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Adrenal Cushing's syndrome — SCE Endocrinology MCQ

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HardAdrenalAdrenal Cushing's syndromeSCE Endocrinology

A 61-year-old has proximal myopathy, easy bruising and failed dexamethasone suppression. ACTH is below 1 pmol/L and CT shows a 3.8-cm homogeneous adrenal adenoma. Which additional biochemical pattern supports chronic ACTH-independent cortisol secretion?

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Correct answer: ELow DHEAS from suppressed ACTH-driven adrenal androgen production

The best answer is “Low DHEAS from suppressed ACTH-driven adrenal androgen production”. Autonomous adrenal cortisol suppresses pituitary ACTH, reducing stimulation of the contralateral adrenal cortex and zona reticularis; DHEAS is therefore often low. “Raised ACTH with bilateral adrenal hyperplasia” is less appropriate because raised ACTH points to ACTH-dependent pituitary or ectopic disease “Raised renin and aldosterone caused by autonomous cortisol” is less appropriate because cortisol excess can cause hypertension but does not specifically produce parallel high renin and aldosterone “Raised calcitonin and CEA from medullary thyroid carcinoma” is less appropriate because calcitonin and CEA are medullary-thyroid markers “Raised TSH with low free T4 as the defining pattern” is less appropriate because primary hypothyroidism neither partitions Cushing syndrome nor follows from ACTH suppression

Reference: European Society of Endocrinology guideline on adrenal incidentalomas. https://academic.oup.com/ejendo/article/189/1/G1/7198474