scispace - formally typeset
Search or ask a question

Showing papers on "Iodine published in 2001"


Journal ArticleDOI
01 May 2001-Thyroid
TL;DR: Iodine induced hyperthyroidism is frequently observed in patients affected by euthyroid iodine deficient goiter when suddenly exposed to excess iodine, possibly the presence of autonomous thyroid function permits the synthesis and release of excess quantities of thyroid hormones.
Abstract: 150 μ g iodine are daily required for thyroid hormone synthesis. The thyroid gland has intrinsic mechanisms that maintain normal thyroid function even in the presence of iodine excess. Large quantities of iodide are present in drugs, antiseptics, contrast media and food preservatives. Iodine induced hyperthyroidism is frequently observed in patients affected by euthyroid iodine deficient goiter when suddenly exposed to excess iodine. Possibly the presence of autonomous thyroid function permits the synthesis and release of excess quantities of thyroid hormones. The presence of thyroid autoimmunity in patients residing in iodine-insufficient areas who develop iodine-induced hyperthyroidism has not been unanimously observed. In iodine-sufficient areas, iodine-induced hyperthyroidism has been reported in euthyroid patients with previous thyroid diseases. Euthyroid patients previously treated with antithyroid drugs for Graves' disease are prone to develop iodine-induced hyperthyroidism. As well, excess iodine ...

242 citations


Journal ArticleDOI
TL;DR: It is reported that a wide variety of bacteria including terrestrial and marine bacteria are capable of methylating the environmental level of iodide (0.1 μM), which strongly indicates that bacteria contribute to iodine transfer from the terrestrial and Marine ecosystems into the atmosphere.
Abstract: Methyl iodide (CH3I) plays an important role in the natural iodine cycle and participates in atmospheric ozone destruction. However, the main source of this compound in nature is still unclear. Here we report that a wide variety of bacteria including terrestrial and marine bacteria are capable of methylating the environmental level of iodide (0.1 μM). Of the strains tested, Rhizobium sp. strain MRCD 19 was chosen for further analysis, and it was found that the cell extract catalyzed the methylation of iodide with S-adenosyl-l-methionine as the methyl donor. These results strongly indicate that bacteria contribute to iodine transfer from the terrestrial and marine ecosystems into the atmosphere.

157 citations


Journal ArticleDOI
TL;DR: After NIS was cloned, several studies in FRTL-5 cells and cultured human thyroid cells showed that treatment with TSH stimulates iodide transport activity as well as NIS gene and protein expression, suggesting that TSH regulates NIS expression through the cAMP signal transduction pathway.
Abstract: Active transport of iodide into the thyroid gland is a crucial and rate-limiting step in the biosynthesis of thyroid hormones that play an important role in the metabolism, growth, and maturation of a variety of organ systems, in particular the nervous system (1) Although it has been known for decades that iodide transport into the thyroid gland is mediated by a specific sodium-dependent iodide transporter located at the basolateral membrane of thyroid follicular cells, the sodium iodide symporter (NIS) gene was cloned just 4 yr ago (2, 3) After cloning of the rat sodium iodide symporter (rNIS) from a Fisher rat thyroid line (FRTL-5)derived complementary DNA (cDNA) library (2), the human sodium iodide symporter (hNIS) was cloned from a human thyroid cDNA library in 1996 (3) The hNIS gene is localized on chromosome 19p12–132 and encodes a glycoprotein of 643 amino acids (aa) with a molecular mass of approximately 70–90 kDa The coding region of hNIS contains 15 exons interrupted by 14 introns and codes for a 39-kb messenger ribonucleic acid (mRNA) transcript (4) As a member of the sodium-dependent transporter family, NIS is an intrinsic membrane protein with 13 putative transmembrane domains, an extracellular amino-terminus, and an intracellular carboxyl-terminus The NIS protein has three potential Nlinked glycosylation sites; 1 is located in the fourth extracellular (seventh extramembranous domain), and 2 are located in the last extracellular (13th extramembranous domain) loop (5) (Fig 1) NIS cotransports two sodium ions along with one iodide ion, with the transmembrane sodium gradient serving as the driving force for iodide uptake The sodium gradient providing the energy for this transfer is generated by the ouabain-sensitive Na/K-adenosine triphosphatase (Na/ K-ATPase) NIS-mediated iodide transport is, therefore, inhibited by the Na/K-ATPase inhibitor ouabain as well as by the competitive inhibitors thiocyanate and perchlorate (1) (Fig 2) After active transport across the basolateral membrane of thyroid follicular cells, iodide is translocated across the apical membrane by pendrin, the Pendred syndrome gene product, which is a chloride/iodide transporter (6–10) (Fig 2) Other apical anion transporters may also be involved At the cell/colloid interface iodide is organified in a complex reaction involving oxidation catalyzed by thyroid peroxidase (TPO) and incorporation into tyrosyl residues along the thyroglobulin (Tg) backbone The thyroid hormones T3 and T4 are synthesized by coupling of two iodotyrosine residues and are stored in the colloid (Fig 2) The iodide organification step can be inhibited by propylthiouracil and methimazole, which are TPO enzyme inhibitors All of these steps are stimulated through pituitary-derived TSH, which interacts with the TSH receptor at the basolateral membrane of thyroidal cells (1) It has been known for many years that TSH stimulates iodide transport into the thyroid gland via the adenylate cyclase-cAMP pathway (1) After NIS was cloned, several studies in FRTL-5 cells and cultured human thyroid cells showed that treatment with TSH stimulates iodide transport activity as well as NIS gene and protein expression (11, 12) Forskolin and dibutyryl cAMP are able to mimic this stimulatory effect on both iodide transport activity as well as NIS gene and protein expression, suggesting that TSH regulates NIS expression through the cAMP signal transduction pathway (11) (Fig 2) In addition to its key role in thyroid physiology, NISmediated iodide accumulation in the thyroid gland is a crucial prerequisite for diagnostic scintigraphic imaging as well as for the highly efficient radioiodine therapy of benign and malignant thyroid diseases The purpose of this review is to summarize and discuss the current knowledge of NIS and its diagnostic and therapeutic implications in thyroidal and nonthyroidal cancer

