I. Concept Thyrotoxicosis refers to a group of clinical syndromes in which excessive thyroid hormones in the blood circulation cause increased excitability and hyper-metabolism in the nervous, circulatory and digestive systems. The thyrotoxicosis is caused by hyperthyroidism (hyperthyroidism), where the thyroid gland itself is hyperfunctioning, resulting in increased synthesis and secretion of thyroid hormones; the thyrotoxicosis is caused by inflammation of the thyroid follicles (e.g., subacute thyroiditis, quiet thyroiditis, postpartum thyroiditis, etc.), and excess thyroid hormones stored in the follicles enter the circulation. Thyrotoxicosis is called destructive thyrotoxicosis, in which thyroid function is not hyperactive. The causes of hyperthyroidism include Graves’ disease, multinodular goiter with hyperthyroidism (toxic multinodular goiter), autonomic hyperfunctional thyroid adenoma, iodine hyperthyroidism, pituitary hyperthyroidism, and chorionic gonadotropin (hCG)-related hyperthyroidism. Among them, Graves’ disease is the most common, accounting for about 85% of all hyperthyroidism. The clinical manifestations are mainly caused by excessive circulating thyroid hormones, and the severity of the symptoms and signs is related to the length of medical history, the degree of hormone elevation and the age of the patient. Symptoms include: agitation, irritability and insomnia, palpitations, fatigue, fear of heat, excessive sweating, weight loss, hyperphagia, increased frequency of stools or diarrhea, and scanty menstruation in women. Graves’ disease is associated with periodic paralysis (common in young adult males in Asia) and progressive muscle weakness and atrophy of the proximal muscles, the latter being called hyperthyroid myopathy, with involvement of the scapular and pelvic girdle muscle groups predominant. 1% of Graves’ disease is associated with myasthenia gravis. A small number of elderly patients have atypical symptoms of hypermetabolism, instead showing weakness, palpitations, anorexia, depression, lethargy, and significant weight loss, called apathetic hyperthyroidism. Signs: Most patients with Graves’ disease have goiter of varying degrees. The goiter is diffuse, moderate in texture (may be firm with a longer history or consumption of iodine-containing foods), and non-compressive. Tremors can be palpated in the upper and lower poles of the thyroid gland and vascular murmurs can be heard. In a few cases, the thyroid gland is not enlarged; in nodular goiter with hyperthyroidism, a nodular enlarged thyroid gland may be palpated; in autonomic hyperfunctional thyroid adenoma, isolated nodules may be seen. Cardiovascular system manifestations include increased heart rate, heart enlargement, arrhythmia, atrial fibrillation, and increased pulse pressure. In a few cases, mucinous edema can be seen in the pre-tibial skin of the lower limbs. The ocular manifestations of hyperthyroidism are divided into two categories: simple proptosis, the cause of which is related to increased sympathetic excitability due to thyrotoxicosis; the other category is infiltrative proptosis, also known as Graves’ ophthalmopathy. In recent years, it is called Graves orbitopathy. The etiology is related to an autoimmune inflammatory response in the periorbital tissues. Simple proptosis includes the following manifestations: 1. mild proptosis: the degree of proptosis does not exceed l8 mm; 2. Stellwag’s sign: reduced transient eyes, eyes shining; 3. upper risk contracture, widening of the risk fissure; 4. von Graefe’s sign: when both eyes look down, white sclera appears because the upper risk cannot fall with the eyes; 5. Joffroy’s sign: when the eyes look up, the forehead skin cannot 6.Mobius sign: When both eyes look at the near object, the eyes are not converging well. These signs are associated with increased sympathetic excitability due to thyrotoxicosis. Laboratory tests: Serum thyrotropin (TSH) and thyroid hormone: The technique of measuring serum TsH has been improved and has entered the fourth generation. The second generation method [represented by the immunoradiometric method (IRMA) with a sensitivity of 0.1~0.2mIU/L] and the third generation method [represented by the immunochemical luminescence method (ICMA) with a sensitivity of 0.01-0.02mIU/L], which are commonly used in China, are called sensitive TSH (sTSH). TSH is an internationally recognized indicator of choice for the diagnosis of hyperthyroidism and can be used as a single indicator for screening of hyperthyroidism.