Speciation of iodine in high iodine groundwater in china associated with goitre and hypothyroidism

Iodine intake affects the occurrence of disease in a population. Excessive iodine intake may be caused by a high iodine content of drinking water. Tap water in few locations in Europe contains up to 139 μg/L mostly bound to humic substances, probably leaching from marine sediments in the aquifers. Even higher iodine contents have been found in Chinese waters, previously shown to associate with goitre and hypothyroidism. The aims were to elucidate speciation of high iodine groundwater from deep wells in China and to compare with high iodine waters from Europe. Water was sampled from eight wells in five villages along Bohai Bay, China. Macro-molecules and low molecular weight (MW) substances were separated by size exclusion chromatography (high performance liquid chromatography, Superose 12 HR 10/30, buffer 0.1 M Tris, pH 7.0). Organic material was evaluated by A280 and iodine in fractions measured by the Ce/As method after alkaline incineration. Iodine content of well water varied from 135 to 880 μg/L (median 287 μg/L). The amount of organic material in water was low with A280, <1–5 mAU. The chromatographic traces were similar between samples: One peak of iodine eluted around K _AV 0.65 corresponding to MW 5 kDa (humic substances) and one peak at V _total (iodide/low MW substances). The fraction of iodine in macro-molecules, suggested to be humic substances, varied from 8% to 70% (median 27%). Iodine and peak absorbance were associated (p = 0.006). In conclusion, iodine in iodine-rich deep well water in northern China may have marine origin and may associate with humic substances, comparable to shallow well iodine-rich water in Europe. High iodine intake from iodine-rich water suggests the cause of endemic goitre and hypothyroidism in some areas in China being iodine.     

Iodine nutrition and the prevalence of thyroid disease after salt iodization: a cross-sectional survey in shanghai, a coastal area in china

Background

Both insufficient and excess iodine may produce thyroid disease. After salt iodization in China, the median urine iodine concentration (UIC) of children aged 8–10 years appeared adequate. However, it is unknown whether dietary changes due to rapid economic development in Shanghai have affected whole population iodine nutrition.

Objective

To assess dietary iodine intake, UIC and the prevalence of thyroid disease in the general population of Shanghai.

Design

A cross-sectional survey was conducted with general participants aged 5–69 years (n = 7,904) plus pregnant and lactating women (n = 380 each) selected by stratified multistage sampling. The iodine concentrations in their salt, drinking water and urine were measured. Daily iodine intake was estimated using the total diet study approach. Serum thyroid hormone concentrations and thyroid-related antibodies were measured and thyroid ultrasonography was performed.

Results

The median iodine concentration in salt was 29.5 mg/kg, and 12.8 µg/L in drinking water. Iodized salt, used by 95.3% of participants, contributed 63.5% of total dietary iodine. Estimated daily iodine intake was 225.96 µg. The median UIC of general participants was 146.7 µg/L; UIC <100 µg/L (iodine insufficiency) was seen in 28.6%; UIC >300 µg/L (iodine excess) in 10.1%. Pregnant women had a median UIC of 135.9 µg/L, with UIC <150 µg/L in 55.4%. Thyroid nodules and subclinical hypothyroidism were found in 27.44% and 9.17%, respectively.

Conclusions

According to published criteria, the current dietary iodine intake in Shanghai was generally sufficient and safe, but insufficient in pregnant women. Thyroid nodules and subclinical hypothyroidism were the commonest thyroid diseases identified.     

