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Thyroid Peroxidase Antibodies


Thyroid peroxidase is an enzyme which is produced in the thyroid gland and is important for converting T4 to the biologically active T3. This test looks for antibodies to thyroid peroxidase which indicates that the body's immune system is attacking the thyroid gland and impairing its function.

What might a low result mean?

It is normal to have low levels of thyroid peroxidase antibodies in your blood.

What might a high result mean?

High levels of thyroid peroxidase antibodies mean that your thyroid gland is under attack from your own immune system. Elevated thyroid peroxidase antibodies are seen in both Hashimoto's thyroiditis, which causes an underactive thyroid, and Graves' disease, which causes your thyroid to be overactive.

Elevated antibodies are often seen in people who already have a diagnosed thyroid condition or who have abnormal thyroid hormones, and can confirm the cause. In some people, thyroid antibodies can be high, but the production of thyroid hormones remains normal. However, having elevated antibodies increases your risk that you will develop a thyroid condition over time. It is therefore important to monitor your thyroid hormones regularly. Some people with raised antibodies never go on to develop a thyroid disorder.