Snapshot A 6-week-old girl presents with lethargy, difficulty feeding, and hypotonia. Her parents report that she was healthy and did not have any apparent symptoms at birth. This is her first time seeing a doctor. On exam, she appears jaundiced and has a large tongue that is protruding. Introduction Clinical definition login to view 2 more bullets Genetics login to view 1 more bullet Epidemiology Demographics login to view 2 more bullets Risk factors login to view 1 more bullet ETIOLOGY Pathogenesis login to view 9 more bullets Presentation Symptoms login to view 6 more bullets Physical exam login to view 8 more bullets Studies Diagnostic testing login to view 14 more bullets Differential Neonatal hypothyroxinemia login to view 2 more bullets Pediatric hypopituitarism login to view 2 more bullets DIAGNOSIS Diagnostic criteria login to view 2 more bullets Treatment Management approach login to view 3 more bullets First-line login to view 1 more bullet Complications Intellectual disability Growth failure Prevention Prevention by newborn screening by law Dietary iodine supplementation can prevent endemic cretinism but is not indicated for sporadic congenital hypothyroidism Prognosis Early diagnosis and treatment improves outcomes and patients can develop normally The most common preventable cause of intellectual disability