Test Overview

Thyroid antibody tests measure the levels of antibodies that can destroy thyroid tissue or make the cells produce thyroid hormones. They are blood tests.

Antibodies that destroy thyroid tissue can lead to hypothyroidism (underactive thyroid). Antibodies that make the cells produce thyroid hormone can lead to hyperthyroidism (overactive thyroid).

The body's immune system makes antibodies to fight infections. But sometime those antibodies attack the body's tissues instead. This is called an autoimmune reaction.

People who have one autoimmune disease may get another one. Tell your doctor if you have any new or worse symptoms.

These tests are not thyroid hormone tests. High or low levels of thyroid hormones also can be signs of thyroid problems. These antibody tests may be done after thyroid hormone tests to find the cause of high or low levels of thyroid hormones.

High levels of these antibodies usually suggest that a person has an autoimmune thyroid problem. But some people who have thyroid problems don't test positive for these antibodies. And some people who have these antibodies don't get thyroid disease.

Why It Is Done

Thyroid antibody tests are usually done if you have a goiter or symptoms of thyroid disease.

The following tests may be done:

• Anti-thyroid peroxidase antibody: This can show Hashimoto's thyroiditis. It also can help your doctor tell if mild hypothyroidism is likely to get worse.
• Thyroid stimulating antibody: This can check for Graves' disease. It also can help a doctor find out if the fetus of a mother with Graves' disease is likely to get a short-term form of the condition.
• Anti-thyroglobulin antibody: This also is used to look for Hashimoto's thyroiditis and to see if mild hypothyroidism might get worse. It also can be used to see if a thyroglobulin test done during treatment for thyroid cancer is accurate.

How To Prepare

In general, there's nothing you have to do before this test, unless your doctor tells you to.

How It Is Done

A health professional uses a needle to take a blood sample, usually from the arm.

How It Feels

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.

Risks

There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Results

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

Negative results for the tests mean that you don't have thyroid antibodies. If you have symptoms of thyroid problems, they are likely caused by something else.

High levels of these antibodies can show that there is a problem with your thyroid. You may have other tests to find out what is wrong.