This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrine System, Subject name: Physiology
[{'content': 'If iodine supplementation in the diet was completely stopped today, thyroid hormone levels in blood will fall to zero after: \nSelect and explain. \nA. 7 days, B. 30 days, C. 90 days, D. 360 days', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The thyroid gland has enough stores of iodine to sustain & to synthesize the thyroid hormone for 90 days even if there is no iodine supplementation.', 'role': 'assistant'}]