Learning disabilities and poor motivation to achieve due to prolonged iodine deficiency

Iodized Salt Consumption and its Association with Intelligence Quotient (IQ) Among 6-12 years Age Group Children in Bihar

OBJECTIVES

To estimate the proportion of households using adequately iodized salt, total goitre rate and intelligence quotient (IQ) and to assess association, if any, between consumption of iodized salt and intelligence quotient of children aged 6-12 y in the selected districts of Bihar.

METHODS

Community based cross-sectional study was conducted in three districts of Bihar by using cluster sampling technique.

RESULTS

Consumption of iodized salt was 73.5% out of 1263 households surveyed and the prevalence of goitre among children was 2.9%. The mean IQ of study population was 82.6 and it was 9 points lower in children consuming inadequately iodized salt in comparison to children consuming adequately iodized salt. Presence of goitre, inadequately iodized salt consumption and increasing age were the factors which were significant predictors of low IQ level.

CONCLUSIONS

The prevalence of goitre has declined from the past but the target of iodized salt consumption has not yet achieved in these districts. This study reinforces the belief that IQ in children is linked to iodine.

Iodine consumption and cognitive performance: Confirmation of adequate consumption

Iodine, a dynamic nutrient present in thyroid hormones, is responsible for regulating thyroid function, supporting a healthy metabolism, and aiding growth and development. Iodine is also essential for brain development during specific time windows influencing neurogenesis, neuronal and glial cell differentiation, myelination, neuronal migration, and synaptogenesis. About 1.5 billion people in 130 countries live in areas at risk of iron deficiencies (IDs). Reduced mental ability due to IDs occurs in almost 300 million people. Ensuring the consumption of minimum recommended daily allowances of iodine remains challenging. The effects of ID disorders range from high mortality of fetuses and children to inhibited mental development (cretinism). Poor socioeconomic development and impaired school performance are also notable. Currently, ID disorders are the single greatest contributor to preventable brain damage in fetuses and infants and arrested psychomotor development in children. Iodized salt may help fulfill iodine requirements. Increases in food salt iodization programs can help overcome ID disorders. Dietary plans can be well adjusted to incorporate iodinated foods. Maternal iodine supplementation for offspring requires adequate attention. Fruits, vegetables, bread, eggs, legumes (beans and peas), nuts, seeds, seafood, lean meats and poultry, and soy products provide small quantities of iodine. Nutrient-dense foods containing essential vitamins and minerals such as iodine may confer positive effects. To some extent, fortified foods and daily dietary supplements can be provided for different nutrients including iodine; otherwise, iodine may be consumed in less than the recommended amounts. This review focuses on aspects of adequate iodine consumption to avoid cognitive impairments.

Iodine Deficiency and the Brain: Effects and Mechanisms

Iodine is an essential micronutrient needed in human diets. As iodine is an integral component of thyroid hormone, it mediates the effects of thyroid hormone on brain development. Iodine deficiency is the most prevalent and preventable cause of mental impairment in the world. The exact mechanism through which iodine influences the brain is unclear, but is generally thought to begin with genetic expression. Many brain structures and systems appear to be affected with iodine deficiency, including areas such as the hippocampus, microstructures such as myelin, and neurotransmitters. The clearest evidence comes from the studies examining cognition in the cases of iodine deprivation or interventions involving iodine supplementation. Nevertheless, there are many inconsistencies and gaps in the literature of iodine deficiency, especially over the lifespan. This paper summarizes the literature on this topic, suggests a causal mechanism for iodine's effect on the brain, and indicates areas for the future research (e.g., using magnetic resonance imaging (MRI) and functional MRI to examine how iodine supplementation facilitates cognitive functioning).

Effects of Health and Nutrition on Cognitive and Behavioural Development in Children in the First Three Years of Life: Part 2: Infections and Micronutrient Deficiencies: Iodine, Iron, and Zinc

The following paper and its accompanying paper (Grantham-McGregor SM, et al. Effects of health and nutrition on cognitive and behavioural development in children in the first three years of life. Part 1: Low birthweight, breastfeeding, and protein-energy malnutrition. Food Nutr Bull 1999;20:53–75) review the literature on the conditions that are prevalent and considered to be likely to affect child development and are therefore of public health importance. the reviews are selective, and we have generally focused on recent work, particularly in areas that remain controversial. the reviews are restricted to nutritional and health insults that are important in the first three years of life. Where possible, we have discussed the better studies. This paper considers the effects of infections and the major micronutrient deficiencies: iodine, iron, and zinc.

Evaluation of Iodine Deficiency in Children with Attention Deficit/Hyperactivity Disorder

OBJECTIVE

To investigate the incidence of iodine deficiency (ID) and its effects on mental function in children referred to the Dr. Sami Ulus Maternity and Children's Training and Research Hospital with a prospective diagnosis of attention deficit/hyperactivity disorder (ADHD).

