page_title: Iodine
section_title: Biological role
hierarchical_section_title: Iodine / Biological role
caption_attribution_description: Français&#160;: Pour quelques régions et départements de France, teneurs moyennes en iode des urines (iodure), mesurée en microgrammes par litres, dans la population française à la fin du XXème siècle (années 1980 à 2000)&#160;; d'après Mornex,1987 et LeGuenelal., 2000, cités par Le Guen &amp; al. (2001). L'Iodurie peut refléter la prise moyenne d'iode et/ou une éventuelle difficulté de l'organisme à fixer l'iode. English: Cornparison of the iodine content in urine in France in microgramme/day For some regions and departments of France, average levels of urine iodine (iodide), measured in micrograms per liter, in the French population at the end of the twentieth century (1980 to 2000); according to Mornex, 1987 and LeGuen &amp; al. 2000, quoted by Le Guen et al. (2001). Ioduria may reflect the average iodine uptake and / or a possible difficulty of the body in fixing iodine.
context_page_description: Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a lustrous, purple-black non-metallic solid at standard conditions that melts to form a deep violet liquid at 114 degrees Celsius, and boils to a violet gas at 184 degrees Celsius. However, it sublimes easily with gentle heat, resulting in a widespread misconception even taught in some science textbooks that it does not melt. The element was discovered by the French chemist Bernard Courtois in 1811, and was named two years later by Joseph Louis Gay-Lussac, after the Greek ἰώδης "violet-coloured".
  Iodine occurs in many oxidation states, including iodide, iodate, and the various periodate anions. It is the least abundant of the stable halogens, being the sixty-first most abundant element. It is the heaviest essential mineral nutrient. Iodine is essential in the synthesis of thyroid hormones. Iodine deficiency affects about two billion people and is the leading preventable cause of intellectual disabilities.
  The dominant producers of iodine today are Chile and Japan. Iodine and its compounds are primarily used in nutrition.
context_section_description: Iodine is an essential element for life and, at atomic number Z = 53, is the heaviest element commonly needed by living organisms. (Lanthanum and the other lanthanides, as well as tungsten with Z = 74, are used by a few microorganisms.) It is required for the synthesis of the growth-regulating thyroid hormones thyroxine and triiodothyronine (T₄ and T₃ respectively, named after their number of iodine atoms). A deficiency of iodine leads to decreased production of T₃ and T₄ and a concomitant enlargement of the thyroid tissue in an attempt to obtain more iodine, causing the disease known as simple goitre. The major form of thyroid hormone in the blood is thyroxine (T₄), which has a longer half-life than T₃. In humans, the ratio of T₄ to T₃ released into the blood is between 14:1 and 20:1. T₄ is converted to the active T₃ (three to four times more potent than T₄) within cells by deiodinases (5'-iodinase). These are further processed by decarboxylation and deiodination to produce iodothyronamine (T₁a) and thyronamine (T₀a'). All three isoforms of the deiodinases are selenium-containing enzymes; thus dietary selenium is essential for T₃ production.
  Iodine accounts for 65% of the molecular weight of T₄ and 59% of T₃. Fifteen to 20 mg of iodine is concentrated in thyroid tissue and hormones, but 70% of all iodine in the body is found in other tissues, including mammary glands, eyes, gastric mucosa, fetal thymus, cerebro-spinal fluid and choroid plexus, arterial walls, the cervix, and salivary glands. In the cells of those tissues, iodide enters directly by sodium-iodide symporter (NIS). The action of iodine in mammary tissue is related to fetal and neonatal development, but in the other tissues, it is (at least) partially unknown.
caption: Comparison of the iodine content in urine in France (in microgramme/day), for some regions and departments (average levels of urine iodine, measured in micrograms per liter at the end of the twentieth century (1980 to 2000)[89]
exif: {"Image Orientation": "Horizontal (normal)", "Image XResolution": "179959/2500", "Image YResolution": "179959/2500", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop CS6 (Windows)", "Image DateTime": "2018:11:11 13:02:44", "Image ExifOffset": "164", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "302", "Thumbnail JPEGInterchangeFormatLength": "9307", "EXIF ColorSpace": "Uncalibrated", "EXIF ExifImageWidth": "665", "EXIF ExifImageLength": "882"}