High serum thyroid hormone is mainly caused by hyperthyroidism, which is mostly seen in Graves’ disease, but also in diseases such as autonomous hyperfunctional adenoma of the thyroid gland, goiter and tumor. The so-called hyperthyroidism is an increase in the synthesis and secretion of thyroid hormone, resulting in high thyroid hormone in the serum, which is clinically manifested as hypermetabolic symptoms, such as emotional excitement, fever, palpitations, excessive sweating, polyphagia, emaciation, easy to starve, hand tremor, protruding eyes and other manifestations. Many diseases can cause hyperthyroidism, the most common of which is Graves’ disease, also known as diffuse toxic goiter, which causes hyperthyroidism through the body’s production of specific antibodies that cause the thyroid cells to produce excessive amounts of thyroid hormones. In addition, diseases such as autonomous hyperfunctioning adenomas of the thyroid gland, goiter, and tumors can lead to an increase in thyroid hormones. It is recommended that patients with high serum thyroid hormone should go to regular hospitals for timely consultation and standardized treatment under the guidance of specialists, so as to avoid delaying the condition.