Thyroglobulin

Thyroglobulin (Tg) is a protein produced exclusively by thyroid cells (normal or cancerous) and is the precursor for thyroid hormones. Its primary clinical use is as a tumor marker to monitor for recurrence of differentiated thyroid cancer after thyroidectomy and ablation. Levels should be undetectable or very low in that context. In individuals with an intact thyroid, levels vary and are less clinically significant unless TgAb are present (which interfere with the Tg assay, making Tg unreliable).