Snap Shot A six-week-old male presents with lethargy and hypotonia. On physical exam he is jaundiced and has a large protruding tongue. Introduction Due to agenesis of thyroid or defects in enzymes most common cause in developed countries Can also be caused by iodine deficiency most common cause in underdeveloped countries T4 is crucial during first two years of life for normal brain development Cretinism refers to untreated congenital hypothyroidism leads to congenital defects and physical abnormalities Presentation Normal Apgars Prolonged jaundice (indirect hyperbilirubinemia) Presents at 6-12 weeks with poor feeding lethargy hypotonia coarse facial features large protuding tounge developmental delay Evaluation Labs show decreased T4 elevated TSH Treatment Treat with levothyroxine replacement Prognosis, Prevention, and Complications Prevention by newborn screeening by law