Increasing Iodine Concentration Research Articles

Availability of iodide and iodate to spinach (Spinacia oleracea L.) in relation to total iodine in soil solution

A greenhouse pot experiment was carried out to investigate the availability of iodide and iodate to soil-grown spinach (Spinacia oleracea L.) in relation to total iodine concentration in soil solution. Four iodine concentrations (0, 0.5, 1, 2 mg kg−1) for iodide (I−) and iodate (IO 3 − ) were used. Results showed that the biomass productions of spinach were not significantly affected by the addition of iodate and iodide to the soil, and that iodine concentrations in spinach plants on the basis of fresh weights increased with increasing addition of iodine. Iodine concentrations in tissues were much greater for plants grown with iodate than with iodide. In contrast to the iodide treatments, in iodate treatment leaves accounted for a larger fraction of the total plant iodine. The soil-to-leaf transfer factors (TFleaf) for plants grown with iodate were about tenfold higher than those grown with iodide. Iodine concentrations in soil solution increased with increasing iodine additions to the soil irrespective of iodine species. However, total iodine in soil solution was generally higher for iodate treatments than iodide both in pots with and without spinach. According to these results, iodate can be considered as potential iodine fertilizer to increase iodine content in vegetables.

Iodine content in raw milk

The paper presents the latest information on iodine content in raw milk, in the CzechRepublic. In 2005, iodine was determined using the Sandell-Kolthoff method in 169 milk samples, taken from transportation tanks (capacity 11 000–13 000 litres) of collecting milk for dairy processing, from 14 areas of South-western Bohemia. The average iodine content in milk samples was 442.5 ± 185.6 µg/l, minimum and maximum value were 68.6 and 1 000.6 µg/l respectively. 81.7% of the samples contained more than 250 µg/l. The average iodine content in milk from the collecting areas ranged from 230.2 ± 133.0 µg/l to 702.7 ± 166.2 µg/l (P < 0.001). In five collecting areas (i.e. 35.7%), means were higher than 500 µg/l. These values document the continuing trend of an increase in iodine content in raw cow’s milk, as well as permanent local and regional differences. Higher mean values were determined in the period of winter feed rations (April 495.9 ± 50.8 and October 494.3 ± 176.4 µg/l), while lower values were measured during the period of summer feed rations (September 350.9 ± 178.4 µg I/l) (P < 0.01). If converted per dry matter, 1 kg of dry milk matter contained, on average, 3.428 ± 1.497 mg iodine, maximum and minimum values were 0.543 and 7.995 mg respectively.

Products of the Triplet Excited State Produced in the Radiolysis of Liquid Benzene

The radiation chemical yields of the products derived from the triplet excited state produced in the radiolysis of liquid benzene with gamma-rays, 10 MeV 4He ions, and 10 MeV 12C ions have been determined. Iodine scavenging techniques have been used to examine the formation and role of radicals, especially the H atom and phenyl radical. For all irradiation types examined here, the increase in hydrogen iodide yields with increasing iodine concentration matches the increase in iodobenzene yields. This agreement suggests that the benzene triplet excited state is the common precursor for the H atom and the phenyl radical. Pulse radiolysis studies in liquid benzene have determined the rate coefficients for the reactions of phenyl radicals with iodine and with the solvent benzene to be 9.3 x 10(9) M(-1) s(-1) and 3.1 x 10(5) M(-1) s(-1), respectively. Direct measurements of polymer formation, which refers to trimers (C18) and higher order compounds (>C18), in liquid benzene radiolysis using gamma-rays, 4He ions, and 12C ions at relatively high doses have been performed using gel permeation chromatography. The yields of trimers increase from gamma-rays to 12C ions due to the increased importance of intratrack radical-radical reactions that can be scavenged by the radical scavenging reactions of iodine. On the other hand, the >C18 product yields decrease from gamma-rays to 12C ions. The structure of the polymer consists of a partly saturated ring as determined by infrared and gas chromatography/mass spectrometry studies. A schematic representation for the radiolytic decomposition of the benzene triplet excited state is presented.

