Medullary Thyroid Carcinoma — RACP Adult Medicine MCQ

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HardEndocrinology & DiabetesMedullary Thyroid CarcinomaRACP Adult Medicine

A 48-year-old man with type 2 diabetes presents with a painless, gradually enlarging neck mass. FNA of a thyroid nodule shows medullary thyroid carcinoma. Serum calcitonin is markedly elevated. What additional investigations are essential before surgery?

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Correct answer: A — Plasma metanephrines and serum calcium/PTH

Medullary thyroid carcinoma (MTC) can be sporadic (~75%) or part of MEN2 syndrome (~25%). ALL patients with MTC must have plasma free metanephrines (to exclude concurrent phaeochromocytoma – which must be operated on FIRST to prevent intraoperative hypertensive crisis) and serum calcium/PTH (to exclude hyperparathyroidism – MEN2A). RET proto-oncogene testing should also be performed. Thyroglobulin is a marker for differentiated (papillary/follicular) thyroid cancer, NOT medullary.

Reference: eTG – 2025 – Endocrinology; ATA – 2015 – MTC Management Guidelines