The mystery of “Hashimoto’s thyroiditis” was unveiled. When patients see such test results, they often feel like the enemy, and are confused by the diagnosis of “Hashimoto’s thyroiditis” given by the endocrinologist: “What is this disease?” “Is it serious?” “Do I need an operation?” Let’s talk about Hashimoto’s thyroiditis and demystify it. So what is Hashimoto’s thyroiditis? Hashimoto’s thyroiditis, also known as chronic lymphocytic thyroiditis, is an autoimmune inflammatory disease of the thyroid gland that occurs more often in women and has a genetic susceptibility and family aggregation. Hashimoto’s thyroiditis is insidious and progresses very slowly, mostly without symptoms, and is often discovered inadvertently or during a physical examination. Some patients present with a thickened neck and a diffusely enlarged thyroid gland on ultrasound, accompanied by pharyngeal discomfort or mild dysphagia, and sometimes a feeling of neck pressure. Most people with Hashimoto’s thyroiditis have normal thyroid function, manifested only by elevated thyroid antibodies (especially TPOAb and TgAb), but as the disease progresses and inflammation continues to destroy the thyroid follicles, about half of the patients eventually develop hypothyroidism, manifested by fear of cold, bradycardia, constipation, and swelling. In order to clarify Hashimoto’s thyroiditis, the following tests are usually required: 1) Thyroid function: In the early stages of Hashimoto’s thyroiditis, thyroid function is mostly normal (T3, T4 and TSH are within normal levels); as the disease progresses, blood TSH gradually increases, while T3 and T4 remain at normal levels, i.e., it becomes subclinical hypothyroidism; as the disease further progresses, thyroid function manifests (2) Thyroid autoantibodies: TgAb and TPOAb are significantly elevated, which is one of the characteristics of this disease. In addition, ultrasonography of the thyroid gland shows an enlarged thyroid gland with diffuse, heterogeneous hypoechoic changes. How is Hashimoto’s thyroiditis treated? Hashimoto’s thyroiditis is usually not treated surgically. Once the diagnosis of Hashimoto’s thyroiditis is confirmed, treatment is determined by thyroid hormone levels and the presence or absence of symptoms. In the case of hypothyroidism, L-T4 replacement therapy is required, starting with a small dose and gradually increasing until the blood TSH drops to the target value, L-T4 replacement therapy is usually required for life and cannot be stopped at will. For Hashimoto’s thyroiditis with elevated antibodies, no treatment is needed, but thyroid hormone levels need to be rechecked every six months to a year to prevent the development of hypothyroidism.