Increasing the iodine concentration in the Swiss iodized salt program markedly improved iodine status in pregnant women and children: a 5-y prospective national study

Many industrialized countries struggle to maintain adequate iodine intake because of changes in dietary habits and the food supply. In Switzerland, because of declining iodine intakes in children and pregnant women, the iodine concentration in table salt was increased from 15 to 20 mg/kg. We evaluated Swiss iodine nutrition after the 1999 increase in the salt iodine concentration. In 1999 and 2004, a 3-stage probability proportionate-to-size cluster sampling was done to obtain a representative national sample of primary schoolchildren and pregnant women. Urine and household salt were collected for iodine measurement. The frequency of elevated thyrotropin concentrations found in the newborn screening program was evaluated before and after the increase. In 1999, median urinary iodine (UI) concentrations among children (n = 610) and pregnant women (n = 511) were 115 microg/L (range: 5-413 microg/L) and 138 microg/L (range: 5-1881 microg/L), respectively, which indicated marginal iodine status. In 2004, median UI concentrations among children (n = 386) and pregnant women (n = 279) were 141 microg/L (range: 0-516 microg/L) and 249 microg/L (range: 8-995 microg/L), respectively (P < 0.01). Newborn thyrotropin concentrations >5 mU/L decreased from 2.9% in 1992-1998 (n = 259 035) to 1.7% in 1999-2004 (n = 218 665) (P < 0.0001). A 25% increase in iodine concentration in iodized table salt markedly improved iodine status in Switzerland, which showed the value of monitoring and adjusting iodine concentrations in national salt programs. The frequency of newborn thyrotropin concentrations >5 mU/L appears to be a sensitive indicator of iodine nutrition during pregnancy.

TECHNOLOGICAL BREAKTHROUGH IN POSTHARVEST SANITATION TREATMENT WITH THE IODINE BASED ISAN PROCESS

Commercial usage of a range of available sanitisers presents a considerable challenge, since accurately maintaining correct levels is very difficult. Further, there is increased consumer concern about undesirable byproducts from sanitizers, specifically the carcinogenic trihalomethanes (THM), especially produced by chlorine treatments. New delivery, control and recycling technologies have been developed and incorporated into a new iodine delivery system called Isan . Control of pH, so essential with chlorine, is not required for iodine dips with pHs below 8.5. Continual removal of sanitiser breakdown products during operation, dramatically further reduces any accumulation of undesirable breakdown products and improves dip effectiveness and accuracy of control. Iodine as a sanitizer together with other features of the system means that it is much more tolerant of dirt and organic matter contamination than chlorine. When used as a general produce sanitiser at levels up to 30ppm, iodine applied in the Isan unit is very effective, with levels even below 15 ppm giving a log reduction in surface microflora of 1.5 (i.e. apples, nectarines, peaches, tomatoes). This log reduction is better than, or at least comparable with other reported sanitisers, such as chlorine or peroxide, used at much higher levels. The combination of heat and iodine together proved to be considerably more effective than either iodine or heat alone. This means that this combination could be a potentially safe organic treatment alternative to treatment of fruits and vegetables with postharvest fungicides. Increasing iodine concentrations above 30 ppm is also possible for select crop/ disease combinations.

