A synacthen test is used to check the function of the adrenal glands. It involves stimulating the adrenal glands and then checking to see if they respond. It can also give doctors information about how the hypothalamus, pituitary and adrenal glands work together. The test may also be used to diagnose Addison's disease.
A synacthen test can be carried out in several different ways. Your local hospital should tell you how the test is to be carried out.
You will usually be asked to come into hospital in the morning. Here a sample of your blood will be taken to see how much cortisol is present before your adrenals are stimulated. You may have a small needle called a cannula put into a vein in the back of the hand. This allows doctors to take blood samples and give the tetracosactide.
You will then be given an injection of tetracosactide either into a vein via the cannula or into a muscle. In the so-called short synacthen test a sample of blood will be taken again approximately 30 minutes after you received the injection of tetracosactide. This is to measure the levels of cortisol in the blood to see if the adrenals have responded to the tetracosactide. If you are having the short test you will then be free to leave.
Less commonly, you may have what is known as a long synacthen test. In this type of test you give a blood sample at the start of the test. You then have an injection of tetracosactide and blood samples are taken at regular intervals over a 24-hour period.
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