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What Does a High Level of Thyroid Peroxidase Mean?

By Kristeen Cherney ; Updated July 27, 2017

Thyroid peroxidase helps in overall thyroid function. Yet, as with overall hormone production within the gland, thyroid peroxidase can pose health problems if its production levels get out of control. Higher levels of thyroid peroxidase are common in those with Graves' disease and Hashimoto’s disease.

The Facts

The thyroid is an organ in the throat that is the shape of a butterfly and about the size of a quarter. Hormones are released by the thyroid that help to that certain bodily functions--such as blood pressure, metabolism and heart functions-- are working properly. Thyroid peroxidase (TPO) is an antibody that can help or disrupt the production of hormones, depending on their working levels.


Thyroid peroxidase is a type of enzyme produced in the thyroid. This enzyme plays a vital role in helping the thyroid gland produce hormones, specifically triiodothyronine (T3) and thyroxine (T4) hormones. If TPO levels are too high, it can indicate that an autoimmune problem exists, thus disrupting the production of T3 and T4 hormones.


A TPO test measures the amount of antibodies that exist in the thyroid gland. Such tests are administered in order to detect thyroid dysfunction, or as a follow-up test to T3, T4, and Thyroid Stimulating Hormone (TSH) tests. An endocrinologist may recommend a TPO tests for patients who exhibit symptoms of hypothyroidism, or before a patient begins taking medications that could lead to hypothyroidism.


A TPO test will read as positive if a thyroiditic condition exists. In patients who have hypothyroidism, this is indicative of Hashimoto’s disease. In hyperthyroid patients, this is indicative of the autoimmune condition of Graves' disease. Moderate thyroid peroxidase levels may indicate that a patient has thyroid cancer, anemia, rheumatoid arthritis or Type 1 diabetes. A high level of thyroid peroxidase means that a patient has Graves' disease or Hashimoto’s disease.


Untreated thyroid peroxidase can lead to reproductive problems in women. Such difficulties include infertility, miscarriage, premature delivery and pre-eclampsia. When Graves' disease and Hashimoto’s disease are left untreated, it can necessitate surgical removal of the thyroid gland.

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