Serum TG measurement is performed mostly for monitoring of thyroid carcinoma patients. Dynamics of TG concentration is used as a marker for evaluation of treatment efficiency, revealing of possible recurrence and metastases in patients after thyrectomia. This parameter is not used for primary diagnostics of thyroid cancer. TG concentration in serum may be useful for exact diagnostics in the case of congenital hypothyrosis. Increased TG concentration permits to differentiate subacute thyroiditis from pharmacological thyrotoxicosis (when TG level remains stable). In patients with Grave’s disease increase in TG concentration is a preliminary sign of recurrency after canceling of suppressive therapy.
TG measurement may be affected by presence of anti-TG autoantibodies in the serum sample. In this case the results may be false-negative. To obtain the reliable results it is recommended always to combine TG and anti-TG autoantibodies determination. Serial TG determinations for patient monitoring should be always done by the same method. The physician should be always informed not only of the results of TG determination but also of the type of assay used. When the type of diagnostic kit is changed, the laboratory must perform the appropriate clinical evaluation and compare the range of the results obtained with two types of kits.