After thyroid cancer surgery, high t4 and low tsh should be considered as hyperthyroidism caused by medication, and it is recommended to review thyroid function and adjust medication. As thyroid cancer surgery needs to remove part or all of the thyroid gland, in order to prevent and control hypothyroidism caused by insufficient secretion of thyroxine after surgery, long-term thyroid hormone replacement therapy is generally required, and if too much medication is taken, it will lead to hyperthyroidism, resulting in higher t4 and lower tsh. Therefore, after thyroidectomy, follow the doctor’s instructions to use the correct medication, should pay attention to regular rechecking of thyroid function, so that the TSH control can be maintained at 0.1-0.5μIU/mL. If the medication is not properly administered after thyroid cancer surgery, overdose of medication will easily lead to hyperthyroidism, while underdose will lead to hypothyroidism. Therefore, it is necessary to review these hormone levels regularly after thyroid cancer surgery and adjust the dosage of levothyroxine tablets as prescribed by the doctor.