METHODS

The study was conducted on 89 children referred in the period from September 2009 to June 2010 with a diagnosis of ADHD. A questionnaire was given to all parents. Conners' rating scales were applied to the parents (CPRS) and teachers (CTRS), and revised Wechsler intelligence scale for children (WISC-R) to the children. Serum thyroid-stimulating hormone, free triiodothyronine and free thyroxine, thyroglobulin, anti-thyroid peroxidase, anti-thyroglobulin, and urinary iodine levels were measured in all children.

RESULTS

Median age was 9.41±1.95 years, and 83.1% of subjects were male. The mean urinary iodine level of the children was 92.56±22.25 μg/L. ID was detected in 71.9% of subjects and all were mild ID. There was no significant relationship between urinary iodine levels with WISC-R subtest scores and CPRS. However, a significant association was found between urinary iodine levels and hyperactivity section of CTRS (p<0.05). Likewise, a significant relationship was found between learning disorder/mental retardation diagnosis and freedom subtest of WISC-R (p<0.05).

CONCLUSION

This study highlights the effects of ID on comprehension, perception, attention, and learning. However, the results need to be supported by new randomized controlled trials.

The effects of breakfast on behavior and academic performance in children and adolescents

Breakfast consumption is associated with positive outcomes for diet quality, micronutrient intake, weight status and lifestyle factors. Breakfast has been suggested to positively affect learning in children in terms of behavior, cognitive, and school performance. However, these assertions are largely based on evidence which demonstrates acute effects of breakfast on cognitive performance. Less research which examines the effects of breakfast on the ecologically valid outcomes of academic performance or in-class behavior is available. The literature was searched for articles published between 1950–2013 indexed in Ovid MEDLINE, Pubmed, Web of Science, the Cochrane Library, EMBASE databases, and PsychINFO. Thirty-six articles examining the effects of breakfast on in-class behavior and academic performance in children and adolescents were included. The effects of breakfast in different populations were considered, including undernourished or well-nourished children and adolescents from differing socio-economic status (SES) backgrounds. The habitual and acute effects of breakfast and the effects of school breakfast programs (SBPs) were considered. The evidence indicated a mainly positive effect of breakfast on on-task behavior in the classroom. There was suggestive evidence that habitual breakfast (frequency and quality) and SBPs have a positive effect on children's academic performance with clearest effects on mathematic and arithmetic grades in undernourished children. Increased frequency of habitual breakfast was consistently positively associated with academic performance. Some evidence suggested that quality of habitual breakfast, in terms of providing a greater variety of food groups and adequate energy, was positively related to school performance. However, these associations can be attributed, in part, to confounders such as SES and to methodological weaknesses such as the subjective nature of the observations of behavior in class.

Maternal thyroid hormone deficiency affects the fetal neocorticogenesis by reducing the proliferating pool, rate of neurogenesis and indirect neurogenesis

Neuronal progenitor cell proliferation and their optimum number are indispensable for neurogenesis, which is determined by cell cycle length and cell cycle quitting rate of the dividing progenitors. These processes are tightly orchestrated by transcription factors like Tbr2, Pax6, and E2f-1. Radial glia and intermediate progenitor cells (IPC) through direct and indirect neurogenesis maintain surface area and neocortical thickness during development. Here we show that fetal neurogenesis is maternal thyroid hormone (MTH) dependent with differential effect on direct and indirect neurogenesis. MTH deficiency (MTHD) impairs direct neurogenesis through initial down-regulation of Pax6 and diminished progenitor pool with recovery even before the onset of fetal thyroid function (FTF). However, persistent decrease in Tbr2 positive IPCs, diminished NeuN positivity in layers I-III of neocortex, and reduced cortical thickness indicate a non-compensatory impairment in indirect neurogenesis. TH deficiency causes disrupted cell cycle kinetics and deranged neurogenesis. It specifically affects indirect neurogenesis governed by intermediate progenitor cells (IPCs). TH replacement in hypothyroid dams partially restored the rate of neurogenesis in the fetal neocortex. Taken together we describe a novel role of maternal TH in promoting IPCs derived neuronal differentiation in developing neo-cortex. We have also shown for the first time that ventricular zone progenitors are TH responsive as they express its receptor, TR alpha-1, transporters (MCT8) and deiodinases. This study highlights the importance of maternal thyroid hormone (TH) even before the start of the fetal thyroid function.

