Hyperthyroidism is the term for overactive tissue within the thyroid gland, resulting in overproduction and thus an excess of circulating free thyroid hormones. It is a common endocrine condition which most often is treated with thyrostatic drugs or radioiodine, less commonly with surgery. Graves' disease is the most common cause of primary hyperthyroidism and is characterized by goiter, palpitation and exophthalmos. This book discusses the pathogenesis, phenotypic expression and challenges in management for Graves' disease. The effectiveness of adrenergic blockers carvedilol, propranolol and verapamil on hyperthroidism associated insulin resistance is also examined. Furthermore, over the past two decades, there are increasing numbers of reports with a newly introduced group of unusual manifestations of hyperthyroidism. These unusual presentations make the diagnosis more challenging especially when they are the only presenting manifestations of the disease, or when the classical manifestations are subtle or overlooked.