Thyroid volumes and urinary iodine in German school children

Several recently published investigations showed a significant improvement in the iodine supply of the German population, but so far Germany is still considered an iodine deficient country. However most of the studies presented do not meet the epidemiological criteria established by WHO, UNICEF and ICCIDD and may therefore suffer from a selection bias with respect to goiter prevalence estimates. School children, owing to their easy recruitment, representativeness of different socio-economic classes and high vulnerability of Iodine deficiency disorders (IDD), are one of the best target groups for surveillance of IDD. In this field study a total of 591 children were investigated. The total sample included 268 females and 323 males aged 7-17 years. The following data were collected: thyroid size by ultrasound, urinary iodine concentration in a first-morning spot urine, weight, height, sex and age. The median urinary iodine concentration of the children was 183 microg/L. The proportion of samples with concentrations below 100 microg/L or below 50 microg/L was 15.4% and 4.3% respectively. Urine samples with high iodine concentrations were also found amounting to 17.3%. Almost all families (97%) declared to use iodized kitchen salt and 19.6% of all children are taking regularly iodine tablets. Application of the WHO/ICCIDD thyroid volume references to the German children resulted in a goiter prevalence of 0.2%, using either age/sex-specific or body surface area (BSA)/sex-specific cut-off values. Comparison with the P97 values of the original normative data of Gutekunst and Martin-Teichert however gives a goiter prevalence of 3% as expected. The thyroid volumes of the children in our study appear comparable with those reported recently for iodine sufficient children from Switzerland and for iodine replete Berlin children and for children with sufficient iodine supply in the region of Leipzig, so that Germany probably has no longer to be considered an iodine deficient country. Our own study and the most recently published studies on iodine replete children give rise to the supposition that the WHO/ICCIDD recommended thyroid volume references are too high.