Effects of iodine supplementation in mild-to-moderately iodine-deficient pregnant women on thyroid function, pregnancy outcomes and newborn development in Thailand

Background: Iodine deficiency (ID) during pregnancy has been recognized as a major cause of hypothyroidism and adverse health consequences in both mothers and children. Although urinary iodine concentration (UIC) in school-aged children is recommended as an indicator to assess ID in the general population, it may not be a good surrogate for directly assessing iodine status in pregnant women. Iodine supplementation of mildly iodine-deficient pregnant women has been recommended worldwide; however, long-term benefit and safety of iodine supplementation in this group is uncertain. Finally, pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) may negatively affect thyroid function and pregnancy outcomes. Objectives: 1) to measure UIC in pairs of pregnant women and their school-aged children living in the same household; 2) to investigate the effects of iodine supplementation on maternal thyroid function, pregnancy and birth outcomes, and newborn development; 3) to evaluate the association between pre-pregnancy BMI and GWG with thyroid function and pregnancy outcomes. Methods: 1) In a cross-sectional pilot study, UIC was measured in spot urine samples from pairs (n=302) of healthy pregnant mothers and their school-aged children in Bangkok; 2) Arandomized controlled trial was conducted with 200 µg iodine per day or placebo given to mildly ID pregnant Thai women from ndand 3rdtrimester, at delivery and 6-week postpartum. Birth outcomes were collected from hospital records. Neonatal thyroid function, UIC and thyroid volume were measured at delivery and 6 weeks after birth. The Neonatal Behavioral Assessment Scales (NBAS) was used to assess newborn development. Results: 1) In the pilot study, median UIC in the pregnant women was 108 (11–558) µg/L and was lower than UIC in their school-aged children [200 (25–835) µg/L] (P500 µg/L. Maternal thyroid function, thyroid volume and the prevalence of all thyroid dysfunction subtypes did not differ significantly between treatment groups during the study (p>0.05). At 6-week postpartum, the prevalence of postpartum thyroiditis (hyperthyroidism) was significantly lower in the iodine group (3%) as compared to the placebo group (9%) (OR: 95%CI, 0.17: 0.04-0.70). There were no significant differences between newborn groups in thyroid function, thyroid volume, birth characteristics, UIC and NBAS score (p>0.05); 3) Pre-pregnancy BMI was a negative predictor of free thyroxine (fT4) (β=-0.20, P Conclusion: 1) UIC in school-aged children should not be used as a surrogate for monitoring iodine status in pregnancy; 2) iodine supplementation (200 µg/d) in mildly iodine-deficient pregnant Thai women was effective in increasing iodine intakes into the adequate range but had no benefit on antenatal maternal thyroid function or newborn outcomes out to 6 weeks; however, it significantly reduced the risk of maternal postpartum thyroid dysfunction; 3) excess maternal body weight both before and during pregnancy may have adverse impacts on maternal thyroid function as well as birth weight. Therefore, maintaining normal body weight before and throughout pregnancy should be recommended.</p

The prevalence of insufficient iodine intake in pregnancy in Africa: Protocol for a systematic review and meta-analysis

Background: Insufficient iodine intake in pregnancy is associated with many adverse pregnancy outcomes. About 90% of African countries are at risk of iodine deficiency due to poor soils and dietary goitrogens. Pregnancy predisposes to insufficient iodine nutrition secondary to increased physiological demand and increased renal loss. Iodine deficiency is re-emerging in countries thought to be replete with pregnant women being the most affected. This review seeks to identify the degree of iodine nutrition in pregnancy on the entire African continent before and after the implementation of national iodization programmes. Methods: A systematic search of published literature will be conducted for observational studies that directly determined the prevalence of insufficient iodine intake among pregnant women in Africa. Electronic databases and grey literature will be searched for baseline data before the implementation of population-based iodine supplementation and for follow-up data up to December 2018. Screening of identified articles and data extraction will be conducted independently by two investigators. Risk of bias and methodological quality of the included studies will be assessed using a risk of bias tool. Appropriate meta-analytic techniques will be used to pool prevalence estimates from studies with similar features, overall and by major characteristics including the region of the study, time period (before and after implementation of iodization programmes), sample size and age. Heterogeneity of the estimates across studies will be quantified and publication bias investigated. This protocol is reported according to Preferred Reporting Items for Systematic reviews and Meta-Analysis protocols (PRISMA-P) 2015 guidelines. Discussion This review will help ascertain the impact of national iodization programmes on the iodine nutrition status in pregnancy in Africa and advise policy on the necessity for monitoring and mitigating iodine deficiency in pregnancy in Africa. This review is part of a thesis that will be submitted to the Faculty of Health Sciences, University of Cape Town, for the award of a PhD in Medicine whose protocol has been granted ethics approval (UCT HREC 135/2018). In addition, the results will be published in a peer-reviewed journal

Overweight increases risk of trimester hypothyroxinaemia in iodine-deficient pregnant woman

Hypothyroxinaemia early in pregnancy may impair fetal brain development. Increased body weight has been associated with low thyroxine concentrations in non-pregnant women. In pregnant women, morbid maternal obesity is a risk factor for thyroid dysfunction. But whether lesser degrees of overweight that are much more common could be a risk factor for hypothyroxinaemia in pregnancy is unclear. The objective of this study was to investigate if overweight increases risk for thyroid dysfunction, and specifically hypothyroxinaemia, in iodine-deficient pregnant women. We performed a cross-sectional study at first hospital visit among healthy Thai pregnant women. We measured weight and height, urinary iodine concentration (UIC), serum thyroid hormones and thyroglobulin. Pre-pregnancy weight and relevant dietary factors were determined by questionnaire, and body mass index (BMI) was used to classify weight status. Among 514 women (mean gestational age, 11 weeks) with a median UIC of 111¿µg¿dL–1, indicating mild iodine deficiency, 12% had low free thyroxine (fT4) concentrations: 3% had overt hypothyroidism; 7% had subclinical hypothyroidism; and 8% had isolated hypothyroxinaemia. Based on pre-pregnancy BMI, 26% of women were overweight or obese. In a multiple regression model, BMI was a negative predictor of fT4 (ß¿=¿-0.20, P

