Dexamethasone overnight test
(Low-dose, 1 mg)
Indication | Suspicion of Cushing syndrome. The dexamethasone overnight test is the best screening test, also in the outpatient sector. |
Principle | Dexamethasone inhibits ACTH-release and therefore endogenous cortisol production by the adrenal cortex. In the immunological evaluation of cortisol, dexamethasone does not show cross-reactions with endogenous cortisol. |
Evaluation parameters | Cortisol |
Material | 2 ml serum on the day after dexamethasone administration. |
Procedure |
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Evaluation | A decrease in cortisol levels to ≤ 1,8 µg/dl excludes Cushing syndrome with high probability. A value ≥ 5 µg/dl points toward Cushing syndrome or pseudo-Cushing respectively. Values between 1,8 and 5 µg/dl are to be considered “autonomous cortisol secretion” and potentially require treatment, if a diabetic metabolic condition, osteoporosis or muscle weakness occurs or deteriorates. Pseudo-Cushing describes a condition of hypercortisolism, which is not caused by ectopic nor autonomous adrenal cortisol production but can rather be seen in cases of severe depression, extreme obesity (especially in the context of PCO syndrome), alcoholism (rare), insufficiently controlled diabetes mellitus and during pregnancy. Differential diagnosis of Cushing syndrome can be obtained by a combined dexamethasone overnight test and immediate subsequent CRH stimulation test. Cortisol levels of > 1,4 µg/dl 15 min after CRH administration contradict Pseudo-Cushing. |
More Results for the letter D
- Dexamethasone overnight test
- Low-dose, 1 mg
- Dexamethasone overnight test
- High-dose, 8 mg
- Dexamethasone test, long-term