Iodine deficiency
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Iodine deficiency | |
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Specialty | Endocrinology |
Iodine deficiency is a lack of the
Prevention includes adding small amounts of iodine to table salt, a product known as
In the U.S., the use of iodine has decreased over concerns of overdoses since mid-20th century, and the iodine antagonists bromine, perchlorate and fluoride have become more ubiquitous.[4] In particular, around 1980 the practice of using potassium iodate as dough conditioner in bread and baked goods was gradually replaced by the use of other conditioning agents[5] such as bromide.[citation needed]
Iodine deficiency resulting in goiter occurs in 187 million people globally as of 2010[update] (2.7% of the population).[6] It resulted in 2700 deaths in 2013, up from 2100 deaths in 1990.[7]
Signs and symptoms
Goiter
A low amount of
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.
Congenital iodine deficiency syndrome
Congenital iodine deficiency syndrome, previously known as cretinism, is a condition associated with iodine deficiency and goiter, commonly characterised by mental deficiency, deafness, squint, disorders of stance and gait and stunted growth due to hypothyroidism. Paracelsus was the first to point out the relation between goitrous parents and their mentally disabled children.[9]
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
While reporting recent progress towards overcoming iodine-deficiency disorders worldwide, The Lancet noted: "According to World Health Organization, in 2007, nearly 2 billion individuals had insufficient iodine intake, a third being of school age." A conclusion was made that the single most preventable cause of intellectual disability is that of iodine deficiency.[10]
Fibrocystic breast changes
There is preliminary evidence that iodine deficiency enhances the sensitivity of breast tissue to estrogen.[11][12] In rats treated with estradiol, iodine deficiency has been shown to lead to changes similar to benign breast changes that are reversible by increased iodine in the diet.[11][12] In a few studies, iodine supplementation had beneficial effects (such as reducing the presence of breast cyst, fibrous tissue plaques and breast pain) in women with fibrocystic breast changes.[11][13][unreliable medical source?]
Protective effects of iodine on breast cancer have been postulated[by whom?] from epidemiologic evidence and described in animal models.[14][unreliable medical source?][15][unreliable medical source?][16] In view of the antiproliferative properties of iodine in breast tissue, molecular iodine supplementation has been suggested as an adjuvant in breast cancer therapy.[16][citation needed]
Risk factors
Following is a list of potential risk factors that may lead to iodine deficiency:[17]
- Low dietary iodine
- Selenium deficiency
- Pregnancy[18]
- Exposure to radiation
- Increased intake/plasma levels of goitrogens, such as calcium
- Sex (higher occurrence in women)
- Smoking tobacco
- Alcohol (reduced prevalence in users)
- Oral contraceptives (reduced prevalence in users)
- Perchlorates
- Thiocyanates
- Age (for different types of iodine deficiency at different ages)
Pathophysiology
Iodine accounts for 65% of the molecular weight of T4 and 59% of T3. There is a total of 15–20 mg of iodine in the human body, primarily concentrated in thyroid tissue and hormones. Thirty percent of iodine is distributed in other tissues, including the mammary glands, eyes, gastric mucosa, choroid plexus, arterial walls, the cervix, and salivary glands. In the cells of these tissues, iodide enters directly by
- Venturi S, Guidi A, Venturi M (1996). "[Extrathyroid iodine deficiency disorders: what is the real iodine requirement?]"". Le Basi Razionali della Terapia. 16: 267–275.
- Pellerin P (1961). "La tecnique d'autoradiographie anatomique a la temperature de l'azote liquide". Path Biol. 232 (9): 233–252.
Diagnosis
The diagnostic workup of a suspected iodine deficiency includes signs and symptoms as well as possible risk factors mentioned above. A 24-hour urine iodine collection is a useful medical test, as approximately 90% of ingested iodine is excreted in the urine.[20] For the standardized 24-hour test, a 50 mg iodine load is given first, and 90% of this load is expected to be recovered in the urine of the following 24 hours. Recovery of less than 90% is taken to mean high retention, that is, iodine deficiency. The recovery may, however, be well less than 90% during pregnancy, and an intake of goitrogens can alter the test results.[21]
If a 24-hour urine collection is not practical, a random urine iodine-to-creatinine ratio can alternatively be used.[20] However, the 24-hour test is found to be more reliable.[22]
A general idea of whether a deficiency exists can be determined through a functional iodine test in the form of an iodine skin test. In this test, the skin is painted with an iodine solution: if the iodine patch disappears quickly, this is taken as a sign of iodine deficiency. However, no accepted norms exist on the expected time interval for the patch to disappear, and in persons with dark skin color the disappearance of the patch may be difficult to assess. If a urine test is taken shortly after, the results may be altered due to the iodine absorbed previously in a skin test.[21]
Treatment
Iodine deficiency is treated by ingestion of iodine salts, such as found in
The recommended daily intake of iodine for non-pregnant adults is 150 µg for maintenance of normal thyroid function. In pregnant women, the amount increases to 220 µg; in breastfeeding women, the amount is 290 µg.[20]
Prognosis
With iodine supplementation, goiters caused by iodine deficiency decrease in size in very young children and pregnant women. Generally, however, long-standing goiters caused by iodine deficiency respond with only small amounts of shrinkage after iodine supplementation, and patients are at risk for developing hyperthyroidism.[20]
Being pregnant while iodine-deficient additionally carries the risk of causing
Epidemiology
Iodine deficiency resulting in goiter occurs in 187 million people globally as of 2010[update] (2.7% of the population).
