Excerpt from Dr. Izabella Wentz's article - Hashimoto’s And TPO Antibodies...
"Thyroid ultrasounds, as well as blood tests, are used to diagnose Hashimoto’s. Laboratory tests are available to check thyroid function and autoimmune thyroid markers.
If we were to perform blood tests in advanced untreated Hashimoto’s, we would find an elevated TSH and low levels of T3 and T4. Thyroid Antibodies are also found in most cases of Hashimoto’s. The TSH is a widely used screening test, however, is not the most reliable test for identifying Hashimoto’s, as it may fluctuate depending on the amount of thyroid hormone present, which is often the case in Hashimoto’s when thyroid tissue is broken down and thyroid hormone released into the blood stream.
Best Test for Hashimoto’s
In most cases of Hashimoto’s thyroiditis, blood tests will reveal one or two types of anti-thyroid antibodies. Thyroid peroxidase antibody (TPOAb) is the most common antibody present (in up to 95% of those with Hashimoto’s), and often antibodies against thyroglobulin (TGAb) are found as well (around 80%). These antibodies may appear decades before a change in TSH is detected.
Elevated thyroid antibodies have been connected with a feeling of distress, anxiety, and depression in those with Hashimoto’s. Also, the higher the antibodies, the more likely you are to experience symptoms of hyperthyroidism when the thyroid cells are broken down, and stored hormone is dumped into the bloodstream, as well as hypothyroidism when we don’t have enough thyroid hormone.
Additionally, the higher the TPO Antibodies, the higher your likelihood of developing overt hypothyroidism, and possibly additional autoimmune conditions."