ACTH (cosyntropin) stimulation test
DefinitionACTH (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.
Alternative NamesTests of adrenal reserve; Cortrosyn stimulation test
How the test is performedThe health care provider will measure the cortisol in your blood before and 60 minutes after an ACTH injection.A blood sample is needed. For information on how this is done, see: VenipunctureOnce 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.
How to prepare for the testYou 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. Sometimes, no special preparation is needed.
How the test will feelWhen 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 performedThis 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.
Normal ValuesAn increase in cortisol after stimulation by ACTH is normal. Blood cortisol after ACTH stimulation should be greater than 18 - 20 mcg/dL, depending on the dose of cosyntropin used.Note: mcg/dL = micrograms per deciliterThe examples above are common measurements for results for these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different specimens.Talk to your doctor about the meaning of your specific test results.
What abnormal results meanThis test is helpful in determining if you have:Acute adrenal crisisAddison's disease, when the adrenal glands do not produce enough cortisolLow pituitary functionPituitary tumors
What the risks areVeins 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 bleedingFainting or feeling light-headedHematoma (blood accumulating under the skin)Infection (a slight risk any time the skin is broken)
ReferencesStewart PM, Krone NP. The adrenal cortex. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 15.