Steroid inhalers: If you're using a steroid inhaler for asthma or COPD, don't use it for 12 hours before the test.
• Oestrogen tablets: If you're taking oestrogen tablets, such as the combined oral contraceptive pill or for menopausal hormone therapy, it's important to let your healthcare provider know well before having the test. You may continue using oestrogen gel or patches.

Apart from the medicines mentioned above you can continue to take your other regular prescribed medicines.

A cannula (tiny plastic tube) is inserted into a vein in your arm or hand

1. A blood test will be done when the cannula is inserted, to check your cortisol levels at the start.
2. You will then be given an injection of Synacthen through the cannula. Synacthen stimulates your adrenal glands to produce cortisol.
3. 30 minutes after the Synacthen injection has been given, another blood test will be done to compare your body’s response to the Synacthen injection.
4. Once the test is completed the cannula will be removed and you will be able to go home.
5. If you're taking steroid medicines, you can continue to take them as before.

Side effects of Synacthen

You may not have any side effects. However, you may feel all or some of the following symptoms during or immediately after the Synacthen injection:

• flushing (a warm sensation)
• nausea (feeling sick)
• light-headedness or dizziness
• a metallic taste in your mouth.

These side effects usually only last a few minutes because Synacthen doesn't stay in your body for very long. Most of the injected Synacthen leaves your body quickly. 

You will receive your test result from the healthcare provider who ordered the test.