Iodine supplementation in pregnancy and its effect on child cognition

Maternal hypothyroidism and hypothyroxenemia due to iodine deficiency have been shown to affect development of the newborn negatively. Maternal iodine supplementation may therefore improve cognitive performance of the offspring, even in areas of mild-to-moderate iodine deficiency (ID). Several iodine supplementation studies have been performed in mildly ID pregnant women in Europe. These studies have shown that iodine supplementation increases maternal urinary iodine (UI) excretion and reduces thyroid volume, as well as prevents increases in infant thyroid volume and thyroglobuline. However, randomized controlled studies with long-term outcomes are lacking. Therefore, two trials were started in 2008 in areas of low iodine status; one in Bangalore, India (n=325), and another in Bangkok, Thailand (n=514). Pregnant women were recruited <14 weeks gestational age and randomized to either receive a daily dose of 200 μg I (as KI) or an identical placebo throughout pregnancy. Both trials are ongoing, and women are followed up during pregnancy and at delivery. UI, thyroid hormones, and thyroid size are measured. Birth outcomes are recorded, such as gestational age at delivery, height, weight, and APGAR scores, and cord blood and heel stick blood (<72 h) is collected from the child. Child development is assessed at 6 weeks of age using the Neonatal Behavioral Assessment Scale (NBAS), and at 12 and 24 months of age using the Bayley Scales of Infant Development. The outcomes of these trials will contribute importantly to the evidence base for iodine supplementation of pregnant women living in areas of mild iodine deficiency.

Combating iodine deficiency disorders to achieve millennium development goal 4 in India: reduction in infant mortality rate

In severe iodine deficient areas, iodine deficiency has been documented to be an important etiological factor leading to poor fetal growth and development. Iodine is essential for physical growth and development of the central nervous system of the fetus. Iodine deficiency in pregnant mothers leads to increased incidence of infertility and abortions, perinatal mortality and infant child mortality. The clinical iodine supplementation trials have documented adverse health consequences due to iodine deficiency. Evidence from observational studies concludes that prevention of iodine deficiency can lead to reduction in infant mortality rate and facilitate to achieve millennium development goal-4.

Iodine

Iodine levels in the United States have dropped precipitously over the past few decades, whereas antagonists such as bromine, perchlorate, and fluoride have become more ubiquitous. These changes have placed a nutritional burden on the human body and increased the potential for pathophysiological change at the cellular level. This review examines the clinical and peer-reviewed literature and provides perspective related to health-compromising trends that warrant close scrutiny in clinical practice and future research mandates.

The measurement, definition, aetiology and clinical consequences of neonatal transient hypothyroxinaemia

This review focuses on neonatal transient hypothyroxinaemia, a condition characterized by temporary postnatal reductions in concentrations of Total T4 or Free T4, with normal or low concentrations of thyroid stimulating hormone (TSH). There is neither an agreed quantitative definition, nor an agreed mode of measurement for the condition. Transient hypothyroxinaemia is not routinely monitored yet it is thought to affect about 50% of preterm infants; it was thought to be without long-term sequelae but observational studies indicate that neurodevelopment may be compromised. The aetiology of transient hypothyroxinaemia is complex. There are significant contributions from the withdrawal of maternal-placental thyroxine transfer, hypothalamic-pituitary-thyroid immaturity, developmental constraints on the synthesis and peripheral metabolism of iodothyronines and iodine deficiency. It is not possible to distinguish clinically, or from laboratory measurements, whether transient hypothyroxinaemia is an independent condition or simply a consequence of non-thyroidal illness and/or drug usage. An answer to this question is important because studies of thyroid hormone replacement have been instigated, with mixed results. Until the aetiology of transient hypothyroxinaemia is better understood it would seem prudent not to routinely supplement preterm infants with thyroid hormones. Iodine deficiency, non-thyroidal illness and drug usage are the most modifiable risk factors for transient hypothyroxinaemia and are the clear choices for attempts at reducing its incidence. We suggest that transient hypothyroxinaemia in preterm infants is defined as a normal or low TSH concentration in conjunction with a concentration of Total T4, that is ≤10th percentile of cord Total T4 of the equivalent gestational age had the infant remained in utero.

Iodine deficiency in pregnancy, infancy and childhood and its consequences for brain development

Iodine deficiency during foetal development and early childhood is associated with cognitive impairment. Randomised clinical studies in school-aged children encountered in the literature indicate that cognitive performance can be improved by iodine supplementation, but most studies suffer from methodological constraints. Tests to assess cognitive performance in the domains that are potentially affected by iodine deficiency need to be refined. Maternal iodine supplementation in areas of mild-to-moderate iodine deficiency may improve cognitive performance of the offspring, but randomised controlled studies with long-term outcomes are lacking. Studies in infants or young children have not been conducted. The best indicators for iodine deficiency in children are thyroid-stimulating hormone (TSH) in newborns and thyroglobulin (Tg) in older children. Urinary iodine may also be useful but only at the population level. Adequate salt iodisation will cover the requirements of infants and children as well as pregnant women. However, close monitoring remains essential.

