**2. Epidemiology**

GD with an annual incidence of 20 to 50 cases per 100,000 persons is the most common cause of hyperthyroidism [8]. The incidence of GD peaks between 30 to 50 years of age, but people can be affected at any age. The lifetime risk for women is 3% and for men it is 0.5%. The risk of GD is not influenced by Long-term variations in iodine intake, but rapid repletion can transiently increase the incidence. The GD–associated incidence of ophthalmopathy is 16 cases per 100,000 in women and in men it is 3 cases per 100,000 annually. It is more common in whites than in Asians [9]. Older men develop severe ophthalmopathy more likely than younger persons [10]. Subtle abnormalities are revealed in 70% of patients by orbital imaging with GD [11]. In up to 50% of patients in specialized centres, clinically consequential ophthalmopathy is detected with GD, and as a consequence of corneal breakdown or optic neuropathy in 3 to 5% of such patients, sight is threatned [12]. The thyroid levels remain normal or autoimmune hypothyroidism develops either in 10% of the persons with ophthalmopathy [10–12]. In the *Whickham study* a population-based survey in England, the annual incidence of Graves' Disease was approximately 80 per 100,000 women, with most other surveys reporting incidence rates ranging from 15 to 50 per 100,000 persons per year while as the annual incidence in English men was approximately eight to ten fold lower than women (10 per 100,000) in keeping with gender differences seen in other thyroid diseases [13]. The incidence of Graves' hyperthyroidism in area of particularly high iodine intake (Japan), has been reported to be as high as 200 cases per 100,000 general population [14]. Similarly, following the introduction of iodine supplementation, an increases in the apparent incidence of GD have been reported, although in an area of mild to moderate iodine deficiency (Switzerland), a 33% reduction in the incidence of GD was associated with iodine supplementation [15].
