Congenital hypothyroidism occurs in approximately 1 in 6,000 infants (literature range, 1-3/10,000), which makes it about 3 times as common as phenylketonuria (PKU). Approximately 85% of cases are due to thyroid agenesis and 10% are defects of enzymes in thyroid hormone synthesis, so that about 95% of all cases are primary hypothyroidism and 3%-5% are […]