Improved iodine status is associated with improved mental performance of schoolchildren in Benin. Dual fortification of salt with iodine and microencapsulated iron: a randomized, double-blind, controlled trial in Moroccan schoolchildren. Serum thyroglobulin and urinary iodine concentration are the most appropriate indicators of iodine status and thyroid function under conditions of increasing iodine supply in schoolchildren in Benin. Addition of microencapsulated iron to iodized salt improves the efficacy of iodine in goitrous, iron-deficient children: a randomized, double-blind, controlled trial. Dual fortification of salt with iodine and micronized ferric pyrophosphate: a randomized, double-blind, controlled trial. Iodine supplementation improves cognition in mildly iodine-deficient children. Persistence of goiter despite oral iodine supplementation in goitrous children with iron deficiency anemia in Côte d'Ivoire. The Danish investigation on iodine intake and thyroid disease, DanThyr: status and perspectives. Assessment of iodine status using dried blood spot thyroglobulin: development of reference material and establishment of an international reference range in iodine-sufficient children. Iodine supplementation improves cognition in iodine-deficient schoolchildren in Albania: a randomized, controlled, double-blind study. Thyroglobulin as a marker of iodine nutrition status in the general population. Reappraisal of the risk of iodine-induced hyperthyroidism: An epidemiological population survey Iodine status and thyroid function of pregnant, lactating women and infants (0-1 yr) residing in areas with an effective Universal Salt Iodization program. The Relationship Between Iron Status and Thyroid Hormones in Adolescents Living in an Iodine Deficient Area [Effects of three different iodine interventions on the speed of normalization of enlarged thyroid gland due to iodine deficiency]. A cross-sectional survey of urinary iodine status in Latvia. Randomized clinical trial comparing different iodine interventions in school children.
BACKGROUND An adequate iodine supply in utero and shortly after birth is known to be crucial to an individual 's physical and mental development . The question of whether iodine supplementation later in life can exert a favorable influence on the mental performance of iodine-deficient population s was addressed in various studies , but with contradictory results . OBJECTIVE The aim of this study was to examine the effect of an improvement in iodine status on mental and psychomotor performance of schoolchildren ( 7 - 11 y ) who were moderately to severely iodine deficient . DESIGN The study , which was originally planned as a double-blind , r and omized , placebo-controlled intervention , was carried out in an iodine-deficient population of schoolchildren ( n = 196 ) in northern Benin . As the population began to have access to iodized salt during the 1-y intervention period , the study population was split post hoc-on the basis of urinary iodine concentrations-into a group with improved iodine status and a group with unchanged iodine status . Changes in mental and psychomotor performance over the intervention period were compared . RESULTS Children with increased urinary iodine concentrations had a significantly greater increase in performance on the combination of mental tests than did the group with no change in urinary iodine concentrations . CONCLUSIONS An improvement in iodine status , rather than iodine status itself , determined mental performance in this population , which was initially iodine deficient . These findings suggest a " catch-up " effect in terms of mental performance BACKGROUND In many developing countries , children are at high risk of both goiter and iron deficiency anemia . OBJECTIVE In a series of studies in northern Morocco , we developed and tested a dual-fortified salt ( DFS ) containing iodine and microencapsulated iron . DESIGN To establish the DFS fortification concentration , we measured salt intake by 3-d weighed food records and estimated iron bioavailability from the local diet by using published algorithms . We then formulated a DFS containing 25 micro g iodine/g salt ( as potassium iodide ) and 1 mg iron/g salt ( as ferrous sulfate hydrate encapsulated with partially hydrogenated vegetable oil ) . After storage and acceptability trials , we compared the efficacy of the DFS to that of iodized salt in a 9-mo , r and omized , double-blind trial in iodine-deficient , 6 - 