Thyroid Antibodies: MedlinePlus Medical Test

What is a thyroid antibodies test?

This test measures the level of thyroid antibodies in your blood. The thyroid is a small, butterfly-shaped gland located near the throat. Your thyroid makes hormones that regulate the way your body uses energy. It also plays an important role in regulating your weight, body temperature, muscle strength, and even your mood.

Antibodies are proteins made by the immune system to fight foreign substances like viruses and bacteria. But sometimes antibodies attack the body’s own cells, tissues, and organs by mistake. This is known as an autoimmune response. When thyroid antibodies attack healthy thyroid cells, it can lead to an autoimmune disorder of the thyroid. These disorders can cause serious health problems if not treated.

There are different types of thyroid antibodies. Some antibodies destroy thyroid tissue. Others cause the thyroid to make too much of certain thyroid hormones. A thyroid antibodies test usually measures one or more of the following types of antibodies:

• Thyroid peroxidase antibodies (TPO). These antibodies can be a sign of:
  • Hashimoto disease, also known as Hashimoto thyroiditis. This is an autoimmune disease and the most common cause of hypothyroidism. Hypothyroidism is a condition in which the thyroid doesn’t make enough thyroid hormones.
  • Graves’ disease. This is also an autoimmune disease and the most common cause of hyperthyroidism. Hyperthyroidism is a condition in which the thyroid makes too much of certain thyroid hormones.
• Thyroglobulin antibodies (Tg). These antibodies can also be a sign of Hashimoto disease. Most people with Hashimoto disease have high levels of both Tg and TPO antibodies.
• Thyroid-stimulating hormone (TSH) receptor. These antibodies can be a sign of Grave’s disease.

Other names: thyroid autoantibodies, thyroid peroxidase antibody, TPO, Anti-TPO, thyroid- stimulating immunoglobulin, TSI