What Are Antithyroid Antibodies?

Medically Reviewed by Sabrina Felson, MD on February 05, 2022
3 min read

The thyroid is a gland at the bottom of your neck, just below your Adam’s apple. It makes hormones that help your body use energy, stay warm, and keep the brain, heart, muscles, and other organs working.

Antibodies are made by your immune system to protect your body from bacteria and viruses. When harmful things invade your body, antibodies destroy them. Antithyroid antibodies, for example, attack your thyroid gland by mistake. That can lead to too much or not enough thyroid hormones.

Antithyroid antibodies target specific parts of the thyroid gland, including:

Thyroid peroxidase (TPO). TPO is an enzyme that plays an important role in making thyroid hormones.
Thyroglobulin (Tg). This substance also helps your body make thyroid hormones.
Thyroid stimulating hormone (TSH) receptor. TSH sticks to the receptor on thyroid cells, which causes the gland to make and release thyroid hormone into the blood.

The antibodies can damage the gland, make it swell, and affect how it works. This can lead to medical conditions like:

Hashimoto’s disease. This is the most common form of underactive thyroid, called hypothyroidism. When the thyroid gland is inflamed, it can’t make hormones as well as it normally does. Over many years, the thyroid becomes damaged. This leads to a drop in thyroid hormone levels in your blood. When the levels get too low, your body’s cells can’t get enough thyroid hormone and they can’t work as they should.

Signs of Hashimoto’s disease include:

Graves’ disease. This happens when antibodies cause the cells in your gland to work overtime. An overactive thyroid, or hyperthyroidism, makes and releases too much thyroid hormones into your blood. When that happens, all your body functions tend to speed up.

Symptoms of Graves’ disease include:

After doing routine blood testing to check for hormone levels, your doctor may order an antibodies test to look for Hashimoto’s disease or Graves’ disease. An antibody test can help your doctor figure out if your immune system is attacking the thyroid gland, or if something else might be the cause. They might also order antibodies testing for:

Goiter. This is an enlarged thyroid gland. It can be caused by several conditions, including Hashimoto’s disease or Graves’ disease.

Autoimmune disease, like lupus or rheumatoid arthritis. These and other disorders may raise your chance of having a thyroid problem.

Your doctor or a lab technician will take a sample of your blood to measure how many antithyroid antibodies are in it.

Some medicines can affect test results. Tell your doctor if you take any drugs, herbs, vitamins, and supplements. Being pregnant may also affect results, so let your doctor know if you’re expecting or think you may be.

If the test finds no antibodies, it likely means your immune system is not the cause of your symptoms.

If your results show high levels of antibodies against thyroid peroxidase or thyroglobulin, you may have Hashimoto’s disease. If you have lots of antibodies against the thyroid stimulating hormone receptor, you may have Graves’ disease.

The higher your level of antibodies, the more likely that you have a thyroid disease caused by your immune system.