This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Calcitonin is secreted by: \nSelect and explain. \nA. Thyroid gland, B. Parathyroid gland, C. Adrenal glands, D. Ovaries', 'role': 'user'}, {'content': "Answer: A \nExplanation: Calcitonin is primarily secreted by the parafollicular C cells of the Thyroid gland. It is a hormone secreted in response to elevated blood calcium. It stimulates calcium deposition in bone and calcium excretion by the kidneys, thus reducing blood calcium. Ref: Essentials of Pharmacology By K D Tripathi, 5th, Edition, Page 301; Ganong's Review of Medical Physiology, 22nd Edition, Page 393.", 'role': 'assistant'}]