Woman with goitre, a swelling of the neck caused by the enlargement of the thyroid gland. This may be due to a number of causes, including Graves's disease, lack of dietary iodine, simple overgrowth or the prescence of a tumour. A lack of dietary iodine, which is necessary for the production of thyroid hormones, causes the gland to enlarge in an attempt to increase hormone production. Iodine deficiency was the cause of endemic goitre, formerly common in regions where the diet lacked iodine. In Graves's disease (exophthalmic goitre) the swelling is associated with over- activity of the gland and is accompanied by other symptoms including protrusion of the eyes.