Thyroglobulin

Thyroglobulin is a large glycoprotein produced and stored in thyroid follicular cells’ colloid, serving as the precursor scaffold for synthesis of thyroid hormones T4 and T3. Blood thyroglobulin levels are used as a tumor marker after thyroid cancer treatment: detectable or rising levels may indicate residual or recurrent disease. Measurements can be affected by anti‑thyroglobulin antibodies, so lab interpretation requires context.

There’s no single thyroglobulin (Tg) cutoff that proves cancer. After total thyroidectomy and radioiodine ablation, an undetectable Tg (often <0.2 ng/mL) is reassuring. Persistently detectable Tg >1–2 ng/mL is suspicious and warrants imaging; levels >10 ng/mL strongly suggest persistent or metastatic differentiated thyroid cancer. Interpret results with assay sensitivity and anti‑thyroglobulin antibodies in mind.

Thyroglobulin is not T3 or T4. It is a large glycoprotein produced by thyroid follicular cells that serves as the precursor and storage scaffold in the colloid. Iodination and coupling of tyrosine residues on thyroglobulin form T3 and T4, which are later cleaved from thyroglobulin by proteolysis and released into the bloodstream as active thyroid hormones.

Thyroglobulin is a large glycoprotein produced and stored by thyroid follicular cells as a precursor to T3/T4 and is used mainly as a tumor marker or to assess remaining thyroid tissue after surgery. TSH (thyroid‑stimulating hormone) is a pituitary hormone that regulates thyroid activity; its blood level indicates thyroid function (high in primary hypothyroidism, low in hyperthyroidism).

If thyroglobulin is high, it may indicate residual or recurrent differentiated thyroid cancer, remaining normal thyroid tissue, thyroid inflammation (thyroiditis), or recent biopsy/surgery. Anti-thyroglobulin antibodies can interfere with measurements. Your doctor will review trends, check for antibodies, and may order ultrasound, radioiodine scan, or repeat testing. Follow-up with an endocrinologist is recommended for interpretation and management.

Lower thyroglobulin (Tg) by treating residual thyroid tissue or cancer: total thyroidectomy and, when indicated, radioactive iodine ablation. Use levothyroxine to suppress TSH to clinician‑targeted levels. Follow a low‑iodine diet before radioiodine therapy, monitor and treat residual/recurrent disease, and check anti‑thyroglobulin antibodies (which can skew results). Regular surveillance and specialist follow‑up guide adjustments.