15-y-old children ( n = 377 ) . RESULTS Mean salt intake in school-age children was 7 - 12 g/d , and estimated iron bioavailability from the local diet was 0.4 - 4.3 % . After storage for 20 wk , the DFS and iodized salt were not significantly different in iodine content , and color stability was acceptable when the compounds were added to local meals . During the efficacy trial , urinary iodine concentrations and thyroid volumes improved significantly ( P < 0.001 and < 0.05 , respectively ) from baseline in both groups . At 40 wk , mean hemoglobin concentrations in the DFS group had increased by 14 g/L ( P < 0.01 ) , and serum ferritin , transferrin receptor , and zinc protoporphyrin concentrations were significantly better ( P < 0.05 ) in the DFS group than in the iodized salt group . The prevalence of iron deficiency anemia in the DFS group decreased from 35 % at baseline to 8 % at 40 wk ( P < 0.001 ) . CONCLUSION A DFS containing iodine and encapsulated iron can be an effective fortification strategy Iodine deficiency control programs have greatly reduced iodine deficiency disorders worldwide . For monitoring changes in iodine status , different indicators may be used . The aim of this study was to evaluate the suitability of indicators of iodine status and thyroid function , thyroglobulin ( Tg ) , thyroid-stimulating hormone ( TSH ) and free thyroxine ( FT4 ) in serum , thyroid volume and urinary iodine concentration , in iodine-deficient schoolchildren under conditions of increasing iodine supply . The study was established as a double-blind , placebo-controlled oral administration of a single dose of iodized oil to schoolchildren ( 7 - 10 y old ) , living in an iodine-deficient area of Benin , with an observation period of 10 mo . However , 3 - 4 mo after supplementation , iodized salt became available in the area . The study population therefore comprised an iodized oil-supplemented group  and a nonsupplemented group  , both of which had variable , uncontrolled intakes of iodized salt during the last 6 mo of the study . Initial mean serum concentrations of TSH and FT4 were within the normal range , whereas serum Tg concentration , urinary iodine concentration and thyroid volume were indicative of moderate-to-severe iodine deficiency . At the end of the study , all indicators had improved significantly , except thyroid volume , which had decreased only in the supplemented group . The supplemented group also still had significantly lower serum Tg and higher urinary iodine concentrations than the nonsupplemented group . Serum Tg and urinary iodine concentrations are the indicators most influenced by a changing iodine supply . Current normal reference ranges of serum concentrations of TSH and FT4 are too wide for detecting iodine deficiency in this age group OBJECTIVE In many developing countries , children are at high risk for both goiter and anemia . Iron ( Fe ) deficiency adversely effects thyroid metabolism and reduces efficacy of iodine prophylaxis in areas of endemic goiter . The study aim was to determine if co-fortification of iodized salt with Fe would improve efficacy of the iodine in goitrous children with a high prevalence of anemia . DESIGN AND METHODS In a 9-month , r and omized , double-blind trial , 6 - 15 year-old children ( n=377 ) were given iodized salt ( 25 microg iodine/g salt ) or dual-fortified salt with iodine ( 25 microg iodine/g salt ) and Fe ( 1 mg Fe/g salt , as ferrous sulfate microencapsulated with partially hydrogenated vegetable oil ) . RESULTS In the dual-fortified salt group , hemoglobin and Fe status improved significantly compared with the iodized salt group ( P<0.05 ) . At 40 weeks , the mean decrease in thyroid volume measured by ultrasound in the dual-fortified salt group ( -38 % ) was twice that of the iodized salt group ( -18 % ) ( P<0.01 ) . Compared with the iodized salt group , serum thyroxine was significantly increased ( P<0.05 ) and the prevalence of hypothyroidism and goiter decreased ( P<0.01 ) in the dual-fortified salt group . CONCLUSION Addition of encapsulated Fe to iodized salt improves the efficacy of iodine in goitrous children with a high prevalence of anemia BACKGROUND In many developing countries , children are at high risk for both goiter and anemia . In areas of subsistence farming in rural Africa , salt is one of the few regularly purchased food items and could be a good fortification vehicle for iodine and iron , provided that a stable yet bioavailable iron fortificant