142 citations


Journal ArticleDOI
01 May 2001-Thyroid
TL;DR: The data indicate a negligible risk of the small oral long-term doses achieved with iodate-fortified salt, and the proven genotoxic and carcinogenic effects of bromate raise the possibility of analogous activities of iodate.
Abstract: Because it is more stable than iodide, most health authorities preferentially recommend iodate as an additive to salt for correcting iodine deficiency. Even though this results in a low exposure of at most 1700 mg/d, doubts have recently been raised whether the safety of iodate has been adequately documented. In humans and rats, oral bioavailability of iodine from iodate is virtually equivalent to that from iodide. When given intravenously to rats, or when added to whole blood or tissue homogenates in vitro or to foodstuff, iodate is quantitatively reduced to iodide by nonenzymatic reactions, and thus becomes available to the body as iodide. Therefore, except perhaps for the gastrointestinal mucosa, exposure of tissues to iodate might be minimal. At much higher doses given intravenously (i.e., above 10 mg/kg), iodate is highly toxic to the retina. Ocular toxicity in humans has occurred only after exposure to doses of 600 to 1200 mg per individual. Oral exposures of several animal species to high doses, exceeding the human intake from fortified salt by orders of magnitude, pointed to corrosive effects in the gastrointestinal tract, hemolysis, nephrotoxicity, and hepatic injury. The studies do not meet current standards of toxicity testing, mostly because they lacked toxicokinetic data and did not separate iodatespecific effects from the effects of an overdose of any form of iodine. With regard to tissue injury, however, the data indicate a negligible risk of the small oral long-term doses achieved with iodate-fortified salt. Genotoxicity and carcinogenicity data for iodate are scarce or nonexisting. The proven genotoxic and carcinogenic effects of bromate raise the possibility of analogous activities of iodate. However, iodate has a lower oxidative potential than bromate, and it did not induce the formation of oxidized bases in DNA under conditions in which bromate did, and it may therefore present a lower genotoxic and carcinogenic hazard. This assumption needs experimental confirmation by proper genotoxicity and carcinogenicity data. These in turn will have to be related to toxicokinetic studies, which take into account the potential reduction of iodate to iodide in food, in the intestinal lumen or mucosa, or eventually during the liver passage.

127 citations


Journal Article
TL;DR: The transduction of the hNIS gene per se is sufficient to induce 125I transport in Morris hepatoma cells in vitro and in vivo, however, additional conditions need to be defined that inhibit the iodide efflux from the tumor cells.
Abstract: The characteristic feature of thyroid cells of taking up iodide enables benign thyroid diseases and differentiated thyroid carcinoma to be successfully treated with radioiodide therapy. The transport of iodide across the cell membrane is mediated by the human NaI symporter (hNIS). We therefore investigated whether the accumulation of iodide may be induced by the retroviral transfer of the hNIS gene in nonthyroid tumor cells. Methods: With use of a bicistronic retroviral vector for the transfer of the hNIS coding sequence and the hygromycin resistance gene, rat Morris hepatoma (MH3924A) cells were infected with retroviral particles and 32 hNIS-expressing cell lines were generated by hygromycin selection. After incubation of the genetically modified and wild-type hepatoma cells and the rat thyroid cell line FRTL5 with Na125I, the uptake and efflux of iodide were determined. In addition, the iodide distribution in rats bearing wild-type and genetically modified hepatomas was monitored. Results: Genetically modified MH3924A cell lines accumulated up to 235 times more iodide than did noninfected hepatoma cells. The maximal iodide uptake in the cells was observed after 60 min incubation time. Competition experiments in the presence of sodium perchlorate revealed a dose-dependent decrease of iodide uptake (87%–92%). Moreover, carbonyl cyanide p-trifluoromethoxyphenylhydrazone led to a loss of accumulated I− (32%), whereas 4,4′-diisothiocyano-2,2′-disulfonic acid stilbene increased the I− uptake into the cells (22%). However, a rapid efflux of the radioactivity (80%) was observed during the first 10 min after 125I−-containing medium had been replaced by nonradioactive medium. In rats, the hNIS-expressing tumors accumulated six times more iodide than did the contralateral wild-type tumor as monitored by scintigraphy. The ex vivo quantitation of the iodide content performed 1 h after tracer administration in 1g of tumor tissue revealed a 17-fold higher iodide accumulation in the genetically modified tumors. In accordance with the in vitro data, we also observed a rapid efflux of radioactivity from the tumor in vivo. Conclusion: The transduction of the hNIS gene per se is sufficient to induce 125I− transport in Morris hepatoma cells in vitro and in vivo. With regard to a therapeutic application, however, additional conditions need to be defined that inhibit the iodide efflux from the tumor cells.

