Frequently Asked Questions (FAQs)
This test is used as an adjunct in the diagnosis of autoimmune thyroid diseases: Hashimoto disease, postpartum thyroiditis, neonatal hypothyroidism and Graves disease. In individuals with autoimmune hypothyroidism 30% to 50% will have detectable anti-Tg autoantibodies while 50% to 90% will have detectable anti-TPO autoantibodies. In Graves disease both types of autoantibodies are observed at approximately half these rates. The presence of anti-Tg which occurs in 15% to 30% of thyroid cancer patients could result in misleading Tg results. Anti-Tg may result in both falsely-low and less commonly falsely high serum Tg measurements. Therefore in anti-Tg-positive patients serum Tg measurements should not be used as the sole measurement for thyroid cancer follow-up and should be interpreted with caution.