is used . OBJECTIVE We tested the efficacy of salt dual-fortified with iodine and micronized ferric pyrophosphate for reducing the prevalence of iodine and iron deficiencies in children . DESIGN In rural northern Morocco , we fortified local salt with 25 microg I ( as potassium io date ) /g salt and 2 mg Fe ( as micronized ferric pyrophosphate ; mean particle size = 2.5 microm)/g salt . After storage and acceptability trials , we compared the efficacy of the dual-fortified salt ( DFS ) with that of iodized salt in a 10-mo , r and omized , double-blind trial in iodine-deficient 6 - 15-y-old children ( n = 158 ) with a high prevalence of anemia . RESULTS After storage for 6 mo , there were no significant differences in iodine content or color lightness between the DFS and iodized salt . During the efficacy trial , the DFS provided approximately 18 mg Fe/d ; iron absorption was estimated to be approximately 2 % . After 10 mo of treatment in the DFS group , mean hemoglobin increased by 16 g/L ( P < 0.01 ) , iron status and body iron stores increased significantly ( P < 0.01 ) , and the prevalence of iron deficiency anemia decreased from 30 % at baseline to 5 % ( P < 0.001 ) . In both groups , urinary iodine ( P < 0.001 ) and thyroid volume ( P < 0.01 ) improved significantly from baseline . CONCLUSION A DFS containing iodine and micronized ferric pyrophosphate can be an effective fortification strategy in rural Africa BACKGROUND The effects of severe iodine deficiency during critical periods of brain development are well documented . There is little known about the consequences of milder forms of iodine deficiency on neurodevelopment . OBJECTIVE The objective was to determine whether supplementing mildly iodine-deficient children with iodine improves cognition . DESIGN A r and omized , placebo-controlled , double-blind trial was conducted in 184 children aged 10 - 13 y in Dunedin , New Zeal and . Children were r and omly assigned to receive a daily tablet containing either 150 microg I or placebo for 28 wk .  Biochemical , anthropometric , and dietary data were collected from each child at baseline and after 28 wk . Cognitive performance was assessed through 4 subtests from the Wechsler Intelligence Scale for Children . RESULTS At baseline , children were mildly iodine deficient [ median urinary iodine concentration ( UIC ) : 63 microg/L ; thyroglobulin concentration : 16.4 microg/L ] . After 28 wk , iodine status improved in the supplemented group ( UIC : 145 microg/L ; thyroglobulin : 8.5 microg/L ) , whereas the placebo group remained iodine deficient ( UIC : 81 microg/L ; thyroglobulin : 11.6 microg/L ) . Iodine supplementation significantly improved scores for 2 of the 4 cognitive subtests [ picture concepts ( P = 0.023 ) and matrix reasoning ( P = 0.040 ) ] but not for letter-number sequencing ( P = 0.480 ) or symbol search ( P = 0.608 ) . The overall cognitive score of the iodine-supplemented group was 0.19 SDs higher than that of the placebo group ( P = 0.011 ) . CONCLUSIONS Iodine supplementation improved perceptual reasoning in mildly iodine-deficient children and suggests that mild iodine deficiency could prevent children from attaining their full intellectual potential . The trial was registered with the Australia New Zeal and Clinical Trials Register as ACTRN12608000222347 BACKGROUND In developing countries , many children are at high risk of goiter and iron deficiency anemia . Because iron deficiency can have adverse effects on thyroid metabolism , iron deficiency may influence the response to supplemental iodine in areas of endemic goiter . OBJECTIVE The aim of this study was to determine whether goitrous children with iron deficiency anemia would respond to oral iodine supplementation . DESIGN A trial of oral iodine supplementation was carried out in an area of endemic goiter in western Côte d'Ivoire in goitrous children ( n = 109 ) aged 6 - 12 y. Group 1 ( n = 53 ) consisted of goitrous children who were not anemic . Group 2 ( n = 56 ) consisted of goitrous children who had iron deficiency anemia . At baseline , thyroid gl and volume and urinary iodine , thyrotropin , and thyroxine were measured by using ultrasound . Each child received 200 mg I orally and was observed for 30 wk , during which urinary iodine , thyrotropin , thyroxine , hemoglobin , and thyroid gl and volume were measured . RESULTS The prevalence of goiter at 30 wk was 12 % in group 1 and 64 % in group 2 . The mean percentage change from baseline