119 citations


Journal ArticleDOI
TL;DR: The 2 methods used to determine iodine in seafood from the Barents Sea, the Norwegian Sea, and the North Sea showed great variation between different fish species as well as between individuals within a species.
Abstract: A method was developed for determination of total iodine content in different standard reference materials (SRMs) and seafood products by inductively coupled plasma/mass spectrometry (ICP/MS). If iodine is present as iodide and nitric acid is used in the wet digestion system, the observed signal is not stable when iodine is measured by ICP/MS at m/z 127. To stabilize the iodine signal, 3% ammonia solution (1 + 1, v/v) was added to the digest. The limit of quantitation of the method, defined as 6 times the standard deviation in the blank solution (n = 20) was estimated to be 15 mg/kg (using 0.2 g dry mass and a dilution factor of 50). The precision, expressed as repeatability of the iodine concentration, varied between 3.2 and 12% in SRMs, with concentrations of 4.70-0.17 mg/kg dry matter. The described method was compared with a method using tetramethylammonium hydroxide extraction. Both methods showed good precision and trueness by analyses of SRMs. The 2 methods were used to determine iodine in seafood from the Barents Sea, the Norwegian Sea, and the North Sea. The results showed great variation between different fish species as well as between individuals within a species. The lowest values of iodine were recorded in muscle of ling (Molva molva) with a mean of 0.07 mg/kg fresh weight and a variation between 0.03 and 0.11 mg/kg fresh weight. The highest values were found in cod (Gadus morhua) from the Barents Sea, with a mean of 2.5 mg/kg and a variation between 0.7 and 12.7 mg/kg fresh weight.

117 citations


Journal ArticleDOI
Mu Li1, Gary Ma1, Karmala Guttikonda1, Steven C Boyages1, Creswell J Eastman1 
TL;DR: Evaluating the urinary iodine excretion (UIE), as the indicator of iodine nutrition, in samples obtained from various demographic groups in the Sydney metropolitian area confirmed that iodine deficiency has reemerged in Sydney, Australia.
Abstract: Iodine is an essential nutrient for human growth and development. The thyroid gland is dependent upon iodine for production of thyroid hormone. It is a common perception that iodine deficiency is not a major public health concern in mainland Australia, with sporadic studies carried out about a decade ago showing average urinary iodine excretion levels of around 200 µg/day. Recent evidence, however, has shown that the consumption of iodine is declining in Australia. A similar situation has occurred in the USA. The present study was designed to evaluate the urinary iodine excretion (UIE), as the indicator of iodine nutrition, in samples obtained from various demographic groups in the Sydney metropolitian area, namely: schoolchildren, healthy adult volunteers, pregnant women and patients with diabetes. Urinary iodine in spot urine sample was measured in a Technicon II autoanalyser using an in-house, semiautomated method. The results in this communication show that all four study groups had the median UIE below 100 µg/L, the criteria set by the World Health Organization for iodine repletion, and confirm what has been described previously, that iodine deficiency has reemerged in Sydney, Australia. One of the major causes of the reduced iodine intake is the reduction of iodine in milk since the dairy industry replaced iodine-rich cleaning solutions with other sanitisers. Secondly, less than 10% of the population are currently using iodised salt. A national survey into the iodine nutrition status in Australia is urgently required as part of the establishment of a systematic surveillance and legislation is required to iodise all edible salt.

115 citations


Journal ArticleDOI
TL;DR: Seven per cent of individual urine samples indicated severe iodine deficiency without this being present in the group studied, and Dispersion was reduced by 24% when using estimated 24 h urinary iodine excretion rather than urinary iodine concentration.
Abstract: Objective: The iodine intake level in a population is determined in cross-sectional studies. A fraction of samples with iodine content below a certain level, e.g. 25 mg/l, may suggest iodine deficiency in part of the population. However, urinary iodine varies considerably from day to day and the fraction of low samples caused by dispersion remains unsettled. Design: A longitudinal study of 16 healthy men living in an area of mild to moderate iodine deficiency. Methods: We measured urinary iodine and creatinine concentrations, and serum TSH, total thyroxine (T4), free T4 index and total tri-iodothyronine (T3) in samples collected monthly for 1 year. Results: Average urinary iodine excretion was 57.0 mg/l (49.1 mg/24 h (corrected for creatinine excretion)) and varied from 29 to 81 mg/l (28 to 81 mg/24 h) between participants. Individual samples varied between 10 and 260 mg/l, and the variation around the mean was 2.4 times larger when calculated for the 180 individual samples compared with the 15 average annual values (1.7 times larger for estimated 24 h iodine excretion values). The fraction of individual samples below 25 mg/l was 6.7% (7.2% ,25 mg/24 h), whereas none of the participants had average iodine excretion below 25 mg/l or 25 mg/24 h. Participants with average annual iodine excretion below 50 mg/24 h had a negative correlation between iodine excretion and TSH, whereas a positive correlation was observed when average annual iodine excretion was above this level. Conclusions: Seven per cent of individual urine samples indicated severe iodine deficiency without this being present in the group studied. Dispersion was reduced by 24% when using estimated 24 h urinary iodine excretion rather than urinary iodine concentration. Participants with moderate iodine deficiency (average annual urinary iodine excretion 25‐50 mg/24 h) showed clear signs of substrate deficiency for thyroid hormone synthesis while participants with mild iodine deficiency (50‐100 mg/ 24 h) did not.