Effect of iodine doping on the luminescent properties of the photochromic material CdBr2:Cu+

The effect of iodine doping on the roentgenoluminescence (RL) and thermoluminescence (TL) of CdBr2:Cu+ is studied using CdBr2:(Cu+ ,I-) crystals grown by the Bridgman-Stockbarger method from melts containing 0.5 wt % CuBr and 0.15, 0.5, or 5.0 wt % CdI2. The results demonstrate that, with increasing iodine content, the RL intensity first rises and then drops; in addition, the RL band shifts from 560 to 490–510 nm. At low CdI2 levels, the TL curve shows peaks at 110, 130, 152, and 168 K, characteristic of CdBr2:Cu+. At the maximum iodine concentration, the TL curve shows a weak peak at 115 K. The TL spectrum of lightly iodine-doped crystals is dominated by the 490-nm emission, which is attributable to heteronuclear anion excitons. The formation of nI- clusters in heavily doped CdBr2:(Cu+,I-) crystals reduces the concentration of (BrI)- hetero-nuclear centers. The nature of the trapping levels responsible for the TL of the crystals is discussed.

Impact of iodine supplementation of dairy cows on milk production and iodine concentrations in milk

AIM: To determine the effect of iodine supplementation on milk production and iodine concentrations in milk for pasture-fed, seasonally calving dairy cows. METHODS: The study was run over two consecutive seasons on the same dairy farm. In Trial One, 294 Friesian dairy cows were either untreated or injected intramuscularly three times with iodised oil (2,370 mg iodine/dose) at the start of lactation (Day 1) and at about 100-day intervals thereafter. Iodine concentrations in milk were determined prior to each injection on Days 1, 98 and 210, and milk, fat and protein yields measured on Days 43, 98, 176 and 238. In Trial Two, 234 Friesian dairy cows were either untreated or injected intramuscularly with iodised oil (2,370 mg iodine/dose) in early lactation (Day 1) and 99 days later. Iodine concentrations in milk were determined prior to treatment on Days 1, 55 and 161. Serum thyroxine (T4) and triiodothyronine (T3) concentrations were determined in the latter two samples and milk, protein and fat yields were determined on Days 25, 119, 182 and 221. In both trials, pasture was sampled at 1- or 3-monthly intervals and iodine concentrations in herbage measured. RESULTS: Iodine concentrations in pasture averaged 0.24 mg/kg dry matter (DM) in both seasons and varied little over the experimental period. Iodine concentrations in milk from un-supplemented cows were <20 µg/L in both trials. Three iodine injections at about 100-day intervals increased iodine concentrations in milk to 58 µg/L for at least 98 days after each treatment. Two iodine injections at about 100-day intervals raised milk iodine concentrations to 160 µg/L and 211 µg/L at least 55 days after each treatment, but had no effect on serum thyroid hormone concentrations. Iodine supplementation had no significant effect on milk, milkfat or milk protein yield. CONCLUSIONS: Pastures in New Zealand that contained 0.24 mg iodine/kg DM appeared to provide an adequate iodine intake for dairy cows. Intramuscular injections of iodine resulted in significant increases in iodine concentrations in milk. CLINICAL SIGNIFICANCE: Increasing iodine concentrations in milk via intramuscular injection of iodine could provide a method for significantly increasing iodine intakes of humans, in particular, children.

Pilot Study: Tendency of Increasing Iodine Content in Human Milk and Cow's Milk

The iodine supply in Germany has improved throughout the last decade, albeit with enormous differences between individuals and regions. In the Thuringian city of Jena, analyses of the iodine content of human milk have been undertaken regularly since 1982. Significantly increasing iodine concentrations in human and cow's milk have been found. Therefore, the current situation and the effectiveness of measures to prevent iodine deficiency demands re-evaluation. The iodine content of human milk from 32 lactating mothers was analysed on the 5th day (mean) postpartum and mothers' dietary iodine intake during the last two months of pregnancy was assessed by means of a food frequency questionnaire. To corroborate the assumption that the increasing iodine levels of cow's milk are one of the main reasons for the improved iodine supply, the iodine concentration of 34 cow's milk bulk-samples was also determined. Both human and cow's milk samples were analysed by the ICP-MS method. Twenty women took iodine supplements (mean daily intake = 175 microg). The average daily iodine intake of the 20 supplemented and 12 non-supplemented women was 258 microg and 116 microg, respectively. Daily iodine intake from food and beverages was significantly lower in supplemented women (83 microg/day). The average iodine content of human milk was 169 +/- 88 microg/l with a range of 33 - 348 microg/l. This content is two times higher than levels from 1994 in the same area. There was no difference in the human milk iodine content between mothers taking supplements and those who did not. Cow's milk samples showed a mean iodine concentration of 178 +/- 131 microg/l (range 48 - 661 microg/l).

