condition in which iodine is insufficient or is not utilized properly. Iodine is an element that directly affects thyroid gland secretions, which themselves to a great extent control heart action, nerve response to stimuli, rate of body growth, and metabolism.

A simple goitre (enlargement of the thyroid gland) is the most common form of iodine deficiency illness and is found particularly in mountainous regions and areas far from salt water. The lowest incidence of this disease occurs along seacoasts. When the supply of iodine is only moderately deficient, the thyroid gland works harder to synthesize hormones in normal quantities, but the affected individual may continue in general good health despite the possible presence of goitre. In cases of severe and prolonged deficiency, however, there may be a deficit of thyroid hormones, resulting in hypothyroidism, a condition characterized by dry skin, loss of hair, puffy face, weakness, weight increase, fatigue, and mental sluggishness.

Prevention of iodine deficiency is most simply accomplished by eating seafood regularly or by using iodized table salt. To overcome natural iodine deficits, government health officials in Canada and other countries have made dietary iodine additives mandatory.