A mother brings her one month old baby for the establishment of care in your pediatrics office. She is concerned that the baby feels extremely cold, has puffy eyelids, and has feeding difficulties.On physical examination, you notice hypothermia, large anterior and posterior fontanels, macroglossia, hoarse cry, depressed nasal bridge, thick, dry and cold mottled skin, bradycardia, hypotonia and hyporeflexia. They are recent immigrants from Myanmar, who arrived in the United States two weeks ago. Laboratory evaluation reveals a TSH of 68 mIU/L (normal 0.58 – 5.57 mU/L) and a free T4 of 0.1 ng/dL (normal 0.8 – 2.8 ng/dL). Of the following, which is the most common cause of this disorder in children born in a developing nation?
