A 65-year-old man with MEN2A syndrome has a 1.8 cm medullary thyroid carcinoma with elevated basal calcitonin (840 pg/mL). Preoperative imaging shows no distant metastasis. Which of the following is the most critical preoperative evaluation before thyroidectomy?
- A Serum TSH and thyroglobulin levels
- B Serum gastrin levels to exclude Zollinger-Ellison syndrome
- C Serum VIP levels to rule out VIPoma
- D 24-hour urinary catecholamines / plasma metanephrines to exclude phaeochromocytoma ✓
Explanation
In MEN2A (RET proto-oncogene mutation), phaeochromocytoma occurs in 40-50% of cases and must be excluded BEFORE thyroid surgery to avoid a hypertensive crisis under anaesthesia. Measurement of plasma free metanephrines (sensitivity ~99%) or 24-hour urinary catecholamines/metanephrines is mandatory preoperatively. If a phaeochromocytoma is identified, adrenalectomy must precede thyroidectomy. Serum calcium/PTH should also be checked (as hyperparathyroidism occurs in MEN2A), but phaeochromocytoma exclusion is the most critical safety step. Gastrin (MEN1) and VIP are not MEN2A components.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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