This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Pathology
Medullary ca of thyroid is associated with increase in- 
Select and explain. 
A. Calcitonin, B. Thyroglobulin, C. T3, D. T4
A: Calcitonin
Answer: A: Calcitonin 
Explanation: Medullary carcinomas of thyroid are neuroendocrine tumours derived from the parafollicular cells or C cells. They secrete calcitonin,the measurement of which plays an impoant role in the diagnosis and post operative follow - up of patients.Calcitonin is readily demonstrable within the cytoplasm of tumour cells as well as in stromal amyloid by immunohistochemical methods. Ref: Robbins and cotrans 9e Pg 1099