1. Treatment of congenital hypothyroidism in newborns L-T4 therapy should be started as soon as congenital hypothyroidism in newborns is diagnosed. The treatment dose is generally 10-15ug/(kg.d) (37.5-50ug/d for full-term infants), starting with a single dose. ▪ After 2 weeks, the dose should be adjusted according to clinical and blood T4 levels, increasing by 12.5ug each time. ▪ After 4 weeks, serum T4 should be maintained at normal high (10-16ug/dl) for one year, T3 levels should be normal and TSH should decrease, otherwise bone age will not reach normal. ▪ TSH should be lower than 15mU/L after 3 months, and T4 and TSH should be rechecked every 1-2 months or 2 weeks after each dose change, while paying attention to the manifestation of hypothyroidism or hyperthyroidism symptoms in children. ▪ Premature closure of cranial suture and early bone age can occur if T4 is applied in excess for a long time. Whether or not temporary hypothyroidism in preterm infants requires thyroid hormone therapy is a matter of differing expert opinion, with some experts suggesting early replacement therapy.