<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 isT4 TSH assayKaryoptypingRectal mucosal biopsyKnee X ray  <response>: It is typical presentation of hypothyroidism. 