Cushing Disease Diagnosis — RACP Adult Medicine MCQ

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ModerateEndocrinology & DiabetesCushing Disease DiagnosisRACP Adult Medicine

A 55-year-old woman with Cushing syndrome has elevated ACTH. High-dose dexamethasone suppresses cortisol by 70%. Most likely source?

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Correct answer: C — Pituitary ACTH-secreting adenoma (Cushing disease)

ACTH-dependent + high-dose dexa suppression >50% = pituitary source (Cushing disease, ~90% sensitivity). IPSS for definitive localisation.

Reference: eTG – 2025 – Endocrinology; Endocrine Society – 2015