Transient Absorption Studies and Numerical Modeling of Iodine Photoreduction by Nanocrystalline TiO2 Films

We have used transient absorption spectroscopy to study the reaction between photogenerated electrons in a dye-free nanocrystalline titanium dioxide film and an iodine/iodide redox couple. Recombination kinetics was measured by recording the transient optical signal following band gap excitation by a UV laser pulse. In the presence of a methanol hole scavenger in the electrolyte, a long-lived (0.1-1 s) red/infrared absorbance is observed and assigned to photogenerated electrons forming Ti(3+) species. In the presence of iodine and excess iodide in the electrolyte, the signal decays on a millisecond-microsecond time scale, assigned to reduction of the redox couple by photogenerated electrons in the TiO(2). The electron lifetime decreases inversely with increasing iodine concentration, indicating that the back reaction is first order in [I(2)]. No evidence for I(2)(-) is observed, indicating that the reaction mechanism does not involve the formation of I(2)(-) as an intermediate. The shape of the kinetics evolves from monoexponential at low [I(2)] to stretched-exponential as [I(2)] increases. A Monte Carlo continuous-time random walk model is implemented to simulate the kinetics and its [I(2)] dependence and used to address the order of the recombination reaction with respect to electron density, n. The model incorporates the diffusion of oxidized species from the electrolyte toward the TiO(2) surface as well as electron trapping and transport in the TiO(2). In the limit of low [I(2)], the monoexponential kinetics is explained by the recombination reaction being rate limited by the diffusion of the oxidized species in the electrolyte. The stretched-exponential behavior at high [I(2)] can be explained by the reaction being rate limited by the transport of electrons through a distribution of trap states toward reactive sites at the TiO(2)-electrolyte interface, similar to the mechanism proposed previously for the kinetics of electron-dye cation recombination. Such trap-limited recombination can also explain the superlinear dependence of electron recombination rate on electron density, which has been reported elsewhere, without the need for a reaction mechanism that is second order in n. In contrast, a second-order reaction mechanism in a trap-free medium cannot explain the observed kinetics, although a second-order mechanism incorporating electron trapping cannot be conclusively ruled out by the data. We propose that the most likely reaction scheme, that is first order in both [I(2)] and n, is the dissociative reduction of I(2) onto the metal oxide surface, followed by a second electron reduction of the resulting adsorbed iodine radical, and that empirical second-order behavior of the electron lifetime is most likely explained by electron trapping rather than by a second-order recombination mechanism.

ABFP'S 2005 COMPUTER-BASED EXAMINATIONS

<h3>BACKGROUND</h3> Low levels of circulating thyroid hormones have been associated with poorer general and neurodevelopmental outcome in preterm babies and it has been speculated that the association is causal. Low levels of circulating thyroid hormone have been reported after inadequate intake of iodine in preterm infants being fed milk formula. <h3>AIM</h3> To investigate whether increased iodine intake from supplemented preterm formula would improve thyroid hormone levels in preterm babies (this study) and hence improve neurodevelopmental status (planned subsequent study). <h3>METHOD</h3> A total of 121 preterm infants were entered into a randomised controlled trial of standard (68 μg/l) versus increased (272 μg/l) iodine in preterm formula. <h3>RESULTS</h3> The two groups were comparable at recruitment. No evidence of an effect of the intervention on thyroid hormone levels was seen up to 41 weeks after conception. <h3>CONCLUSION</h3> Calls for increased iodine content of preterm infant formulas are not justified by this study. <h3>Key message</h3> Increasing milk iodine content in line with the latest recommendations for preterm babies had no effect on thyroid hormone levels in the perinatal period

