Thyroid antibody tests measure the levels of antibodies that can destroy thyroid tissue or make the cells produce thyroid hormones. They are blood tests.
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
You do not need to do anything special to prepare for this test.
How It Is Done
The health professional taking a sample of your blood will:
- Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
- Clean the needle site with alcohol.
- Put the needle into the vein. More than one needle stick may be needed.
- Attach a tube to the needle to fill it with blood.
- Remove the band from your arm when enough blood is collected.
- Put a gauze pad or cotton ball over the needle site as the needle is removed.
- Put pressure on the site and then put on a bandage.
How It Feels
The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
There is very little chance of a problem from having a blood sample taken from a vein.
- You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
- In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. You can use a warm compress several times a day to treat this.
Thyroid antibody tests look for and measure the levels of antibodies that can destroy thyroid tissue. They also can be used to find and measure antibodies that make thyroid cells produce thyroid hormone.
These numbers are just a guide. The range for "normal" for these tests can vary widely from lab to lab. Your lab may have a different range. Your lab report should show what range your lab uses for "normal." Also, your doctor will evaluate your results based on your health and other factors. So a number that is outside the normal range here may still be normal for you.
Thyroglobulin and thyroid microsomal antibodies:
Less than 1:100. (This test is measured in titres.)
Less than 9 IU/mL
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.
What Affects the Test
If you have thyroid cancer and you have anti-thyroglobulin antibodies, your doctor may not be able to get accurate test results for your thyroglobulin levels.
What To Think About
Your doctor will use the results of a physical examination, your symptoms, and the results of these tests to find out if you have a thyroid disease.
Current as of: March 31, 2020
Author: Healthwise Staff
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine
Kathleen Romito MD - Family Medicine
Matthew I. Kim MD - Endocrinology
Current as of: March 31, 2020