Iodine status in pregnancy: role of dietary habits and geographical origin

Improving Pregnant Women's Iodine Intake Estimates and Its Prevalence of Inadequacy through the Use of Salt and Seasoning Covariates

(1) Measuring usual iodine intake is a complex task due to the food consumption variability and its natural concentration in food. Therefore, the use of covariates to adjust statistical methods to estimate usual intake could improve the estimates obtained through dietary surveys. This study aims to evaluate the influence of salt and seasoning usage covariates on the estimates of usual iodine intake and the prevalence of its inadequacy. (2) A cross-sectional study was conducted with Brazilian pregnant women's food consumption data obtained with 24-h recall (n = 2247). The usual iodine intake was adjusted for intraindividual variability, supplement use, temporal effects, data collection methods, and sociodemographic characteristics with the tool UCD/NCI SIMPLE in the SAS software. Then, salt and seasoning usage covariates were used to adjust the distribution. The harmonized intake reference values for populations were used to assess intake adequacy. (3) The adjustments for salt and seasoning usage yielded a higher mean of usual iodine intakes. The only exception was the adjustment for the "habit of adding salt to meals after preparing/cooking", which produced a lower mean of usual intake and increased the prevalence of insufficient intake. (4) Salt and seasoning usage covariates affect the estimates evaluated. However, more studies are necessary to evaluate the influence observed.

Iodine monitoring models contribute to avoid adverse birth outcomes related more than adequate iodine intake

BACKGROUND

Iodine plays an important role in pregnancy. How to maintain adequate iodine intake amongst pregnant women in each trimester of pregnancy to prevent adverse birth outcomes in central China is a challenge for clinical practice.

METHODS

870 pregnant women and their infants were enrolled in the study. Urinary iodine concentration (UIC) was measured using an inductively coupled plasma mass spectrometry (ICP-MS). Maternal and newborn information were obtained during follow-up. Multinomial logistic regression models were established.

RESULTS

Median UIC of pregnant women was 172 ± 135 μg/L which is currently considered to be sufficient. Multivitamin supplements containing iodine, iodized salt intake and frequent milk intake were significantly associated with higher UIC. Multivariate logistic regression analysis showed that multivitamin supplements containing iodine and milk consumption were risk factors for more than adequate iodine (UIC ≥ 250 μg/L). Iodine-rich diet was significantly related to heavier birthweight, larger head circumference and longer femur length of the newborns while more than adequate iodine intake (UIC ≥ 250 μg/L) was a risk factor for macrosomia. Logistic regression models based on potential risk factors involving iodine containing supplements and iodine-rich diet were established to predict and screen pregnant women with high risk of more than adequate iodine intake among local pregnant women in different trimesters and guide them to supplement iodine reasonably to prevent the risk.

CONCLUSIONS

Multivitamin supplements containing iodine and milk consumption were risk factors for maternal UIC ≥ 250 μg/L which was a risk factor for macrosomia. Iodine monitoring models were established to provide guidance for pregnant women to reduce the risk of more than adequate iodine intake, thereby contributing to reduce the risk of having a macrosomia.

Prevalence of goiter and iodine deficiency in indigenous pregnant women from five nonmetropolitan areas of Colombia 2019

Objective: To assess the prevalence of goiter and iodine deficiency in indigenous pregnant women coming from five non-metropolitan areas in Colombia. Materials and methods: Descriptive cross-sectional cohort study that included pregnant women of any gestational age with no pregnancy-related conditions, seen in community health centers or in their homes. Patients with comorbidities at the time of pregnancy and those who were receiving iodine supplementation were excluded. Simple random sampling was used. The sociodemographic and obstetric characteristics, urinary iodine concentration and the presence of goiter were measured in accordance with the World Health Organization methodology. A descriptive analysis was performed. Results: Of 189 indigenous pregnant women who were candidates to enter the study, 2 declined participation, and 62 had exclusion criteria, and 125 were included in the final analysis. The mean urinary iodine concentration was 184.4 μg/L (min-max: 12.0-390.0). A total of 42 women (33.6%) had iodine deficiency (< 100 μg/L), and goiter (grade 1-2) was found in 43 (34.4%). No grade 3 or 4 goiter was identified. Conclusions: A high prevalence of goiter and iodine deficiency was found in indigenous pregnant women living in non-metropolitan areas. There is a need to assess maternal and perinatal effects and to implement nutritional interventions.

