Blood Test: Thyroglobulin Antibodies (TgAb)

What Is a Blood Test?

By taking and testing a small sample of a person’s blood, doctors can check for many kinds of diseases and conditions. Blood tests help doctors check how the body’s organs are working and see if medical treatments are helpful.

To help your child 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 anxious about it, work together on ways to stay calm.

What Is TgAb?

Thyroglobulin 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 metabolism and growth.

Thyroglobulin antibodies (TgAb) are 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 thyroglobulin antibodies in blood may rise in people with a thyroid-related autoimmune condition.

Why Are TgAb Tests Done?

Doctors order TgAb tests:

• to diagnose and monitor autoimmune conditions involving the thyroid
• to diagnose thyroid disorders such as thyroiditis (inflammation of the thyroid) or goiter (an enlarged thyroid)
• if other blood tests to check levels of T3, T4, or thyroid stimulating hormone (TSH) show a problem

What if I Have Questions?

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