Which tumor marker is elevated in medullary thyroid carcinoma?

• A. Calcitonin
• B. Thyroglobulin
• C. CEA
• D. Calcitonin gene-related peptide

Answer: (A)

Medullary thyroid carcinoma arises from parafollicular C cells that secrete calcitonin, so calcitonin levels in the blood are typically elevated and serve as a useful marker for diagnosis and for monitoring response to treatment or recurrence after surgery. This marker directly reflects the tumor’s biology, making it the most informative indicator in this cancer. Thyroglobulin is produced by follicular cells and is mainly a marker for differentiated thyroid cancers such as papillary or follicular types, so it isn’t reliable for medullary carcinoma. CEA can be elevated in medullary thyroid carcinoma but is nonspecific and less helpful for direct disease monitoring. Calcitonin gene-related peptide isn’t used clinically as a tumor marker for this cancer.