What does the Thyroglobulin Antibody test measure?

Why is Thyroglobulin Antibody measured?

TgAb serves two roles: as a marker of autoimmune thyroid disease (though less sensitive than TPOAb) and as an essential quality-control check when measuring serum thyroglobulin. In thyroid cancer follow-up, positive TgAb renders thyroglobulin unreliable, and the trend of TgAb titre itself can serve as a surrogate tumour marker. In autoimmune thyroid disease diagnosis, TgAb adds little when TPOAb is already positive, but about 5–10 per cent of Hashimoto patients are TPOAb-negative yet TgAb-positive, so both antibodies are often ordered together.

Reference ranges

Standard reference

Typically <4–40 IU/mL; method- and laboratory-specific.

Functional medicine optimal

Undetectable or below the assay-specific cut-off. When TgAb is positive in the cancer-surveillance setting, serial TgAb titres are followed — rising titres may signal recurrence even when serum thyroglobulin is undetectable.

Units

IU/mL, kU/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.