A 22-year-old man with MEN2B is diagnosed with medullary thyroid carcinoma. Before proceeding with thyroidectomy, which investigation is mandatory to avoid a perioperative catastrophe?

• A Plasma free metanephrines to exclude phaeochromocytoma ✓
• B Serum prolactin to exclude prolactinoma
• C Colonoscopy to exclude ganglioneuromatosis
• D Echocardiography to exclude mitral valve prolapse

Explanation

MEN2B comprises medullary thyroid carcinoma, phaeochromocytoma, and mucosal neuromas with marfanoid habitus. Phaeochromocytoma must be excluded before any operation, including thyroidectomy, because an undiagnosed catecholamine excess can precipitate a fatal hypertensive crisis under anaesthesia. Plasma free or 24-hour urinary metanephrines are the recommended screening tests, and a confirmed phaeochromocytoma requires alpha blockade and adrenalectomy first. Mitral valve prolapse occurs in MEN2B but does not contraindicate surgery, and ganglioneuromatosis does not require colonoscopy beforehand.

Reference: Williams Textbook of Endocrinology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.