What is thyroid peroxidase?
Thyroid peroxidase (TPO) is an enzyme made in the thyroid gland that is important in the production of thyroid hormone. TPO is found in thyroid follicle cells where it converts the thyroid hormone T4 to T3.
What is the thyroid peroxidase test?
What does a positive thyroid peroxidase test mean?
- Most people with chronic thyroiditis display a positive TPO test. The test is also positive in lesser numbers of people with other thyroid diseases.
- Other autoimmune disorders that may cause a positive TPOAb test include:
- About 3% of people with a positive TPOAb test show no evidence of disease.
- The chance of having a positive TPOAb test is greater in females and increases with age.
What are other names for thyroid peroxidase test?
This test goes by a confusing number of names, including:
- thyroid peroxidase (TPO) antibody (TPOAb) test,
- thyroid peroxidase autoantibody test,
- antimicrosomal antibody test, and
- antithyroid microsomal antibody test.
Previous contributing author: Frederick Hecht, MD, FAAP
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