TPO Antibodies and Thyroid Autoimmunity: What Causes Elevated Results?

Thyroid peroxidase antibodies, commonly called TPO antibodies, are laboratory markers associated with thyroid autoimmunity.

Thyroid peroxidase is an enzyme involved in the production of thyroid hormones. When the immune system produces antibodies against thyroid peroxidase, TPO antibody testing may show an elevated result.

One of the primary conditions associated with elevated TPO antibodies is Hashimoto’s thyroiditis. Hashimoto’s can cause progressive inflammation and damage of the thyroid and may eventually result in hypothyroidism.

TPO antibodies may also be detected in Graves’ disease, an autoimmune condition that usually causes hyperthyroidism.

Postpartum thyroiditis is another condition in which thyroid antibodies may be relevant. It can develop after childbirth and cause temporary changes in thyroid function.

It is important to distinguish antibody status from thyroid function. A person may have elevated TPO antibodies while TSH and free T4 are normal. Conversely, thyroid dysfunction can have causes unrelated to TPO antibodies.

For that reason, healthcare professionals generally consider the complete clinical picture rather than treating an antibody result in isolation.

The appropriate interpretation may depend on symptoms, age, pregnancy status, previous thyroid history, family history, and thyroid hormone measurements.

People who receive an abnormal TPO antibody result should discuss it with an appropriate healthcare professional rather than trying to interpret the number without context.