The only known physiological  role of iodine  in the human body is in the synthesis  of thyroid hormones  by the thyroid gland. Iodine from diet  is absorbed  throughout  the gastrointestinal  tract and converted  into the iodide ion before it’s  absorbed.

Thyroid hormones help   control the metabolic process in the body including  carbohydrate, fat, protein, vitamin, and mineral metabolism.  They also play an important role in  the growth and development of brain  and central nervous system.  Iodine deficiency causes  an irreversible derangement  in the development of brain and central nervous system.

Iodine deficiency can also cause congenital anomalies and  neurological cretinism.

The excretion of iodine in  the urine is a good measure  of iodine intake.

Iodine content of food depends on the iodine content of the soil in which it is grown.  Seaweed and reef fish are a good source of iodine.