A Comparative Toxicological Assessment of Perchlorate and Thiocyanate Based on Competitive Inhibition of Iodide Uptake as the Common Mode of Action

Thiocyanate and perchlorate are known to competitively inhibit thyroidal iodide uptake at the sodium-iodide symporter. Estimates of their relative potencies have recently been refined; thiocyanate is 15 times less potent than perchlorate on a serum concentration basis. Numerous studies have been published relating serum thiocyanate concentrations (or surrogate measures) with thyroid function in various populations including pregnant women and neonates in regions with varying degrees of iodine deficiency. Fifteen published studies were located that relate serum thiocyanate concentrations with thyroid function. In the absence of severe iodine deficiency or iodine excess, adverse thyroidal effects occur with chronic serum thiocyanate concentrations ≥ 200 μ mol/L whereas non-adverse effects are observed with concentrations in the range of 65–85 μ mol/L. No adverse or non-adverse effects are observed at serum concentrations below 50 μ mol/L, even among sensitive subpopulations. Recently, studies relating serum perchlorate concentrations with perchlorate dose have become available, thus making it possible to predict the perchlorate dose associated with a serum perchlorate concentration. Serum thiocyanate concentrations found to induce non-adverse or adverse thyroid effects can thereby be used to predict the perchlorate concentration and thus the perchlorate dose that would be expected to induce similar effects. To place a perspective on environmental perchlorate exposure, a serum thiocyanate concentration of 50 μ mol/L is equivalent to a serum perchlorate concentration of 3.3 μ mol/L in terms of iodine uptake inhibition. This serum perchlorate concentration would require a perchlorate dose of 0.27 mg/kg-day, or a drinking water equivalent level of 9 mg/L using standard default assumptions of a 70 kg adult drinking 2 liters of water daily.     

Iodine Distribution in the Environment as a Limiting Factor for Roe Deer Antler Development

The iodine-containing hormones produced by the thyroid gland play a role in the complex neuro-hormonal regulation of antler development. The proper function of the thyroid depends on the adequate iodine supply of the organism, which is directly related to the iodine content of food and drinking water. The purpose of this study was to explore the connection between the iodine content of the water base, which has a strong correlation with the iodine concentration of environmental components available to animals, and the antler weight of roe deer (Capreolus capreolus) shot in Hungarian hunting areas. Using a general linear model, controlling for the collective effects of other environmental factors (deer population density, harvest rate, land use, and soil fertility information), the iodine content of the water base explained 51.4% of the total variance of antler weights. The results suggest that antler weights increase with increasing iodine concentration regardless of other factors; thus, the environmental iodine distribution can be a limiting factor suppressing roe deer performance assessed here as antler weight. Further experimental studies of controlled iodine uptake are needed to define the exact physiological iodine requirements of roe deer bucks.     

Effects of iodine repletion on thyroid morphology in iodine and/or selenium deficient rat term fetuses, pups and mothers.

It has been suggested that selenium deficiency aggravates the iodine-induced thyroid inflammation and necrosis in iodine-deficient Wistar rats and possibly in man. Studies were carried out to determine whether large amounts of iodine given to iodine-deficient pregnant Sprague-Dawley rats with or without selenium deficiency would induce inflammation and necrosis in their term fetal thyroids. Iodine deficiency was induced in the dams by a low iodine diet or perchlorate in the drinking water and iodine excess was achieved by iodinated drinking water during pregnancy or daily subcutaneous injections of iodine from days 20 to 22 of pregnancy, 1 day after perchlorate was discontinued. Studies were also carried out in 30-day-old pups whose nursing mothers were iodine-deficient (perchlorate) with or without selenium deficiency from conception onward. The administration of iodine restored the morphologic changes in the thyroid induced by iodine deficiency, irrespective of selenium status, toward normal without inflammatory changes or necrosis. Possible explanations for these unexpected findings are discussed.     

Effects of humic substances on fluorometric DNA quantification and DNA hybridization

