The radioactive iodine is given when the patient is hypothyroid in preparation for the scan. A serum thyroglobulin level should also be obtained since persistent disease is present when it is elevated. After scanning or treatment, patients are again placed on thyroid hormone in order to avoid hypothyroidism and to suppress the TSH levels, which might stimulate residual tumor cells to grow. Some patients will require retreatment with radioactive iodine if the serum thyroglobulin level again becomes elevated or recurrent disease becomes evident.
