1. The main purpose of iodine therapy is to control distant metastases, while local recurrence in the thyroid area and metastases in the cervical lymph nodes are mainly solved by surgery, rather than relying on iodine therapy. Therefore, iodine therapy is needed for distant metastases, but even the efficiency of iodine therapy for distant metastases is only 38%, and most of them are ineffective. 2. When there are more lymph node metastases in the neck, it indicates that distant metastases are likely to occur, so this situation can also be treated with iodine, especially if there are double neck lymph node metastases, in order to control the possible lung metastases. It is not necessary to use iodine therapy if there are lymph node metastases. 3.Patients with very advanced thyroid cancer who feel that they cannot achieve the surgical result of most people after surgery, and the scope of surgery is large and the borders cannot be excised to the ideal extent, can also do iodine therapy, which is to control the possible safe range of the operation field, rather than all need iodine therapy, which is not necessary as long as they feel that the excision is clean. 4. There are many people who advocate iodine therapy after total excision of thyroid cancer in order to observe the postoperative thyroglobulin changes to predict recurrence or metastasis. I do not agree with this view. Iodine therapy is not without side effects. It is not necessary to rely on thyroglobulin, as thyroid cancer can be reviewed by ultrasound after surgery. Even if the globulin is high, we still rely on ultrasound to check it. 5. The efficiency of distant metastases is not very high, and we have to apply iodine therapy everywhere, hoping to control local recurrence and lymph node metastases in the neck. I think it is a bit over-treatment.