DNA extracts from sediment and water samples are often contaminated with coextracted humic-like impurities. Estuarine humic substances and vascular plant extract were used to evaluate the effect of the presence of such impurities on DNA hybridization and quantification. The presence of humic substances and vascular plant extract interfered with the fluorometric measurement of DNA concentration using Hoechst dye H33258 and PicoGreen reagent. Quantification of DNA amended with humic substances (20-80 ng/microl) using the Hoechst dye assay was more reliable than with PicoGreen reagent. A simple procedure was developed to improve the accuracy for determining the DNA concentration in the presence of humic substances. In samples containing up to 80 ng/microl of humic acids, the fluorescence of the samples were measured twice: first without Hoechst dye to ascertain any fluorescence from impurities in the DNA sample, followed with Hoechst dye addition to obtain the total sample fluorescence. The fluorescence of the Hoechst dye-DNA complex was calculated by subtracting the fluorescence of the impurities from the fluorescence of the sample. Vascular plant extract and humic substances reduced the binding of DNA onto the nylon membrane. Low amounts (<2.0 microg) of humic substances derived from estuarine waters did not affect the binding of 100 ng of target DNA to nylon membranes. DNA samples containing 1.0 microg of humic substances performed well in DNA hybridizations with DIG-labeled oliogonucleotide and chromosomal probes. Therefore, we suggest that DNA samples containing low concentrations of humic substances (<20 ng/microl) could be used in quantitative membrane hybridization without further purification.     

Physiological interactions of silver and humic substances in Daphnia magna: effects on reproduction and silver accumulation following an acute silver challenge

Silver (Ag) in aquatic environments mediates its toxic actions by inhibiting sodium influx. Humic substances protect against silver toxicity by complexing the toxic, ionic form of the metal, but may also directly stimulate sodium influx in aquatic organisms. This study investigated the effects of silver and humic substances on the water flea Daphnia magna. Acute silver challenge (24 h; 1 microg L(-1)) and the chronic exposure to humic substances (Aldrich humic acid; 7 mg C L(-1)) had considerable influence on daphnid physiology and reproduction. In particular silver exposure in the absence of humic substances stimulated reproduction, resulted in enhanced adult mass, and altered both the response of the animal to subsequent silver exposure and a physiological surrogate measure of silver toxicity (whole body sodium concentration). The presence of humic substances countered the effects on adult mass and reproduction, returning these parameters to control levels. Humic substances also lowered silver body burden, but with significantly improved whole body sodium status than previously silver-exposed animals. These changes may distort the correlation between silver body burden and indicators of toxic action, an important tenet of site-specific risk assessment tools such as the biotic ligand model.     

Effect of long-term administration of arsenic (III) and bromine with and without selenium and iodine supplementation on the element level in the thyroid of rat

The aim of this study was to evaluate the influence of arsenic and bromine exposure with or without iodine and selenium supplementation on the element level in the thyroid of rats. Four major groups of Wistar female rats were fed with respective diets: group A - standard diet, group B - iodine rich diet (10 mg I/kg food), group C - selenium rich diet (1 mg Se/kg) and group D - iodine and selenium rich diet (as in group B and C). Each group was divided into four subgroups per 7 animals each receiving either NaAsO(2) ip (6.5 mg.kg(-1) twice a week for two weeks and 3.25 mg.kg(-1) for six weeks) or KBr in drinking water (58.8 mg.l(-1)) for 8 weeks or combined administration of both substances. Remaining subgroup served as controls. After 8 weeks thyroid glands were analyzed by ICP-MS for As, Br, Se, and I content. The exposition of rat to arsenic or bromine causes the accumulation of these elements in the thyroid gland ( approximately 18 ppm of As, approximately 90 ppm of Br) and significantly affects iodine and selenium concentration in the thyroid. In iodine and/or selenium supplemented rats the bromine intake into the thyroid was lowered to approximately 50% of the level in unsupplemented animals. Also selenium thyroid level elevated due to KBr administration was lowered by iodine supplementation in the diet. The accumulation of arsenic in the thyroid was not influenced by selenium or iodine supplementation; however, As(III) administration increased iodine thyroid level and suppressed selenium thyroid level in selenium or iodine supplemented group of animals.     

