Iodine is nutritionally essential, being necessary for synthesis of the thyroid hormones, thyroxine and triiodothyronine.
Worldwide, iodine deficiency is a major cause of goitre, hypothyroidism and cretinism. In developing countries, it typically occurs in mountainous regions which often exhibit 'endemic goitre'. Most individuals are euthyroid with normal or elevated TSH becoming hypothyroid as the deficiency becomes more severe.
Last reviewed 01/2018