Iodine deficiency

Iodine is an essential trace element; the thyroid hormones thyroxine and triiodotyronine contain iodine. In areas where there is little iodine in the diet&mdash;typically remote inland areas where no marine foods are eaten&mdash;iodine deficiency gives rise to goiter (so-called endemic goitre), as well as cretinism, which results in developmental delays and other health problems

In some such areas, this is now combatted by the addition of small amounts of iodine to table salt in form of sodium iodide, potassium iodide, potassium iodate&mdash;this product is known as iodized salt. Iodine compounds have also been added to other foodstuffs, such as flour, in areas of deficiency.

Goiter
The mechanism is that low amounts of thyroid hormone in the blood due to lack of iodine to make them, give rise to high levels of the pituitary hormone TSH, which in turn stimulates abnormal growth of the thyroid gland.

Cretinism
Iodine deficiency is the leading cause of mental retardation, producing typical reductions in IQ of 10 to 15 IQ points. It has been speculated that deficiency of iodine and other micronutrients may be a possible factor in observed differences in IQ between ethnic groups: see race and intelligence for a further discussion of this controversial issue.

Local impact
Certain areas of the world, due to natural deficiency and governmental inaction, are severely affected by iodine deficiency, which effects approximately two billion people worldwide. It is particularly common in the Western Pacific, South-East Asia and Africa.

Iodine deficiency is also associated with poverty.

India is the most outstanding, with 500 million suffering from deficiency, 54 million from goiter, and two million from cretinism.

Among other nations affected by iodine deficiency, China and Kazakhstan have begun taking action, while Russia has not. Successful campaigns for the adoption of the use of iodized salt require education and regulation of salt producers and sellers and a public relations campaign directed at the public. The cost of adding iodine to salt is negligible.

Misc.
In a not widely accepted theory, geographer Jeremy Dobson has suggested that Neandertals exhibit characteristics similar to modern humans with iodine deficiency, or cretinism.