ACTH (cosyntropin) stimulation test measures how well the adrenal glands respond to the hormone ACTH. ACTH is a hormone produced in the pituitary gland that stimulates the adrenal glands to release cortisol.

This test can help determine whether your adrenal and pituitary glands are normal. It is most often used when the health care provider suspects adrenal gland disorders, such as Addison's disease or pituitary insufficiency.

The health care provider will measure the cortisol in your blood before and 60 minutes after an ACTH injection.

Blood is typically drawn from a vein, usually on 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.

Once the blood has been collected, the health care provider will use a needle to inject cosyntropin. Other timed specimens are also collected.

Along with the blood tests, sometimes you may also have a urinary free cortisol test or urinary 17-ketosteroids test in which the urine is collected over a 24-hour period.

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.

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.