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 was adopted in Australia in October 2009.[28] In a study of the United Kingdom published in 2011, almost 70% of test subjects were found to be iodine deficient.[29] The study's authors suggested an investigation regarding "evidence-based recommendations for iodine supplementation".[29]
Micronutrient deficiencies, including iodine deficiency, impair the development of intelligence. Lacking iodine during human development causes a fall, in average, of 12 intelligence quotient (IQ) points in China.[30] A study of U.S. military data collected during the First and Second World Wars found that the introduction of salt iodization in the U.S. in the 1920s resulted in an increase in IQ, by approximately one standard deviation, for the quarter of the U.S. population most deficient in iodine, explaining about "one decade's worth of the upward trend in IQ" in the U.S. (i.e., the Flynn effect).[31] The same study documented "a large increase in thyroid-related deaths following the countrywide adoption of iodized salt, which affected mostly older individuals in localities with high prevalence of iodine deficiency".[31]
In iodine-deficient or mildly iodine-deficient areas of Europe, iodine deficiency is frequent during pregnancy despite the widespread use of iodised salt, posing risks to the neurodevelopment of foetuses.[32] In one study performed in a mildly iodine-deficient area, iodine deficiency was found to be present in more than half of breastfeeding women; in contrast, the majority of their newborns had iodine excess, mostly due to neonatal exposure to iodine-containing disinfectants.[33] A 2014 meta-analysis found that iodine supplementation "improves some maternal thyroid indices and may benefit aspects of cognitive function in school-age children, even in marginally iodine-deficient areas".[34]
Deficient populations
In areas where there is little iodine in the diet, typically remote inland areas and semi-arid equatorial climates where no marine foods are eaten, iodine deficiency gives rise to
Iodine deficiency is the leading cause of preventable
Iodine deficiency is also a problem in certain areas of Europe. In Germany it has been estimated to cause a billion dollars in health care costs per year.[13] A modelling analysis suggests universal iodine supplementation for pregnant women in England may save £199 (2013 UK pounds) to the health service per pregnant woman and save £4476 per pregnant woman in societal costs.[37]
Iodine deficiency was previously a common disease in Norway, because the content of iodine in the drinking water was low. Before 1950 goiter was a widespread disease caused by iodine deficiency.[38] Up to 80 per cent of the population were affected in inland areas. In the coastal communities, saltwater fish were an important part of the diet, and because of the presence of iodine in seawater, goiter was less common than in the inland districts. From the 1950s, Norwegians started adding iodine to dairy cow feed. Since milk was an essential part of the Norwegian diet, the incidence of goiter decreased in the population.[38]
See also
- Basil Hetzel
- International Council for the Control of Iodine Deficiency Disorders
- Lugol's iodine
References
- ^ "Risiko For Jodmangel i Norge" (PDF). Ernæringsrådet (in Norwegian). June 2016.
- ^ Creswell J. Eastman, Michael Zimmermann (12 February 2014). "The Iodine Deficiency Disorders". Thyroid Disease Manager. Retrieved 2016-12-11.
- ^ "Iodine in Seaweed". Archived from the original on 2012-07-31. Retrieved 2008-01-04.
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- ^ T.E.C. Jr. (August 1, 1974). "Paracelsus on What the Physician Should Know". Pediatrics. 54 (2). American Academy of Pediatrics. Retrieved 2008-12-05.
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- ^ ISBN 978-1-4377-2333-5.
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- ^ S2CID 16838840.
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- ^ a b c d e Stephanie L. Lee, Elizabeth N. Pearce, Sonia Ananthakrishnan (16 December 2015). "Iodine Deficiency". Medscape. Retrieved 2016-12-11.
- ^ ISBN 978-0-9673949-4-7.
- ISBN 978-0-9673949-4-7.
- ISBN 978-92-4-154765-9.
- ISBN 978-0-323-18907-1.
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- ^ "Mortality and Burden of Disease Estimates for WHO Member States in 2002" (xls). World Health Organization. 2002.
- ^ "In Raising the World's I.Q., the Secret's in the Salt", article by Donald G. McNeil, Jr., The New York Times, December 16, 2006.
- ^ l "Iodine Fortification" Archived 2013-04-10 at the Wayback Machine, article appearing on March 5, 2013, from Food Standards.
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- ^ PMID 31853231.)
{{cite journal}}
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- ^ "Micronutrients — Iodine, Iron and Vitamin A". UNICEF.
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- ^ a b "Fakta om jod" [Facts about iodine]. Folkehelseinstituttet (in Norwegian). 11 July 2018. Retrieved 2018-07-11.
Further reading
- 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. PMID 17174717.