This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology and breast, Subject name: Surgery
[{'content': 'After thyroidectomy for medullary carcinoma of thyroid, which is impoant for determining recurrence of a tumour? \nSelect and explain. \nA. Thyroglobulin, B. TSH, C. Calcitonin, D. Thyroxine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: High levels of serum calcitonin and carcinoembryonic antigen are produced by many medullary tumours, which should be tested for in suspected cases.Calcitonin levels fall after resection and rise again with recurrence, making it a valuable tumour marker in the follow-up of patients with this disease.Ref: Bailey and Love, page no: 820', 'role': 'assistant'}]