The challenges of iodine supplementation: a public health programme perspective

An adequate iodine intake during pregnancy, lactation and early childhood is particularly critical for optimal brain development of the foetus and of children 7-24 months of age. While the primary strategy for sustainable elimination of iodine deficiency remains universal salt iodisation, the World Health Organization and the United Nations Children's Fund recommend a complementary strategy of iodine supplements as a temporary measure when salt iodisation could not be implemented. This article aims to review current evidence on efficacy and implications of implementing iodine supplementation as a public health measure to address iodine deficiency. Iodine supplementation seems unlikely to reach high coverage in a rapid, equitable and sustained way. Implementing the programme requires political commitment, effective and efficient supply, distribution and targeting, continuous education and communication and a robust monitoring system. Thus, universal salt iodisation should remain the primary strategy to eliminate iodine deficiency.

Iodine deficiency

Iodine deficiency has multiple adverse effects in humans, termed iodine deficiency disorders, due to inadequate thyroid hormone production. Globally, it is estimated that 2 billion individuals have an insufficient iodine intake, and South Asia and sub-Saharan Africa are particularly affected. However, about 50% of Europe remains mildly iodine deficient, and iodine intakes in other industrialized countries, including the United States and Australia, have fallen in recent years. Iodine deficiency during pregnancy and infancy may impair growth and neurodevelopment of the offspring and increase infant mortality. Deficiency during childhood reduces somatic growth and cognitive and motor function. Assessment methods include urinary iodine concentration, goiter, newborn TSH, and blood thyroglobulin. But assessment of iodine status in pregnancy is difficult, and it remains unclear whether iodine intakes are sufficient in this group, leading to calls for iodine supplementation during pregnancy in several industrialized countries. In most countries, the best strategy to control iodine deficiency in populations is carefully monitored universal salt iodization, one of the most cost-effective ways to contribute to economic and social development. Achieving optimal iodine intakes from iodized salt (in the range of 150-250 microg/d for adults) may minimize the amount of thyroid dysfunction in populations. Ensuring adequate iodine status during parenteral nutrition has become important, particularly in preterm infants, as the use of povidone-iodine disinfectants has declined. Introduction of iodized salt to regions of chronic iodine deficiency may transiently increase the incidence of thyroid disorders, but overall, the relatively small risks of iodine excess are far outweighed by the substantial risks of iodine deficiency.

Maternal thyroid hormone: a strong repressor of neuronal nitric oxide synthase in rat embryonic neocortex

Understanding of how maternal thyroid inadequacy during early gestation poses a risk for developmental outcomes is still a challenge for the neuroendocrine community. Early neocortical neurogenesis is accompanied by maternal thyroid hormone (TH) transfer to fetal brain, appearance of TH receptors, and absence of antineurogenesis signals, followed by optimization of neuronal numbers through apoptosis. However, the effects of TH deprivation on neurogenesis and neuronal cell death before the onset of fetal thyroid are still not clear. We show that maternal TH deficiency during early gestational period causes massive premature elevation in the expression of neuronal nitric oxide synthase (nNOS) with an associated neuronal death in embryonic rat neocortex. Maternal hypothyroidism was induced by feeding methimazole (0.025% wt/vol) in the drinking water to pregnant Sprague Dawley rats from embryonic d 6. Cerebral cortices from fetuses were harvested at different embryonic stages (embryonic d 14, 16, and 18) of hypothyroid and euthyroid groups. Immunoblotting and real-time PCR results showed that both protein and RNA levels of nNOS were prematurely increased under maternal hypothyroidism, and showed reversibility upon T4 administration. Immunohistochemistry revealed an increased nNOS immunoreactivity in both the cortical plate and proliferative zone of neocortex along with a corroborative decrease in the microtubule associated protein-2 positive neurons under maternal TH insufficiency. Results combined, put forth nNOS as a novel target of maternal TH action in embryonic neocortex, and underscore the importance of prenatal screening and timely rectification of maternal TH insufficiency, even of a moderate degree.

Iodine deficiency and its association with intelligence quotient in schoolchildren from Colima, Mexico

Objective

To determine the prevalence of iodine deficiency, its causes and its association with intelligence quotient (IQ) in Mexican schoolchildren.

Design

Cross-sectional analytical study, in which determinations of thyroid gland size, urinary iodine excretion, IQ, iron nutritional status, physical anthropometry, family consumption of goitrogenic foods, type/origin and iodine saturation of salt consumed at home and coliform organisms in drinking water were performed, and the association of each variable with IQ scores was evaluated by multiple regression analyses.

Setting

Municipality of Cuauhtémoc, in Colima, Mexico (altitude: 600–2700 m above sea level). Sea salt is extracted manually nearby and often used for human consumption. Goitre remains present in the region despite over half a century of mandatory salt iodination in the country.