98 citations


Journal ArticleDOI
G. Jahreis1, W. Hausmann, G. Kiessling, K. Franke, M. Leiterer 
TL;DR: During the last decade the iodine supply in Germany has increased significantly, but there is still a high frequency of goitre, and in a two-period study 12 women given a mixed diet of ordinary foods with milk and milk products no differences were observed concerning the high bioavailability of iodine.
Abstract: During the last decade the iodine supply in Germany has increased significantly, but there is still a high frequency of goitre. Therefore the question of iodine bioavailability has arisen. In a two-period study 12 women were given a mixed diet of ordinary foods with milk and milk products of different batches. None of the volunteers suffered from an iodine deficiency according to WHO-criteria. Each period ended with a 9-day balance-study protocol in which all foods were provided. Food and fluid intake were registered, and urine and faeces were quantitatively collected. The iodine content was determined by ICP-MS. The mean intake in the form of solid food amounted to 175 +/- 10 micrograms I/d and to 27 +/- 15 micrograms I/d in fluid form. Milk and dairy products represented the main source of iodine (37%). Iodine was predominantly excreted in the urine (89%, 171 +/- 45 micrograms I/d) and the faeces 11% (20 +/- 11 micrograms I/d). The resulting iodine balance was approximately . In one case an iodine-rich erythrosine preparation with a low iodine bioavailability was used. Between the two periods of consuming different batches of milk and milk products no differences were observed concerning the high bioavailability of iodine.

92 citations


Journal ArticleDOI
TL;DR: In this paper, a method was developed for the determination of the 129I and 127I in iodide and iodate species in seawater, and the results indicated that this method can be also used for the investigation of the transport, dispersion and mixture of water masses by using 129I discharged from reprocessing facilities as a tracer.

91 citations


Journal ArticleDOI
TL;DR: The concentration and speciation of I− was determined in wet and dry deposition at a coastal site over a 15-month period as discussed by the authors, and it was found that I− constituted a significant fraction (5−100%) of iodide in both rain and aerosol.
Abstract: The concentration and speciation of iodine have been determined in wet and dry deposition at a coastal site over a 15-month period. Deposition fluxes in rain (2.7 μmol m−2 yr−1) and aerosol (3.6–6.5 μmol m−2 yr−1) are the major routes for removal of iodine from the marine atmosphere onto the Earth's surface, with only a minor contribution from direct deposition of methyl iodide (0.003–0.17 μmol m−2 yr−1). Iodate (IO3−) is often considered to be the only species of iodine that is permanently removed to the aerosol phase, and IO3− may therefore be expected to be the dominant form of iodine in precipitation. However, iodide (I−) was found to constitute a significant fraction (5–100%) of iodine in both rain and aerosol. This implies that the rates of iodate formation and iodide volatilization (through reaction with hypohalous acids) are relatively slow. A third pool of aerosol iodine (nonvolatile organic compounds) may also contribute to removal of iodine from the atmosphere in dry or wet deposition.

Journal ArticleDOI
01 Apr 2001-Thyroid
TL;DR: The risk of radiation-induced thyroid cancer in case of accidental exposure to radioactive iodine justifies KI prophylaxis, despite the risk of hypothyroidism, especially in newborns and for the elderly, the benefits of KI may be lower than therisk of iodine-induced hyperthyroidism.
Abstract: Ingestion of potassium iodide (KI) offers effective protection against irradiation of the thyroid after accidental exposure to radioactive iodine. This prophylaxis aims at rapidly obtaining maximal thyroid protection without adverse effects. This article reviews studies on iodine kinetics in humans and on the efficacy of KI in protecting the thyroid. In adults with normal thyroid function, ingestion of 100 mg of iodide just before exposure to radioactive iodine blocks at least 95% of the thyroid dose. If exposure persists after iodide ingestion (100 mg), the percentage of averted dose may decrease significantly. Daily ingestion of a dose of 15 mg of KI would then maintain the thyroid blockade at a level above 90%. The efficacy of iodide and the occurrence of antithyroid effects also depend on external and individual factors such as dietary iodine intake, thyroid function, and age. The KI dosage regimen should be adjusted for age at exposure. For the fetus, the newborn, children, and adolescents, the risk of radiation-induced thyroid cancer in case of accidental exposure to radioactive iodine justifies KI prophylaxis, despite the risk of hypothyroidism, especially in newborns. For the elderly, the benefits of KI may be lower than the risk of iodine-induced hyperthyroidism.

Journal ArticleDOI
TL;DR: It is hypothesized that dietary iodine deficiency is associated with the development of mammary pathology and cancer and a review of the literature on this correlation and of the author's own work on the antioxidant function of iodide in iodide-concentrating extrathyroidal cells is reported.

Journal ArticleDOI
TL;DR: A combination of ion chromatography (IC) and inductively coupled plasma-mass spectrometry (ICP-MS) was used to determine iodine species in Thuringian milk samples as discussed by the authors.
Abstract: A combination of ion chromatography (IC) and inductively coupled plasma-mass spectrometry (ICP-MS) was used to determine iodine species in Thuringian milk samples. The developed method allows the fast and sensitive determination of iodine species with limits of determination for iodide and iodate <2 µg/L. Iodide was identified as the main iodine species in milk, but in a few samples also traces of iodate and several unidentified, presumably organoiodine compounds were observed as well. In addition, the total iodine concentration in the samples was determined by ICP-MS and gives an idea about the actual iodine state in Thuringian milk.