Supplemental Selenium Alleviates the Toxic Effects of Excessive Iodine on Thyroid

As excessive iodine intake is associated with a decrease of the activities of selenocysteine-containing enzymes, supplemental selenium was hypothesized to alleviate the toxic effects of excessive iodine. In order to verify this hypothesis, Balb/C mice were tested by giving tap water with or without potassium iodate and/or sodium selenite for 16 weeks, and the levels of iodine in urine and thyroid, the hepatic selenium level, the activities of glutathione peroxidase (GSHPx), type 1 deiodinase (D1), and thyroid peroxidase (TPO) were assayed. It had been observed in excessive iodine group that hepatic selenium, the activities of GSHPx, D1, and TPO decreased, while in the groups of 0.2 mg/L, 0.3 mg/L and 0.4 mg/L supplemental selenium, the urinary iodine increased significantly. Compared with the group of excessive iodine intake alone, supplemental selenium groups had higher activities of GSHPx, D1, and TPO. We could draw the conclusion that supplemental selenium could alleviate toxic effect of excessive iodine on thyroid. The optimal dosage of selenium ranges from 0.2 to 0.3 mg/L which can protect against thyroid hormone dysfunction induced by excessive iodine intake.     

Reference values of thyroid volume in a healthy, non-iodine-deficient Spanish population.

Our aim was to assess reference values of thyroid volume by ultrasonography in healthy adult subjects. We conducted an epidemiological cross-sectional study where 880 subjects were randomly selected from the town census of L'Hospitalet de Llobregat after being invited to participate in our study directly by mail and phone call. We made a clinical history of each subject and determined serum thyrotropin, antiperoxidase antibodies, urinary iodine excretion and thyroid volume by ultrasonography. Subjects with thyroid disease were excluded. We finally studied 268 representative subjects. The reference thyroid volume was median 7.31 ml, mean 8.22 ml (Confidence Interval: 7.75 - 8.69 ml). In men: median 9.19 ml, mean 9.87 ml (CI: 9.09 - 10.65 ml); in women: median 6.19 ml, mean 6.57 ml (CI: 6.22 - 9.92 ml) (p < 0.0001). We grouped the subjects into decades, and found that thyroid volume was different (p = 0.0034) in males because the younger group had lower volume. We did not find any differences among age groups in women. The mean of the urinary iodine excretion was 154.23 microg/l. We have determined reference values of thyroid volume measured by ultrasonography in our iodine non-deficient population and prepared tables that distribute thyroid volume by sex and age.     

Excessive iodine intake and thyroid dysfunction among lactating Saharawi women

ObjectivesExcessive iodine intake may lead to thyroid dysfunction, which may be particularly harmful during pregnancy and lactation. The main objective was to describe iodine status and the prevalence of thyroid dysfunction among lactating women in areas with high iodine (HI) and very high iodine (VHI) concentrations in drinking water.Design and methodsA cross-sectional survey was performed among 111 lactating women in the Saharawi refugee camps, Algeria. Breast milk iodine concentration (BMIC), urinary iodine concentration (UIC) and the iodine concentration in the most commonly consumed foods/drinks were measured. A 24-h dietary recall was used to estimate iodine intake. Thyroid hormones and antibodies were measured in serum.ResultsMedian UIC, BMIC and iodine intake across both areas was 350 μg/L, 479 μg/L and 407 μg/day, respectively. In multiple regression analyses, we discovered that being from VHI area was associated with higher UIC and BMIC. BMIC was also positively associated with iodine intake. Thyroid dysfunction and/or positive thyroid antibodies were found in 33.3% of the women, of which 18.9% had hypothyroidism and 8.1% had hyperthyroidism and 6.3% had positive antibodies with normal thyroid function. Elevated thyroid antibodies were in total found in 17.1%. We found no difference in distribution of thyroid dysfunction or positive antibodies between HI and VHI areas. BMI, BMIC and elevated thyroglobulin (Tg) predicted abnormal thyroid function tests.ConclusionsThe high prevalence of thyroid dysfunction may be caused by excessive iodine intake over several years.     