Subjects

Three hundred and three children, similar proportions of boys and girls, mean age 9·3 years, randomly selected from 19 public elementary schools.

Results

Overall goitre rate was 21·4 %; low urinary iodine excretion was found in 19·5 % of the children, high urinary iodine excretion in 32·0 %. IQ scores were transformed into percentile values, with the following categorisation: ≤P5 (low IQ), 48·5 %; >P5 to ≤P25 (below average), 24·2 %; >P25 to <P75 (average), 18·8 %; ≥P75 to <P95 (above average), 3·6 %; ≥P95 (high IQ), 4·9 %. Ninety-two per cent of the population used iodinated salt, but deficient iodine saturation (<50 ppm) was found in 86·8 % of salt samples. The main goitrogenic foods consumed were peanuts (by 31·5 % of the sample), cabbage (30·1 %), broccoli (27·7 %) and cauliflower (25·7 %). Median counts of coliform organisms (colony-forming units/100 ml of drinking water) were: 207·5 (well water), 151 (cisterns), 52 (private homes), 25 (elementary schools) and 12 (kindergartens). Moderate iodine deficiency was associated (P< 0·05) with a 4·26 times higher risk of low IQ.

Conclusions

There is a perturbing negative impact of these findings on human capital acquisition for the region and the country. More attention is needed to ensure effective salt iodination processes, particularly in regions where goitrogens may contribute to the negative effects of iodine deficiency on the intellectual development of children.

School performance: the pediatrician's role

When children begin having difficulties in school, the first stop for parents is often the pediatrician's office. Although school performance problems may seem outside the realm of routine primary health care, there are many important roles that the primary care provider may play. These include identifying medical issues that may impact performance, helping the family form an intervention team, and acting as the child's advocate when interacting with the school. In addition, it is important for pediatricians to be familiar with cognitive, emotional, and developmental problems that affect school performance and to assist parents in becoming active participants in their children's education.

The adverse effects of mild-to-moderate iodine deficiency during pregnancy and childhood: a review

Iodine is required for the production of thyroid hormones, which are essential for normal brain development, and the fetus, newborn, and young child are particularly vulnerable to iodine deficiency. The iodine requirement increases during pregnancy and recommended intakes are in the range of 220-250 microg/day. Monitoring iodine status during pregnancy is a challenge. New recommendations from World Health Organization suggest that a median urinary iodine concentration >250 microg/L and <500 microg/L indicates adequate iodine intake in pregnancy. Based on this range, it appears that many pregnant women in Western Europe have inadequate intakes. A recent Swiss study has suggested that thyroid-stimulating hormone concentration in the newborn is a sensitive indicator of mild iodine deficiency in late pregnancy. The potential adverse effects of mild iodine deficiency during pregnancy are uncertain. Controlled trials of iodine supplementation in mildly iodine-deficient pregnant women suggest beneficial effects on maternal and newborn serum thyroglobulin and thyroid volume, but no effects on maternal and newborn total or free thyroid hormone concentrations. There are no long-term data on the effect of iodine supplementation on birth outcomes or infant development. New data from well-controlled studies indicate that iodine repletion in moderately iodine-deficient school-age children has clear benefits: it improves cognitive and motor function; it also increases concentrations of insulin-like growth factor 1 and insulin-like growth factor-binding protein 3, and improves somatic growth.

Iodine supplementation improves cognition in iodine-deficient schoolchildren in Albania: a randomized, controlled, double-blind study

BACKGROUND

Iodine is required for the production of thyroid hormones, which are necessary for normal brain development and cognition. Although several randomized trials examined the effect of iodine supplementation on cognitive performance in schoolchildren, the results were equivocal.

OBJECTIVE

We aimed 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 randomly 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 gland 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.

Pilot study of urinary iodine concentration and of biochemical thyroid parameters before and after cautious public health intervention on salt iodide content: The Swiss longitudinal 1996–2000 iodine study

OBJECTIVE AND DESIGN

Iodide concentration (IC) in salt was cautiously increased in Switzerland (15 --> 20 ppm iodide). We evaluated the dynamics of the effect of this intervention on urinary iodine concentration (UIC, microg/l) and on thyroid parameters.

SETTING

University Hospital in Bern, Switzerland.

SUBJECTS

A cohort of 36 subjects (12 children, 11 women, 13 men) out of 44 were recruited.

INTERVENTIONS

During the study periods PRE (May 1996-May 1998) and POST (October 1998-December 2000, subdivided into equal subperiods POST1 and POST2), that is, before and after the increase of IC in salt, subjects collected 6248 urine spots for analysis of UIC. Thyroid volumes (n=2/subject) and serum thyroid parameters (n=8/subject) were sequentially evaluated.

