Mild diffuse changes in the thyroid gland are described by performing an ultrasound of the thyroid gland as a form of imaging. It is necessary to check thyroid function, thyroglobulin antibodies and anti-thyroid peroxidase antibody levels. If the thyroid function is normal and the level of antibodies to the thyroid gland is normal, there is no need to deal with it or to worry about it. If the thyroid function is normal and the levels of thyroglobulin antibodies or anti-thyroid peroxidase antibodies are significantly elevated, this is consistent with one of the ultrasound changes of chronic lymphocytic thyroiditis and the patient does not need treatment for the time being, but thyroid function should be closely monitored to prevent hypothyroidism in the future. If the patient’s thyroid function test already indicates combined hypothyroidism, he or she should start oral eugenol replacement therapy immediately.