Py-GC/MS analysis of sediments from Lake Biwa,Japan: characterization and sources of humic acids

Humic substances extracted and purified from bottom sediments of northern Lake Biwa, Japan, in November 2012 and 2013 were characterized using elemental analysis, Fourier-transform infrared spectroscopy, hydrogen-1 nuclear magnetic resonance (¹H NMR) analysis, and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). The infrared (IR) bands in the spectra of humic acids showed the presence of amide linkages and polysaccharides. Results of ¹H NMR analysis showed that the humic acids contained approximately twice the number of aliphatic protons as those in the Japanese soil standards used for comparison. Results of the Py-GC/MS analysis, which evaluates pyrolysis temperature dependency of the amount of pyrolysis products, showed that the generation of pyrolysis products in humic acids also differed from that in Japanese soil standards but was similar to that of phytoplankton in Lake Biwa. This analysis method is the first to provide extensive information about the chemical structure of humic substances; conventional Py-GC/MS provides limited information for a single temperature. Data suggest that humic acids in lake sediments are related to chemical characteristics of phytoplankton. Results shed new light on the origins of humic substances in deep-water-lake sediments and provide insights into material recycling in such sediments.     

Thyroid hormones modify susceptibility to lidocaine-kindling in rats.

Lidocaine, a local anesthetic, produces seizures by unknown central mechanisms. The objective of this study was to investigate the effect of cellular metabolism alteration, by changing thyroid hormones levels, on susceptibility to lidocaine-kindling. Lidocaine was administered daily (60 mg/Kg x day, i.p.) to rats treated with thyroxine (300 microg/Kg x day) or methimazole (60 mg/Kg day), dissolved in drinking water. After the 18th lidocaine administration, the cumulative percent of animals convulsed was higher (100%) for the methimazole-treated group and lower (20%) for the thyroxine-treated group, compared to the control group (40%). The results suggest that susceptibility to lidocaine-kindling depends on neuronal metabolism, which probably affects monoamines uptake mechanisms.     

Degradation of softwood [14C lignin] lignocelluloses and its relation to the formation of humic substances in river and pond environments

The fate of lignin in water and sediment of the Garonne river (France) and of a pond in its floodplain was examined using specifically labeled [¹⁴C-lignin] lignocelluloses. No significant differences appeared in the mineralization rate of alder, poplar or willow [¹⁴C-lignin] in running water samples. Conversion of total radioactivity to ¹⁴CO₂ ranged between 18.7% and 24.4% after 120 days of incubation. Degree of ¹⁴C-labeled lignin mineralization in standing water and sediments was clearly lower, especially in submerged sediments, and was correlated with oxygen supply. After 60 days of incubation 3.3% to 7.9% of the ¹⁴C-labeled lignin was recovered in water samples as dissolved organic carbon originating from microbial metabolism. In water extracts from sediment the percentage of dissolved organic ¹⁴C was only 0.4% to 1.3% of the applied activity. In the humic fraction extracted from sediments it did not exceed 4.4% which was much lower than in soils. No significant difference appeared between river and pond conditions for humic substances formation.     

High levels of mutagenic activity in chlorinated drinking water in Finland

The organic extract from the drinking water of Kuopio, Eastern Finland, turned out to be highly mutagenic in the Ames test. The direct mutagenic activities of the acid/neutral fractions of 48 drinking water samples were on an average 1700 net revertants/l in strain TA100. The highest activities were more than 6000 net revertants/l, and one drinking water sample exceeded 10 000 net revertants/l. The drinking water of Kuopio is produced from lake water which has a relatively high content of humic substances. Water processing involved two chlorination phases. The organic constituents of the water samples were isolated either by continuous liquid-liquid extraction or by absorption on XAD 8 resin.     

