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ACTH blood test

The ACTH test measures the level of adrenocorticotropic hormone (ACTH) in the blood. ACTH is a hormone released from the pituitary gland in the brain.

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

Your doctor will likely ask you to have the test be done early in the morning. This is important, because cortisol level varies throughout the day.

You may also be told to stop taking medicines that can affect the test results. These medicines include glucocorticoids such as prednisone, hydrocortisone, or dexamethasone.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.

Why the Test is Performed

The main function of ACTH is to regulate the steroid hormone cortisol. Cortisol is released by the adrenal gland. It regulates blood pressure and blood sugar.

This test can help find the causes of certain hormone problems.

Normal Results

Normal values for a blood sample taken early in the morning are 9 to 52 picograms per milliliter (pg/mL).

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different specimens. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

A higher-than-normal level of ACTH may indicate:

A lower-than-normal level of ACTH may indicate:

Other conditions under which the test may be performed:

Risks

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

  • Excessive bleeding
  • Fainting or feeling lightheaded
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)

Alternative Names

Serum adrenocorticotropic hormone; Adrenocorticotropic hormone; Highly-sensitive ACTH

References

Guber HA, Farag AF. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 24.

Stewart PM, Krone NP. The adrenal cortex. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, Pa: Elsevier Saunders; 2011: chap 15.

Melmed S, Kleinberg D. Pituitary masses and tumors. Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, Pa: Elsevier Saunders; 2011: chap 9.

Update Date: 11/7/2013

Updated by: Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.

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