Thyroid Peroxidase (TPO) Antibodies

Differential diagnosis of hypothyroidism and thyroiditis.

Should be used in conjunction with antithyroglobulin test, since autoimmune thyroiditis may demonstrate a response to antigens other than thyroid microsomes. To order both antithyroglobulin and antimicrosomal tests, use profile 006684. Other autoimmune disorders such as Sjögren's syndrome, lupus erythematosus, rheumatoid arthritis, pernicious anemia, and others may be positive for antimicrosomal and antithyroglobulin. Patients with myxedema, granulomatous thyroiditis, nontoxic nodular goiter, and thyroid carcinoma may occasionally produce thyroid antibodies.

Antibodies to thyroid microsomes (thyroid peroxidase) are present in 70% to 90% of patients with chronic thyroiditis. They are also present in smaller percentages of patients of other thyroid diseases. Antibody production may be confined to lymphocytes within the thyroid, and serum may be negative. Small numbers (3%) of people with no evidence of disease may have antibody. This is more frequent in females and increases with age.

1. Reference Intervals for Children and Adults. Elecsys Thyroid Test. Manneheim, Germany: Roche Diagnostics Corporation; 2009.