Thyroglobulin antibodies (TgAb) are autoantibodies directed against thyroglobulin, a protein produced by the thyroid gland, and are often used as a marker for autoimmune thyroid diseases such as Hashimoto's thyroiditis and Graves' disease. Their presence can interfere with the measurement of thyroglobulin levels, which is crucial for monitoring patients with differentiated thyroid cancer post-thyroidectomy.