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: Social & Preventive Medicine
[{'content': 'The most sensitive indicator of environmental iodine deficiency is \nSelect and explain. \nA. Serum T4 levels, B. Serum T3 levels, C. Urine iodine excretion, D. Neonatal hypothyroidism', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. d. Neonatal hypothyroidism', 'role': 'assistant'}]