Sample with dexamethasone - Causes, symptoms and treatment. MF.

A probe with dexamethasone( or prednisolone) is used to determine the genesis of hyperandrogenism and differential diagnosis of hormone-reactive tumors of the adrenal cortex and adrenal hyperplasia, as well as for the differential diagnosis of hypercorticism due to the tumor of the hypothalamic-pituitary region( the Itzenko-Cushing disease) and adrenal genesis( Isenko-Cushing's).The sample is recommended for increased excretion of 17-CS and 17-ACS( or for high concentrations of 11-ACS in the blood).

The test is based on the inhibitory effect of the glucocorticoid drug on the secretion of corticotropin, which is manifested by a decrease in hormone formation in the cortical substance of the adrenal glands. The hormone-producing cells of the adrenal cortex are under the control of corticotropin, while the hormone production of tumor cells does not depend on the function of the pituitary.

The test consists in the appointment of dexamethasone 2 mg / day( in 4 divided doses) for 2-3 days or prednisolone 20 mg( in 4 divided doses) for 5 days( small test).Less commonly used a large test, consisting in the appointment of 8 mg dexamethasone( in 4 divided doses).Before and after the test, excretion of 17-CS, 17-ACS or 11-ACS in the blood is determined. Reduction of these indicators by 50% or more( positive test) indicates hyperplasia of the adrenal cortex, no changes( negative test) - a tumor of the cortex of the adrenal glands.

With Isenko-Cushing's disease, these tests are positive, since the adrenal glands retain sensitivity to a decrease in the level of corticotropin, and in the case of the Itenko-Cushing syndrome, they are negative.

To clarify the genesis of hyperandrogenism, a sample with dexamethasone is performed in this way:

Patient is assigned dexamethasone 0.5 mg every 6 hours for 2 days. Two days before the sample is taken and on the 2nd day of taking the drug, 24 hours urine is collected to determine the level of 17-CS or DEA-C.

With a positive sample, the studied parameters decrease by more than 50%, which indicates functional disorders in the adrenal cortex.

With a negative sample, i.e.when the level of 17-CS and DEA-C falls by less than 25-50%, the tumor genesis of hyperandrogenia is diagnosed.