How long have you been having thyroid disease? TPO test is thyroid peroxidase antibody test. Thyroid peroxidase is an enzyme normally found in thyroid gland.It plays an important role in the production of thyroid hormones. TPO tests detects antibody against thyroid peroxidase enzyme. TPO test helps us to detect autoimmune diseases like Hashimoto's disease,where your immune system attacks your own normal tissue. And in pregnancy a thyroid peroxidase test (TPO)helps to detect whether your baby is at risk of thyroid disease.. And if you have a normal thyroid with TPO antibodies ,a future thyroid problem is likely so periodic checkups are necessary.