Definition:
The metyrapone test measures the ability of the pituitary gland to release adrenocorticotropic hormone (ACTH) in response to decreased blood cortisol levels.
Alternative Names:
How the test is performed:
There are two different types of metyrapone tests. The first is an overnight test. A single dose of metyrapone is given at 11 p.m. and blood is drawn at 8 a.m. for measurement of serum cortisol, ACTH, and another hormone called 11-deoxycortisol. In the second form of the test, metyrapone is given 6 times a day for 24 hours and then a 24-hour urine sample is collected for measurement of 17-OHCS (a metabolic product of cortisol). Blood samples for serum cortisol, ACTH, and 11-deoxycortisol may also be drawn.
How to prepare for the test:
The health care provider may tell you to temporarily stop taking any drugs that may affect test results. This may include rifampin, phenobarbital, or phenytoin. The drugs may have to be stopped for several weeks before to the test. Other drugs that can affect metyrapone test results include chlorpromazine, corticosteroids, birth control pills, and other estrogen-containing medications.
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:
The test is done to determine whether the pituitary gland is working properly.
References:
Nieman LK. Dynamic evaluation of adrenal hypofunction. J Endocrinol Invest. 2003;26 & Suppl):74-82.
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