METHODS

Average PRE-POST data were compared (multiple regression analysis).

RESULTS

UIC increased overall by 5.1% (P=0.0003). Increase of UIC was highest in children (11.3%, P<0.0001), significant in women (8%, P=0.0016), but not significant in men (P=0.143). Comparison between periods POST1 and POST2 showed that UIC changed more gradually in women than in children. Thyroid volumes were normal, no nonphysiological change occurred. TSH indicated euthyroidism; it decreased in children (1.98 ==> 1.74 mU/l, P=0.04) and increased in men (1.65 ==> 1.91mU/l, P=0.025). FT3 decreased in children (P<0.004) and FT4 decreased in men (P=0.017), both within normal ranges. TSH, FT3 and FT4 were unchanged in women. FT3/FT4 ratios were stable. Anti-TPO-Ab titers were stable (P=0.9). Anti-Tg-Ab titers decreased (P=0.009).

CONCLUSION

The significant UIC effects were of uncertain metabolic relevance. No pathological side effects occurred. Differential delays and penetrances of UIC increase in children and adults were hitherto unknown. The unspectacular stepwise policy seems to be safe. Our pilot results in a population with moderate iodine deficiency in women should be confirmed in population-based cluster studies.

SPONSORSHIP

This work was supported by grants from the University Hospital in Bern, the Swiss Federal Office of Public Health (SFOPH), the 'Swiss National Foundation for Scientific Research' (32-49424.96), the 'Fondation Genevoise de Bienfaisance Valerie Rossi di Montelera', the 'Schweizerische Lebensversicherungs- und Rentenanstalt' and the 'Schüpbach Foundation of the University of Bern'.

Spermidine/spermine N1-acetyltransferase overexpression in mice induces hypoactivity and spatial learning impairment

The present work addresses the role of polyamines in learning and general behavior by subjecting transgenic mice overexpressing polyamine catabolic enzyme, spermidine/spermine N(1)-acetyltransferase (SSAT) and their syngenic littermates to neurobehavioral profiling assessment (SHIRPA) and to radial eight-arm maze. The general health and physiological conditions as well as the entire behavioral battery comprising of 34 parameters were recorded. The eight-arm radial maze (8-RAM) task included an initial acquisition task for 9 days followed by a 2-day retention test after a 2-week break. In addition, blood samples were taken for hormone analysis. Transgenic mice, which showed reduced motor activity, aggression and muscle tone, spent more time in the radial maze during initial acquisition and retention tasks as compared with syngenic mice. Moreover, the learning performance of transgenic females was significantly inferior to syngenic females. Interestingly, the levels of several hormones were significantly altered in SSAT transgenic mice; circulating adrenocorticotropic hormone (ACTH) and corticosterone levels were markedly increased while testosterone and thyroidal hormone levels were decreased. These changes may be related to the dramatic increase in brain putrescine levels in SSAT-overexpressing (SSAT-OE) mice, but it is likewise possible that the behavioral changes and learning impairment are attributable to more peripheral mechanisms (such as alterations in steroid hormone metabolism), which in turn, could be a consequence of the disturbed polyamine homeostasis.

Rapid relapse of thyroid dysfunction and goiter in school-age children after discontinuation of salt iodization

BACKGROUND

In programs to control iodine deficiency disorders (IDD), sustainability is a major concern. IDD has recently recurred in countries where salt iodization programs have lapsed.

OBJECTIVE

The objective of the study was to describe the evolution of thyroid dysfunction after the discontinuation of salt iodization in a cohort of children in an area of severe endemic goiter.

DESIGN

Moroccan children (aged 6-16 y, n = 159) with severe IDD received iodized salt (IS) for 1 y. Because of practical and financial constraints, including a lack of infrastructure and electricity at the production site, salt iodization abruptly ceased. The children were followed for another 14 mo, and concentrations of urinary iodine, thyrotropin, total thyroxine, and thyroglobulin and thyroid volume were measured.

RESULTS

Before iodization, median urinary iodine was 18 microg/L, 88% of children had elevated serum thyroglobulin concentrations, and 72% were goitrous. One year after the introduction of IS, median urinary iodine and thyroglobulin concentrations had normalized, mean thyroid volume had decreased by 34%, and median thyrotropin and mean total thyroxine concentrations were improved. Five months after the discontinuation of salt iodization, median urinary iodine had fallen to 20 microg/L. Fourteen months after the discontinuation of salt iodization, the rate of goiter was again similar to the rate before salt iodization; median thyrotropin and thyroglobulin concentrations were sharply higher than before the introduction of IS (P < 0.001); and the prevalence of hypothyroidism was 10%, compared with 3% before the introduction of IS (P < 0.001).

