AntiTPO

Anti-thyroid peroxidase antibodies (anti-TPO or TPOAb) are autoantibodies directed against thyroid peroxidase, an enzyme involved in the synthesis of thyroid hormones. They are a common finding in autoimmune thyroid diseases, most notably Hashimoto's thyroiditis, and can also be present in Graves’ disease and other autoimmune conditions. A portion of the general population, particularly older adults and women, may have detectable anti-TPO without current thyroid dysfunction.

Testing and interpretation

Anti-TPO is measured using immunoassays such as chemiluminescent immunoassays or ELISA. Results are assay-specific, with no universal cutoff. A positive or elevated result supports an autoimmune etiology for thyroid disease when correlated with thyroid-stimulating hormone (TSH) and free thyroxine (T4) levels and clinical findings. Anti-TPO positivity is highly sensitive for Hashimoto’s thyroiditis but is not exclusively diagnostic, as it can occur in euthyroid individuals and in other autoimmune conditions. The prevalence and titer tend to be higher in women and increase with age.

Clinical significance

The presence of anti-TPO antibodies is associated with an increased risk of developing autoimmune thyroid disease and with progression from subclinical to overt hypothyroidism, especially in older adults. In pregnancy, maternal anti-TPO positivity is linked to higher risks of miscarriage, preterm birth, and postpartum thyroiditis, and can influence neonatal thyroid function.

Management

There is no specific treatment for anti-TPO itself. Management focuses on thyroid hormone status, with regular monitoring of TSH and free T4 as indicated, and treating hypothyroidism if it develops. In pregnancy, thyroid function is monitored according to obstetric guidelines.