Characterization and thermal stability of iodinated amorphous conducting carbon films

In this work, we discuss the structural and transport properties of iodine intercalated amorphous conducting carbon (a-C:I) films prepared by vapor phase pyrolysis of maleic anhydride and iodine. X-ray photoelectron spectroscopy studies reveal the presence of iodine in the a-C:I samples. Microhardness measurements of the films show a decrease in the value of the hardness with an increase in iodine concentration. Iodine incorporation accounts for a change in electrical conductivity of the a-C samples. Magnetoresistance measurements performed on a-C:I samples show a decrease in the value of magnetoresistance. The thermal stability of a-C:I samples has been studied by thermogravimetric analysis, which is found to depend on the host structure and amount of intercalated iodine.

Selecting Iodine-Enriched Vegetables and the Residual Effect of Iodate Application to Soil

A greenhouse pot experiment was conducted to select vegetables for iodine uptake. The residual effect of iodate fertilization on the growth of and iodine uptake by spinach plants were also investigated. Six vegetables, including leafy vegetables (pakchoi [Brassica chinensis L.], spinach [Spinacia oleracea L.]), tuber vegetables (onion [Allium cepa L.]), shoot vegetables (water spinach [Ipomoea aquatica Forsk.], celery [Apium graveolens L.]), and root vegetables (carrot [Daucus carota var. sativa DC.]) were examined. Results showed that the concentrations of iodate in soil had significant effect on the biomass of edible parts of pakchoi and spinach (p<0.01), whereas the concentrations of iodate in soil had no significant effect on that of carrots, water spinach, celery, and onion. Iodine concentrations in edible parts of vegetables and the transfer factors (TFedible parts) of soil-to-edible parts of vegetables significantly increased with increasing iodine concentrations in soil (p<0.001), and iodine concentrations in edible parts and TFedible parts of spinach were much higher than those of other vegetables at any treatment. Both transfer coefficients for edible parts (TCedible parts) and for aerial parts (TCaerial parts) of vegetables changed differently with increasing iodine concentrations in the soil, and TCedible parts and TCaerial parts of spinach were higher than those of other vegetables. Therefore, spinach was considered as an efficient vegetable for iodine biofortification. Further experiment showed that there is considerable residual effect of soil fertilization with iodate.

Comparative cytotoxicity of low-osmolar nonionic and high-osmolar ionic contrast media to dog gallbladder epithelial cells

Background: Most studies of the adverse effects of x-ray contrast media used in ERCP have focused on post-ERCP pancreatitis. However, the biliary epithelial cells are also exposed to contrast media during ERCP and acute cholangitis is also a serious complication of ERCP. The present study compared the cytotoxicity with gallbladder epithelial cells of ionic and nonionic contrast agents. Methods: A high-osmolar ionic contrast agent (meglumine ioxithalamate) and a low-osmolar nonionic contrast agent (iopromide) were tested. Monolayer cell cultures of dog gallbladder epithelial cells were used. The cells were exposed to the 2 contrast agents with increasing iodine concentration and osmolality for 2 days. Cell number, S-phase fraction, aneuploidy, and supernatant LDH activities were measured each day. Results: Cell growth was more severely inhibited by ioxithalamate than iopromide (p < 0.05) and strongly dependent on the osmolality of contrast agent. The cytostatic effect estimated by S-phase fraction was more pronounced for ioxithalamate. Chromosomal damage determined by aneuploidy was more frequently detected with ioxithalamate. Conclusions: High-osmolar ionic contrast media are more cytotoxic than low-osmolar nonionic contrast media to gallbladder epithelial cells. Animal and clinical studies are needed to estimate the clinical implications of these findings. (Gastrointest Endosc 2002;55:382-6.)

