An ACTH test measures ACTH, a hormone released from the anterior pituitary gland in the brain.

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

The levels of ACTH change with the body's natural 24-hour cycle of processes (circadian rhythms). This test is most accurate if it is performed early in the morning.

The health care provider may advise you to stop taking steroid drugs. You may need to be at the laboratory or office where the blood is being drawn by or before 8 a.m.

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

This test can help find the causes of hormone problems.

The main function of ACTH is to regulate the steroid hormone cortisol, which is released by the adrenal cortex.

Normal values: 9 - 52 pg/mL

Note: pg/mL = picograms per milliliter

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

Higher than normal levels of ACTH may be due to:

• Addison's disease
• Adrenoleukodystrophy (very rare)
• Cushing's disease
• Ectopic tumor producing ACTH
• Nelson's syndrome (very rare)

Lower than normal levels of ACTH may be due to:

• Cushing syndrome related to adrenal tumor
• Exogenous Cushing syndrome
• Pituitary insufficiency

Other conditions under which the test may be performed:

• Hypopituitarism
• Multiple endocrine neoplasia (MEN) I

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 light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Special handling of the blood sample is required.

Stewart PM. The adrenal cortex. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 11th ed. Philadelphia, PA: Saunders Elsevier; 2008: chap 14.

Melmed S, Kleinberg D. Anterior pituitary. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 11th ed. Philadelphia, PA: Saunders Elsevier; 2008: chap 8.