Thyroid Peroxidase Test

1 What is a Thyroid Peroxidase Test?

Thyroid peroxidase test (also called: thyroid peroxidase autoantibody test, thyroid peroxidase (TPO) antibody (TPOAb) test, an antithyroid microsomal antibody test, and anti-microsomal antibody test) detects antibodies against the TPO in the body – TPOAb.

The thyroid gland is located in the lower part of the neck, below Adam's apple. The gland wraps around the windpipe (trachea) and has a shape that is similar to a butterfly - formed by two wings (lobes) and attached by a middle part (isthmus).

It is responsible for producing and storing essential hormones that help regulate the heart rate, blood pressure, body temperature, and the rate of chemical reactions (metabolism) in the body, but it is also the main part of the body that takes up iodine.

Thyroid peroxidase (TPO) is an enzyme made in the thyroid gland important for the production of thyroid hormone. It is found in thyroid follicle cells where it converts the thyroid hormone T4 to T3.

It is positive in most people with chronic thyroiditis (70%-90%) but the test also can be positive in patients with other autoimmune disorders like:

The chance of having a positive test increases with age and it is greater in females. Also, about 3% of people with a positive test show no evidence of disease.