Overactivity of the thyroid gland, leading to excessive secretion of thyroid hormones and resulting in increased basal metabolic rate. Hyperthyroid subjects are lean and have tense nervous activity. May be due to overstimulation of the thyroid gland. Iodine-induced thyrotoxicosis affects mostly elderly people who have lived for a long time in iodine-deficient areas, have a long-standing goitre, and have then been given extra iodine. Also known as Jodbasedow, thyrotoxicosis and Graves’ disease.