Adrenocorticotropic Hormone (ACTH) Test
Reviewed
Also called: Adrenocorticotropic hormone blood test, corticotropin
This test measures the level of adrenocorticotropic hormone (ACTH) in a sample of your blood.
Specimen: Blood
Why this test may be ordered
- To help diagnose the cause of abnormal cortisol levels
- To evaluate symptoms of too much cortisol (e.g., weight gain, easy bruising) or too little cortisol (e.g., fatigue, weight loss)
- To monitor conditions affecting the pituitary or adrenal glands
Preparation and collection
Your health care provider will tell you how to prepare for your test. You may need to fast (not eat or drink) for several hours before your test. Blood samples for ACTH testing are often taken early in the morning when ACTH levels are at their highest for the day. You may need to stop taking certain medicines before this test, so tell your provider about everything you take. But don't stop taking any medicines unless your provider tells you to.
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
To understand what the results of your ACTH test mean, your provider will usually compare your ACTH level with your cortisol level. If your results are abnormal, you may need other tests to confirm the specific cause.
- High ACTH and high cortisol levels: High ACTH and high cortisol levels are a sign of pituitary tumor that makes ACTH (Cushing's disease). Limitation: The high level of ACTH could also be from other causes including: A rare type of tumor in your lung, pancreas, or thyroid gland, A condition called multiple endocrine neoplasia. Next step: You'll likely need more tests, such as a CT or MRI scan, to confirm whether you have a pituitary tumor.
- High ACTH and low cortisol levels: High ACTH and low cortisol levels are a sign of damage to your adrenal glands (Addison disease). Limitation: To understand what the results of your ACTH test mean, your provider will usually compare your ACTH level with your cortisol level. Next step: For example, an ACTH stimulation test is commonly used to help find out if a problem with your adrenal glands is causing low cortisol levels.
- Low ACTH and high cortisol levels: Low ACTH and high cortisol levels are a sign of Cushing's syndrome. This means that high cortisol levels may be caused by long-term use of steroid medicines or an adrenal gland tumor that makes extra cortisol. Limitation: To understand what the results of your ACTH test mean, your provider will usually compare your ACTH level with your cortisol level. Next step: If your results are abnormal, you may need other tests to confirm the specific cause.
- Low or normal ACTH and low cortisol levels: Low or normal ACTH and low cortisol levels are a sign of hypopituitarism. This means that a pituitary tumor or damage to your pituitary gland may prevent it from making enough ACTH. Limitation: To understand what the results of your ACTH test mean, your provider will usually compare your ACTH level with your cortisol level. Next step: Ask your provider to explain what your test results say about your health.
- Results are not sufficient for diagnosis on their own.
- Your healthcare provider will interpret your ACTH and cortisol levels together.
- Additional tests are often needed to confirm the specific cause of abnormal results.
What to do next
Ask your provider to explain what your test results say about your health. Several other tests may be used to help diagnose the specific cause of abnormal cortisol levels.
- What do my ACTH and cortisol levels together indicate?
- Will I need additional tests to confirm the diagnosis?
- How should I prepare for the test, especially regarding fasting and medications?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.
U.S. National Library of Medicine: Adrenocorticotropic Hormone (ACTH) Test