Journal ArticleDOI
TL;DR: In this article, the half-life of dissolved organic iodine relative to its photochemical decomposition was shown to be on the order of hours at a typical irradiance of 0.5-1 kW m −2 for a noon-day sun under a clear sky.

Journal ArticleDOI
Christine D. Thomson1, S Woodruffe1, A J Colls1, J Joseph1, T C Doyle1 
TL;DR: The results of this study confirm the low iodide excretions of Otago residents, and indicate that the fall in iodine status is being reflected in clinical measures of thyroid status, including enlarged thyroid glands and elevated thyroglobulin.
Abstract: Objectives: The aim of this project was to assess the clinical significance of our low iodine excretions in terms of thyroid hormone status and thyroid volume in an adult population in a low soil iodine area of the South Island of New Zealand. Design and setting: Two-hundred and thirty-three residents of Otago, New Zealand collected two 24 h urine samples for assessment of iodine status. Thyroid status was determined from serum total T4, TSH and thyroglobulin, and thyroid volumes. Relationships between urinary iodide excretion and measures of thyroid status were determined and subjects were allocated to one of three groups according to low, medium and high iodide excretion, for comparison of thyroid hormones and thyroid volumes. Results: Significant correlations were found for relationships between measures of urinary iodide excretion and thyroid volume and thyroglobulin. Multiple regression analysis of data for subjects divided into three groups according to 24 h urinary iodide excretion ( 90 μg iodide/day) or iodide/creatinine ratio ( 60 μg/g Cr) showed significant differences in thyroid volume (P=0.029; P=0.035, respectively) and thyroglobulin (P=0.019; P=0.005, respectively) among the groups. Conclusions: The results of this study confirm the low iodide excretions of Otago residents, and indicate that the fall in iodine status is being reflected in clinical measures of thyroid status, including enlarged thyroid glands and elevated thyroglobulin. Our observations suggest the possible re-emergence of mild iodine deficiency and goitres in New Zealand. This situation is likely to worsen should iodine intakes continue to fall and continued monitoring of the situation is imperative. Sponsorship: Health Research Council of New Zealand European Journal of Clinical Nutrition (2001) 55, 387–392

Journal ArticleDOI
TL;DR: In this paper, the suitability of indicators of iodine status and thyroid function, including thyroid-stimulating hormone (TSH) and free thyroxine (FT4), in serum, thyroid volume and urinary iodine concentration, under conditions of increasing iodine supply was evaluated.
Abstract: Iodine deficiency control programs have greatly reduced iodine deficiency disorders worldwide. For monitoring changes in iodine status, different indicators may be used. The aim of this study was to evaluate the suitability of indicators of iodine status and thyroid function, thyroglobulin (Tg), thyroid-stimulating hormone (TSH) and free thyroxine (FT4) in serum, thyroid volume and urinary iodine concentration, in iodine-deficient schoolchil- dren under conditions of increasing iodine supply. The study was established as a double-blind, placebo- controlled oral administration of a single dose of iodized oil to schoolchildren (7-10 y old), living in an iodine- deficient area of Benin, with an observation period of 10 mo. However, 3- 4 mo after supplementation, iodized salt became available in the area. The study population therefore comprised an iodized oil-supplemented group and a nonsupplemented group, both of which had variable, uncontrolled intakes of iodized salt during the last 6 mo of the study. Initial mean serum concentrations of TSH and FT4 were within the normal range, whereas serum Tg concentration, urinary iodine concentration and thyroid volume were indicative of moderate-to-severe iodine deficiency. At the end of the study, all indicators had improved significantly, except thyroid volume, which had decreased only in the supplemented group. The supplemented group also still had significantly lower serum Tg and higher urinary iodine concentrations than the nonsupplemented group. Serum Tg and urinary iodine concentrations are the indicators most influenced by a changing iodine supply. Current normal reference ranges of serum concentrations of TSH and FT4 are too wide for detecting iodine deficiency in this age group. J. Nutr. 131: 2701-2706, 2001.

Journal ArticleDOI
TL;DR: Iodination of thyroglobulin, the key event in the synthesis of thyroid hormone, is an extracellular process that takes place inside the thyroid follicles at the apical membrane surface that faces the follicular lumen.
Abstract: Iodination of thyroglobulin, the key event in the synthesis of thyroid hormone, is an extracellular process that takes place inside the thyroid follicles at the apical membrane surface that faces the follicular lumen. The supply of iodide involves two steps of TSH-regulated transport, basolateral uptake and apical efflux, that imprint the polarized phenotype of the thyroid cell. Iodide uptake is generated by the sodium/iodide symporter present in the basolateral plasma membrane. A candidate for the apical iodide-permeating mechanism is pendrin, a chloride/iodide transporting protein recently identified in the apical membrane. In physiological conditions, transepithelial iodide transport occurs without intracellular iodination, despite the presence of large amounts of thyroglobulin and thyroperoxidase inside the cells. The reason is that hydrogen peroxide, serving as electron acceptor in iodide-protein binding and normally produced at the apical cell surface, is rapidly degraded by cytosolic glutathione peroxidase once it enters the cells. Iodinated thyroglobulin in the lumen stores not only thyroid hormone but iodine incorporated in iodotyrosine residues as well. After endocytic uptake and degradation of thyroglobulin, intracellular deiodination provides a mechanism for recycling of iodide to participate in the synthesis of new thyroid hormone at the apical cell surface.

