Low thyroid hormone after thyroidectomy may be caused by overdose of levothyroxine, it is recommended to adjust the dosage under the guidance of a doctor. 1. too much medication: after thyroidectomy need to take levothyroxine sodium tablets to supplement hormones, thyroid hormone may be low due to overdose of drugs, need to be under the guidance of a professional doctor to adjust the dose of drugs. 2. Subclinical hyperthyroidism: seen after surgical treatment of hyperthyroidism, thyroid stimulating hormone reduction, serum total thyroxine and serum total triiodothyronine levels are normal. The decision of whether to give anti-hyperthyroidism treatment is based on the patient’s thyrotropin reduction and the patient’s clinical manifestations. There are many reasons for low thyroid hormone after thyroidectomy, and it is better to have low thyroid hormone after thyroid cancer surgery to reduce the risk of recurrence, and it is recommended to go to the hospital in time to improve the examination and treatment under the guidance of the doctor.