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: 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 a polypeptide hormone secreted by the parafollicular or C cells of the thyroid gland; it is involved in plasma calcium homeostasis and acts to decrease the rate of bone resorption. Preparations of calcitonin are called either calcitonin-human or calcitonin-salmon; the former is a synthetic polypeptide with the same sequence as that occurring naturally in humans, and the latter is either derived from salmon or is a synthetic polypeptide of the same sequence as that found in salmon. They are used in the treatment of severe hypercalcemia, Paget&;s disease of bone, and postmenopausal osteoporosis. Ref: Ganong&;s review of medical physiology; 24th edition; page no:-377', 'role': 'assistant'}]