CONCLUSIONS

In IDD-affected areas, cessation of salt iodization is associated with a rapid deterioration of thyroid function in school-age children. These findings underline the importance of sustainability in IDD control and the vulnerability of children to even short-term lapses in IS programs.

Subclinical Prenatal Iodine Deficiency Negatively Affects Infant Development in Northern China

Although mild-to-moderate levels of iodine deficiency (ID) have been associated with poor cognitive outcomes in children, little is known about subclinical prenatal ID and infant development. In this study, the association between elevated cord blood thyroid stimulating hormone (TSH, thyrotropin) and infant development was examined in Northern China. Three groups of infants with elevated cord blood TSH were compared with infants with normal TSH levels on an information processing task at 7 mo, and in cognitive and motor developmental assessments at 13 mo. Infants with elevated TSH had poorer information processing skills and lower scores on the cognitive development index. There were no differences in motor abilities. Relationships between socioenvironmental factors and iodine status were assessed. Infants from more rural settings and those whose mothers had completed fewer years of schooling and had lower paying occupations had higher cord blood TSH levels. A regression analysis indicated that maternal education was predictive of cognitive performance among infants with elevated TSH but not control infants. The findings suggest that subclinical prenatal ID has negative effects on infant development and that, in some instances, maternal education may ameliorate these effects.

Iodine deficiency and goitre in schoolchildren in Melbourne, 2001

OBJECTIVE

To assess iodine status and goitre prevalence in a sample of schoolchildren in Melbourne.

DESIGN

Cross-sectional study of urinary iodine excretion and presence of goitre in a sample of schoolchildren from Years 5-12 attending two urban schools.

PARTICIPANTS

607 children aged 11-18 years consented to thyroid gland palpation and 577 provided a urine sample on the day of examination in August 2001.

OUTCOME MEASURE

Iodine status of the study population, based on median urinary iodine values categorised as normal (> or = 100 microg/L), mild (50-99 microg/L) or moderate-severe (< 50 microg/L), and classified according to sex, school year and presence of goitre.

RESULTS

76% (439/577) of students had abnormal urinary iodine values, with 27% (156/577) having values consistent with moderate-severe deficiency. The median urinary iodine excretion for the total group was 70 microg/L, with values for school years 5-12 ranging from 62 microg/L (Year 12) to 76 microg/L (Year 9). The median urinary iodine value in girls was lower than that in boys (64 microg/L v 82 microg/L), and girls had significantly lower urinary iodine values overall (P < 0.002). There was no association between goitre grade and moderate-severe (< 50 microg/L; P = 0.39) or mild (50-99 microg/L; P = 0.07) urinary iodine deficiency.

CONCLUSIONS

We found mild iodine deficiency in a cohort of schoolchildren in Melbourne. Our results support other data showing mild iodine deficiency in Sydney and Tasmania and the argument for a national study of iodine nutrition.

Comparison of Urinary Iodine Excretion in Neonates and Their Mothers in Isfahan, Iran

OBJECTIVE

To determine the urinary iodine excretion of neonates (28 days of age or younger) and their mothers in Isfahan, a centrally located city in Iran, in 1997 after 8 years of iodized salt distribution in an effort to ameliorate iodine deficiency.

METHODS

Through a cross-sectional study and by means of convenient sampling, 146 mother-neonate pairs were selected among neonates born in Shahid Sadoughi Hospital in Isfahan. In order to eliminate the effect of povidone-iodine on breast milk and urinary iodine, Savlon antiseptic solution was used in normal vaginal delivery and on the umbilical cord. Normal values of urinary iodine concentration for the mothers and their neonates were > or = 10.0 microg/dL and >5.0 microg/dL, respectively. The data were analyzed and compared by the Student t test and Pearson correlation coefficient in SPSS software. P values <0.05 were considered statistically significant.

RESULTS

In only 3% of the neonates and 14% of the mothers, urinary iodine excretion was below the normal range. No mother or neonate had severe iodine deficiency. In 2% of the mothers and 2% of the neonates, mild iodine deficiency was found. The mean urinary iodine concentration of neonates whose mothers were iodine deficient was significantly lower than that of neonates whose mothers were iodine sufficient (17.34 +/- 7.83 microg/dL versus 22.21 +/- 7.57 microg/dL; P<0.01). A direct significant correlation was noted between the urinary iodine excretion of neonates and that of their mothers (r = 0.37; P<0.01).

