What is a Synacthen test?
A Synacthen test establishes whether your body is producing enough steroid hormone (cortisol). Cortisol is needed to keep blood sugar levels stable, look after blood pressure, and for our metabolism, immune system and fluid level balance.
If you do not have enough cortisol, you will probably have felt tired, weak and irritable.
You will be given an intravenous injection in order to assess your cortisol production. ACTH is a hormone secreted by the pituitary gland to control the adrenal gland's production of cortisol. ACTH or Synacthen is injected to assess your adrenal function.
The test takes approximately one hour. You may eat and drink normally before the test.
Process
On arrival at the medical investigation unit (MIU) we will insert an intravenous
cannula (tiny tube) into a vein in your arm. You then relax for approximately 30 minutes before we start the test to allow the stress hormones to return to their resting state.
After this rest, we take a sample of blood from the tube and inject Synacthen into the same tube. We then take one more blood sample 30 minutes later. The cannula is removed, and you will be offered tea, coffee and biscuits.
Side effects
Occasionally patients feel light headed or dizzy soon after the injection, but this passes within a few minutes.
Extended Synacthen test
Sometimes, when you have been taking steroids, your doctor may request an extended test. If you are on steroids, you will be advised either to change to dexamethasone or to stop taking your steroids for three days prior to the test.
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For prolonged steroid use – a Synacthen test over three consecutive days.
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If steroid use has not been prolonged – a one day extended Synacthen test which requires blood tests for eight hours on one day and further blood tests the following morning.
