<prompt> A 6 month old infant is brought with a history of constipation and excessive sleepiness. On exmination, he is lethargic, has periorbital puffines, large tongue and umbilical hernia. The investigation which will help to diagnose this condition is ?T4 TSH assayKaryoptypingRectal mucosal biopsyKnee X ray  <response>: Ans. is a i.e., T4 TSH assary o It is typical presentation of hypothyroidism. 