Library · Test
Dexamethasone suppression test
Make it clearer
The dexamethasone suppression test is not looking for a number: it is looking for a response. The person is given dexamethasone, a synthetic corticosteroid, and the point is to see whether the body obeys the order to shut down cortisol production. That is how endogenous Cushing syndrome, an excess of cortisol produced by the body itself, is evaluated.
The chain of command works in sequence and is called the hypothalamic-pituitary-adrenal axis. The hypothalamus, in the brain, sends a hormone to the pituitary; the pituitary sends another hormone through the blood to the adrenal glands, which sit on top of the kidneys; and those glands make cortisol. And cortisol, once in the blood, comes back to put the brakes on the hypothalamus and the pituitary so they stop asking for more. The return signal that switches off the order is called negative feedback.
When the excess of cortisol is pathologic, the axis stops responding to that brake, either completely or in part. The test presses the brake to see whether the car responds. The test comes in either an overnight version or a two-day version.
In brief
The dexamethasone suppression test is used to diagnose endogenous Cushing syndrome by seeing whether the hypothalamic-pituitary-adrenal axis shuts down in response to a corticosteroid given from outside the body.
In that axis the hypothalamus signals the pituitary, the pituitary signals the adrenal gland, and the resulting cortisol shuts down both by negative feedback.
In pathologic hypercortisolism the axis becomes resistant to that brake, and the test is done as an overnight or a two-day version.
The test presses the brake to see whether the car responds.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingDexamethasone Suppression Test, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated