TG and thyroid gland carcinoma: It is produced by thyroid follicular cells, iodized as active thyroid hormone, and released into circulation through exocytosis.[1] Clinicians use the serum concentration of Tg to monitor thyroid cancer[2–4]; several studies have suggested using it as a biomarker of iodine status at both the individual and population level,[5–7] which requires a region-specific Tg reference.