in thyroid volume 30 wk after administration of oral iodine was -45.1 % in group 1 and -21.8 % in group 2 ( P < 0.001 ) . Among the anemic children , there was a strong correlation between the percentage decrease in thyroid volume and hemoglobin concentration ( r(2 ) = 0.65 ) . CONCLUSION The therapeutic response to oral iodine was impaired in goitrous children with iron deficiency anemia , suggesting that the presence of iron deficiency anemia in children limits the effectiveness of iodine intervention programs OBJECTIVE Denmark was an area of iodine deficiency , and m and atory iodine fortification of table salt and salt in bread ( 13 p.p.m . iodine ) was initiated in 2000/2001 . The Danish investigation on iodine intake and thyroid disease ( DanThyr ) is the monitoring of the iodine fortification program . DESIGN AND METHODS DanThyr consists of three main parts : a study of population cohorts initialized before ( n=4649 ) and after ( n=3570 ) iodization of salt  , a prospect i ve identification of incident cases of overt hyper- and hypothyroidism in a population of around 550,000 people since 1997 , and compilation of data from the national registers on the use of thyroid medication , thyroid surgery , and radioiodine therapy . Studies were carried-out in parallel in subcohorts living in areas with differences in iodine content of ground water . RESULTS The study showed profound effects of even small differences in iodine intake level on the prevalence of goiter , nodules , and thyroid dysfunction . Mild and moderate iodine deficiency was associated with a decrease in serum TSH with age . Other environmental factors were also important for goiter development ( increase in risk , smoking and pregnancy ; decrease in risk , oral contraception and alcohol consumption ) , and the individual risk depended on the genetic background . Environmental factors had only a minor influence on the prevalence of thyroid autoantibodies in the population . There were more cases of overt hypothyroidism in mild than in moderate iodine deficiency caused by a 53 % higher incidence of spontaneous ( presumably autoimmune ) hypothyroidism . On the other h and , there were 49 % more cases of overt hyperthyroidism in the area with moderate iodine deficiency . The cautious iodine fortification program , aim ing at an average increase in iodine intake of 50 mug/day has been associated with a 50 % increase in incidence of hyperthyroidism in the area with the most severe iodine deficiency . The incidence is expected to decrease in the future , but there may be more cases of Graves ' hyperthyroidism in young people . CONCLUSION A number of environmental factors influence the epidemiology of thyroid disorders , and even relatively small abnormalities and differences in the level of iodine intake of a population have profound effects on the occurrence of thyroid abnormalities . Monitoring and adjustment of iodine intake in the population is an important part of preventive medicine CONTEXT Thyroglobulin ( Tg ) may be a valuable indicator of improving thyroid function in children after salt iodization . A recently developed Tg assay for use on dried whole blood spots ( DBS ) makes sampling practical , even in remote areas . OBJECTIVE The study aim was to develop a reference st and ard for DBS-Tg , establish an international reference range for DBS-Tg in iodine-sufficient children , and test the st and ardized DBS-Tg assay in an intervention trial . DESIGN , PARTICIPANTS , AND INTERVENTIONS Serum Tg reference material of the European Community Bureau of Reference ( CRM-457 ) was adapted for DBS and its stability tested over 1 yr . DBS-Tg was determined in an international sample of 5- to 14-yr-old children ( n = 700 ) who were euthyroid , anti-Tg antibody negative , and residing in areas of long-term iodine sufficiency . In a 10-month trial in iodine-deficient children , DBS-Tg and other indicators of iodine status were measured before and after introduction of iodized salt . RESULTS Stability of the CRM-457 Tg reference st and ard on DBS over 1 yr of storage at -20 and -50 C was acceptable . In the international sample of children , the third and 97th percentiles of DBS-Tg were 4 and 40 microg/liter , respectively . In the intervention , before introduction of iodized salt , median DBS-Tg was 49 microg/liter , and more than two thirds of children had DBS-Tg values greater than 40 microg/liter . After 5 and 10 months of iodized salt use , median DBS-Tg decreased to 