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ACTH Suppression Test



 Submitted by Nic on April 11, 2011
ACTH suppression test

An ACTH suppression test can be described as the test that is performed on a person, in case any adrenal diseases are suspected. This test helps to differentiate adrenal diseases, from pituitary disorders. This is because when a person is suffering from an adrenal disease there is an altered response to the Adreno Cortico Trophic Hormone (ACTH) in the body, but is case of a pituitary disorder the production of ACTH is altered. The levels of cortisol in the plasma help to regulate the secretion of ACTH in the pituitary glands. The ACTH stimulates the adrenal cortex, into producing cortisol. When the levels of cortisol in the plasma increase, the secretion of ACTH is suppressed and as the cortisol level in the plasma decreases, the ACTH increases. There is synthetic steroid, known as Dexamethasone, which is quite similar to cortisol, as it suppresses the secretion of ACTH in normal people. Hence, with dexamethasone is administered, it reduces the levels of ACTH, which in turn reduces the levels of cortisol. The ACTH suppression test should not be mistaken for the ACTH stimulation test, which is conducted to check the response of the adrenal gland to a particular hormone.

The ACTH suppression test can be performed in two ways. The first method is the rapid method and the other one is known as the 6-day method. In the rapid method ACTH test, 1 milligram of dexamthasone is administered to the patient and around 9 hours later a sample of blood is drawn, to check for the levels of cortisol in the blood. In case there is no decrease in the amount of cortisol then the same procedure is repeated, but the dose given this time, is of 8 milligrams. In case a person is given the 6-day ACTH suppression test, urine samples are collected every 24 hours, for a period of 6 days and the cortisol is measured. On the third day, a low dose of dexamethasone is given to the patient orally, every 6 hours, for one entire day. On the fifth day, this is repeated, with a higher dose of dexamethasone.

Aldosterone suppression test

Aldosterone refers to a corticosteroid that is secreted by the adrenal gland. It performs several important functions, like regulating the balance of water and salt, controlling blood pressure and balancing electrolytes in the body. At times, a medical health care provider may advise a patient to undergo an aldosterone suppression test to measure the amount of aldosterone that is being released into the body. This test may also help identify causes for high blood pressure or low potassium.
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