A serological test to detect autoantibodies directed against thyroglobulin, a glycoprotein produced by follicular cells in the thyroid gland that serves as a reservoir for thyroid hormones (T3 and T4). These antibodies are present in autoimmune thyroid diseases, particularly Hashimoto's thyroiditis and Graves' disease. The test is also used in follow-up after thyroid cancer surgery (papillary or follicular carcinoma) to detect recurrence.