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Adrenal Cushing's syndrome — SCE Endocrinology MCQ

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HardAdrenalAdrenal Cushing's syndromeSCE Endocrinology

A 52-year-old man has central obesity, proximal myopathy and osteoporosis. Late-night salivary cortisol is raised twice and 24-hour urinary free cortisol is three times the upper limit. ACTH is suppressed and CT shows a 4.8 cm heterogeneous adrenal mass. What is the most likely diagnosis?

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Correct answer: C — ACTH-independent Cushing's syndrome from an adrenal tumour

ACTH-independent Cushing's syndrome from an adrenal tumour is best because suppressed ACTH with confirmed cortisol excess localises the source to autonomous adrenal cortisol secretion. The alternatives are less appropriate because pituitary and ectopic ACTH syndromes are ACTH-dependent; pseudo-Cushing's lacks this adrenal localisation; adrenal insufficiency is cortisol deficiency. The SCE teaching point is to integrate the clinical pattern, biochemistry and context rather than treating an isolated result.

Reference: Endocrine Society Cushing's syndrome guideline; ESE adrenal incidentaloma guideline