The iodine requirements in humans are 90 μg/day in infants and children aged 0–6 years, 120 μg/day in prepubertal children, 150 μg/day in adolescents and adults and 200 μg/day in pregnant and lactating women (1, 2). When the physiological requirements of iodine are not met in a given population, a series of functional and developmental abnormalities occur, including thyroid function abnormalities and, when iodine deficiency is severe, endemic goiter and cretinism, endemic mental retardation, decreased fertility rate, increased perinatal death and infant mortality. These complications, which constitute a hindrance to the development of the affected populations, are grouped under the general heading of iodine deficiency disorders (IDD) (3). Based on the most recent evaluation (4), IDD currently represent a significant public health problem for 1571 million people in 118 countries. Twenty million of these are believed to be significantly mentally handicapped as a result of iodine deficiency (5), which, therefore, constitutes probably the
S. Orts, P. Dustin and F. Delange
The aim of the present work has been to verify the determining influence of the environmental factor on the geographical distribution of goitre in Idjwi Island (Lake Kivu, Dem. Rep. of the Congo). The weight and histology of the thyroid of wild rats have been compared in the areas of high (North Idjwi) and low (South West Idjwi) prevalence of goitre in man. This animal has been chosen because its food consists mainly of the remains of human food and because it abounds in the two areas investigated.
The mean thyroid weight in 114 rats captured in the North of the Island is 18.3 ± 0.5 mg. This result is significantly higher than the value of 12.1 ± 0.3 mg obtained in 101 animals captured in the South West of the Island (P < 0.001). Furthermore, an aspect of hyperstimulation characterized by a reduction or disappearance of the colloid of the thyroid vesicles was observed in 66.7% of the glands in the first area, as compared to 8.5% only in those of the second area (P < 0.0005).
This investigation thus shows the existence of a goitrous enzootic in the wild rat in Idjwi Island, which is geographically superimposable on the endemic human goitre.
Since the North and the South West of the Island have a similar iodine deficiency, the present data support the hypothesis of the existence in the North of the Island of an additional goitrogenic factor, distinct from the iodine deficiency.
F Delange, A Van Onderbergen, W Shabana, E Vandemeulebroucke, F Vertongen, D Gnat and M Dramaix
OBJECTIVE: Belgium is one of the Western European countries in which no program of iodine-deficiency correction using iodized salt has been implemented, in spite of well-documented mild iodine deficiency. In 1995, the median urinary iodine concentration was 55 microg/l (normal: 100-200) and the prevalence of goiter was 11% (normal: below 5%) in representative samples of schoolchildren aged 6-12 years. Based on these results, the authors of the present study and others had emphasized to health professionals and to the public the necessity for iodine supplementation. The objective of this study was to evaluate as to whether these efforts had resulted in an improvement in the status of iodine nutrition. DESIGN: We performed a national survey of the status of iodine nutrition in Belgium based on the determination of thyroid volume, obtained by ultrasonography, and urinary iodine concentrations in schoolchildren. METHODS: A mobile van equipped with an ultrasound instrument, a computer and a deep-freeze visited 23 schools selected from across the country. The sample included 2855 schoolchildren (1365 boys and 1490 girls) aged 6-12 years. RESULTS: The results show a homogeneous situation in the whole country, with a median urinary iodine concentration of 80 microg/l and a goiter prevalence of 5.7%. Urinary iodine slightly decreases with age in girls and reaches a critical value of 59 microg/l at the age of 12 years, together with a goiter prevalence of 18.4%. CONCLUSION: Iodine nutrition has improved slightly in Belgium but mild iodine deficiency continues, with public-health consequences. The improvement indicates silent iodine prophylaxis, as no official salt-iodization measures have been taken. Silent iodine prophylaxis only partly corrects iodine deficiency in Western Europe. Active measures, including the implementation of a program of salt iodization, are urgently required.
