Iodin is necessary for thyroid gland function. It participates in thyroxin formation, a hormone of thyroid gland.

Need in iodine varies from 50 to 200 mkg/day. It is accumulated in thyroid gland.
Iodine concentration in ordinary food is not much – 4-15 mkg%. However, sea fish contains about 70mkg%, cod liver contains up to 800 mkg%, there is 50- 70000 mkg% in sea staff depending on the kind and time of picking. It should be pointed that at long time keeping and thermal conditioning the biggest part of iodine is lost. Iodine concentration in plants and animal products strongly depends on its quantity in soil. That’s why to prevent goitrous disease potassium iodide is put into salt (25 mg per 1 kg). Storage life of this salt is no longer than 6 months because iodine disappears in storage.

Lack of iodine causes goitrous disease. School children are especially sensitive to the lack of iodine. It also leads to slow development of central nervous system. Excess of iodine reduces to weakening of iodine compound synthesis in thyroid gland and hypothyroidism.