Are you experiencing thyroid symptoms, but your basic TSH test is normal? This test is the critical next step. The Anti-TPO test detects antibodies that attack your thyroid gland. Its presence is the hallmark of Hashimoto's disease, the most common cause of hypothyroidism. This test is essential for diagnosing autoimmune thyroiditis, providing a definitive answer for your symptoms. A simple blood draw can uncover the root cause of your thyroid issue, allowing for a precise treatment plan.