Thyroglobulin is a large glycoprotein secreted by thyroid follicular epithelial cells and is a carrier of thyroid hormone synthesis and storage. Thyroglobulin can be used as a tumor marker for differentiated thyroid cancer and as an important monitoring indicator for patients with differentiated thyroid cancer after surgery. Its normal value ranges from 5 to 40 μg/L. Any test result higher or lower than the normal value should be taken seriously. A thyroglobulin value of 500 μg/L indicates that the patient may have an autoimmune disease of the thyroid gland and does not mean that it is caused by cancer, which needs to be diagnosed by pathological examination. Elevated thyroglobulin values can be seen in Hashimoto’s thyroiditis, painless thyroiditis, thyroid adenoma, subacute thyroiditis, nodular goiter, and thyroid cancer. In addition, patients with liver disease, diabetes mellitus, rheumatism, and some normal people may also have elevated thyroglobulin. It should be noted that thyroglobulin is very important for the prognosis and monitoring of the treatment effect of differentiated thyroid cancer. Therefore, if thyroglobulin is found to be abnormally high during regular monitoring after total thyroidectomy for patients diagnosed with thyroid cancer, it should be considered as a result of recurrence or metastasis of thyroid cancer.