ACTH 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.

Alternative Names

DST; ACTH suppression test; Cortisol suppression test

Why the ACTH suppression test is Performed

This test is performed when overproduction of cortisol is suspected. The low-dose test can help differentiate healthy people from those who produce too much cortisol. The high-dose test can help determine if the abnormality is in the pituitary gland (Cushing's Disease).

The secretion of ACTH from the pituitary gland is normally regulated by the level of cortisol in the blood plasma. ACTH stimulates the adrenal cortex to produce cortisol. As plasma cortisol levels increase, ACTH secretion is suppressed. As cortisol levels decrease, ACTH increases.

Dexamethasone is a synthetic steroid similar to cortisol, which suppresses ACTH secretion in normal people. Therefore, giving dexamethasone should reduce ACTH levels, resulting in decreased cortisol levels. People with pituitary glands which produce too much ACTH will have an abnormal response to the low-dose test, but a normal response to the high dose.

How the ACTH suppression 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 3 days (stored in 24-hour collection containers) 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 over 3 days (stored in 24-hour collection containers) 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 ACTH suppression test

The health care provider may advise you to stop taking drugs that may affect the test. Drugs that can affect test results include barbiturates, estrogens, corticosteroids, oral contraceptives, phenytoin, spironolactone, and tetracyclines.

How the ACTH suppression 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.

Risks

• Excessive bleeding
• Fainting or feeling lightheaded
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)
• Multiple punctures to locate veins

Considerations

There are none.

Normal Results

Low Dose:

• Overnight: 8 a.m. plasma cortisol < 1.8 mcg/dl
• Standard: Urinary free cortisol on day 3 < 10 mcg/day

High Dose:

• Overnight: > 50 % reduction in plasma cortisol
• Standard: > 90% reduction in urinary free cortisol

Normal value ranges may vary slightly among different laboratories.

What Abnormal Results Mean

If there is not a normal response on the low-dose test, abnormal secretion of cortisol is likely (Cushing's Syndrome). This could be a result of a cortisol-producing adrenal tumor, a pituitary tumor that produces ACTH, or a tumor in the body that inappropriately produces ACTH. The high-dose test can help distinguish a pituitary cause (Cushing's Disease) from the others.

Cushing's syndrome caused by adrenal tumor

• Low dose: no change
• High dose: no change

Cushing's syndrome related to ectopic ACTH-producing tumor

• Low dose: no change
• High dose: no change

Cushing's Syndrome caused by pituitary tumor (Cushing's Disease)

• Low dose: no change
• High dose: normal suppression

Email to a Friend

Typical mistypes for ACTH suppression test
zcth suppression test, scth suppression test, wcth suppression test, qcth suppression test, axth suppression test, avth suppression test, afth suppression test, adth suppression test, acrh suppression test, acfh suppression test, acgh suppression test, acyh suppression test, ac6h suppression test, ac5h suppression test, actg suppression test, actb suppression test, actn suppression test, actj suppression test, actu suppression test, acty suppression test, acth auppression test, acth zuppression test, acth xuppression test, acth duppression test, acth euppression test, acth wuppression test, acth syppression test, acth shppression test, acth sjppression test, acth sippression test, acth s8ppression test, acth s7ppression test, acth suopression test, acth sulpression test, acth su-pression test, acth su0pression test, acth suporession test, acth suplression test, acth sup-ression test, acth sup0ression test, acth suppeession test, acth suppdession test, acth suppfession test, acth supptession test, acth supp5ession test, acth supp4ession test, acth supprwssion test, acth supprsssion test, acth supprdssion test, acth supprrssion test, acth suppr4ssion test, acth suppr3ssion test, acth suppreasion test, acth supprezsion test, acth supprexsion test, acth suppredsion test, acth suppreesion test, acth supprewsion test, acth suppresaion test, acth suppreszion test, acth suppresxion test, acth suppresdion test, acth suppreseion test, acth suppreswion test, acth suppressuon test, acth suppressjon test, acth suppresskon test, acth suppressoon test, acth suppress9on test, acth suppress8on test, acth suppressiin test, acth suppressikn test, acth suppressiln test, acth suppressipn test, acth suppressi0n test, acth suppressi9n test, acth suppressiob test, acth suppressiom test, acth suppressioj test, acth suppressioh test, acth suppression rest, acth suppression fest, acth suppression gest, acth suppression yest, acth suppression 6est, acth suppression 5est, acth suppression twst, acth suppression tsst, acth suppression tdst, acth suppression trst, acth suppression t4st, acth suppression t3st, acth suppression teat, acth suppression tezt, acth suppression text, acth suppression tedt, acth suppression teet, acth suppression tewt, acth suppression tesr, acth suppression tesf, acth suppression tesg, acth suppression tesy, acth suppression tes6, acth suppression tes5, cth suppression test, ath suppression test, ach suppression test, act suppression test, acthsuppression test, acth uppression test, acth sppression test, acth supression test, acth supression test, acth suppession test, acth supprssion test, acth suppresion test, acth suppresion test, acth suppresson test, acth suppressin test, acth suppressio test, acth suppressiontest, acth suppression est, acth suppression tst, acth suppression tet, acth suppression tes, cath suppression test, atch suppression test, acht suppression test, act hsuppression test, acths uppression test, acth usppression test, acth spupression test, acth suprpession test, acth supperssion test, acth supprsesion test, acth suppresison test, acth suppressoin test, acth suppressino test, acth suppressio ntest, acth suppressiont est, acth suppression etst, acth suppression tset, acth suppression tets, aacth suppression test, accth suppression test, actth suppression test, acthh suppression test, acth suppression test, acth ssuppression test, acth suuppression test, acth supppression test, acth supppression test, acth supprression test, acth suppreession test, acth suppresssion test, acth suppresssion test, acth suppressiion test, acth suppressioon test, acth suppressionn test, acth suppression test, acth suppression ttest, acth suppression teest, acth suppression tesst, acth suppression testt, etc.