13 and 8 microg/liter , respectively , and only 7 and 3 % of children , respectively , had values greater than 40 microg/liter . DBS-Tg correlated well at baseline and 5 months with urinary iodine and thyroid volume . CONCLUSIONS The availability of reference material and an international reference range facilitates the use of DBS-Tg for monitoring of iodine nutrition in school-age children BACKGROUND Iodine is required for the production of thyroid hormones , which are necessary for normal brain development and cognition . Although several r and omized trials examined the effect of iodine supplementation on cognitive performance in schoolchildren , the results were equivocal . OBJECTIVE We aim ed to ascertain whether providing iodized oil to iodine-deficient children would affect their cognitive and motor performance . DESIGN In a double-blind intervention trial , 10 - 12-y-old children ( n = 310 ) in primary schools in rural southeastern Albania were r and omly assigned to receive 400 mg I ( as oral iodized oil ) or placebo . We measured urinary iodine ( UI ) , thyroid-stimulating hormone ( TSH ) , and total thyroxine ( TT4 ) concentrations and thyroid gl and volume ( by ultrasound ) . The children were given a battery of 7 cognitive and motor tests , which included measures of information processing , working memory , visual problem solving , visual search , and fine motor skills .  Thyroid ultrasound and the biochemical and psychological tests were repeated after 24 wk . RESULTS At baseline , the children 's median UI concentration was 43 microg/L ; 87 % were goitrous , and nearly one-third had low concentrations of circulating TT4 . Treatment with iodine markedly improved iodine and thyroid status : at 24 wk , median UI in the treated group was 172 microg/L , mean TT4 was approximately 40 % higher , and the prevalence of hypothyroxinemia was < 1 % . In the placebo group after the intervention , these variables did not differ significantly from baseline . Compared with placebo , iodine treatment significantly improved performance on 4 of 7 tests : rapid target marking , symbol search , rapid object naming , and Raven 's Coloured Progressive Matrices ( P < 0.0001 ) . CONCLUSION Information processing , fine motor skills , and visual problem solving are improved by iodine repletion in moderately iodine-deficient schoolchildren OBJECTIVE The iodine status of a population is traditionally evaluated by either urinary iodine ( UI ) excretion or by some measure of thyroid volume and the prevalence of goitre . In this prospect i ve study of a m and atory iodization programme , we aim ed to evaluate serum thyroglobulin ( Tg ) as a marker of iodine status in the population . METHODS Two identical cross-sectional studies were performed before ( 1997 - 1998 , n=4649 ) and after ( 2004 - 2005 , n=3570 ) the initiation of the Danish iodization programme in two areas with mild and moderate iodine deficiency .  Serum Tg was measured from blood sample s. Thyroid volume was measured by ultrasonography . RESULTS Before iodization , the median serum Tg was considerably higher in moderate than in mild iodine deficiency . Iodization led to a lower serum Tg in all examined age groups . The marked pre-iodization difference in Tg level between the regions was eliminated . The prevalence of Tg above the suggested reference limit ( 40 microg/l ) decreased from 11.3 to 3.7 % ( P<0.0001 ) . Using bootstrapping , we demonstrated a higher efficacy of Tg than of thyroid volume to show a difference between pre- and post-iodization values . CONCLUSION We found serum Tg to be a suitable marker of iodine nutrition status in the population . The results may suggest that the Danish iodization programme has led to a sufficient iodine intake , even if the median UI excretion is still marginally low according to WHO criteria The occurrence of iodine-induced hyperthyroidism ( IIH ) has been reported after iodine supplementation from clinics and hospitals , but not following an epidemiologic survey . We studied the prevalence of thyroid derangement in a population following iodine supplementation . One yr after more than 75 % of the population had been consuming 40 ppm iodized salt ; information regarding history of endemic goiter and iodized salt production , distribution , consumption and monitoring were collected in four cities of the Islamic Republic of Iran . A total of 6048 subjects were r and omly selected . All subjects were assessed for size of goiter , and