The ACTH stimulation test measures cortisol levels in response to ACTH injection to diagnose adrenal gland problems. Preparation is important for valid results, and abnormal results may require further testing such as imaging or blood tests.
ACTH, also called cosyntropin, causes the adrenal glands to release cortisol into the bloodstream. An ACTH stimulation test is used to measure how well the adrenal glands react when stimulated by ACTH injected into the patient. The results of this test help diagnose health problems such as Addison’s disease or the presence of pituitary tumors.
The ACTH stimulation test measures the amount of cortisol in the blood. Levels are checked at the start of the test and then again one hour after the ACTH injection. Before ACTH is injected, blood is drawn from a vein in the crook of the arm. For infants and very young children, a lancet is used to make a small wound so that a few drops of blood can be collected for testing. This first blood sample is used to determine baseline cortisol levels.
ACTH is then injected. Once 60 minutes have passed, another blood draw is taken and cortisol levels are checked to determine how the adrenal glands have responded. Low cortisol levels indicate decreased functioning of the adrenal glands and could be indicative of Addison’s disease or another adrenal gland deficiency. Very high levels may be indicative of other serious problems and require further investigation. A urinalysis can also be done in combination with the ACTH stimulation test.
For ACTH stimulation test results to be valid, it is important that the patient prepares in advance. General guidelines require the patient to limit activity in the 24 hours leading up to the test, avoiding strenuous exercise such as jogging, cycling and tennis. Second, you should eat a high carbohydrate diet the day before the test. In some cases the patient may be asked to fast for the last few hours before the test is administered. Compliance with all of these requirements helps ensure valid results from the ACTH stimulation test.
If a person has abnormal results from the ACTH stimulation test, further tests will be done to determine the exact reason for the problem. Imaging such as a computed tomography (CT) scan of the adrenal glands is common, and a magnetic resonance imaging (MRI) can be used to identify problems with the pituitary gland. Blood and insulin tests may also be performed, all with the ultimate goal of diagnosing the problem quickly and helping the patient get back to health as quickly as possible.
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