Does this test have other names?

Thyroid antibody test, thyroglobulin antibody test, antiTg antibody test

What is this test?

This blood test looks for antibodies made by your body in response to thyroglobulin. This is a protein made by the thyroid gland. The thyroid is a small, butterfly-shaped gland near the base of your throat, above your collarbone. It makes the hormones T3 and T4. They help control your metabolism, the process in which your body uses energy to do its work. They affect your energy levels, mood, weight, and other important parts of your health.

The thyroglobulin antibody test can help diagnose thyroid problems. These include Hashimoto thyroiditis and autoimmune thyroid disease. It may be used with other tests to check on thyroid cancer.

Why do I need this test?

You may need this test if your doctor thinks you have a thyroid disorder. Thyroglobulin antibodies may be found in people who have a thyroid problem. You may have an underactive thyroid (hypothyroidism) or overactive thyroid (hyperthyroidism). Thyroglobulin antibodies attack thyroglobulin proteins and can destroy the thyroid gland.

If you've been treated for thyroid cancer, this test could be part of regular checkups to keep track of your condition.

Symptoms of overactive thyroid include:

• Feeling weak and tired.

• Trembling hands and fingers.

• Losing weight.

• Feeling anxious, nervous, or irritable.

• Sweating heavily.

• Fast or irregular heartbeat.

• Low tolerance for heat.

Symptoms of underactive thyroid include:

• Digestive problems, including constipation.

• Problems with menstruation.

• Tiredness and a lack of energy.

• Dry hair and skin.

• Swelling around the eyes.

• A frequent feeling of being cold.

• Weight gain.

• Depression.

• Forgetfulness.

• Painful joints.

What other tests might I have along with this test?

You may also have blood tests to measure levels of other hormones involved in thyroid functions. They are:

• Thyroid-stimulating hormone, which is made in the pituitary gland.

• T4 hormone, also known as thyroxine.

• T3 hormone, also known as triiodothyronine.

You may also have a thyroglobulin test.

What do my test results mean?

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. Ask your doctor what your test results mean for you.

Negative test results mean you have no thyroglobulin antibodies in your blood. A positive test result means that you have thyroglobulin antibodies in your blood. This may mean you have a problem with your thyroid gland. A positive thyroglobulin antibody test result may also mean that your thyroglobulin test measurement is incorrect.

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. 

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore.

What might affect my test results?

Taking thyroid hormone medicines can affect your test results.  Taking over the counter medicines or herbs, such as biotin, can also affect your results.

How do I get ready for this test?

Ask your doctor if you should skip any medicines you are taking on the day of your test. Most likely, you should delay taking your thyroid medicine the day of your test until after your blood has been drawn. You may also be asked to not eat the night before the test.

In addition, be sure your doctor knows about all the medicines, herbs, vitamins, and supplements you are taking (especially if you're taking biotin and estrogens). This includes medicines that don't need a prescription and any illegal drugs you may use.