Dexamethasone suppression test
Key points
- Dexamethasone suppression test measures the response of the adrenal glands to ACTH.
- There are two different types of dexamethasone suppression tests: the low-dose test and the high-dose test.
- The health care provider may advise you to discontinue drugs that may affect the test.
- The preparation you can provide for this test depends on your child's age, previous experiences, and level of trust.
Alternative names
DST; ACTH suppression test; Cortisol suppression test
Definition
Dexamethasone suppression test measures the response of the adrenal glands to ACTH. Dexamethasone is given and levels of cortisol are measured. Cortisol levels should decrease in response to the administration of dexamethasone.
How the test is performed
There are two different types of dexamethasone suppression tests: the low-dose test and the high-dose test. Each type can either be done in an overnight or standard (3-day) way.
For the low-dose overnight method, 1 mg of dexamethasone is given at 11 p.m., and the blood is drawn at 8 a.m. for a cortisol measurement (see venipuncture).
In the standard low-dose method, urine is collected at 24-hour intervals over 3 days for measurement of cortisol. On day 2, a low dose (0.5 mg) of dexamethasone is given by mouth every 6 hours for 48 hours.
For the high-dose overnight method, a baseline cortisol is measured on the morning of the test, then 8 mg of dexamethasone is given at 11 p.m.. Blood is drawn at 8 a.m. for a cortisol measurement. For the standard high-dose test, urine is collected at 24-hour intervals over 3 days for measurement of cortisol. On day 2, a high dose (2 mg) of dexamethasone is given by mouth every 6 hours for 48 hours.
How to prepare for the test
The health care provider may advise you to discontinue drugs that may affect the test. Drugs that can affect test results include barbiturates, estrogens, corticosteroids, oral contraceptives, phenytoin, spironolactone, and tetracyclines.
Infants and children:
The preparation you can provide for this test depends on your child's age, previous experiences, and level of trust. For general information regarding how you can prepare your child, see the following topics:
- Infant test or procedure preparation (birth to 1 year)
- Toddler test or procedure preparation (1 to 3 years)
- Preschooler test or procedure preparation (3 to 6 years)
- Schoolage test or procedure preparation (6 to 12 years)
- Adolescent test or procedure preparation (12 to 18 years)
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
Written and revised by
Gerald Hurowitz, M.D.
Our doctors write and review articles for accuracy and keep them up to date.
health.am provides general information, not medical advice. Always consult a qualified health professional about your own health.