Cross-sectional analysis of trace element status in thyroid disease

BackgroundThe synthesis of thyroid hormone depends on a set of trace elements, most importantly selenium and iodine. The dietary supply with certain micronutrients is limited in many areas of the world, including central Europe and large parts of Asia and Africa. Moreover, both thyroid disease risk and therapy effects are modulated by trace element supply and status.ObjectiveAssessment of trace element status in thyroid patients in a European metropolis.Material and MethodsAdult patients visiting a medical praxis in Berlin, Germany, were enrolled into a cross-sectional analysis, and serum samples were obtained from thyroid patients (n = 323) with different conditions including goitre, hypothyroidism, malignancy or autoimmune thyroid disease. Trace elements (iodine, selenium, copper and zinc) were assessed by ICP-MS/MS or total reflection X-ray analysis, along with two protein biomarkers of selenium status (selenoprotein P, glutathione peroxidase), and compared to the clinical phenotype.ResultsThe patients displayed relatively low serum zinc and selenium concentrations as compared to a set (n = 200) of healthy subjects (zinc; 1025+/-233 vs. 1068+/−230 μg/L, p < 0.01, selenium; 76.9+/18.8 vs. 85.1+/−17.4 μg/L, p < 0.0001). A high fraction of patients (37.5%) was classified as selenium-deficient (serum selenium concentrations <70 μg/L), in particular the patients with thyroid malignancy (59%). Serum copper was not different between the groups, and total serum iodine concentrations were unrelated to thyroid disease. Explorative statistical analyses yielded no significant interactions between the trace elements and disease parameters, except for free thyroxine inversely correlating to the copper/selenium ratio.ConclusionsIn adult thyroid patients, there is no relation of circulating copper, iodine, selenium or zinc concentrations to thyroid hormone. However, a large fraction of German thyroid patients displays a considerable selenium deficit, known to constitute a disease risk potentially impairing convalescence and aggravating autoimmune disease processes. It appears advisable to testing thyroid patients for selenium deficiency, and once diagnosed, an increased supply via dietary counselling or active supplementation should be considered.     

腐殖质在环境污染物生物降解中的作用研究进展

腐殖质物质在地球的生态环境中大量存在,它不仅可以在有毒化合物的生物降解和生物转化过程中起到氧化还原中间体的作用,加速有毒物质的降解和转化。也可以作为唯一末端电子受体,接受来自一些有机酸或者甲苯等环境中有毒物质提供的电子,偶联能量的产生,支持菌体的生长,形成一种新的细菌厌氧呼吸形式——腐殖质呼吸。因此,对腐殖质在环境有毒物质的生物降解和生物转化过程中的作用进行研究,不仪对于深入理解细菌呼吸的本质具有重要的理论意义,而且对于环境有毒物质的降解和转化以及元素的生物地球化学循环具有重要的生态学意义,同时对地球表面的有毒物质进行更有效的生物降解具有重要的现实意义。     

Serum thyroglobulin as a biomarker of iodine excess and thyroid disease occurrence in adults

BackgroundThyroglobulin (Tg) is considered a sensitive indicator of iodine deficiency. However, the usefulness of Tg as a biomarker of excess iodine is uncertain. The present study aimed to determine the influence of different iodine intake on serum Tg levels, evaluate the influence of thyroid diseases on the distribution of Tg, and identify the factors that may affect Tg levels.MethodsA cross-sectional survey with a total of 1208 adults was conducted in different water iodine areas in China. Urinary iodine concentration (UIC), water iodine concentration (WIC), serum Tg, thyroid-stimulating hormone (TSH), and thyroid antibodies were measured. The thyroid volumes and nodules were measured by B-scan ultrasound.ResultsBased on the WIC data, subjects were divided into three groups. Based on the median urinary iodine concentration (MUIC) data, the iodine levels were adequate, more than adequate, and excess for the WIC < 10 μg/L group, 10 μg/L ≤ WIC ≤ 100 μg/L g, and WIC > 100 μg/L groups, respectively. The median Tg was significantly higher in the excess iodine group than in the adequate iodine group and the more than adequate iodine group (14.6 μg/L vs.12.7 μg/L, P = 0.042; 14.6 μg/L vs.12.5 μg/L, P = 0.004). Multiple linear regression analysis showed that excess iodine intake, goitre, thyroid nodules, and hypothyroidism were significantly related to higher serum Tg levels.ConclusionSerum Tg level can be a promising biomarker of excessive iodine intake, but other factors, especially the presence of thyroid disease, should be considered when using this parameter.     

