title: Effects of iodine supplementation during pregnancy on child growth and development at school age. Effects of maternal iodine supplementation during pregnancy. Improved iodine status is associated with improved mental performance of schoolchildren in Benin. The effects of oral iodized oil on intelligence, thyroid status, and somatic growth in school-age children from an area of endemic goiter. Cognitive and motor functions of iodine-deficient but euthyroid children in Bangladesh do not benefit from iodized poppy seed oil (Lipiodol). Iodine supplementation improves cognition in iodine-deficient schoolchildren in Albania: a randomized, controlled, double-blind study. Iodine supplementation improves cognition in mildly iodine-deficient children. Neurological damage to the fetus resulting from severe iodine deficiency during pregnancy. FETAL IODINE DEFICIENCY AND MOTOR PERFORMANCE DURING CHILDHOOD Iodine prophylaxis using iodized salt and risk of maternal thyroid failure in conditions of mild iodine deficiency. The Relation between Neonatal Thyroxine Levels and Neurodevelopmental Outcome at Age 5 and 9 Years in a National Cohort of Very Preterm and/or Very Low Birth Weight Infants Prophylaxis of endemic goiter with iodized oil in rural Peru. Maternal thyroid peroxidase antibodies during pregnancy: a marker of impaired child development? The Neurologic Development of the Newborn and Young Child in Relation to Maternal Thyroid Function
abstract: Growth and development of 207 children ( 49 % males ; mean age 5.4 years [ SD 0.2 ] , range 4 to 7.3 years whose mothers received iodine during pregnancy , and children who received iodine first in their 2nd year , were examined in 1996 ; 192 children ( 49 % males ; mean age 6.5 years [ SD 0.2 ] , range 5.8 to 6.9 years ) whose mothers received iodine while pregnant were seen in 1998 . Children were from the southern part of China 's Xinjiang Province which has the lowest levels of iodine in water and soil ever recorded .  Head circumference but not height was improved for those who received iodine during pregnancy ( compared with those receiving iodine at age 2 ) and for those supplemented before the end of the 2nd trimester ( relative to those supplemented during the 3rd trimester ) . Iodine before the 3rd trimester predicted higher psychomotor test scores for children relative to those provided iodine later in pregnancy or at 2 years . Results from the test for cognitive development result ed in trend only differences between those children supplemented during pregnancy versus later . The results address the question of when maternal iodine supplements should begin in public health programs world wide . Findings may be relevant to the treatment of maternal and newborn thyroid deficiency in industrialized countries , particularly for those infants delivered before the end of the second trimester Reduced maternal thyroid hormone concentrations during pregnancy can adversely affect fetal neurological development . In the context of national iodine supplementation programmes , concern has been expressed over the theoretical possibility that iodine supplementation during pregnancy might adversely affect fetal development as a result of maternal thyroid inhibition from the Wolff-Chaikoff effect . In a double blind controlled trial in five villages in Papua New Guinea , several measures of motor and cognitive function showed no significant differences at either age 11 or 15 years between those children whose mothers had received supplementary iodine during pregnancy and the control children whose mothers had received the placebo 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 One hundred goitrous school children received 475 mg iodized oil by mouth , while 100 controls received mineral oil , on a double-blind basis . On follow-up 22 months later the urinary iodine had increased and goiter size had decreased in both groups , more strikingly in the iodine-treated children . There were no consistent differences between the two treatment groups in rate of somatic growth or performance on the Stanford-Binet and Bender tests . Because of the complexities introduced by increases in urinary iodine in the controls , we compared goiter reduction with improvement in IQ score in all children , regardless of group , and found a significant relationship ( p = 0.014 ) , particularly in girls ( p = 0.029 ) . We conclude that oral iodized oil is an attractive alternative to its injection but we recommend an approximate doubling of the dose used here for more effective control . Also , while our data are not conclusive , they support the possibility that correction of iodine deficiency may improve mental performance in school age children , particularly girls Iodine supplementation before pregnancy in iodine-deficient women prevents cretinism and neuromotor deficits in their offspring . It is unclear whether iodine supplementation benefits cognitive function in iodine-deficient school-aged children . We therefore conducted a double-blind , r and omized , controlled trial of the effects of iodized poppy seed oil ( Lipiodol ) on cognitive and motor function and weight gain of iodine-deficient school children . The study was conducted with 305 children in grade s 1 and 2 from 10 primary schools in two iodine-deficient areas in Bangladesh . The children were stratified by school and grade and r and omly assigned to receive 400 mg of oral Lipiodol or a placebo . All children were given a battery of cognitive and motor function tests and had their weights , serum thyroxine ( T4 ) and thyroid-stimulating