Iodine deficiency can reflect low environmental availability or impaired intestinal absorption.
Requirement and deficiency
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The daily iodine requirement is approximately 0.1–0.15 mg.
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Nearly all districts with endemic simple goitre have very low iodide levels in food and water.
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Failure of intestinal absorption can cause iodine deficiency despite adequate iodide in food and water.
Environmental distribution
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Mountainous endemic areas include the Rocky Mountains, Alps, Andes and Himalayas; Derbyshire and Yorkshire are also cited.
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Lowland endemic goitre occurs where soil lacks iodide or water comes from distant mountain ranges. Examples include the Great Lakes of North America, Lombardy, the Struma Valley, the Nile Valley and the Congo.
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Calcium is goitrogenic. Goitre is common in low-iodine areas on chalk or limestone, including Derbyshire and southern Ireland.