Thyroid Peroxidase Antibodies Blood Test

Thyroid Peroxidase Antibodies Blood Test

What Is a Thyroid Peroxidase Antibodies Test and Why Is It Done?

A thyroid peroxidase (pr-AAK-suh-days) (TPO) antibodies test measures the amount of antibodies that exist against a person's TPO enzyme in the blood.

Doctors order TPO antibodies tests:

• to diagnose and monitor autoimmune conditions involving the thyroid, like Hashimoto thyroiditis and Graves disease
• 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

What Are Thyroid Peroxidase Antibodies?

The TPO enzyme (a kind of protein) is made by the thyroid gland. The thyroid uses iodine, with the help of TPO, to make the hormones triiodothyronine (T3) and thyroxine (T4). These both help control metabolism and growth.

A TPO antibody test checks for antibodies made against the TPO enzyme. 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 TPO 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 TPO antibodies in blood may rise in people who have an autoimmune condition that involves the thyroid.

Top Things to Know

• The thyroid peroxidase (TPO) antibodies blood test checks the levels of antibodies to an enzyme in the blood called TPO.
• The test can help show if the immune system is causing a problem with the thyroid.
• 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 your child has TPO antibodies.

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 the Test Results Mean?

If the results show TPO antibodies, it often means that a person has an autoimmune condition involving the thyroid.

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

The results are also based on the results of other thyroid blood tests, like the:

• TSH test
• T3 blood test
• T4 blood test

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