THE DISTRIBUTION OF IODINE WITH SPECIAL REFERENCE TO GOITER

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Abstract
The exact amount of I necessary to prevent goitre is not known but an adult thyroid can get along with 10 mgm. of iodine without showing symptoms of goitre. In the more goitrous regions of America more than 50 % of the girls at the age of puberty may show enlarged thyroids. Iodine in rocks may be several hundred parts per billion. A few minerals show secondary enrichment, mainly silver but also some CU2O. The I content of soils which arose from the weathering of rocks seems to be higher than that of the rocks. The I content of drinking water in goitrous regions is very low, usually less than one part per billion. That in non-goitrous regions is very variable and may vary inversely with the rainfall. It may be higher than 100 parts per billion. No I is detected in filtered air. Iodine is more abundant in leafy vegetables than in cereal grains grown on the same soil but is more abundant in non-goitrous regions than in goitrous regions. Sea food is high in I. Many marine fish contain over 1000 parts per billion. Sponges and gor-gonians are extremely high in I but are not used as food. Intake of I in the food of non-goitrous persons may be as low as 0.02 mgm. per day. It is possible to select food with about half this I content. In I starvation traces of I appear in the urine. Iodine starvation of white rats produces enlargement of the thyroid. Many of the older determinations of I in food and drink have been incorrect. Perhaps the most reliable method is the isolation of I. Organic matter must be burned in order to liberate the I and special precautions taken against I loss during combustion either by burning a mixture with an alkaline ash slowly at a low temp. or by passing the smoke through an alkaline solution in order to hold back the I. In order to prevent the formation of tarry products, O is used in the combustion.

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