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Borderline metanephrines — SCE Endocrinology MCQ

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HardAdrenalBorderline metanephrinesSCE Endocrinology

A 50-year-old man presents with episodic hypertension and sweating. Plasma normetanephrine is borderline raised while he is taking venlafaxine and has obstructive sleep apnoea. Repeat sampling after rest remains borderline. CT adrenal is normal. What is the most appropriate next investigation?

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Correct answer: C — Repeat optimised biochemical testing after addressing confounders and consider clonidine suppression if available

Repeat optimised biochemical testing after addressing confounders and consider clonidine suppression if available is best because borderline metanephrine results need careful pre-analytical review because drugs, stress and sleep apnoea can cause false positives. The alternatives are less appropriate because one borderline result is not enough for surgery; normal CT does not fully exclude disease; metyrapone tests cortisol synthesis rather than catecholamine excess. The SCE teaching point is to integrate the clinical pattern, biochemistry and context rather than treating an isolated result.

Reference: Endocrine Society phaeochromocytoma/paraganglioma guideline