Why is dexamethasone used for suppression test?
The overnight dexamethasone suppression test checks to see how taking a steroid 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 (Cushing’s syndrome).
Do you need to fast for dexamethasone suppression test?
Your doctor may tell you to avoid taking any food or drink 10 to 12 hours before the morning blood test, but that’s about it. Make sure to tell your doctor about any medicines and supplements you’re taking — some medications, such as birth control pills and seizure medicine, can affect your results.
What is a normal dexamethasone level?
Most often, the dexamethasone level in the blood is measured in the morning along with the cortisol level. For the test result to be considered accurate, the dexamethasone level should be higher than 200 nanograms per deciliter (ng/dL) or 4.5 nanomoles per liter (nmol/L).
Can you still have Cushings with normal cortisol levels?
Although the majority of patients with Cushing’s syndrome have elevated levels of cortisol, it is becoming increasingly evident that many patients with a mild case of Cushing’s syndrome may also have normal levels of cortisol resulting in several 24-hour urine collections to confirm a diagnosis.
How do I prepare for a dexamethasone suppression test?
The night before the test (usually at 11:00 p.m.), you will swallow a pill that contains 1 milligram (mg) of dexamethasone. Take the pill with milk or an antacid. This can help prevent an upset stomach or heartburn. The next morning (usually at 8:00 a.m.), you will have a sample of your blood drawn.
Can I drink water before dexamethasone test?
Your doctor may tell you to avoid taking any food or drink 10 to 12 hours before the morning blood test, but that’s about it.
How is the dexamethasone suppression test performed?
Alternative Names: DST; ACTH suppression test; Cortisol suppression test 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.
Can a high dose of dexamethasone reduce cortisol levels?
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 does dexamethasone work to suppress ACTH secretion?
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.