The association of milk and dairy consumption with iodine status in pregnant women in Oporto region

The role of milk and dairy products in supplying iodine to pregnant women is unknown in Portugal. The aim of this study was to evaluate the association between milk and dairy product consumption and the iodine status of pregnant women in the IoMum cohort of the Oporto region. Pregnant women were recruited between 10 and 13 weeks of gestation, when they provided a spot urine sample and information on lifestyle and intake of iodine-rich foods. Urinary iodine concentration (UIC) was determined by inductively coupled plasma MS. A total of 468 pregnant women (269 iodine supplement users and 199 non-supplement users) were considered eligible for analysis. Milk (but not yogurt or cheese) intake was positively associated with UIC, in the whole population (P = 0·02) and in the non-supplement users (P = 0·002), but not in the supplement users (P = 0·29). In non-supplement users, adjusted multinomial logistic regression analysis showed that milk consumption <3 times/month was associated with a five times increased risk of having UIC < 50 µg/l when compared with milk consumption ≥2 times/d (OR 5·4; 95 % CI 1·55, 18·78; P = 0·008). The highest UIC was observed in supplement users who reported consuming milk once per d (160 µg/l). Milk, but not yogurt or cheese, was positively associated with iodine status of pregnant women. Despite the observed positive association, daily milk consumption may not be sufficient to ensure adequate iodine intake in this population.

Iodine Intake in Norwegian Women and Men: The Population-Based Tromsø Study 2015-2016

Ensuring sufficient iodine intake is a public health priority, but we lack knowledge about the status of iodine in a nationally representative population in Norway. We aimed to assess the current iodine status and intake in a Norwegian adult population. In the population-based Tromsø Study 2015-2016, 493 women and men aged 40-69 years collected 24-h urine samples and 450 participants also completed a food frequency questionnaire (FFQ). The 24-h urinary iodine concentration (UIC) was analyzed using the Sandell-Kolthoff reaction on microplates followed by colorimetric measurement. Iodine intake was estimated from the FFQ using a food and nutrient calculation system at the University of Oslo. The mean urine volume in 24 h was 1.74 L. The median daily iodine intake estimated (UIE) from 24-h UIC was 159 µg/day (133 and 174 µg/day in women and men). The median daily iodine intake estimated from FFQ was 281 µg/day (263 and 318 µg/day in women and men, respectively). Iodine intake estimated from 24-h UIC and FFQ were moderately correlated (Spearman rank correlation coefficient r = 0.39, p < 0.01). The consumption of milk and milk products, fish and fish products, and eggs were positively associated with estimated iodine intake from FFQ. In conclusion, this shows that iodine intake estimated from 24-h UIC describes a mildly iodine deficient female population, while the male population is iodine sufficient. Concurrent use of an extensive FFQ describes both sexes as iodine sufficient. Further studies, applying a dietary assessment method validated for estimating iodine intake and repeated individual urine collections, are required to determine the habitual iodine intake in this population.

Is iodized salt efficient to overcome iodine deficiency in pregnants?

Objective:

Iodine is a trace element that synthesizes thyroid hormones necessary for optimal human growth and development. The relationship between dietary iodine intake and spot urinary iodine excretion in pregnant women has not been previously evaluated in Trabzon city, which is an endemic area of iodine deficiency in the Black Sea region of Turkey. This study aimed to evaluate the relationship between dietary iodine intake and urine iodine excretion in pregnant women.

Materials and Methods:

This study enrolled 150 pregnant women aged between 19 and 45 years who applied to Clinic of Gynecology and Obstetrics in Trabzon. Spot urine specimens were taken, and dietary iodine intake data were collected using a food frequency questionnaire (FFQ) and 24-hours dietary recall (24-h DR) method.

Results:

The median urinary iodine concentration (UIC) in the general specimen was 100.6 μg/L. Of the pregnant women, 80.0% had insufficient and 20.0% had sufficient iodine levels, according to UIC. Although total iodine-rich food intake determined by FFQ was sufficient in 20.7% (n=31) of participants, 24-h DR iodine intake was sufficient only 10.7% (n=16). A significant association between urinary iodine excretion and iodine intake was observed in both 24-h DR and FFQ intake estimates (p<0.05). The iodine intake values obtained in both 24-h DR and FFQ and the iodized salt effect were correlated with UIC in all models (p<0.05). Even though 96.0% of pregnant women used iodized salt, its effect on UIC was 15.2%.

Conclusion:

Both methods indicate that the iodine intake of pregnant women might be insufficient in Trabzon area. Also, although iodized salt use is high in pregnant women in Trabzon, it is not enough to prevent iodine deficiency.

Similarities and differences of dietary and other determinants of iodine status in pregnant women from three European birth cohorts

PURPOSE

As a component of thyroid hormones, adequate iodine intake is essential during pregnancy for fetal neurodevelopment. Across Europe, iodine deficiency is common in pregnancy, but data are lacking on the predictors of iodine status at this life stage. We, therefore, aimed to explore determinants of iodine status during pregnancy in three European populations of differing iodine status.