Iodine concentrations in porcine blood, urine, and tissues after a single dose of iodised oil

Experimental groups of pigs were treated orally with 120 mg (Group O 120), or 480 mg (Group O 480) of iodine per animal, or intramuscularly with 240 mg (Group I 240) of iodine per animal. Iodine was administered in the form of iodised fatty acid esters (IFAE). The treatment resulted in significantly increased iodine concentrations in tissues and a single dose was sufficient to meet the requirement for the whole fattening period (180 days). Urinary iodine concentrations in all the experimental groups were higher than in the control group C receiving iodine only from conventional feed. Urinary excretion of iodine between days 2 and 5 was more distinctive in orally treated than in intramuscularly treated animals (Figure 1). Iodine concentrations at the end of the fattening period (day 180) were higher in the treated than in the control groups. The treatment effect was more marked in Groups O 480 and I 240 than in Group O 120. The dynamics of blood serum iodine concentrations was similar to urinary concentrations (Figure 2). Mean thyroid gland weights in the groups O 120, O 480, I 240, and C were 9.19, 8.51, 7.10, and 12.01 g, respectively. An opposite tendency was observed for iodine concentrations in thyroid gland dry matter (Figure 3). No effects of any of the treatments on total protein, albumin, total lipids, or cholesterol concentrations in blood serum were observed. Group C showed lower tissue iodine concentrations than any of the experimental groups. The only exception was hepatic tissue in which approximately the same iodine concentrations were found in all the groups. Data obtained in Groups O 120, O 480, and I 240 indicate that decisive for tissue concentrations was rather the dose of iodine than the route of administration. Iodine is stored above all in the thyroid gland and adipose tissue. As can be seen in Figure 4, its concentration was higher in muscles with a higher proportion of fat (neck) than in lean muscles (ham).

Randomised trial of iodine intake and thyroid status in preterm infants

BACKGROUNDLow levels of circulating thyroid hormones have been associated with poorer general and neurodevelopmental outcome in preterm babies and it has been speculated that the association is causal. Low levels...

Investigation of 2 liquid phase separation characteristics on the iodine–sulfur thermochemical hydrogen production process

Separation characteristics of 2 liquid phase, sulfuric acid phase and poly-hydriodic acid phase, in HI-H 2SO 4-I 2 solution of the iodine–sulfur (IS) thermochemical hydrogen production process were measured in the wide operation temperature range, from 273 to 368 K in order to establish the closed-cycle operation technology and to improve thermal efficiency of the process. The effects of solution temperature and composition of initial solution on the separation characteristics were investigated. The effect of iodine concentration in the solution on the separation characteristics was also evaluated. The separation characteristics were found to improve with the increase in iodine concentration. Iodine concentration at the point where the solution starts to separate and at the point that iodine saturates, were determined by using measured data.

Evaluation of pseudoenhancement of renal cysts during contrast-enhanced CT.

The purpose of our study was to evaluate renal cyst pseudoenhancement during helical CT in a phantom model and in patients. Iodine baths containing water-filled spheres and cylinders were constructed to simulate cysts in enhancing renal parenchyma. Iodine concentration, cyst size and location, collimation, and peak kilovoltage were varied and cyst attenuation was measured. Data were analyzed with the mixed linear models and Mantel-Haenszel tests. Subsequently, a paired t test compared CT attenuation values before and after contrast material enhancement in 40 patients with 68 renal cysts (radiographic stability >3 months). The attenuation values of phantom cysts increased when placed in a contrast media bath (p = 0.001). The increase in attenuation values became more pronounced with increasing iodine concentrations, decreasing peak kilovoltage, and smaller sphere sizes. In patients, mean cyst attenuation increased 3.4 +/- 6.2 H after administration of contrast material (p = 0.00002). The attenuation did not increase more than 10 H in any of the 37 cysts larger than 2 cm found in patients. Eight (26%) of the 31 cysts smaller than 2 cm found in patients increased by at least 10 H. In a phantom model, at simulated physiologic levels of renal enhancement, cysts may pseudoenhance by more than 10 H. Similarly, in patients, cysts may also pseudoenhance; however, most pseudoenhancement does not exceed 10 H. In patients, pseudoenhancement of at least 10 H is more likely in cysts smaller than 2 cm.

