Thyroid iodine determination,

Heedman PA, Jacobson B. 1964. Thyroid iodine determined by x-ray spectrophotometry. J.Clin.Endocrin. 24 246. 

Thyroid Iodine-131 Determine rate of iodine uptake by thyroid... 

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. 

X-ray fluorescence (XRF) analysis can be used for determination of thyroid iodine content and distribution. 

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. 

Figure 55.4 Iodine excretion and prevalence of enlarged thyroid gland in four European oountries. The figure shows the iodine excretion ((xg/l) and prevalence of thyroid enlargement determined by ultrasonography in four studies in European adults (Knudsen et al., 2000 Maravall et al., 2004 Valentino et al., 2004 Brauer et al., 2005).

Since iodine is concentrated in the thyroid gland, a radioassay of the thyroid can determine the level of exposure to many of its isotopes. However, 1-129 has very low activity and emits extremely low energy beta particles, making a radioassay much more difficult. Tests for 1-131 in the body should be available through most major medical centers. 

The effect of sample preservation on determination of F in healthy and pathological human thyroids has also been studied (Blazewicz et al., 2011). It was pointed out that the way of tissue preservation (either in formalin or by freezing) had no significant effect on the iodine determination result (a = 0.1) by ion chromatography combined with the pulsed amparometic detection method (IC-PAD). Sample decomposition is a critical step in iodides analysis as well. All reported methods have a digestion or ashing step prior to the final determination of... 

A common method of determining thyroid function is the use of radioactive iodine uptake (RAIU). Taken orally, the radioisotope iodine-131 mixes with the iodine already present in the thyroid. Twenty-four hours later, the amount of iodine taken up by the thyroid is determined. A detection tube held up to the area of the thyroid gland detects the radiation coming from the iodine-131 that has located there (see Figure 16.5). 

Eq. (5-2) may be utilized in estimating thyroidal uptake. If a daily intake of 0.15 mg is assumed, then thyroidal uptakes at 24 hours would remain at about 27 percent for dosages of less than 1 nCi (5.9 ng iodine). However, at higher dosages of there would be a considerable reduction in thyroidal uptake, to about 10 percent from 0.1 ltd I (0.59 mg -I- 0,15 mg), to about 3 percent from 1 tCi (5.9 mg -I- 0.15 mg). Since the radiologic dose to the thyroid is determined by the concentration in the gland, a similar decrease in dose per unit intake would be predicted. 

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... 

Gutekunst R., R. Fierro-Benitez, Teichert H. M., J. B. Stanbury. The effect of iodinated oil and salt on thyroid volume determined by ultrasonography in two villages in Ecuador. 10th International Thyroid Congress, The Hague 1991... 

Neonatal thyroid screening is an important additional tool for evaluating the potential consequences of iodine deficiency on brain development and for monitoring iodine prophylaxis at the population level. Indeed, neonates, whose very low thyroidal iodine stores make them hypersensitive to iodine deficiaicy, frequently have altered thyroid function tests (elevated serum TSH, possibly low T4) even at moderate degrees of iodine deficiency that do not appear to affect thyroid function in the adults. Therefore, a shift towards higher neonatal TSH values has been proposed as a useful tool to detect and monitor iodine deficient newborn populations. However, such a shift can be interpreted validly if representative sampling of newborns is carried out (at least one hundred determinations in randomly selected populations), with the use of sensitive assays for TSH measurements. 

Iodine is incorporated in thyroid proteins to form thyroxin and 3-I-thyroxine, both hormones essential for life. They are determined by immunochemical methods. Deficiency of I may lead to crop disease. 

Studies of low-dose perchlorate exposure in healthy human subjects A small number of studies have been published investigating the effects of low doses of perchlorate in thyroid function in healthy adults (without thyroid disease). One study was conducted in healthy male volunteers, involving the administration of 10 mg of perchlorate in drinking water for 14 days. A significant decrease in the uptake of iodine by the thyroid was observed at this dose, but there was no evidence of adverse effects on thyroid hormones or TSH concentrations [262]. Another recent study was conducted in healthy adults to determine the highest dose of perchlorate at which there is no effect on the uptake of iodine by the thyroid gland [263]. 

Thyroid suppression therapy- 75 to 100 mcg/day for 7 days radioactive iodine uptake is determined before and after administration of the hormone. 

Countries affected by iodine deficiency require to develop national programmes to assess the extent and severity of the problem. Once an IDD control programme is initiated monitoring and evaluation are required. There are three major components needed to meet this goal, namely determination of thyroid size and goitre prevalence, the determination of urinary iodine excretion, and the measurement of thyroid function, including serum TSH levels. 

Like iodine, astatine tends to accumulate in the thyroid gland of the living animal (31). The radioactivity of the element thus concentrated seems to cause severe damage to thyroid tissue without affecting the adjacent parathyroid glands. It may therefore be useful in cases of hyperthyroidism (32). Therefore it is important to determine the amount... 

Medical x-rays provided one of the first applications of radioisotopes. In 1914, the wounded from World War 1 were pouring into Paris hospitals. Marie Curie converted a Renault car into the first mobile radiological unit and drove it from hospital to hospital. Radioisotopes are now widely used in medicine to diagnose, study, and treat illness. A physician can determine, for example, how and at what rate the thyroid gland takes up iodine by using iodine-131 as a radioactive tracer and cobalt-60 is used to kill rapidly growing cancer cells. 

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