The Thyroglobulin – Serum test measures the level of thyroglobulin, a protein produced only by the thyroid gland. Thyroglobulin plays a key role in the production of thyroid hormones (T3 and T4).

This test is most commonly used as a tumor marker in patients who have been treated for differentiated thyroid cancer (such as papillary or follicular thyroid cancer). After complete removal or destruction of the thyroid gland, thyroglobulin levels should be very low or undetectable. Detectable or rising levels may indicate residual, recurrent, or metastatic thyroid tissue.