The metyrapone test evaluates how the adrenal glands respond to adrenocorticotrophic hormone, or ACTH. ACTH is made in the pituitary gland and travels through the bloodstream to the adrenal glands. There it triggers the release of another hormone called cortisol.

Cortisol affects the breakdown and use of fats, carbohydrates, sodium, potassium, and protein. In this test, the medication metyrapone is given to a person to evaluate the ability of the adrenal gland to make cortisol.

Who is a candidate for the test?

The metyrapone test may be done if a problem is suspected in a person's:

How is the test performed?

Metyrapone is given in 4 doses over a 24-hour period, or sometimes as a single dose at 11 p.m. Metyrapone is given orally in tablet form. At 8 a.m., a blood sample is taken from a vein on the forearm or hand.

First, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube, or tourniquet, is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow. A fine needle is gently inserted into a vein and the tourniquet is removed. Blood flows from the vein through the needle. It is collected in a syringe or vial. After the needle is withdrawn, the puncture site is covered to prevent bleeding . The blood sample is sent to a lab. There, cortisol and ACTH in the blood sample are measured.