Standardized Map of Iodine Status in Europe

Till Ittermann, Diana Albrecht, Petra Arohonka, Radovan Bílek, Lisbeth Dahl, João Jácome Castro, Helena Filipsson Nyström, Simona Gaberšček, Eduardo Garcia-Fuentes, Monica Gheorghiu, Alicija Hubalewska-Dydejczyk, Sandra Hunziker, Tomislav Jukic, Borislav Karanfilski, Seppo Koskinen, Zvonko Kusic, Venjamin Majstorov, Konstantinos Makris, Kostas Markou, Christa MeisingerNeda Milevska Kostova, Karen R Mullan, Endre V Nagy, Valdis Pīrāgs, Gemma Rojo-Martinez, Mira Samardzic, Ljiljana Saranac, Ieva Strele, Işık Top, Michael Thamm, Malgorzata Trofimiuk-Müldner, Belgin Unal, Liisa Valsta, Lluis Vila, Paolo Vitti, Benjamin Winter, Jayne Woodside, Katja Zaletel, Vaclav Zamrazil, Michael Zimmermann, Iris Erlund, Henry Völzke

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Background Knowledge about the population's iodine status is important, because it allows adjustment of iodine supply and prevention of iodine deficiency. The validity and comparability of iodine related population studies can be improved by standardization, which was one of the goals of the EUthyroid project. The aim of this study was to establish the first standardized map of iodine status in Europe by using standardized UIC data. Methods We established a gold-standard laboratory in Helsinki measuring UIC by inductively-coupled plasma-mass spectrometry. A total of 40 studies from 23 European countries provided 75 urine samples covering the whole range of concentrations. Conversion formulas for UIC derived from the gold-standard values were established by linear regression models and were used to post-harmonize the studies by standardizing the UIC data of the individual studies. Results In comparison to the EUthyroid gold-standard, mean UIC measurements were higher in 11 laboratories and lower in 10 laboratories. The mean differences ranged from -36.6% to 49.5%. Of the 40 post-harmonized studies providing data for the standardization, 16 were conducted in schoolchildren, 13 in adults and 11 in pregnant women. Median standardized UIC was < 100 µg/L in 1 out of 16 (6.3%) studies in schoolchildren, while in adults 7 out of 13 (53.8%) studies had a median standardized UIC < 100 µg/L. Seven out of 11 (63.6%) studies in pregnant women revealed a median UIC < 150 µg/L. Conclusions We demonstrated that iodine deficiency is still present in Europe, using standardized data from a large number of studies. Adults and pregnant women, particularly, are at risk for iodine deficiency, which calls for action. For instance, a more uniform European legislation on iodine fortification is warranted to ensure that non-iodized salt is replaced by iodized salt more often. In addition, further efforts should be put on harmonizing iodine related studies and iodine measurements to improve the validity and comparability of results.

Original languageEnglish
JournalThyroid : official journal of the American Thyroid Association
Early online date15 Jul 2020
Publication statusEarly online date - 15 Jul 2020


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