hormone ( TSH ) and urinary iodine levels measured before and 4 mo after the intervention . On enrollment , both groups were moderately iodine deficient ( median urinary iodine values : placebo group = 3.3 micromol/L , n = 148 ; iodine group = 3.1 micromol/L , n = 152 ; goiter prevalence in both groups > 95 % ) . However , their T4 and TSH levels were within the normal range . After 4 mo , there was a significant treatment effect on urinary iodine levels ( P < 0.0001 ) , but the levels of the treated group were still below normal ( median = 7.9 micromol/L ) . No significant differences were found in T4 and TSH levels , weight gain , cognitive or motor function . The findings suggest that Lipiodol supplementation in moderately iodine-deficient children with normal T4 levels is unlikely to benefit their cognitive function . However , it remains possible that other iodine preparations may have benefits 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 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 Abstract Endemic cretinism is characterised by multiple neurological defects including deaf-mutism , diplegia , squint , and mental deficiency . The condition is widely prevalent in the Highl and s of New Guinea in association with severe iodine deficiency . Previous studies have shown that iodised oil provides a very satisfactory correction of severe iodine deficiency in New Guinea . A controlled trial on the use of intramuscular iodised oil in the prevention of endemic cretinism was carried out in the Western Highl and s of New Guinea and involved a population of approximately 8000 . Subsequent follow-up over four years revealed 26 endemic cretins out of a total of 534 children born to mothers who had not received iodised oil ; the mothers of 5 of these cretins were pregnant at the start of the trial . In comparison , 7 cases of endemic cretinism occurred among 498 children born to mothers who had been treated with iodised oil ;  in 6 of these 7 cases , the mother was pregnant when the trial commenced . It is concluded that intramuscular iodised oil is effective in the prevention of endemic cretinism and that , for it to be effective , it should be given prior to conception . This suggests that severe iodine deficiency in the mother produces neurological damage during fetal development Motor performance of children born to mothers living in an iodine-deficient region was assessed . The mothers were participants in a controlled trial of intramuscular iodised oil in the prevention of endemic cretinism carried out in the Western Highl and s of Papua New Guinea . Mothers received either iodised oil or placebo saline . Children born to mothers given iodine were significantly faster and more accurate in tests of manual function than children from control mothers . The findings indicate that iodine deficiency may lead to a spectrum of sub clinical deficits which place the children at a developmental disadvantage CONTEXT Mild to moderate iodine deficiency during pregnancy can cause transient maternal hypothyroidism and impaired mental development of the progeny . These unfavorable effects are preventable by iodine supplementation . In Europe , however , less than 50 % pregnant women receive iodine-containing supplements , thus representing dietary iodized salt the only carrier of iodine for most women in this life stage . OBJECTIVE / DESIGN This longitudinal study is aim ed to investigate the effects of long-term iodized salt consumption on maternal thyroid function during gestation . PARTICIPANTS / OUTCOME MEASURES : We prospect ively evaluated thyroid function in 100 consecutive thyroperoxidase antibody-negative pregnant women from a mildly iodine-deficient area . Sixty-two women who had regularly used iodized salt for at least 2 yr prior to becoming pregnant and 38 who commenced iodized salt consumption upon becoming pregnant were classified as long-term ( LT ) and short-term ( ST ) iodine supplemented , respectively . RESULTS Long-term iodized salt consumption result ed in a very low prevalence of maternal thyroid failure ( MTF ) in LT women . Conversely , short-term iodine prophylaxis does not seem to protect against the risk of MTF , the prevalence of which was almost 6-fold higher in ST than LT women ( 36.8 % vs. 6.4 % ; chi(2 ) 14.7 , P < 0.0005 ; relative risk 5.7 , 95 % confidence interval 2.03 - 16.08 , P < 0.001 ) . The relative risk reduction amounted to 82.5 % , this measure indicating the extent to which long-term iodine prophylaxis using iodized salt would reduce the risk of MTF in ST women . CONCLUSIONS Prolonged iodized salt significantly improves maternal thyroid economy and reduces the risk of maternal thyroid insufficiency during gestation , probably because of a nearly restoring intrathyroidal iodine stores Transient neonatal hypothyroxinemia is very common in preterm infants . The literature on the effect of this hypothyroxinemia is , however , controversial , and large or long-term follow-up studies are not available . In a nationwide prospect i ve follow-up study on very preterm and ( or ) very low birth weight infants ( n = 717 ) , we studied the relationship between thyroxine levels in the 1st wk of life and neurodevelopmental outcome at 5 y of age and school performance at 9 y of age .  