METHODS

Data were from 6566 pregnant women from three prospective population-based birth cohorts from the United Kingdom (ALSPAC, n = 2852), Spain (INMA, n = 1460), and The Netherlands (Generation R, n = 2254). Urinary iodine-to-creatinine ratio (UI/Creat, µg/g) was measured in spot-urine samples in pregnancy (≤ 18-weeks gestation). Maternal dietary intake, categorised by food groups (g/day), was estimated from food-frequency questionnaires (FFQs). Multivariable regression models used dietary variables (energy-adjusted) and maternal characteristics as predictors of iodine status.

RESULTS

Median UI/Creat in pregnant women of ALSPAC, INMA, and Generation R was 121, 151, and 210 µg/g, respectively. Maternal age was positively associated with UI/Creat in all cohorts (P < 0.001), while UI/Creat varied by ethnicity only in Generation R (P < 0.05). Of the dietary predictors, intake of milk and dairy products (per 100 g/day) was positively associated with UI/Creat in all cohorts [ALSPAC (B = 3.73, P < 0.0001); INMA (B = 6.92, P = 0.002); Generation R (B = 2.34, P = 0.001)]. Cohort-specific dietary determinants positively associated with UI/Creat included fish and shellfish in ALSPAC and INMA, and eggs and cereal/cereal products in Generation R.

CONCLUSIONS

The cohort-specific dietary determinants probably reflect not only dietary habits but iodine-fortification policies; hence, public-health interventions to improve iodine intake in pregnancy need to be country-specific.

Iron and Iodine Status in Pregnant Women from A Developing Country and Its Relation to Pregnancy Outcomes

Birth related complications and comorbidities are highly associated with a poor nutritional status of pregnant women, whereas iron and iodine are among especially important trace elements for healthy maternal and fetal outcomes. The study compares the status of iron, iodine, and related functional parameters in pregnant and non-pregnant women from a developing country and associates the data with pregnancy complications. The concentrations of ferritin, hemoglobin (Hb), total triiodothyronine (TT3), total thyroxine (TT4), and thyroid-stimulating hormone (TSH) were determined in the blood serum of 80 pregnant women at the time of delivery and compared with 40 non-pregnant healthy controls. Spot urine samples were taken to evaluate the urinary iodine concentration (UIC). In pregnant women, ferritin, Hb concentrations, and UIC were significantly lower, and TT4 values were significantly higher compared to controls. Higher Hb levels were tendentially associated with a reduced risk for pregnancy complications (OR = 0.747, CI (95%) 0.556–1.004; p = 0.053). Regarding covariates, only previous miscarriages were marginally associated with pregnancy complications. High consumption of dairy products was associated with lower Hb and ferritin values. Our results suggest that pregnant women from a developing country have lower iron status with Hb levels being possibly associated with pregnancy complications.

The Effects of Iodine Supplementation in Pregnancy on Iodine Status, Thyroglobulin Levels and Thyroid Function Parameters: Results from a Randomized Controlled Clinical Trial in a Mild-to-Moderate Iodine Deficiency Area

BACKGROUND

Iodine supplementation during pregnancy in areas with mild-to-moderate iodine deficiency is still debated.

METHODS

A single-center, randomized, single-blind and placebo-controlled (3:2) trial was conducted. We enrolled 90 women before 12 weeks of gestation. From enrollment up until 8 weeks after delivery, 52 women were given an iodine supplement (225 ug/day, potassium iodide tablets) and 38 were given placebo. At recruitment (T0), in the second (T1) and third trimesters (T2), and 8 weeks after delivery (T3), we measured participants' urinary iodine-to-creatinine ratio (UI/Creat), thyroid function parameters (thyroglobulin (Tg), TSH, FT3, and FT4), and thyroid volume (TV). The newborns' urinary iodine concentrations were evaluated in 16 cases.

RESULTS

Median UI/Creat at recruitment was 53.3 ug/g. UI/Creat was significantly higher in supplemented women at T1 and T2. Tg levels were lower at T1 and T2 in women with UI/Creat ≥ 150 ug/g, and in the Iodine group at T2 (p = 0.02). There was a negative correlation between Tg and UI/Creat throughout the study (p = 0.03, r = -0.1268). A lower TSH level was found in the Iodine group at T3 (p = 0.001). TV increased by +Δ7.43% in the Iodine group, and by +Δ11.17% in the Placebo group. No differences were found between the newborns' TSH levels on screening the two groups.

CONCLUSION

Tg proved a good parameter for measuring iodine intake in our placebo-controlled series. Iodine supplementation did not prove harmful to pregnancy in areas of mild-to-moderate iodine deficiency, with no appreciable harmful effect on thyroid function.

