The Fractionation of the Iodine of the Blood in Thyroid Disease.

Investigations concerning the level of iodine in the blood have been an aid in the better understanding of the metabolism of iodine in normal individuals and in patients with goiter. Experimental studies have established a relation between the thyroid gland and the metabolism of iodine. Clinical observations have shown that. the abnormal physiological processes manifest in exophthalmic goiter may be alleviated by effecting transitory involution of the hyperplastic thyroid tissue with iodine medication and subtotal resection of the thyroid gland. It is generally agreed that clinical hyperthyroidism is associated with the release of abnormal amounts of iodine from the thyroid. In this connection, the affinity of the thyroid gland for iodine, together with the capacity of thyroid tissue to synthesize organic iodine compounds, plays an important role. Based on the foregoing, the quantitative estimation of the organic iodine in blood should be a closer index of the amount of thyroid secretion than assumptions based on total blood iodine analyses. The purpose of the present communication is to report the results of a study of the fractionation of the iodine in the blood in cases of nontoxic goiter, exophthalrnic goiter and primary myxedema. The quantitative estimation of the iodine in the blood is not a simple procedure. The additional technic of fractionating the blood iodine adds greater complexity. A satisfactory method of fractionation should be accurate to the degree that the sum of the iodine analyses of the two fractions should equal the iodine analysis of an aliquot amount of untreated whole blood. In addition, it is important to know approximately the chemical nature of the iodine recovered in each of the fractions. The limits of the method of blood iodine fractionation can best be estimated by adding specific forms of iodine to blood and determining in which fraction the iodine is recovered. In this present study, an alcohol precipitation method was used for fractionating the iodine of the blood. The procedure was as follows: 20 cc. of blood is secured by venous puncture; 10 cc. of this blood is placed in a clean dry test tube for total iodine analysis, the remaining 10 cc. of blood is placed in a test tube containing a sufficient amount of iodine-free sodium oxalate to prevent clotting. The sample of oxalated blood is added directly to 10 volumes of ethyl alcohol. The precipitate is separated from the alcohol-blood mixture by filtering through a Whatman (Number 5) filter paper. The residue in the filter paper is washed 3 times with alcohol, using 15 cc. each time. The filter paper containing the precipitate (the so-called organic iodine fraction) is placed directly in a nickel crucible for iodine analysis (1). The filtrate (the so-called inorganic iodine fraction) is evaporated to dryness and transferred to a nickel crucible for iodine analysis. By exercising care to avoid contamination and loss of iodine (2) in the above procedure, the sum of iodine analyses of the 2 fractions should equal the iodine analysis of the sample of untreated blood. The adequacy of the above method in fractionating the iodine of the blood was determined in the following manner: A supply of oxalated beef blood was secured from the abattoir. Six samples of 10 cc. each of this blood were used for total blood iodine analysis. To an additional 5 samples (10 cc. each), 3.8 micrograms of iodine in an organic form were added and total iodine analysis was carried out. These estimations constituted the control results for the fractional analyses. Five samples (10 cc. each) were fractionated according to the procedure outlined above. To an additional 5 samples, 3.8 micrograms of iodine in an organic form were added and, after mixing, these bloods were fractionated for their iodine content. To another 5 samples of 10 cc. each of blood, 2.5 micrograms of iodine as inorganic