CONCENTRATION OF PRECIPITABLE IODINE IN THE SERUM 1

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Abstract
The concn. of precipitable iodine in the serum (SPI) lies between 3.8 and 7.8 [mu]g.% in normal individuals. In a given person SPI is quite constant from day to day. In 200 patients with hyper-thyroidism SPI is 8.0 [mu]g.% or more except in 4 instances where SPI fell in the upper normal range. In untreated hypothyroidism SPI is 3.0 [mu]g.% or less. In a few diseases, particularly cirrhosis, nephrosis, adrenal disease, pituitary disease, and conditions associated with an injury reaction, SPI may be lower than 3.8 [mu]g.%. Rarely, except in hyperthyroidism and pregnancy, does the SPI rise above 7.8 [mu]g.%. A micro method employing 1 ml. of serum for the detn. of SPI is described. The proteins are precipitated with ZnSO4 and NaOH in a pyrex flask which, without transfer of the precipitate, is used for centrifugation, digestion and distillation. The precipitate is digested with KMNO4 and H2SO4. The digest is reduced with oxalic and arsenious acids during distillation. The distilling head has an interchangeable glass joint to fit the digestion flask and a water-cooled condenser. After concn. of the distillate iodide is estimated by the rate of fading of ceric sulfate when reduced by arsenite in Chaney''s recording colorimeter.