Iodine is an important part of the hormone thyroxine. The thyroid gland, which is located in the neck, secretes this hormone. Thyroxine regulates some important metabolic processes related to growth and oxidation.
Deficiency of iodine results in a disease called GOITRE. Iodine deficiency causes disorders resulting in retarded growth and mental disability. It also causes abnormal enlargement of the thyroid gland.
Girls and women are more prone to iodine deficiency than boys and men, the chances of iodine deficiency increase further during periods of adolescence and pregnancy.
Goitre is more common in mountainous regions where the iodine content of the soil and water is low. The affected area in India lies in the foot hills of the Himalayas from Kashmir to Arunachal Pradesh. The reason for this is that iodine is very soluble in water and is easily washed away by rains or malting snow. So in mountainous regions soil contains very less amount of iodine and so that concentration of iodine in plants growing in these regions is also very low.
Such diseases, which are restricted to a specific region because of the specific environmental condition, are called ENDEMIC DISEASES. Goitre is rare among people living along seacoast because sea plants, the fishes which feed upon them and the sea salts are rich in iodine.
In many countries of the world, common salt is enriched by the addition of iodine in the form of potassium iodine or potassium iodate. On account of its stability potassium iodate is preferred to potassium iodide for the iodization of common salt or the drinking water supply. The common salt enriched with iodine salts is known as iodized salt. Consumption of iodized salt helps in normal function of thyroid gland and prevents goitre.