Iodine supplementation in pregnancy and its effest 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 recruite

Iron metabolism in heterozygotes for hemoglobin E (HbE), alpha-thalassemia1, or beta-thalassemia and in compound heterozygotes for HbE/ beta-thalassemia

BACKGROUND: Despite large populations carrying traits for thalassemia in countries implementing universal iron fortification, there are few data on the absorption and utilization of iron in these persons. OBJECTIVE: We aimed to determine whether iron absorption or utilization (or both) in women heterozygous for beta-thalassemia, alpha-thalassemia 1, or hemoglobin E (HbE) differed from that in control subjects and compound HbE/beta-thalassemia heterozygotes. DESIGN: In Thai women (n = 103), red blood cell indexes, iron status, non-transferrin-bound iron, and growth differentiation factor 15 were measured, and body iron was calculated. Fractional iron absorption was measured from meals fortified with isotopically labeled ((57)Fe) Fe sulfate, and iron utilization was measured by the infusion of ((58)Fe) Fe citrate. RESULTS: Iron utilization was approximately 15% lower in alpha-thalassemia 1 or beta-thalassemia heterozygotes than in controls. When corrected for differences in serum ferritin, absorption was significantly higher in the alpha- and beta-thalassemia groups, but not the HbE heterozygotes, than in controls. HbE/beta-thalassemia compound heterozygotes had lower iron utilization and higher iron absorption and body iron than did controls. Nontransferrin-bound iron and growth differentiation factor 15 were higher in the compound heterozygotes, but not in the other groups, than in the controls. CONCLUSIONS: In alpha-thalassemia 1 and beta-thalassemia heterozygotes with ineffective erythropoesis, dietary iron absorption is not adequately down-regulated, despite a modest increase in body iron stores. In populations with a high prevalence of these traits, a program of iron fortification could include monitoring for possible iron excess and for iron deficiency

Data from: Vitamin D status among Thai school children and the association with 1,25-dihydroxyvitamin D and parathyroid hormone levels

In several low latitude countries, vitamin D deficiency is emerging as a public health issue. Adequate vitamin D is essential for bone health in rapidly growing children. In the Thai population, little is known about serum 25-hydroxyvitamin D [25(OH)D] status of infants and children. Moreover, the association between 25(OH)D and the biological active form of 1,25-dihydroxyvitamin D [1,25(OH)]2D is not clear. The specific aims of this study were to characterize circulating serum 25(OH)D, 1,25(OH)2D and their determinants including parathyroid hormone (PTH), age, sex, height and body mass index (BMI) in 529 school-aged Thai children aged 6–14 y. Adjusted linear regression analysis was performed to examine the impact of age and BMI, and its interaction with sex, on serum 25(OH)D concentrations and 1,25(OH)2D concentrations. Serum 25(OH)D, 1,25(OH)2D and PTH concentrations (geometric mean ± geometric SD) were 72.7±1.2 nmol/L, 199.1±1.3 pmol/L and 35.0±1.5 ng/L, respectively. Only 4% (21 of 529) participants had a serum 25(OH)D level below 50 nmol/L. There was statistically significant evidence for an interaction between sex and age with regard to 25(OH)D concentrations. Specifically, 25(OH)D concentrations were 19% higher in males. Moreover, females experienced a statistically significant 4% decline in serum 25(OH)D levels for each increasing year of age (P = 0.001); no decline was seen in male participants with increasing age (P = 0.93). When BMI, age, sex, height and serum 25(OH)D were individually regressed on 1,25(OH)2D, height and sex were associated with 1,25(OH)2D with females exhibiting statistically significantly higher serum 1,25(OH)2D levels compared with males (P<0.001). Serum 1,25(OH)2D among our sample of children exhibiting fairly sufficient vitamin D status were higher than previous reports suggesting an adaptive mechanism to maximize calcium absorption

Vitamin D status of Thai school children

This dataset includes the following: demographic, anthropometric and vitamin D status (25-hydroxyvitamin D, 1,25-dihydroxyvitamin D and parathyroid hormone concentrations) of a group of northeast Thai schoolchildre

Serum 25-hydroxyvitamin D, 1,25-dihyroxyvitamin D and parathyroid hormone concentrations in school-aged children by sex and age group¹.

1<p>Values are geometric mean ± geometric SD. <i>Note:</i> Geometric SD is a factor, not a quantity. Powers of the geometric SD can be either multiplied by (or divided into) the geometric mean to determine the set of values that lie <i>n</i> geometric SDs from the mean.</p

Selected characteristics of the study sample¹.

1<p>Values are geometric mean ± geometric SD or median (IQR) unless specified. <i>Note</i>: Geometric SD is a factor, not a quantity. <i>Powers</i> of the geometric SD can be either multiplied by (or divided into) the geometric mean to determine the set of values that lie <i>n</i> geometric SDs from the mean.</p>2<p>WHO Reference 2007 does not provide weight-for-age charts beyond 10 years of age.</p

Relation between age in years and serum 25-hydroxyvitamin D (nmol/L) concentrations stratified by gender.

<p>Relation between age in years and serum 25-hydroxyvitamin D (nmol/L) concentrations stratified by gender.</p