This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thyroid disorders, Subject name: Pediatrics
[{'content': 'A 6-month-old infant is brought with a history of constipation and excessive sleepiness. On examination, he is lethargic, has periorbital puffiness, large tongue and umbilical hernia. The investigation which will help to diagnose this condition is: \nSelect and explain. \nA. Karyoptyping, B. T4, TSH assay, C. Rectal mucosal biopsy, D. Knee X-ray', 'role': 'user'}, {'content': 'Answer: B \nExplanation: - History given in question shows typical presentation of hypothyroidism, so thyroid hormone assay is required. DIAGNOSIS OF HYPOTHYROIDISM: T4 levels - low Primary hypothyroidism - TSH usually > 100 mu/L Central / secondary hypothyroidism - low TSH levels TSH T4 Thyroid dyshormonogenesis ELEVATED LOW Thyroid dysgenesis ELEVATED LOW Central hypothyroidism LOW LOW TREATMENT - Oral Levothyroxine(early morning with empty stomach)', 'role': 'assistant'}]