Iodine deficiency

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Iodine is an essential trace element; the thyroid hormones thyroxine and triiodotyronine contain iodine. In areas where there is little iodine in the diet—typically remote inland areas where no marine foods are eaten—iodine deficiency gives rise to goiter (so-called endemic goiter), as well as cretinism, which results in developmental delays and other health problems. While noting recent progress, The Lancet noted, "According to WHO, in 2007, nearly 2 billion individuals had insufficient iodine intake, a third being of school age. ... Thus iodine deficiency, as the single greatest preventable cause of mental retardation, is an important public-health problem."^[1]

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, and/or potassium iodate—this product is known as iodized salt. Iodine compounds have also been added to other foodstuffs, such as flour, water and milk in areas of deficiency.^[2] Seafood is also a well known source of iodine.^[3] Thus iodine deficiency is more common in mountainous regions of the world where food is grown in soil poor in iodine.

Signs and symptoms

Goiter

A low amount of triiodiothyronine (T₃, one of the two thyroid hormones) in the blood, due to lack of dietary iodine to make it, should (but doesn't always) give rise to high levels of thyroid stimulating hormone TSH, which stimulates the thyroid gland to increase many biochemical processes; the cellular growth and proliferation can result in the characteristic swelling or hyperplasia of the thyroid gland, or goiter. The introduction of iodized salt since the early 1900s has eliminated this condition in many affluent countries; however, in Australia, New Zealand, and several European countries, iodine deficiency is a significant public health problem.^[4] It is more common in third-world nations. Public health initiatives to lower the risk of cardiovascular disease have resulted in lower discretionary salt use at the table, and with a trend towards consuming more processed foods. The non-iodized salt used in these foods also means that people are less likely to obtain iodine from adding salt during cooking.

Goiter is said to be endemic when the prevalence in a population is > 5%, and in most cases goiter can be treated with iodine supplementation. If goiter is untreated for around five years, however, iodine supplementation or thyroxine treatment may not reduce the size of the thyroid gland because the thyroid is permanently damaged.

Cretinism

Iodine deficiency is one of the leading cause of preventable 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.

Cretinism is a condition associated with iodine deficiency and goitre, commonly characterised by mental deficiency, deaf-mutism, squint, disorders of stance and gait, stunted growth and hypothyroidism. Paracelsus was the first to point out the relation between goitrous parents and mentally retarded children.^[5] As a result of restricted diet, isolation, intermarriage, etc., as well as low iodine content in their food, children often had peculiar stunted bodies and retarded mental faculties, a condition later known to be associated with thyroid deficiency. Diderot in his 1754 Encyclopédie described these patients as "crétins". In French, the term "crétin des Alpes" also became current, since the condition was observed in remote valleys of the Alps in particular. The word cretin appeared in English in 1779.

Epidemiology

Disability-adjusted life year for iodine deficiency per 100,000 inhabitants in 2002.^[6]

     no data      less than 50      50-100      100-150      150-200      200-250      250-300      300-350      350-400      400-450      450-500      500-800      more than 800

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

India is the most outstanding, with 500 million suffering from deficiency, 54 million from goiter, and two million from cretinism.^[7]

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 communication campaign directed at the public, the salt trade, politicians and policy makers. The cost of adding iodine to salt is negligible—"Only a few cents a ton."^[7]

Iodine deficiency has largely been confined to the developing world for several generations, but reductions in salt consumption and changes in dairy processing practices eliminating the use of iodine-based disinfectants have led to increasing prevalence of the condition in Australia and New Zealand in recent years. A proposal to mandate the use of iodized salt in most commercial breadmaking is expected to be adopted in 2009.^[8][9]

See also

• Basil Hetzel
• Lugol's iodine
• "Iodine Deficiency: studies by dr. Sebastiano Venturi (Italy)". http://web.tiscali.it/iodio/. Retrieved 2008-05-15. 

References

External links

• International Council for the Control of Iodine Deficiency Disorders
• Can Africa meet the goal of eliminating iodine-deficiency disorders by the year 2000?
• Network for Sustained Elimination of Iodine Deficiency
• Kotwal A, Priya R, Qadeer I (2007). "Goiter and other iodine deficiency disorders: A systematic review of epidemiological studies to deconstruct the complex web". Arch. Med. Res. 38 (1): 1–14. doi:10.1016/j.arcmed.2006.08.006. PMID 17174717.