Dexamethasone Suppression test-High dose for ACTH

Dexamethasone Suppression Test – High Dose for ACTH

Test Name: Dexamethasone Suppression Test – High Dose for ACTH
Sample Type: Serum
Purpose: Evaluates ACTH-dependent causes of Cushing syndrome and helps differentiate pituitary ACTH-dependent Cushing disease from ectopic ACTH production.

What is measured?

The test assesses serum cortisol response after administration of a high dose of dexamethasone, a synthetic glucocorticoid that normally suppresses ACTH secretion.

Why is it done?

It may be used to:

• Investigate suspected Cushing syndrome
• Help identify a pituitary source of excess ACTH
• Differentiate Cushing disease from ectopic ACTH secretion in selected clinical situations

Test Principle

Dexamethasone is administered at a high dose, followed by measurement of serum cortisol. Suppression of cortisol may support a pituitary ACTH source, while lack of suppression can suggest ectopic ACTH production. Results should always be interpreted along with clinical findings and other investigations.

Patient Preparation

• Follow the physician's instructions regarding dexamethasone administration and blood collection.
• Inform the doctor about all medications, particularly corticosteroids and drugs that may affect dexamethasone metabolism.
• Timing of the dose and blood collection is important for accurate interpretation.

Clinical Significance

This test is an adjunctive investigation in the evaluation of ACTH-dependent hypercortisolism. It is not usually interpreted as a standalone diagnostic test.

Sample: Serum
Report: Cortisol level after high-dose dexamethasone suppression
Interpretation: As per laboratory reference range and clinical correlation.