[Serum thyroglobulin measurement and its clinical significance]

The tissue specific origin of thyroglobulin (Tg) in the blood has made this protein very applicable as a diagnostic marker in various thyroid diseases such as differentiated thyroid cancer (DTC), subacute thyroiditis (ST), destructive thyroiditis, Graves' disease (GD) and congenital thyroid diseases, although the mechanism by which Tg is released and the molecular structure in which it appears in the circulation are not fully understood. This review first describes serum Tg measurements using the immuno-radiometric assay kits available in Japan and the problem of this assay in relation to interference by the autoantibody to Tg. Finally, future directions of serum Tg measurement and its clinical application are considered based on the recent evidence that the molecular form of Tg in the circulation has characteristics that differ for specific thyroid diseases (DTC, ST or GD), and that the detection of the Tg molecule by reverse transcriptase polymerase chain reaction (RT-PCR) is possible from using thyroid cells in peripheral circulation and is effective in diagnosis and monitoring of DTC.