Preliminary process analysis for the closed cycle operation of the iodine–sulfur thermochemical hydrogen production process

In the iodine–sulfur thermochemical hydrogen production process, a separation characteristic of 2-liquid phase (H 2SO 4 phase and HI x phase) in the separator at 0°C was measured. Two-phase separation began to occur at about 0.32 of I 2 molar fraction and over. The separation characteristic became better with the increase in iodine concentration in the solution. The effect of flow rate variations of HI solution and I 2 solution from the HI x distillation column on the process was evaluated. The flow rate increase in HI solution from the distillation column did not have a large effect on the flow rate of HI solution fed to the distillation column from the separator. The decreasing flow rate of I 2 solution from the distillation column decreased the flow rate of I 2 solution fed to the distillation column from the separator. The variation of I 2 molar fraction in the H 2SO 4 phase in the separator was sensitive to the variation in flow rate of both solutions from the distillation column. The tolerance level of the variation was investigated by considering I 2 solubility, 2-liquid phase disappearance and SO 2 reaction amount.

Seasonal and regional variations of iodine in Danish dairy products determined by inductively coupled plasma mass spectrometry

The content of iodine in 72 samples of Danish dairy products was determined by direct flow injection (FI) sample introduction of whole milk into the ICP-MS instrument, or by bomb ashing of cream and cheese samples prior to the ICP-MS measurement. The performance of the FI-based method was superior to the bomb ashing method in terms of the limit of detection which was 9 ng g –1 and 60 ng g –1 for the two methods, respectively, and in repeatability which was 8.4 and 45 ng g –1 , respectively. Both methods of analysis were accurate as demonstrated by analyses of the CRM 063R Skim Milk Powder. The iodine content of the milk samples varied between 42-162 ng g –1 . A geographical difference in the iodine content showed that milk from Jutland contained less iodine than milk from Sealand. This can be explained by the lower natural iodine content in the drinking water resources in Jutland. A temporal difference showed a general increase in iodine concentration in milk from all regions during the winter months over the summer months. This can be explained by the use of iodine-enriched fodder during the winter months. The poorer repeatability of the analyses of cream and cheese samples obscured any possible geographical and temporal variation of iodine in these samples.

Iode et fonction thyroïdienne

Iodine is a raw material for the thyroid production of hormone which is on the major external control of TSH. The thyroid adaptation to iodine deficiency consists in an increasing iodine concentration from the circulation, an enhancing iodination of the tyrosyl residues in thyroglobulin, a decreasing iodine storage associated to a better recycling of non hormonal iodine and thyroid hyperplasia to provide more synthetic possibilities. Genetic variation and environmental factors explain the wide variation of individuals response to iodine deficiency resulting in a high prevalence of goiter, a mild TSH level increase or overt hypothyroidism. At long term iodine deficiency may have severe pathological consequences and induce neuropsychological deficits in school-children. A policy of iodine supplementation mainly by iodized salt must be undertaken in many areas in the world. Effects of an iodine excess on thyroid function are variable depending upon the underlying thyroid disorder and ambient iodine intake. The most subjects remain euthyroid by mechanisms of autoregulation based on an inhibition of thyroid hormone synthesis and a decrease in the thyroid iodide trap. Euthyroid individuals from high iodine intake areas or those with a history of lymphocytic thyroiditis, treated Graves' disease or subtotal thyroidectomy develop hypothyroidism. On the other hand iodine induced hyperthyroidism is more common in areas of iodine deficiency and in older patients with nodular goiter.