Journal ArticleDOI
TL;DR: Although the up-regulation of Na/I symporter expression in fetal thyroid and placenta in the low iodine diet, not supplemented group did not lead to restoration of a normal absolute iodide uptake, the data show that all adaptive and/or defending mechanisms against iodine deficiency are already present in the fetus.
Abstract: Is the fetal thyroid already capable to increase its iodide uptake in response to iodine deficiency? To answer this question, we analyzed the expression of the Na(+)/I(-) symporter and several other genes in the thyroid of rat fetuses at 21 d of gestation from control mothers presenting a mild or more severe iodine deficiency. Female rats were placed on a low iodine diet, not supplemented, or supplemented with iodide or perchlorate for 3 months. The maternal and fetal thyroidal iodide uptake was measured 24 h after injection of 10 microCi Na (125)I into the dams. The absolute iodide uptake of the maternal thyroid was unchanged in a low iodine diet, not supplemented, compared with one supplemented with iodide. In contrast, the fetal thyroid absolute iodide uptake of a low iodine diet, not supplemented, and one supplemented with perchlorate was decreased by 70% and 95% compared with that supplemented with iodide. Na(+)/I(-) symporter mRNA was detected in the fetal thyroid of supplemented with iodide and increased about 2- and 4- fold in the thyroid of fetuses from a low iodine diet, not supplemented, and one supplemented with perchlorate, respectively. Na(+)/I(-) symporter expression was induced in the fetal side of the placenta in both a low iodine diet, not supplemented, and one supplemented with perchlorate; in contrast, Na(+)/I(-) symporter mRNA was never detected in the maternal side of the placenta. Fetal thyroid thyroglobulin and type I deiodinase mRNA contents were only significantly increased with a diet supplemented with perchlorate. Glucose transporter 4 mRNA was decreased in the fetal thyroid of both a low iodine diet, not supplemented, and one supplemented with perchlorate compared with one supplemented with iodide. In conclusion, although the up-regulation of Na(+)/I(-) symporter expression in fetal thyroid and placenta in the low iodine diet, not supplemented group did not lead to restoration of a normal absolute iodide uptake, our data show that all adaptive and/or defending mechanisms against iodine deficiency are already present in the fetus.

Journal ArticleDOI
01 Jan 2001
TL;DR: In this paper, the distributions of nitrate reductase activity (NRA), iodate and iodide were determined in May 1996 in the southern East China Sea in a transect that traversed across the upwelling center northeast of Taiwan where topographically induced upwells occurred as the Kuroshio interacted with the shelf edge.
Abstract: The distributions of nitrate reductase activity (NRA), iodate and iodide were determined in May 1996 in the southern East China Sea in a transect that traversed across the upwelling center northeast of Taiwan where topographically induced upwelling occurred as the Kuroshio interacted with the shelf edge. Rationalized iodate (R-iodate or R-IO3− in nM) and iodide (R-iodide or R-I− in nM), the concentrations of iodate and iodide normalized to a salinity of 35, were strongly correlated to each other so that [R-IO 3 − ]=−1.06(±0.06)[R-I − ]+424(±15), r 2 =0.87. Since the slope was indistinguishable from −1 mol-IO3− mol−1-I−, this implies that, if iodate is depleted in the surface oceans by biologically mediated uptake, it re-appears almost quantitatively as iodide so that little iodate is retained in the particulate phase. In the upwelling zone, R-iodate and R-iodide were also strongly correlated to NRA (in nM-N h−1) such that [R-IO 3 − ]=−10.2(±1.0)NRA+392(±12), r 2 =0.84, [R-I − ]=9.8(±1.1)NRA+27(±5), r 2 =0.76. Since NRA is an indicator of nitrate uptake and the source water to the upwelling zone, the Kuroshio Subsurface Water, is rich in iodate and almost devoid of iodide, these relationships are consistent with the conceptual model that iodate reduction and nitrate uptake occur in tandem through the activities of the enzyme nitrate reductase. Since NRA represents an instantaneous rate while [R-IO3−] and [R-I−] are concentrations, these strong correlations also suggest that iodate reduction and hence nitrate uptake had operated at approximately constant rates during the residence time of the water in the upwelling zone. Thus, the depletion of iodate and the gain in iodide in the upwelled water relative to its source water were integrations of the uptake and reduction of iodate over this residence time. The slope of the relationship between R-iodate and NRA represented the product of this residence time and the biological discrimination of iodate reduction relative to nitrate uptake by the enzyme. Outside of the upwelling area, R-iodate and R-iodide did not correlate well with NRA, probably as a result of the masking effect of mixing among water masses with undefined concentrations of pre-existing iodate and iodide.

