Which initial screening test is recommended to establish hypercortisolemia in a patient with central obesity, moon facies, and purple abdominal striae?
Answer and explanation
Correct answer: B. 24-hour urinary free cortisol excretion
- Step 1: Clinical suspicion of Cushing syndrome requires biochemical confirmation of autonomous, non-suppressible cortisol excess.
- Step 2: Validated first-line screening tests include 24-hour urinary free cortisol, late-night salivary cortisol, or an overnight 1-mg dexamethasone suppression test.
Answer
24-hour urinary free cortisol excretion.
Why not the others: Plasma ACTH is useful only after hypercortisolemia is established to distinguish ACTH-dependent from ACTH-independent causes. A random spot serum cortisol is non-diagnostic due to circadian fluctuations and stress reactivity. Adrenal imaging is premature before biochemical confirmation of hypercortisolemia.
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