urinary iodine and serum T4 , T3 , TSH , anti-thyroglobulin and antithyroperoxide were measured . Before iodine supplementation , all four cities were areas of endemic goiter . The rate of household consumption of iodized salt was 50 , 75 and 90 % in 1994 , 1995 and 1996 , respectively . Ninety-one percent of the salt sample s contained 15–55 ppm iodide . Total goiter rate was 57 , 62 and 68 % ; median urinary iodine was 188 , 197 and 190 μg/l in the age groups of 6–18 , 19–40 and > 40 yr , respectively . Prevalence of clinical and sub clinical hyperthyroidism was 0.34 and 0.41 and those of clinical and sub clinical hypothyroidism were 0.51 and 1.07 % , respectively . Nine point eight and 18 % in the 19–40 yr age group and 17.6 and 25.6 % in > 40 yr old subjects had positive anti-thyroperoxidase and antithyroglobulin , respectively . This systemic epidemiologic study in an iodine deficient population showed that , following a well-executed iodine supplementation program , the occurrence of IIH is rare OBJECTIVE To assess the iodine nutrition and thyroid function of pregnant women , lactating women and infants residing in areas where the Universal Salt Iodization program is in place . METHODS Pregnant women , lactating women and infants were selected r and omly in the regions where iodized salt coverage rate is more than 90 % since 2000 .  Urine iodine levels of pregnant woman , lactating woman and infants , milk iodine of lactating woman , thyroid-stimulating hormone ( TSH ) and free T4 of women were tested respectively . RESULTS Median Urinary Iodine ( MUI ) of infants , three groups of pregnant women ( first , second and third trimester ) and two groups lactating women ( breastfeeding less than or more than six months ) were 233 , 174 , 180 , 147 , 126 and 145 microg/L , respectively . Median milk iodine of lactating women was 163 microg/L. Percentage of milk iodine < 150 microg/L of early lactating women was 40 % less than that of late lactating women ( p < 0.01).There was a positive correlation between urine iodine of infants and milk iodine of lactating women ( r = 0.526 , p = 0.000 ) . T4 of two women were above or below the reference range . Total 15.4 % women 's TSH were abnormal . Most of these women 's urinary iodine were lower than 150 microg/L. CONCLUSION Iodine status of most of the target population for Universal Salt Iodization program is adequate , but iodine deficiency still existed in some . To assure every new life 's brain not be damaged by iodine deficiency , iodine status of targeted population s should be monitored and supplements provided according to the monitoring outcomes BACKGROUND Iron may be only one of many nutritional factors that influence thyroid hormone metabolism in iodine-deficient areas . OBJECTIVE To evaluate the effect of iron status on thyroid hormone profile in adolescents living in a mild iodine-deficient area in Turkey . SUBJECTS Three hundred and thirty school-aged children with mean age 14 years were examined . METHODS Free triiodothyronine , free tetraiodothyronine and thyrotropin levels were analyzed by chemiluminescent enzyme immunoassay .  Hemoglobin and mean corpuscular volume were measured with a Hemocounter . Iron and total iron binding capacity concentration were determined by colorimetric photometric methods . Ferritin level was determined by immunoturbidimetry . RESULTS Thyroid hormone levels of the children with anemia were not significantly different compared to children without anemia . No significant correlation was found between thyroid hormones and iron status . CONCLUSION The thyroid hormone profile was not significantly affected in this area . This survey showed no correlation between iron status and thyroid hormone levels OBJECTIVE To compare the effects of three different iodine interventions on the speed of normalization of enlarged thyroid gl and . METHODS Schoolchildren aged 8 - 10 years were r and omized divided into one of three groups : group A was given iodized salt by research ers with an iodine concentration of 25 mg/kg ; group B used iodized salt purchased from the market ; and group C was similar to group B with additional intake of iodized oil capsules containing 400 mg iodine at the beginning of the study . Salt iodine content was measured bimonthly for 18 months and indicators of iodine deficiency were measured at baseline and 6 , 9 , 12 and 18 months thereafter . RESULTS The prevalence of goiter measured by ultrasound , based on the World Health Organization ( WHO ) body surface area reference > 97(th ) percentile , was 18 % at baseline and declined to less than 5 % by 12 month in groups A and C respectively , and to 9 % after 18 months in group B. Rates of goiter were similar by palpation or by ultrasound . The median urinary iodine was 94 micro g/L at baseline and increased in all groups to > 200 micro g/L at the 6-month follow-up . CONCLUSIONS In this sample of schoolchildren with initially low or moderate level of iodine deficiency , the group receiving salt with 25 mg/kg ( group A ) recovered from iodine deficient on all indicators after 18 months of study . However when the iodine content of salt was floating , as seen in group B , the sizes of thyroid did not yet achieve normal status by 18 months BACKGROUND AND OBJECTIVE A nationwide survey of schoolchildren was conducted to detect regional differences in urinary iodine excretion in Latvia and to compare the results with data from the newborn thyroid-stimulating hormone ( TSH ) screening data base as well with the results of a similar study performed in Latvia 10 years ago . MATERIAL S AND METHODS We conducted a cross-sectional school-based cluster survey of 915 children aged 9 - 12 years in 46 r and omly selected schools in all regions of Latvia .  Urine sample s , question naires on the consumption of iodized salt and information on socioeconomic status were collected . TSH levels in newborns were also measured . RESULTS The median creatinine-st and ardized urinary iodine concentration ( UIC ) in our study was 107.3μg/g Cr . UIC measurements indicative of mild iodine deficiency were present in 31.6 % , moderate deficiency in 11.9 % and severe deficiency in 2.8 % of the participants . The prevalence of iodine deficiency was the highest in the southeastern region of Latgale and the northeastern region of Vidzeme . The prevalence of TSH values > 5mIU/L followed a similar pattern . The self-reported prevalence of regular iodized salt consumption was 10.2 % . Children from urban schools had a significantly lower UIC than children from rural schools . CONCLUSIONS Our findings suggest that although the overall median UIC in Latvian schoolchildren falls within the lower normal range , almost 50 % of the schoolchildren are iodine deficient , especially in urban schools and in the eastern part of Latvia . The absence of a m and atory salt iodization program puts a significant number of children and pregnant women at risk OBJECTIVE The purpose of this trial was to compare three different iodine interventions . DESIGN School children aged 8 - 10 years were r and omized into one of three groups : group A was provided with iodized salt by research ers with an iodine concentration of 25 ppm ; group B purchased iodized salt from the market ; and group C was similar to group B with the exception that they were given iodized oil capsules containing 400 mg iodine at the beginning of the study . Salt iodine content was measured bimonthly for 18 months and indicators of iodine deficiency were measured at baseline and 6 , 9 , 12 and 18 months after r and omization . RESULTS The prevalence of abnormal thyroid volumes , based on the World Health Organization ( WHO ) body surface area reference > 97th percentile , was 18 % at baseline and declined to less than 5 % by 12 months in groups A and C , and to 9 % after 18 months in group B. Results for goitre by palpation were similar . The median urinary iodine was 94 microg l(-1 ) at baseline and increased in all groups to > 200 microg l(-1 ) at the 6-month follow-up . CONCLUSIONS In this population of school children with initially a low to moderate level of iodine deficiency , the group receiving salt with 25 ppm ( group A ) was not iodine deficient on all indicators after 18 months of study . When the iodine content of the salt varied , such as in group B , by 18 months thyroid sizes had not yet achieved normal status
Despite the high risk of bias of many of the included studies , the results suggested that urinary iodine , thyroglobin , serum thyroxine , and thyroid-stimulating hormone are useful biomarkers of iodine status , at least in some groups .
BACKGROUND Biomarkers of iodine status are required to study iodine deficiency disorders in different parts of the world and to evaluate the effects of fortification strategies .
OBJECTIVE The objective was to assess the usefulness of biomarkers of iodine status in humans by systematic ally review ing intervention studies that altered iodine status .