Generally speaking, for patients with differentiated thyroid cancer who have cleared all thyroid tissue, it is best to have a non-stimulated serum Tg level of less than 1ng/mL in the case of TgAb negative; in the case of TgAb positive, it is best if the TgAb value does not show a progressive upward trend. Otherwise, the possibility of tumor recurrence needs to be considered. tg refers to thyroglobulin, a specific protein produced by the thyroid gland and secreted by thyroid follicular epithelial cells. Serum Tg can be a tumor marker for differentiated thyroid cancer after total thyroidectomy, and its level is positively correlated with the tumor load of differentiated thyroid cancer in patients, and can be used as a clinical marker to assess tumor recurrence and metastasis. Since serum Tg detection is affected by the level of TgAb in the body, TgAb should be routinely detected along with serum Tg. For the first detection of serum Tg and TgAb, it should be generally 3-4 weeks after surgery or radioactive iodine nail clearance, and continuous monitoring of Tg and TgAb is recommended to assess the risk of tumor recurrence and treatment response after surgery through the trend of changes.