Thyroid surgery may cause hypothyroidism, mainly depending on the scope of thyroid tissue removed in thyroid surgery and other circumstances. 1. Total thyroidectomy or subtotal thyroidectomy, due to the large amount of thyroid tissue removed, the body can not synthesize thyroxine or the synthesized thyroxine can not meet the physiological needs of the body, will lead to postoperative hypothyroidism, and additional physiological needs of thyroxine needs to be supplemented after surgery. 2. Partial thyroidectomy, such as the removal of one lobe of the thyroid gland or one lobe of the combined isthmus, the remaining part of the thyroid tissue can compensate for the synthesis of the body’s physiological needs, then there will be no hypothyroidism. After thyroidectomy, regular review of thyroid function is required, and the dose of thyroxine should be adjusted as prescribed by the doctor to avoid hypothyroidism.