What is the purpose of a dexamethasone suppression test?
wo tests use dexamethasone (a synthetic cortisol) for diagnosing Cushing’s disease or Cushing’s syndrome. They are the “LOW DOSE” and the “HIGH DOSE” dexamethasone suppression test. The low dose dexamethasone suppression test can be used to screen for the presence of hyperadrenocorticism (Cushing’s disease) and in many cases, it will differentiate the type of Cushing’s disease that is present. The high dose dexamethasone test is used when the patient has been confirmed with Cushing’s disease by means of the low dose test, but the low dose test has not clearly differentiated the type of Cushing’s disease that is present. Both the low dose and the high dose dexamethasone suppression tests take 8 hours to complete and involve three blood samples. The first sample is taken prior to the injection of dexamethasone, and the second and third samples are taken at 4 and 8 hours following the dexamethasone injection. The difference between the two tests is in the amount of dexamethasone that is i
