Adrenocorticotropic hormone blood test, corticotropin

This is a blood test that measures the amount of adrenocorticotropic hormone (ACTH) the pituitary gland produces. The pituitary gland is a tiny organ that sits just below your brain. It secretes adrenocorticotropic hormone, which controls the production of another hormone called cortisol.

Cortisol is made by your adrenal glands, which are located at the top of your kidneys. Cortisol helps break down protein, sugar, and fat in your food. It also helps to regulate your blood pressure and your body's ability to fight infection. Cortisol is also one of the hormones that help you deal with stress. Cortisol levels should peak in the morning and be at their lowest in the evening.

You might have this test if your doctor suspects you have hormone problems. This test is used along with other tests to diagnose conditions, including:

• Cushing disease, in which the pituitary gland makes too much ACTH.
• Cushing syndrome, in which the adrenal glands make too much cortisol.
• Addison disease, in which the adrenal glands don't make enough cortisol.
• Hypopituitarism, a disorder of the pituitary gland that keeps it from producing enough vital hormones.

Your doctor also might order tests to measure your cortisol levels, including:

• Adrenocorticotropic hormone stimulation test to determine why your adrenal glands aren't working correctly.
• Dexamethasone suppression test to find an underlying reason for Cushing.
• Adrenocorticotropic hormone stimulation with metyrapone test also to find an underlying reason for Cushing.

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your doctor.

ACTH is measured in picograms per milliliter (pg/mL). Test results are influenced by the time of day the test was done. Normal results are:

• Adults: 10–60 pg/ml (1.3–16.7 pmol/L) for an early morning sample (8 a.m.); less than 20 pg/ml (4.5 pmol/L) for a late afternoon sample (4 p.m.).

If your ACTH level is low or high, you may have Cushing syndrome. If your ACTH level is high, you may have Addison disease. A low ACTH level can also indicate hypopituitarism.

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

You may have blood drawn in the morning and in the afternoon or evening. This is to check for variations in your levels of ACTH hormone.

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.

Your test results might be affected if you:

• Are under a great deal of stress.
• Recently had a trauma.
• Are menstruating or pregnant.
• Are taking certain medicines, including steroids, hormones, or insulin.
• Did not sleep well the night before the test.

Don't eat after midnight on the day of your test. Get a good night's sleep. Follow any other directions from your doctor. Be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.