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 made in the pituitary gland in response to
the release of another hormone, called corticotropin-releasing hormone (CRH),
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 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
Why It Is Done
A test to measure ACTH is done to check
- 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
- Overproduction of ACTH. This may be caused by an overactive
pituitary gland. In response, the adrenal glands release too much cortisol (one
- 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.
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.
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?).