This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: JIPMER 2017, Subject name: Surgery
A biopsy from a mass in front of the neck revealed parafollicular cells. How do you follow up? 
Select and explain. 
A. Calcitonin, B. T4, C. Thyroxine, D. Thyroglobulin
A: Calcitonin
Answer: A: Calcitonin 
Explanation: Biopsy from the mass in front of the neck revealed parafollicular cells indicating that it's a case of Medullary carcinoma of the thyroid. Medullary carcinoma of the thyroid (MTC): It is a distinct thyroid carcinoma that originates in the parafollicular C cells of the thyroid gland. These C cells produce calcitonin. Hence it is used for follow up of these patients