Thyroid Peroxidase Test

  • Medical Author:

    Robert Ferry Jr., MD, is a U.S. board-certified Pediatric Endocrinologist. After taking his baccalaureate degree from Yale College, receiving his doctoral degree and residency training in pediatrics at University of Texas Health Science Center at San Antonio (UTHSCSA), he completed fellowship training in pediatric endocrinology at The Children's Hospital of Philadelphia.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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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.

The thyroid gland is located in the lower part of the neck, below the Adam's apple, wrapped around the trachea (windpipe).

Picture of the thyroid gland
Picture of the thyroid gland

What is the thyroid peroxidase test?

Thyroid peroxidase test is a test that measures the level of an antibody that is directed against thyroid peroxidase (TPO).

Autoantibodies to thyroid peroxidase (TPOAb) are produced within the body. The presence of TPOAb in the blood reflects a prior attack on the thyroid tissue by the body's immune system.

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

Medically reviewed by John A. Seibel, MD; Board Certified Internal Medicine with a subspecialty in Endocrinology & Metabolism

REFERENCE:

"Laboratory assessment of thyroid function"
uptodate.com

Medically Reviewed by a Doctor on 5/7/2015

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  • Thyroid Peroxidase Test - Diagnosis

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