Hashimoto's thyroiditis is an autoimmune thyroiditis in which the body itself has autoimmune antibodies, leading to the destruction of thyroid follicular cells and the release of a large amount of thyroid hormones, possibly resulting in hyperthyroidism. Some patients may experience hyperthyroidism for years or even decades, which requires anti-hyperthyroidism treatment. However, as the disease progresses, further destruction of thyroid function may occur, resulting in hypothyroidism. For patients with Hashimoto's thyroiditis, once hypothyroidism occurs, it is usually progressive. Therefore, once hypothyroidism occurs in patients with Hashimoto's thyroiditis, lifelong replacement therapy with levothyroxine is necessary, as Hashimoto's thyroiditis cannot be completely cured, but clinical remission can be achieved through replacement therapy.