ACTH (Cortrosyn) stimulation test

Definition

ACTH (Cortrosyn) stimulation test measures the ability of the adrenal cortex to respond to ACTH by producing cortisol appropriately. ACTH is a hormone produced in the pituitary gland that stimulates the adrenal glands.

Alternative Names

How the test is performed

Cortisol in the blood is measured before and again after an ACTH injection.

Blood is drawn from a vein, usually on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band fill with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. The band is then removed to restore circulation. After blood has been collected the needle is removed, and the puncture site is covered to stop any bleeding.

For an infant or young child, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.

Once the blood has been collected, a needle is used to inject Cortrosyn, and additional timed specimens are collected.

Along with the blood tests, sometimes a urinary free cortisol test or urinary 17-ketosteroids may also be measured. The urine is collected over a 24-hour period.

How to prepare for the test

You may need to limit activities and eat a high-carbohydrate diet 12-24 hours before the test. You may be asked to fast for 6 hours before the test.

How the test will feel

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.

Why the test is performed

This test is helpful in determining if the adrenal and pituitary glands are normal. It is most often used when adrenal gland disorders, such as Addison's disease or pituitary insufficiency, are suspected.

Normal Values

An increase in cortisol after stimulation by ACTH is normal. Post-stimulation blood cortisol should be greater than 20 mcg/dl.

Normal value ranges may vary slightly among different laboratories.

Note: mcg/dl = micrograms per deciliter

What abnormal results mean

This test is helpful in determining if you have:

• Addison's disease (decreased adrenal output)
• Low pituitary function
• Pituitary tumors
• Acute adrenal crisis

What the risks are

From venipuncture (having blood drawn):

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

Special considerations

There are none.