General Principles

• Graves disease causes most cases of hyperthyroidism, especially in young patients. This autoimmune disorder may also cause proptosis (Graves orbitopathy) and pretibial myxedema, neither of which is found in other causes of hyperthyroidism.
• Toxic multinodular goiter (MNG) may cause hyperthyroidism, more commonly in older patients.
• Unusual causes include iodine-induced hyperthyroidism (precipitated by drugs such as amiodarone or radiographic contrast media), thyroid adenomas, subacute thyroiditis (painful tender goiter with transient hyperthyroidism), painless thyroiditis (nontender goiter with transient hyperthyroidism, most often seen in the postpartum period), and surreptitious ingestion of thyroid hormone. TSH-induced hyperthyroidism is extremely rare.