Oral levothyroxine (L-T4) is the most common treatment for normalizing thyroid hormone levels in patients with CH.11,12 A review article indicated that infants who began thyroid hormone treatment at age 12 to 30 days had an IQ 15.7 points higher than those who began treatment after age 30 days.12 This evidence concerns the gene TG and cyclic hematopoiesis.