Hashimoto's thyroiditis belongs to autoimmune thyroiditis, which is caused by the presence of autoantibodies that destroy the thyroid follicular cells, leading to the failure of thyroid cells. For patients with Hashimoto's thyroiditis, the erythrocyte sedimentation rate (ESR) generally does not increase. However, if a patient experiences neck discomfort or sore throat, and the ESR increases, even accompanied by fever, it is necessary to rule out whether subacute thyroiditis is present. If the patient has subacute thyroiditis, it indicates that a viral infection has caused the destruction of the thyroid cells, which might increase the ESR.