Thyroglobulin antibodies (TgAb)
Autoantibodies against the thyroid protein thyroglobulin, a marker in Hashimoto's
Also known as
Definition
Thyroglobulin antibodies (TgAb, anti-Tg) are autoantibodies that the immune system makes against thyroglobulin, a protein of the thyroid cells. They can be a sign that the immune system is damaging the thyroid, as in Hashimoto's thyroiditis. They are measured alongside TPO antibodies when autoimmune thyroid disease is suspected, and in follow-up after thyroid cancer, because they can distort the thyroglobulin measurement.
| Parameter | Value |
|---|---|
| Unit | IU/mL (lab-dependent) |
| Reference Range | A negative result is normal, meaning no antibodies were detected or the value is below the lab's cut-off. Cut-offs and units differ by lab and test method; the reference range on your own report is what counts. Discuss your result with your doctor. |
Agree on your personal target range with your doctor.
↓ What a low value means
A negative result is the normal finding: no antibodies against thyroglobulin were found. According to MedlinePlus, a negative thyroid antibody result suggests that thyroid symptoms are probably not caused by an autoimmune disease. Your doctor will interpret it together with TSH and the thyroid hormones.
↑ What a high value means
A positive result may be related to Hashimoto's thyroiditis; most people with Hashimoto's have raised TPO antibodies, thyroglobulin antibodies or both. Positive values also occur with Graves' disease, subacute thyroiditis, an underactive thyroid, systemic lupus erythematosus and type 1 diabetes, as well as in pregnant women and in relatives of people with autoimmune thyroiditis. In cancer follow-up, the antibodies can interfere with the thyroglobulin measurement. Discuss your result with your doctor.
When to test
TgAb are usually measured when TSH, T3 or T4 suggest an underactive or overactive thyroid, when thyroiditis is suspected, with thyroid disease during pregnancy and after treatment for thyroid cancer. Usually no preparation is needed; only stop medicines after talking to your doctor.
Frequently asked questions
How do they differ from TPO antibodies? +
Both are autoantibodies against the thyroid, but they target different proteins: TPO antibodies target thyroid peroxidase, thyroglobulin antibodies target thyroglobulin. When Hashimoto's is suspected, they are often measured together.
Does a positive result automatically mean Hashimoto's? +
No. Thyroglobulin antibodies also occur with other thyroid and autoimmune diseases, during pregnancy and in relatives of affected people. Whether a disease is present is assessed by your doctor together with your thyroid values and symptoms.
Why are the antibodies measured in cancer follow-up? +
If thyroglobulin antibodies are present in the blood, they bind thyroglobulin and can make the measured level appear falsely low. Knowing they are there helps decide which test is best suited for follow-up.
Who has a higher risk of autoimmune thyroid disease? +
MedlinePlus lists, among others, women, people over 50, a family history, other autoimmune conditions, previous thyroid surgery or radiation to the neck, and medicines with a lot of iodine.
Thyroglobulin antibodies (TgAb)
Sources
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.