Autoimmune thyroid disease is the most common cause of hyperthyroidism. Postpartum thyroiditis, although common, is usually biochemical, subclinical, and transient. Graves' disease is the most common cause of clinical hyperthyroidism world-wide, although in areas of iodine deficiency, toxic nodular goitre and toxic adenoma make up a greater proportion of cases. In North America, silent thyroiditis and de Quervain's thyroiditis are seen more frequently than in Europe.
