The goals of testing include detecting thyroid dysfunction, diagnosing Hashimoto thyroiditis, and monitoring Treatment.
For monitoring thyroid function and hormone production:
- TSH — typically elevated in hypothyroidism
- Total or Free T4 — often decreased in primary hypothyroidism
- Total or Free T3 — sometimes decreased but may be within the normal reference range, so is not as useful as T4
To help diagnose Hashimoto thyroiditis:
- Anti-thyroid peroxidase antibody (anti-TPO, see Thyroid Antibodies). This test detects the presence of autoantibodies against a protein found in thyroid cells. A high value usually indicates autoimmune damage to the thyroid due to disorders such as Hashimoto thyroiditis and Graves disease.
- Antithyroglobulin antibody (TgAb) — if positive, may indicate Hashimoto thyroiditis; while thyroglobulin antibodies are often positive, they are not as sensitive or specific as anti-TPO so they are not routinely ordered.
Rarely, those with Hashimoto thyroiditis have no antibodies.