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Radiopharmaceuticals for Diagnostics
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Jim Ballinger, Jacek Koziorowski
The role of the thyroid gland, located in the front of the neck, is to incorporate dietary iodine into the hormones triiodothyronine (T3) and thyroxine (T4) which, when secreted into the circulation, control a variety of metabolic, growth, and development processes. One of the first radiopharmaceuticals was 131I-iodide, which is a perfect probe of thyroid function as it is taken up by what we now know is the sodium iodide symporter (NIS) then organified as hormones. NIS is a transporter located in the basolateral membrane of thyroid epithelial cells, and which simultaneously transports Na+ and I- ions from extracellular fluid into the thyroid epithelial cell via secondary active transport driven by the sodium gradient across the membrane. Because of the suboptimal radionuclidic properties of 131I (long physical half-life, high gamma energy, beta particle emissions), the pure gamma emitter 123I is now the preferred radionuclide. 99mTc-pertechnetate is an alternative radiotracer, which is also taken up by NIS but not organified [28]. 99mTc-pertechnetate is a substrate for NIS because it has some of the chemical properties of iodide (single negative charge, small size, hydrophilic), but it cannot be incorporated into thyroid hormones.
Inorganic Chemicals in Drinking Water
Published in Joseph Cotruvo, Drinking Water Quality and Contaminants Guidebook, 2019
Iodine is an essential nutrient that is toxic, but only at high doses. Iodide or iodate are provided in nutritional supplement tablets to compliment inadequate dietary intake, and used to treat hypothyroidism. Thyroid hormones, triiodothyroxine (T3), and thyroxine (T4) are important in protein synthesis, enzymatic activity and metabolism, as well as for neurological and skeletal development in fetuses and infants. Dietary iodide is transported in the blood stream to the thyroid by the NIS (sodium iodide symporter protein). Many other common anions such as perchlorate, bromate, bromide, thiocyanate, and nitrate are also transported competitively by the same transporter. Inadequate iodine intake can result in thyroid hormone deficiency, and goiter, so it is essential that there be sufficient iodine daily consumption of iodine species to compensate.
Hazard Characterization and Dose–Response Assessment
Published in Ted W. Simon, Environmental Risk Assessment, 2019
Thyroid hormone (TH) acts on all tissues in the body to affect metabolism of food and vitamins, development of the nervous system, and other body functions. The two important enzymes in the production of TH are the sodium/iodide symporter (NIS) that moves iodide into thyroid follicular cells and thyroperoxidase, the enzyme that couples iodine to tyrosine and produces TH.139,140
Nuclear Medicine in Oncology
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2018
Carla Oliveira, Rui Parafita, Ana Canudo, Joana Correia Castanheira, Durval C. Costa
The basis of this therapy lies in the fact that iodine is an integral component of triiodothyronine and thyroxine hormones. During the process of biosynthesis for these hormones, iodine is taken up by the follicular cells in the thyroid – thyrocytes – by active transport (through sodium iodide symporter – NIS) and incorporated in the thyroglobulin (process known as organification), being stored in the glandular colloid until thyroid hormone secretion into the blood stream (Filetti et al. 1999).