Hyperthyroidism, the clinical condition that results from increased circulating levels of free (nonprotein-bound) thyroid hormones, is one of the most common endocrine disorders. It occurs in some 1.8 per cent of the adult population, but is much rarer in childhood. Women are affected more often than men (10:1), and the age of occurrence varies with the variety of hyperthyroidism.
Hyperthyroidism usually results from autoimmune thyroid disease.
