Thyroglobulin (TG) is a prohormone of the thyroid gland, from which hormones are formed: triiodothyronine (T3) and thyroxine (T4). In clinical practice, it is used as an oncomarker – an indicator of the risk of thyroid gland cancer. Normally, the hormone is produced only in the thyroid gland (TG), it enters the bloodstream in small amounts. A slight increase in the level is possible with thyroiditis – inflammation of the TG, and with hyperthyroidism. However, massive prohormone production occurs in cancer cells of the gland. In this case, there is an increase in the level of TG several times. There is also a correlation between the concentration of thyroglobulin and the size of the tumor.

Detection of an over-threshold amount of TG does not give the right to make a diagnosis of thyroid gland cancer. This is a direct indication for the next stage of cancer diagnosis – puncture biopsy. There are factors that lead to a false negative result: the most common is the presence of antibodies to thyroglobulin, since antibodies destroy this prohormone and its concentration becomes lower than the real level of production. Therefore, TG and anti-TG must be prescribed simultaneously. The second variant of a false negative result is less common, but do not forget about it. There are forms of thyroid gland cancer that produce a defective form of thyroglobulin, which the analyzer cannot detect and provides data on its absence.

In addition to screening diagnosis of tumors, the test is used to monitor the effectiveness of treatment: 6 weeks after the tumor removal surgery, thyroglobulin levels should return to normal.

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