Thyroxine concentrations from filter paper eluates were determined in 717 infants : 32 % had levels of more than 3 SD below the mean ( < 60 nmol/L ) . The percentage of infants with such low levels increased with decreasing gestational age . At the age of 5 y , 96 % of survivors(n = 640 ) were available for extensive neurodevelopmental examination : 85 ( 13.3 % ) had a disability and 92 ( 14.3 % ) a h and icap . At the age of 9 y , 83 % of survivors ( n = 552 ) answered a question naire on school performance : 300 ( 54.3 % ) were in mainstream education in a grade appropriate for age , 151 ( 27 % ) were in mainstream education with grade retention , and 101 ( 18.3 % ) were in special education . Both neurologic dysfunction at age 5 y and school failure at age 9 y were significantly related to lower neonatal thyroxine levels even after adjustment for other perinatal factors ( odds ratio , 1.3 ) . Whether this relationship is causal should be investigated . If a causal relationship exists , substitution therapy may at least partially prevent neurologic dysfunction and learning disabilities , both common sequelae of very preterm birth Three And ean villages at altitudes of 3,100 to 3,500 meters above sea level were studied in order to determine the prophylac— ' tic effect of iodized oil administration on endemic goiter \ and cretinism ( 1 ) . At the time of the study the population in | these villages was approximately 4,000 , with an annual growth ' rate of about three percent . In a group of 3,000 subjects i examined in a house-to-house survey , the visible goiter rate , : as defined in an accompanying paper ( 2 ) , was 55 percent . However , ? when the cccurrence of palpable goiter was considered as well , | the incidence of goiter rose to 83 percent . Fifty percent of * the children in the 0 - 5 yr age group were goitrous and of these , | 20 percent demonstrated visible goiter . Goiter prevalence l increased with age , as did nodularity . An example of this is ‘ shown in Fig. 1 . In some families every member was found with ii goiter as illustrated in Fig. 2 . Goiter was also found among 4 the domestic animals . The percentage of defective persons in the i three villages ranged from 1.0 to 3.6 percent . Although these _ . x villages are accessible by automobile , they are still quite remote * , and isolated Women with antibodies against the enzyme thyroid peroxidase [ TPO-Ab ; formerly microsomal antibodies ( MsAb ) ] are at particular risk for developing postpartum thyroid dysfunction ; the latter is significantly associated with postpartum depression . Although the negative effect of postpartum maternal depression on child development is well documented , the consequences of elevated titers of TPO-Ab during pregnancy and subsequent postpartum thyroid dysfunction on child development are not known . In a prospect i ve study of a cohort of 293 pregnant women , the occurrence of TPO-Ab during gestation , thyroid dysfunction , and depression was investigated . Five years after delivery , child development was assessed in 230 children of the original cohort using the Dutch translation of the McCarthy Scales of Children 's Abilities . Children of women with TPO-Ab during late gestation ( n = 19 , with normal thyroid function ) had significantly lower scores ( by t test ) on the McCarthy Scales of Children 's Abilities than antibody-negative women . The difference on the General Cognitive Scale , which reflects IQ scores , was substantial ( 10.5 points ; t = 2.8 ; P = 0.005 ) . After correction for possibly confounding variables , maternal TPO-Ab during gestation was found to be the most important factor related to the scores on the General Cognitive Scale ( odds ratio = 10.5 ; 95 % confidence interval = 3 - 34 ; P = 0.003 ) . We conclude that children of pregnant women who had elevated titers of TPO-Ab but normal thyroid function are at risk for impaired development A prospect i ve observational study was performed in pregnant women with known thyroid disease . We studied the effect of maternal thyroid function in the first half of pregnancy on the neurologic development of the infant in the first 2 y of life . Clinical and thyroid function data were collected from 20 pregnant women with known thyroid disease and their newborn children . Infants were divided into three groups according to their maternal thyroid function within the first half of pregnancy : Group A ( n = 7 ) : maternal sub clinical hypothyroidism , Group B ( n = 6 ) : maternal euthyroidism , and Group C ( n = 7 ) : maternal hyperthyroidism or sub clinical hyperthyroidism .  Neurophysiologic , i.e. motor nerve conduction velocity and somatosensory evoked potentials and neurologic and developmental ( Bayley scales ) assessment s were done . One infant , born to a mother with Graves ' disease , developed transient hyperthyroidism . At the age of 6 and 12 mo , the mean mental developmental index ( MDI ) score was 16 points lower for infants in Group A than for those in Group B ( p = 0.03 and 0.02 , respectively ) . At the age of 24 mo , the mean MDI score was 6 points lower , which was not statistically significant . Neurophysiologic and neurologic assessment s and the mean Psychomotor Developmental scores did not differ among the three groups . In conclusion , maternal sub clinical hypothyroidism in the first half of pregnancy was associated with a lower mean MDI score in their infants during the first year of life
target: Thus , regardless of study design , iodine deficiency had a substantial impact on mental development .
background: Several review s and meta-analyses have examined the effects of iodine on mental development .
  None focused on young children , so they were incomplete in summarizing the effects on this important age group .
  The current systematic review therefore examined the relationship between iodine and mental development of children 5 years old and under .