Thyroglobulin is the glycoprotein precursor of the iodinated thyroid hormones thyroxine (T4) and triiodothyronine (T3). Thyroglobulin is obtained from the thyroid gland and exhibits the general properties of the globulins. The human thyroglobulin (hTG) is a high molecular weight glycoprotein (605 kDa) found in the thyroid follicular cells. It plays a central role in the uptake, incorporation, and regulated biosynthesis of thyroid hormones, T4 and T3. Thyroid disorders are, in large part, due to autoimmune origin, and anti thyroglobulin autoantibodies were the first factor to be discovered. Anti hTG is found in all thyroid autoimmune diseases (Hashimoto's thyroiditis, Graves' diseases), with the highest level observed in Hashimoto's thyroiditis. Anti hTG is also characteristic of thyroid cancer, and its determination can be used for the follow up of cancer patients.