Low-Level Laser Therapy in Chronic Autoimmune Thyroiditis

Inclusion Criteria: * Patients previously diagnosed with hypothyroidism induced by chronic autoimmune thyroiditis (CAT). The presence of hypothyroidism, laboratory measurements and ultrasonography criteria were applied to diagnose CAT. * Significantly elevated concentrations of thyroid peroxidase (TPOAb) and/or thyroglobulin (TgAb) autoantibodies * Ultrasonography results consistent with CAT * Patients undergoing LT4 treatment * Normal (or almost normal) levels of triiodothyronine (T3), thyroxine (T4), free T4 and thyrotropin (TSH) Exclusion Criteria: * Use of immunosuppressants, immunostimulants, or other drugs that could interfere with the production, metabolism and transport of thyroid hormones * CAT with normal thyroid function * CAT with subclinical hypothyroidism * Thyroid nodules * Hypothyroidism stemming from post-partum thyroiditis (up to 18 months after gestation) * History of Graves' disease * Thyrotropin receptor antibody (TRAb) detectable * Prior treatment with radioiodine * Tracheal stenosis * Pregnancy * History of ionizing irradiation and/or neoplasia in the cervical area * Previous surgical intervention in the thyroid * Thyroid hypoplasia * Ectopic thyroid * Serious illness (cancer, ischemic coronary artery disease, stroke, kidney or liver failure, etc.)