What is Thyroglobulin?
Thyroglobulin is the protein precursor of thyroid hormone and is made by normal well differentiated benign thyroid cells or thyroid cancer cells. Thyroglobulin is made by normal thyroid cells, and made by most thyroid cancer cells. For example, for patients with papillary or follicular thyroid cancer, nearly all cancer cells make thyroglobulin. Patients with medullary or anaplastic thyroid cancer will not make any thyroglobulin.
Thyroglobulin testing is primarily used as a tumor marker to evaluate the effectiveness of treatment for differentiated thyroid cancer and to monitor for recurrence.
If the thyroid gland has been removed, the normal range is equal to, or less than 3.
Patients without a known diagnosis of thyroid cancer do not generally benefit from having the levels of thyroglobulin measured. Some patients with antithyroglobulin antibodies may have inaccurate thyroglobulin levels measured in the lab if the antibodies interfere with the assay, but this is uncommon.
Although thyroglobulin levels may be elevated in patients with thyroid cancer, a large number of benign thyroid conditions may also be associated with elevated levels of thyroglobulin, hence an increased thyroglobulin alone in a patient not known to have thyroid cancer is not a sensitive or specific test for the diagnosis of thyroid cancer. Simply examining the thyroid or carrying out a thyroid biopsy can produce significant elevations in the circulating blood level of thyroglobulin. Similarly, patients with thyroid inflammation can have very high levels of thyroglobulin.
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