Which antibodies are most characteristic of Hashimoto's thyroiditis?

• A. Anti-thyroid peroxidase (anti-TPO) antibodies.
• B. Anti-TSH receptor antibodies.
• C. Anti-thyroglobulin antibodies.
• D. ANA.

Answer: (A)

Autoimmune attack on the thyroid often centers on thyroid peroxidase, an enzyme essential for thyroid hormone production. In Hashimoto’s thyroiditis, antibodies against this enzyme are extremely common and strongly associated with the autoimmune destruction of thyroid tissue. Anti-thyroid peroxidase antibodies are detectable in the vast majority of patients with Hashimoto’s, often serving as a sensitive and specific serologic clue to autoimmune thyroiditis.

Antibodies to thyroglobulin can be present as well, but they are less specific and appear in other thyroid conditions and even in some healthy individuals. Antibodies against the TSH receptor are characteristic of Graves disease, where they stimulate the receptor to drive excess thyroid hormone production, not the hypothyroid state of Hashimoto’s. ANA is a nonspecific marker of systemic autoimmune disease and does not point to Hashimoto’s specifically.

So, anti-thyroid peroxidase antibodies are the best fit for Hashimoto’s thyroiditis because they are the most commonly present and most characteristic autoimmune antibody in this condition.