TPO and hypothyroidism: In 57 patients out of 84 (68%), hypothyroidism was due to autoimmune chronic thyroiditis, as proved by the positivity rates of anti-thyroid peroxidase and anti-thyroglobulin autoantibodies; in 21 patients (25%), hypothyroidism was caused by thyroidectomy for benign multinodular goiter; and in six cases (7%), it was due to other causes, mainly antibody-negative autoimmune thyroiditis.