CONCLUSION

The urinary iodine excretion in mothers paralleled the urinary iodine concentration of their neonates. If urinary iodine concentration is considered an index of total body iodine content, this study demonstrated that prolonged iodized salt intake has minimized the occurrence of iodine deficiency in Isfahan.

mRNA differential display identification of thyroid hormone-responsive protein (THRP) gene in association with early phase of long-term potentiation

The process of long-term potentiation (LTP) consists of the early induction and late maintenance phases. Few studies have examined the cellular mechanisms underlying these two phases; their respective mRNA expression profiles have not yet been elucidated. Here we used the technique of PCR differential display to identify genes that are differentially expressed between the early and late phases of LTP in vivo. Our results indicated that the cDNA fragment corresponding to one mRNA with preferentially increased expression during the early, but not late, phase of LTP encodes the rat thyroid hormone-responsive protein (THRP) gene. In situ hybridization analysis confirmed the results obtained from the PCR differential display. Prior NMDA receptor blockade with MK801 prevented induction of LTP and decreased THRP mRNA expression in the dentate gyrus, as assayed by quantitative RT-PCR analysis. THRP antisense oligonucleotide treatment before tetanic stimulation also prevented induction of LTP. However, when THRP antisense oligonucleotide was administered after induction of LTP, it did not affect expression and maintenance of LTP. THRP is known to be responsive to thyroid hormone. Our results indicate that direct thyroid hormone (T3) injection into the dentate gyrus produces a long-lasting enhancement of synaptic efficacy of these neurons. T3 injection also markedly increased THRP mRNA expression in the dentate gyrus. Taken together, our results suggest that THRP mRNA expression plays an important role in the early phase, but not the late phase, of LTP and that both THRP and thyroid hormone are involved in synaptic plasticity in hippocampal neurons.

Improved iodine status is associated with improved mental performance of schoolchildren in Benin

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 populations 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, randomized, 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.

The potential repercussions of maternal, fetal, and neonatal hypothyroxinemia on the progeny

The adequate functioning of both the maternal and fetal thyroid glands play an important role to ensure that the fetal neuropsycho-intellectual development progresses normally. Three sets of clinical disorders are considered, that may eventually lead to impaired brain development. Firstly, in infants with a defect of glandular ontogenesis (congenital hypothyroidism), the participation of maternal thyroid hormones to the fetal circulating thyroxine environment is normal and, therefore, risk of brain damage results exclusively from the insufficient hormone production by the abnormal fetal thyroid gland. Secondly, when it is only the maternal thyroid gland that is functionally deficient (autoimmune hypothyroidism), the severity and temporal occurrence of maternal underfunction will both drive the resulting consequences for impaired fetal neuronal development. Clinical situations of this type may obviously take place already during early gestation (in women with known but untreated hypothyroidism) or appear only during later gestational stages (in women who have AITD and remain euthyroid during the first half of gestation). Lastly, in conditions with iodine deficiency, both maternal and fetal thyroid functions are affected and, therefore, it is primarily the degree and precocity of the maternal hypothyroxinemia due to iodine deficiency during pregnancy that will drive the potential repercussions for fetal neurological development. In the present review, we summarize available data and develop our present concepts concerning the complex feto-maternal thyroid relationships and the potential impacts of thyroid function abnormalities on the ideal development of the offspring.

Neurodevelopmental dysfunction and specific learning disabilities in school-aged twins

The frequency of the developmental dysfunction and specific learning disabilities were assessed in the retrospective study in the group of 56 school-aged twins. The relationships between genetic, perinatal and social factors and learning disability were also determined. It was found that 12.5% of twins had learning disabilities. The most common neurodevelopmental dysfunction were language disorders, poor graphomotor fluency and poor fine motor dexterity. It was also found that educational difficulty were associated with prematurity, low Apgar scores, neonatal complications and familial predisposition.

Biochemical hypothyroidism secondary to iodine deficiency is associated with poor school achievement and cognition in Bangladeshi children

Iodine deficiency in pregnancy leads to poor cognitive function in the offspring; however, the effect of concurrent iodine deficiency on school-aged children is not clear. Several studies have shown that school children in iodine-deficient villages have poorer cognitive function than children in iodine-sufficient villages. However, villages differ in many factors that may also detrimentally affect children's development. In addition, the children's nutritional and health status has not usually been taken into account. In this study, we compared the cognitive function and school achievement levels of 170 children who had recently had low thyroxine (T4) levels [T4 </= 45 nmol/L (hypothyroid)] with children who had not had low T4 levels [T4 >/=70 nmol/L (euthyroid)]. The children were matched for school and grade level and came from the same iodine-deficient regions in rural Bangladesh. They were given a battery of cognitive, motor and school achievement tests. We also measured their nutritional status, examined their stools for geohelminths and assessed their home environments. A factor analysis of cognitive and motor function tests yielded two factors, a general cognitive factor and a fine motor factor. The children's height and arm circumference, experience of hunger, parental characteristics and stimulation in the home made independent contributions to their test scores. Controlling for these variables, the hypothyroid children performed worse than the euthyroid children on reading and spelling and the general cognitive factor. These findings indicate that a large number of disadvantages including hypothyroidism are related to the poor development of these children.