MB Zimmermann, L Molinari, M Spehl, J Weidinger-Toth, J Podoba, S Hess and F Delange
OBJECTIVE: Interpretation of thyroid ultrasonography for assessing goiter prevalence requires valid reference criteria from iodine-sufficient populations. Reports have suggested the current reference criteria for thyroid volume (T(vol)) of WHO/ICCIDD (International Council for the Control of Iodine Deficiency Disorders) may be too high. Our objective was to determine if inter-observer and/or inter-equipment variability contributes to the disagreement in sonographic T(vol) in children reported from iodine-sufficient areas. DESIGN: A 2-day workshop in which four experienced ultrasound examiners from around Europe measured T(vol) in 45 6--12-year-old Swiss schoolchildren using four different portable ultrasound machines. One of the participating examiners (observer A) had generated the T(vol) data in European children that are the basis for the WHO/ICCIDD reference criteria. METHODS: Sonographic T(vol) was measured in each child by all four examiners on all four machines. Six hundred and eighty-four examinations were completed, with examiners having no knowledge of one another's results. Inter-observer and inter-equipment variation was calculated. RESULTS: Mean inter-equipment variation in T(vol) was 15.2% (95% CI: 14.1, 16.3%). There were no significant differences in T(vol) between equipment (P=0.51). For all observers, the mean inter-observer variation in T(vol) was 25.6% (95% CI: 23.9, 27.2%). At all ages and all body surface areas, there was a large systematic measurement bias (+30% volume) between the mean T(vol) of observer A and the mean Tvol of observers B, C and D. Reanalysis using data from observers B, C and D reduced the mean inter-observer variation in T(vol) to 13.3% (95% CI: 11.9, 14.7%). A correction factor for the systematic difference of operator A for the P50 and P97 of T(vol) was estimated using analysis of covariance. When applied to the WHO/ICCIDD reference data, it sharply reduced the discrepancy between the WHO/ICCIDD criteria and those from other iodine-sufficient children around the world. CONCLUSIONS: Inter-equipment error contributes minimally to reported differences in sonographic T(vol). Even among experienced examiners, inter-observer variation in sonographic T(vol) in children can be high, and probably contributes to the current disagreement on normative values in iodine-sufficient children. A systematic bias at least partially explains why the WHO/ICCIDD reference data differ from those reported from other iodine-sufficient children around the world. The findings argue strongly for the standardization of methods used for sonographic measurement of T(vol) in children.
F Delange, G Benker, Ph Caron, O Eber, W Ott, F Peter, J Podoba, M Simescu, Z Szybinsky, F Vertongen, P Vitti, W Wiersinga and V Zamrazil
Up to 1992, most European countries used to be moderately to severely iodine deficient. The present study aimed at evaluating possible changes in the status of iodine nutrition in 12 European countries during the past few years. Thyroid volume was measured by ultrasonography in 7599 schoolchildren aged 7–15 years in one to fifteen sites in The Netherlands, Belgium, Luxemburg, France, Germany, Austria, Italy, Poland, the Czech and Slovak Republics, Hungary and Romania. The concentrations of urinary iodine were measured in 5709 of them. A mobile unit (ThyroMobil van) equipped with a sonographic device and facilities for the collection of urine samples visited all sites in the 12 countries. All ultrasounds and all urinary iodine assays were performed by the same investigators. The status of iodine nutrition in schoolchildren has markedly improved in many European countries and is presently normal in The Netherlands, France and Slovakia. It remains unchanged in other countries such as Belgium. There is an inverse relationship between urinary iodine and thyroid volume in schoolchildren in Europe. Goiter occurs as soon as the urinary iodine is below a critical threshold of 10 μg/dl. Its prevalence is up to 10 to 40% in some remote European areas. This work produced updated recommendations for the normal volume of the thyroid measured by ultrasonography as a function of age, sex and body surface area in iodine-replete schoolchildren in Europe. This study proposes a method for a standardized evaluation of iodine nutrition on a continental basis, which could be used in other continents.
European Journal of Endocrinology 136 180–187
Z Szybinski, F Delange, A Lewinski, J Podoba, M Rybakowa, R Wasik, L Szewczyk, B Huszno, F Golkowski, E Przybylik-Mazurek, M Karbownik, T Zak, J Pantoflinski, M Trofimiuk and I Kinalska
BACKGROUND: Iodine prophylaxis in Poland started in 1935 and has been interrupted twice: by World War II and in 1980 for economic reasons. Epidemiological surveys carried out after the Chernobyl accident in 1989 as well as in 1992/1993 and in 1994 as a 'ThyroMobil' study, revealed increased prevalence of goitre in children and adults. Ninety per cent of Poland was classified as an area of moderate iodine deficiency, and 10%, in the seaside area, as mild iodine deficiency territory. Iodine prophylaxis based on iodisation of household salt was introduced again in 1986 as a voluntary model and in 1997 as a mandatory model with 30+/-10 mg KI/kg salt. OBJECTIVE: The evaluation of the obligatory model of iodine prophylaxis in schoolchildren from the same schools in 1994 and 1999. METHODS: Thyroid volume was determined by ultrasonography. Ioduria in casual morning urine samples was measured using Sandell-Kolthoff's method, within the framework of the ThyroMobil study. RESULTS: Goitre prevalence decreased from 38.4 to 7% and urinary iodine concentration increased from 60.4 to 96.2 microg/l mean values between 1994 and 1999. In four schools the prevalence of goitre diminished below 5%. In 1999, 70% of children excreted over 60 microg I/l, and 36% over 100 microg I/l, whereas in 1994 the values were 44 and 13% respectively. CONCLUSION: The present findings indicate that iodine prophylaxis based only on iodised household salt is highly effective.