For patients with surgically unresectable, residual TSH is required to be controlled below 0.1 mU/L. For patients with complete surgical resection, it is sufficient to control TSH at a slightly lower level than normal (TSH < 0.27 mU/L: TSH monitoring standard at Peking University Cancer Hospital, different facilities). It is not necessary to require TSH to reach a fixed value, because the human body changes every moment, and the same dose of thyroxine will have great fluctuations in the corresponding TSH, and it is impossible to control TSH at a fixed level. After taking the medication for 5 years and checking that the tumor does not recur, the TSH can be controlled at a normal level. If the patient has enough thyroid tissue left, the drug can even be stopped completely.