In neonates with hypothyroidism, replacement therapy with levothyroxine tablets is given. The goal of treatment is to restore serum thyroid stimulating hormone and thyroid hormone levels, to within the normal range. Thyroid tablets are not generally used in clinical practice because they are dried preparations from animal thyroid glands and are rarely used due to their unstable thyroid hormone levels and high T3 levels. The total daily amount of levothyroxine tablet replacement therapy is about 2.0 μg (kg/d); usually start with a small dose, and review the thyroid function every 2-3 weeks to know the level of thyroid hormone and thyroid stimulating hormone, and then according to the review of the level of thyroid hormone, adjust the dosage of levothyroxine tablets until the target of treatment is reached. After the treatment goal is reached, the thyroid function needs to be rechecked every 2-3 months to adjust the dosage.