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: Medicine
[{'content': 'Calcitonin is secreted from - \nSelect and explain. \nA. Ancinar cells of thyroid, B. Chief cells of parathyroid, C. "C" cells of thyroid, D. Oxyphil cells of parathyroids', 'role': 'user'}, {'content': "Answer: C \nExplanation: Calcitonin is a hypocalcemic peptide hormone that in several mammalian species acts as an indirect antagonist to the calcemic actions of PTH. Calcitonin is produced by the thyroid medullary C cells, derived from the neural crest derivatives from the ultimobranchial body. The C cells are interspersed throughout the thyroid gland, although their density is greatest in the juncture of the upper one-third and lower two-thirds of the gland. The C-cells are impoant because of their involvement in medullary thyroid cancer. Reference : page 2283 Harrison's Principles of Internal Medicine 19th edition", 'role': 'assistant'}]