Thyroglobulin antibody (TgAb) testing is closely related to Anti-Tg testing. It measures the same class of autoantibodies against thyroglobulin and is elevated in autoimmune thyroid conditions including Hashimoto's thyroiditis and Graves' disease.
Critically, thyroglobulin antibodies interfere with thyroglobulin immunoassays, causing falsely low thyroglobulin readings. Since thyroglobulin is used as a tumour marker after thyroid cancer surgery, the presence of TgAb must always be measured simultaneously — if TgAb is positive, rising or persistent levels may still indicate cancer recurrence even when the thyroglobulin appears undetectable.
FAQs
Why must TgAb and thyroglobulin always be measured together?
TgAb causes falsely low thyroglobulin results. A cancer patient could appear disease-free based on undetectable thyroglobulin when TgAb is the cause. Both must be measured simultaneously for accurate cancer surveillance.
Can TgAb disappear after thyroid cancer treatment?
Yes. After total thyroidectomy and radioiodine ablation, TgAb typically becomes undetectable over 12-24 months. Persistent or rising TgAb is suspicious for residual or recurrent disease.
Does selenium reduce TgAb?
Yes. Multiple trials show selenium supplementation (200 mcg/day) significantly reduces TgAb titres in Hashimoto's thyroiditis over 3-6 months.
How does TgAb differ from Anti-TPO?
Anti-TPO targets thyroid peroxidase enzyme; TgAb targets thyroglobulin protein. Both are elevated in Hashimoto's but TgAb specifically interferes with thyroglobulin cancer monitoring.