Development of thyroid dysfunction among women with excessive iodine intake – A 3-year follow-up

ObjectivesThyroid dysfunction can be a result of excessive iodine intake, which may have adverse health consequences, particularly for women in fertile age. In 2010, we conducted a cross-sectional study among lactating women with excessive iodine intake in the Saharawi refugee camps in Algeria and found a high prevalence of thyroid dysfunction. Three years later, we conducted a follow-up study to monitor the iodine situation and explore whether thyroid dysfunction still was highly prevalent when the women no longer were post-partum. None of the women were treated for hyper- or hypothyroidism between baseline and follow-up.MethodsIn 2013, we were able to recapture 78 of the 111 women from the baseline. Thyroid hormones and antibodies were measured in serum and thyroid size was assessed by palpation. Urinary iodine concentration (UIC) and drinking water iodine concentration were measured.ResultsThe overall prevalence of thyroid dysfunction and/or positive antibodies was 34.3% and was not significantly changed from baseline. Of the non-pregnant women we reexamined, 17 had hypo- or hyperthyroidism in 2010; among these, 12 women still had abnormal thyroid function at follow-up. In addition, we found 9 new cases with marginally abnormal thyroid function. Women with thyroid dysfunction and/or positive antibodies had significantly higher BMI and thyroglobulin than women with normal thyroid function. We also found that women with high breast milk iodine concentration (BMIC) at baseline had more thyroid dysfunction at follow-up than the women with lower BMIC at baseline.ConclusionsAt follow-up, the prevalence of thyroid dysfunction was still high and had not changed during the 3 years between studies and from a postpartum period. The women still had a high iodine intake indicated by high UIC. Breast milk iodine concentration from baseline predicted thyroid dysfunction at follow-up.     

Current status of iodine intake in Croatia--the results of 2009 survey

In 1996, due to persistence of mild to moderate iodine deficiency, new law on obligatory salt iodination with 25 mg of potassium iodide (KI) per kg of salt was implemented in Croatia. Along with a new law, a new program for monitoring of iodine prophylaxis was implemented. Investigations of goiter and iodine intake performed in 2002, demonstrated sufficient iodine intake in Croatia with overall median of urinary iodine concentration (UIC) for schoolchildren in Croatia of 140 microg/L. In 2002, thyroid volumes (TV) measured by ultrasound in schoolchildren from all four geographic regions of Croatia were for the first time within the normal range according to ICCIDD reference values. Nowadays, Croatia is internationally recognized as iodine sufficient country. The aim of the present study was to assess current status of iodine intake in Croatia. The investigation was carried out in 2009. A total of 386 schoolchildren aged 7-10 years from all four major geographic regions of Croatia, 103 euthyroid pregnant women and 36 women of child-bearing age from Zagreb, the capital, were included in the survey. Urinary iodine concentration (UIC) was measured in all participants. Thyroid volumes were measured by ultrasound in schoolchildren from the capital of Zagreb (N = 101) and the village of Rude (N = 56). In the time period 2002-2009, the content of KI was analyzed in 384 salt samples from Croatian salt plants and samples of imported salt. An overall median UIC for schoolchildren in Croatia was 248 microg/L. Median UIC in pregnant women was 159 microg/L, with 50% of samples below and under 150 microg/L. Median UIC in women of child-bearing age was 136 microg/L. Thyroid volumes in schoolchildren were within the normal range according to the new reference values. Mean value of KI/kg of salt in samples from Croatian salt plants was 25.5 mg/kg and 24.9 mg/kg in samples of imported salt. A total of 72/384 (18.8%) of salt samples didn't corresponded to the Croatian law on obligatory salt iodination. Presented data indicate sufficient iodine intake of the Croatian population. Current medians of UIC in schoolchildren in Croatia are significantly higher than medians measured in 2002. This indicates that other potential sources of iodine are present in Croatian diet that may contribute to overall iodine intake. Due to rising medians of UIC in schoolchildren in Croatia, it is important to conduct nutrition studies to identify potential sources of "silent prophylaxis" in order to avoid iodine excess.