Journal ArticleDOI
TL;DR: In a clinical pilot study to evaluate the feasibility of retinoid redifferentiation in the case of otherwise untreatable thyroid cancers, 21 of 50 patients showed an increase of radioiodide uptake after 5 weeks, indicating that increasing NIS activity and radioiodides uptake by retinoic acidRedifferentiation may be a therapeutic alternative for thyroid cancers refractory to other therapeutic modalities and probably also for mammary cancer.
Abstract: Decrease or loss of iodide uptake, due to impaired expression and/or function of the sodium/iodide-symporter (NIS), is a major obstacle to the treatment of advanced thyroid carcinomas by radioiodide therapy. Several approaches are being evaluated to optimise or restore sufficient iodide transport in those cases, among them retinoid therapy. Retinoids with their growth-inhibiting and differentiation-inducing properties have been repeatedly used for treatment and chemoprevention of various cancers. In thyroid carcinoma cell lines they trigger changes in gene expression that may be interpreted as partial redifferentiation. Especially, they stimulate NIS mRNA expression and iodide uptake in human follicular thyroid carcinoma cells. Moreover, they also increase NIS expression and function in human mammary tumour cells. In a clinical pilot study to evaluate the feasibility of retinoid redifferentiation in the case of otherwise untreatable thyroid cancers, 21 of 50 patients showed an increase of radioiodide uptake after 5 weeks. This indicates that increasing NIS activity and radioiodide uptake by retinoic acid redifferentiation may be a therapeutic alternative for thyroid cancers refractory to other therapeutic modalities and probably also for mammary cancer.

Journal ArticleDOI
TL;DR: A mixture of hypophosphorous acid (H 3 PO 2 ) and iodine in acetic acid reduces a variety of substituted benzhydrols to the corresponding methylene derivatives in very high yields as discussed by the authors.

Journal ArticleDOI
TL;DR: The method was successfully applied to the determination of iodide in seawater and urine and the recovery was from 92% to 103% and the relative standard deviation was in the range of 1.5% to 3.7%.

Journal ArticleDOI
TL;DR: In this paper, Friedel's salt was used as a novel electrode modifier for the accumulation of iodide species and their subsequent voltammetric determination at carbon paste at open circuit and iodide was then detected by differential pulse voltammetry in unbuffered chloride medium.
Abstract: Friedel's salt, a mineral anion exchanger belonging to the family of the layered double hydroxides (LDHs), was synthesized and used as a novel electrode modifier for the accumulation of iodide species and their subsequent voltammetric determination at carbon paste. Beside the preconcentration features of Friedel's salt towards iodide species, its presence at the electrode surface allowed to evidence the oxidation of molecular iodine into iodate (with transient IO−), contrary to most carbon-based electrodes, as demonstrated by cyclic voltammetry. Preconcentration was achieved at open circuit and iodide was then detected by differential pulse voltammetry in unbuffered chloride medium. The sensing process was further improved by optimization of the carbon paste composition, the detection medium, and the accumulation time. The detection limit was 0.06 µM (3σ), with linear calibration ranges extending from 0.1 to 1 µM, 1 to 10 µM, and 10 to 50 µM, giving a dynamic range of over several orders of magnitude. The effect of anionic interferences was evaluated and the sensor was applied to iodide analysis in synthetic ground- and seawaters.

Journal ArticleDOI
TL;DR: In this paper, a microwave distillation method for iodide determination in milk-type samples is proposed, where iodide contained in the sample is oxidized to iodine, which is distilled by means of microwave======energy and reduced back to iodide.
Abstract: To complete these microwave distillation studies, a method for iodide determination in milk-type samples is proposed. The iodide contained in the sample is oxidized to iodine, which is distilled by means of microwave energy and reduced back to iodide. This iodide is combined with Hg(II) and 2,2′-dipyridyl to give an ion pair, which is selectively extracted into IBMK. Mercury is determined in the extract by ETAAS in order to determine iodide. The yield of the distillation process (100%) was evaluated using the Sandell–Kolthoff reaction. In addition, for the solvent extraction, no buffer was needed; 3/5 was the best phase ratio (organic/aqueous); 30 s was the shaking time and the extracts were stable for 24 h, at least. The yield of the extraction procedure (studied also using the Sandell–Kolthoff reaction) was 87.5 and 87.1%, for standards and samples, respectively. Regarding the ETAAS measurements, the ashing temperature selected for both samples and standards was 150 °C; 800 and 1000 °C were the atomization temperatures chosen for samples and standards, respectively. Palladium in IBMK was the chemical modifier at a concentration of 3.0 µg ml−1, both for samples and standards. The sensitivity was 3.50 × 10−3 l µg−1 (standard additions); the LOD and LOQ were 0.2 and 0.6 µg ml−1, referred to sample; the mean characteristic mass within the linear range of concentrations (0–17.5 µg l−1) was 27.3 pg; the mean analytical recovery within that range was 97.5% for a liquid whole milk sample and 100.6% for a CRM, which also gave results within certification. The method was applied to liquid whole milk, milk powder and infant formulae samples.

Journal ArticleDOI
TL;DR: In conclusion, infants and young children in Belgium are as iodine deficient as all other age groups of the population and, consequently, are at risk of brain damage.
Abstract: Iodine deficiency is well documented in Belgium in adults including pregnant women, adolescents, schoolchildren, and neonates, but no data are available in the age group 6 months–3 years. We investigated the status of iodine nutrition in 111 healthy subjects in this age group in an attempt to evaluate the risk of brain damage due to iodine deficiency in Belgium. In 244 casual urine samples collected in these subjects, the median concentration of iodine was 101 μg/l vs 180–220 μg/l under normal conditions. The daily supplementation of the subjects with a physiological dose of 90 μg iodine was followed by a slow and progressive increase of urinary iodine, which reached a normal level only after a delay of about 30 weeks of therapy. This observation suggests that part of the supplement of iodine offered to the children was stored in their thyroid glands until the iodine content of the gland had reverted to normal, reflecting the state of hyperavidity of the thyroid for iodide characteristic of iodine deficiency. In conclusion, infants and young children in Belgium are as iodine deficient as all other age groups of the population and, consequently, are at risk of brain damage. This works further illustrates the need for systematic iodine supplementation of the population in Belgium.

