Determination of iodine in vivo and

Determination of Iodine In Vivo and In Vitro by X-Ray Fluorescence Analysis Methodology and Applications... 

Determination of the thyroid iodine content by X-ray fluorescence (XRF) investigation offers a unique possibility to study the intrathyroidal iodine pool. Apart from clinical applications in subjects with thyroid disease, it is of utmost interest to apply the method in situations of iodine deficiency or iodine overload. This review gives special attention to the XRF technique, and also describes the application of XRF in vivo and in vitro. 

An X-ray fluorescence method has been developed for in vivo determination of iodine in thyroid (Aubert et al., 1981 Jonckheer and Deconinck, 1982). This method is based on the irradiation of iodine in the thyroid by o(-rays provided by a -source, such as Am. The excited iodine atoms emit a characteristic X-ray fluorescence radiation, which is proportional to the amount of iodine present in the gland. The reported detection fimit reaches 0.01 mg/ml thyroid, this value is much lower than the iodine concentration in thyroid. The reported radiation dose equivalent is only 60mSv per measurement. This method has been successfully used for the clinical determination of in thyroid (Milakovic et al., 2006 Reiners et al., 1996, 2006 Briancon et al., 1992). An indirect method was also reported to determine of thyroid iodine in vivo (Imanishi et al., 1991), which is based on the relationship of CT attenuation values with iodine concentration in the thyroid. It was reported that the CT value correlated finearly with iodine concentration in thyroid nodules when iodine concentration was higher than 0.02 mg/g. 

NAA and X-ray fluorescence are used for in vivo determination of stable iodine in the thyroid the most frequently used method for iodine in urine is colorimetry of the Sandell—Koltoff reaction, while ICP-MS is a more accurate and simple method compared to others. 

Radioactive tracer studies are well suited for zone electrophoresis because the components can be located, analytically determined, and investigated for radioactivity using the same strip (see Fig. 7). The rate of formation of the serum proteins has been studied by incorporation in vivo of valine C (Gros et al., 1952) and of methionine S (Niklas and Maurer, 1952). In vivo incorporation of P into serum has also been investigated with this technique the iodine was found to assemble in a nondialyzable fraction between albumin and ai-globulin in rabbit (Maurer and Teichenbach, 1952) and near a2-globulin in man (Larson et al., 1952). 

Acute inhibitory effects of excess iodide was first demonstrated in vitro in 1944 by Morton, Chaikoff and Rosenfeld (i) and in vivo in 1948 by Wolff and Chaikoff (Wolff-Chaikoff effect) (2). As shown in Fig. 1, they injected 100 pg of iodide per rat with a tracer dose of and determined pleisma inorganic iodide concentration, total thyroidal iodine uptake and thyroidal organic iodine uptake until 50 hours after the injection of iodide. Thyroidal organic iodine... 

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