What is the test of dexamethasone suppression?

Dexamethasone suppression test is a blood test used to diagnose Cushing syndrome. This condition develops when the adrenal glands produce too many hormones called cortisol. Cushing syndrome is usually the result of gland pituitary pituit conveniences, but may have other causes. There are two types of dexamethasone suppression tests: high dose test and low dose test. The low -dose test is used to diagnose a pillow syndrome and a high dose test helps determine the cause of elevated cortisol levels.

Blood cortisol is partially regulated by the production of pituitary gland called adrenocorticotropic hormone or ACTH. The relationship between ACTH and cortisol is called a loop of negative feedback because the high level of each substance reduces the production of others. This relationship is important in the dexamethasone suppression test.

Dexamethasone is a synthetic steroid hormone that is structurally and functionally similar to cortisol. When anomeone with normally functioning pituitary has dexamethasone, ACTH is reduced; This in turn reduces hungerIny cortisol. Therefore, the dexamethasone suppression test measures the ability of dexamethasone to suppress cortisol production. In someone with a dysfunctional pituitary, the reaction to dexamethasone is abnormal. For example, if the pituitary gland excessively produces ACTH, the use of dexamethasone may not have any effect on cortisol levels.

Blood test of dexamethasone suppression can be performed overnight or for three days. In the test overnight, the patient receives a dose of dexamethasone in the evening, and the next morning the blood sample is taken for cortisol testing. In a three -day test, the patient must collect urine for three days after dexamethasone. In addition, he gets additional doses of dexamethasone within three days. Thepacient gets high or low doses of dexamethasone depending on whether it is undergoing a high dose or low dose test.

Before the test, the patient could be asked to stop taking certain drugs that could affect the results of TEstu. These include corticosteroids, estrogens, oral contraception and barbiturate control. This test has very few risks because the most invasive part of the procedure is a blood test. Possible side effects include excessive bleeding, infection and hematoma. The risk of any of these events is very low.

In most cases, the person will first undergo a low -dose test of dexamethasone suppression. The results of this test indicate whether a person has abnormal cortisol levels. Because abnormal cortisol levels may have different causes, a high dose test is performed as monitoring. For example, if abnormal cortisol levels are caused by the pituitary tumor, the patient will have an abnormal response to the low -dose test of an anormal reaction in a high dose test. If abnormal cortisol levels are caused by adrenal tumor, the patient will respond abnormally to both low dose test and high dose test.