Journal ArticleDOI
TL;DR: In this article, the nuclear reaction followed by separation of elemental iodine was used to achieve the lowest detection limit of 1 ng. g −1 for food items in terms of accuracy and precision.
Abstract: Activation analysis methods based on the nuclear reactions 127 I(n,γ ) 128 I, 127 I(n,2n)126I and 127 I(γ ,n)126 I were tested in terms ofdetection limits, accuracy and precision, and applicability for iodine determinationat various levels in foodstuffs. Both nondestructive and radiochemical modeswere employed using one of the two separation procedures developed (alkaline-oxidativefusion and iodine separation either by extraction of elemental iodine in chloroformor AgI precipitation). The lowest iodine detection limit of 1 ng . g —1 was achieved by employing the first nuclear reaction followedby separation of elemental iodine. Accuracy and precision of the proceduresdeveloped at largely different iodine levels were proved by analyses of biologicalreference materials having composition similar to that of various food items.

Journal ArticleDOI
TL;DR: An interdigitated microelectrode array (IDA) sensor has been applied to the determination of iodide in mineral water based on reversible charge transfer in the redox system I2/2I– at a platinum micro electrode to reduce the detection and determination limits.
Abstract: An interdigitated microelectrode array (IDA) sensor has been applied to the determination of iodide in mineral water. It is based on reversible charge transfer in the redox system I2/2I– at a platinum microelectrode. The analytical signal from the IDA system was obtained by use of a bipotentiostat in dual mode. One segment of the IDA (generator) was polarized to the limiting current for oxidation of iodide to iodine in 0.1 mol L–1 HClO4. The second segment (collector) was fixed at a potential value corresponding to the limiting current of iodine reduction. The geometrical arrangement of the IDA enables this transfer with high efficiency. Because the diffusion layer of both segments overlaps the iodide produced on the collector, the iodide diffuses back to the generator where it is reoxidized. Therefore, redox cycling will enhance the voltammetric signal of the IDA. The signal obtained with a vertically separated IDA was 20 times higher than that in the single mode. Because multiplication of the signal reduces the detection and determination limits, direct voltammetric determination of iodide in mineral water is possible.

Journal ArticleDOI
01 Dec 2001-Thyroid
TL;DR: Azerbaijan now has mild to moderate ID (median UIE, 54 microg/L) and in the mountainous regions with severe ID and the high prevalence of goiter and the low UIE emphasizes the need for urgent medical reintervention.
Abstract: The goal of this study was to assess the prevalence of iodine deficiency (ID) in Azerbaijan after the discontinuation of an iodine prophylaxis program by assessing the prevalence of goiter, iodine intake, and thyroid function. The study included 942 schoolchildren (475 boys and 467 girls) ages 8-14 years, from 13 distinct regions. The survey included the following: (1) clinical evaluation; (2) assessment of thyroid volume both by ultrasound and by palpation; (3) determination of iodide in a morning urine specimen using the classic Sandel-Kolthoff reaction in 347 schoolchildren; (4) determinations of thyrotropin (TSH), triiodothyronine (T3), thyroxine (T4), thyroglobulin (Tg), and anti-thyroid peroxidase (TPO) in serum (n = 165) and TSH in whole blood spotted on filter paper (n = 942). The prevalence of goiter for the whole country was determined by ultrasound (US) to be 86% and by palpation 66%, reaching 100% in the mountainous regions of Caucasus. The median urinary iodine excretion (UIE) was 54 μg/L, re...

Journal ArticleDOI
TL;DR: Data suggest that protein restriction during lactation was associated with lower iodine secretion into the milk in the beginning of lactation, however, at the end of lactations, an adaptation process seems to occur leading to a higher transfer of iodine through the milk that compensates the impairment of thyroid iodine uptake in these pups.
Abstract: Iodine supply is important to avoid neonatal hypothyroidism. This study evaluated whether protein restriction during lactation affects iodine transfer to the pups through the milk. We studied lactating rats fed an 8% protein-restricted diet (PR), a control 23% protein diet (C), and an energy-restricted diet group (ER). On days 4, 12 and 21, mothers were separated from their pups for 4 h, injected with 131 I IP, and put together with their pups. The animals were killed 2 h later. PR pups had a significant decrease in iodine uptake in the gastric content and duodenal mucosa on the 4th day. On the contrary, at 12 and 21 days radioiodine was increased in the gastric content and in the duodenal mucosa. ER pups had an increase in iodine uptake in the gastric content and in the duodenal mucosa only at the end of lactation. The thyroid iodine uptake in PR pups was significantly decreased on the 4th day and significantly increased on the 21st day compared to control. When injected IP with an equivalent amount of 131 I, the PR pups had a decrease in thyroid iodine uptake on the 4th and 12th day, while ER pups had no significant changes. So, these data suggest that protein restriction during lactation was associated with lower iodine secretion into the milk in the beginning of lactation. However, at the end of lactation, an adaptation process seems to occur leading to a higher transfer of iodine through the milk that compensates the impairment of thyroid iodine uptake in these pups.