dexamethasone suppression test checks to see how taking a
corticosteroid medicine (called dexamethasone) changes
the levels of the hormone
cortisol in the blood. This test checks for a
condition in which large amounts of cortisol are produced by the adrenal glands
Normally, when the pituitary gland make less
adrenocorticotropic hormone (ACTH), the
adrenal glands make less cortisol. Dexamethasone, which is like cortisol, decreases the amount of
ACTH released by the pituitary gland, which in turn decreases the amount of
cortisol released by the adrenal glands.
After taking a dose of
dexamethasone, cortisol levels often stay abnormally high in people who have
Cushing's syndrome. Sometimes other conditions (such as major depression,
alcoholism, stress, obesity, kidney failure, pregnancy, or uncontrolled
diabetes) can keep cortisol levels from going down
after taking a dose of dexamethasone.
The night before the blood
test, you will take a pill containing dexamethasone. The next morning, the
cortisol level in your blood will be measured. If your cortisol level remains
high, Cushing's syndrome may be the cause.
test is sometimes done at the same time as the cortisol test.