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Thyroglobulin Antibodies (TgAb) Blood Test

Análisis de sangre: Anticuerpos tiroglobulina (TgAb)

Thyroglobulin Antibodies (TgAb) Blood Test

What Is a TgAb Blood Test and Why Is It Done?

A thyroglobulin (thigh-ro-GLAB-yuh-lun) antibodies (TgAb) blood test measures the amount of certain proteins in the blood called TgAb.

Doctors order TgAb tests:

to diagnose and monitor autoimmune conditions (when the immune system damages normal, healthy body tissues) involving the thyroid gland
to diagnose thyroid disorders like thyroiditis (inflammation of the thyroid) or goiter (an enlarged thyroid)
if other blood tests to check levels of thyroid hormones or thyroid stimulating hormone (TSH) show a problem
to see how treatment for thyroid cancer is working

What Are Thyroglobulin and Thyroglobulin Antibodies?

Thyroglobulin (or Tg) is a protein made by the thyroid gland. The thyroid uses it to make the hormones triiodothyronine (T3) and thyroxine (T4). These both help control growth and metabolism (the set of chemical reactions in the body's cells that change food into energy).

TgAb are antibodies made against thyroglobulin. Antibodies (also called immunoglobulins) are proteins the immune system makes to recognize and get rid of germs. Usually, the immune system doesn't make a lot of antibodies against thyroglobulin because it's not a germ.

In autoimmune disorders, the immune system attacks the body's healthy tissues as though they were foreign invaders, like germs. So the level of TgAb in blood may rise in people with a thyroid-related autoimmune condition.

Top Things to Know

The thyroglobulin antibodies (TgAb) test checks the levels of TgAb proteins in the blood.
The test can help diagnose and monitor thyroid gland problems.
Kids might need to stop taking certain medicines or not eat or drink before the blood test.
Your doctor can explain what it means if the results show TgAb.

How Can I Help My Child Prepare for a Blood Test?

To help kids get ready for a blood test, find out if they need to fast (not eat or drink) or should stop taking medicines before the test. Explain what to expect during the test. If your child is nervous about it, work together on ways to stay calm. Deep breathing or even imagining being in a place that makes your child feel safe and relaxed can help.

What Do Thyroglobulin Antibody Test Results Mean?

Your doctor will explain what the results of the TgAb test mean for your child. What’s “normal” varies based on things like age and gender.

Positive TgAb Result

If the TgAb test result is positive, it means there are thyroglobulin antibodies in the blood. If the level is elevated (high), it often means that there’s a problem with the thyroid, which could happen with conditions like:

hyperthyroidism (overactive thyroid) or hypothyroidism (underactive thyroid)
thyroiditis
lupus
type 1 diabetes

The TgAb level may also be high during pregnancy and in people related to someone with thyroiditis.

Negative TgAb Result

If the TgAb test result is negative, it means there aren’t any thyroglobulin antibodies in the blood. There could still be a thyroid problem though.

What Else Should I Know?

Doctors may look at TgAb results together with those of other tests, including thyroid blood tests for T3, T4, and TSH.

If you have questions about the TgAb test or what the results mean, talk to your doctor.

Medically reviewed by: Larissa Hirsch, MD

Date reviewed: February 2026

Thyroglobulin Antibodies (TgAb) Blood Test