After surgery for thyroid cancer, many patients can see a decrease in thyroglobulin, but not all patients have low globulin levels. After thyroid cancer surgery, if the thyroid gland is completely removed or cleared, there will be no source of thyroglobulin and the thyroglobulin level will be low. A low thyroglobulin level for a long period of time indicates a low chance of recurrence of thyroid cancer, but if there is a sudden increase in thyroglobulin level, the risk of recurrence is higher and the possibility of recurrence increases. However, in patients with thyroid cancer that is not completely resected, thyroglobulin levels are not necessarily lower, but are evaluated in conjunction with thyroglobulin levels in preoperative and postoperative stable conditions.