[Thyroglobulin - An important tumor marker and laboratory challenge].

Serum/plasma thyroglobulin (TG) levels and neck ultrasonography are currently the mainstay of postoperative monitoring in patients with differentiated thyroid cancer (DTC). TG can be determined as a tumor marker in these patients under required levothyroxine treatment at TSH suppressive doses. The immunologic determination of TG as a laboratory parameter in the follow-up of thyroid malignancies always requires confirmation of the test result in order to detect interfering variables. There are two commonly used options: first, the TG recovery rate and second, the determination of anti-TG autoantibodies (TGAb). However, neither test adequately addresses the issue of correct TG determination. Heterophilic antibodies are another important source of interference. Mass spectroscopic TG determination is a more complex alternative that can be used in inconclusive cases.