Adrenocorticotropic Hormone
An adrenocorticotropic hormone test measures the level of adrenocorticotropic hormone (ACTH) in the blood to check for problems with the pituitary gland or the adrenal glands. See pictures of the pituitary gland 
and adrenal glands .
ACTH is released in bursts, so its levels in the blood can vary from minute to minute. Interpretation of the test results is difficult and often requires the skill of an endocrinologist.
Many medicines can change the results of this test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take. If you take a medicine, such as a corticosteroid, that could change the test results, you will need to stop taking it for up to 48 hours before the test. Your doctor will tell you exactly how long depending on what medicine you take.
Do not exercise for 12 hours before this test.
Try to avoid emotional stress for 12 hours before the test.
Collecting the blood sample at the right time is often important. Your blood will be drawn in the morning if your doctor wants a peak ACTH level. Your blood will be drawn in the evening if your doctor wants a low (trough) ACTH level.
Talk to your doctor about any concerns you have about the need for the test, its risks, how it will be done, or what the results will mean. To help you learn about this test and how important it is, fill out the medical test information form
(What is a PDF document?).
and adrenal glands .ACTH is made in the pituitary gland in response to the release of another hormone, called corticotropin-releasing hormone (CRH), by the hypothalamus. In turn, the adrenal glands then make a hormone called cortisol, which helps your body manage stress. Cortisol is needed for life, so its levels in the blood are closely controlled. When cortisol levels rise, ACTH levels normally fall. When cortisol levels fall, ACTH levels normally rise.
Both ACTH and cortisol levels change throughout the day. ACTH is normally highest in the early morning (between 6 a.m. and 8 a.m.) and lowest in the evening (between 6 p.m. and 11 p.m.). ACTH levels may be tested in the morning or evening if your doctor thinks that they are abnormal. Cortisol levels are often measured at the same time as ACTH.ACTH is released in bursts, so its levels in the blood can vary from minute to minute. Interpretation of the test results is difficult and often requires the skill of an endocrinologist.
Why It Is Done
A test to measure ACTH is done to check for:- A problem with the adrenal glands or pituitary gland. A high level of ACTH and a low level of cortisol (or low ACTH and high cortisol levels) could be caused by a problem with the adrenal glands. Low levels of ACTH and cortisol could be caused by a problem with the pituitary gland.
- Overproduction of ACTH. This may be caused by an overactive pituitary gland. In response, the adrenal glands release too much cortisol (one form of Cushing's syndrome).
- The correct dose of corticosteroid medicine.
How To Prepare
You may not be able to eat or drink for 10 to 12 hours before an ACTH test. Your doctor may ask you to eat low-carbohydrate foods for 48 hours before the test. Be sure to ask your doctor if there are any foods that you should not eat.Many medicines can change the results of this test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take. If you take a medicine, such as a corticosteroid, that could change the test results, you will need to stop taking it for up to 48 hours before the test. Your doctor will tell you exactly how long depending on what medicine you take.
Do not exercise for 12 hours before this test.
Try to avoid emotional stress for 12 hours before the test.
Collecting the blood sample at the right time is often important. Your blood will be drawn in the morning if your doctor wants a peak ACTH level. Your blood will be drawn in the evening if your doctor wants a low (trough) ACTH level.
Talk to your doctor about any concerns you have about the need for the test, its risks, how it will be done, or what the results will mean. To help you learn about this test and how important it is, fill out the medical test information form
(What is a PDF document?).
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