Dysphagia and hoarseness are predominant. The thyroid gland is not necessarily large (e.g., degree I) and is due to toxic disease. Hyperthyroidism with gynecomastia and lymph node growth is due to the conversion of testosterone and androstenedione to estrone and androstenediol in the surrounding tissues in the former case, and to an autoimmune reaction in the lymph nodes in the latter case. Nausea and vomiting may be caused by direct inhibition of phosphocreatine kinase by thyroid hormone, resulting in a decrease in phosphocreatine and ATP and other energy substances in myocytes, or by hypokalemia, as reported in 3% of cases in China. The predominance of arrhythmias with other symptoms is not obvious, accounting for 4.8% of hyperthyroidism. The symptoms are similar to those of pheochromocytoma, which may be caused by excessive secretion of thyroid hormone and enhanced peripheral effect of catecholamines.