Reference intervals for thyrotropin in an area of Northern Italy: the Pordenone thyroid study (TRIPP)

PURPOSE

Thyrotropin (TSH) is the most accurate marker of thyroid dysfunction in the absence of pituitary or hypothalamic disease. Studies on TSH reference intervals (RIs) showed wide inter-individual variability and prompted an intense debate about the best estimation of TSH RIs.

DESIGN

We performed a population study on TSH RIs, using current data stored in the laboratory information system (LIS), at the Hospital Department of Laboratory Medicine, Pordenone (Italy), historically an area of mild-moderate iodine deficiency with a relatively high goiter prevalence.

METHODS

136,650 individuals constituted the final sample. A TSH immunoassay was performed on fasting serum samples with the Dimension Vista 1500 analyzer (Siemens Healthineers). We adopted the Kairisto's procedure to analyze TSH data downloaded by the LIS, applying the indirect strategy for deriving RIs.

RESULTS

TSH RIs of the entire population were 0.32-3.36 mIU/L with a distribution skewed towards higher values. RIs were 0.26-3.61 mIU/L for females, and 0.32-3.01 mIU/L for males. Unlike other studies, TSH median levels progressively decreased from 0-4 to 85-104 years in the overall population, both in male and in female subgroups, showing an inverse correlation between TSH and age in all groups.

CONCLUSIONS

This study is the first to analyze a high percentage (40%) of individuals from an ethnically homogenous Caucasian population. The results obtained emphasize the opportunity to define the TSH RIs according to age, gender and race, in addition to assay methods, and provide further insight about the possible role of iodine status.

Iodine Deficiency in a Study Population of Norwegian Pregnant Women-Results from the Little in Norway Study (LiN)

Iodine sufficiency is particularly important in pregnancy, where median urinary iodine concentration (UIC) in the range of 150⁻250 &micro;g/L indicates adequate iodine status. The aims of this study were to determine UIC and assess if dietary and maternal characteristics influence the iodine status in pregnant Norwegian women. The study comprises a cross-sectional population-based prospective cohort of pregnant women (Little in Norway (LiN)). Median UIC in 954 urine samples was 85 &micro;g/L and 78.4% of the samples (n = 748) were &le;150 &micro;g/L. 23.2% (n = 221) of the samples were &le;50 &micro;g/L and 5.2% (n = 50) were above the requirements of iodine intake (>250 &micro;g/L). Frequent iodine-supplement users (n = 144) had significantly higher UIC (120 &micro;g/L) than non-frequent users (75 &micro;g/L). Frequent milk and dairy product consumers (4⁻9 portions/day) had significantly higher UIC (99 &micro;g/L) than women consuming 0⁻1 portion/day (57 &micro;g/L) or 2⁻3 portions/day (83 &micro;g/L). Women living in mid-Norway (n = 255) had lowest UIC (72 &micro;g/L). In conclusion, this study shows that the diet of the pregnant women did not necessarily secure a sufficient iodine intake. There is an urgent need for public health strategies to secure adequate iodine nutrition among pregnant women in Norway.

Efficacy of educational intervention to improve awareness of the importance of iodine, use of iodized salt, and dietary iodine intake in northeastern Italian schoolchildren

OBJECTIVE

An educational program was conducted among school-aged children to improve their knowledge about iodine prophylaxis, their iodine status, and their dietary habits.

METHODS

At the baseline (T0) and after 6 mo (T1), participants (970 at T0 and 949 at T1) answered questionnaires testing their knowledge about iodine prophylaxis and their eating habits. Urine samples were collected from a randomly selected subgroup of participants (313 at T0 and 312 at T1).

RESULTS

From T0 to T1 there was a significant improvement in respondents' knowledge about iodine prophylaxis (from 44% to 70%), iodized salt consumption (from 78% to 84%), and median urine iodine concentrations (from 70 µg/L to 91 µg/L). Milk and iodized salt intakes were associated with a better iodine status per se, and more so when used simultaneously. Girls drank milk less often than boys did (daily in 52% and 59% of cases, respectively). Children of foreign origin ate sodium-rich food more often than Italians did.

CONCLUSION

Educational intervention improved the children's knowledge about iodine prophylaxis and use of iodized salt. Consuming salt in addition to milk improves iodine status. Children of foreign origin have different eating habits.

Iodine Status among Somali Immigrants in Norway

We lack knowledge about iodine status in the Norwegian population in general, and particularly among immigrants. We aimed to estimate the iodine status and potentially associated factors in a Somali population in Norway. Somali men and women aged 20–73, who were living in one district in Oslo, were recruited between December 2015 and October 2016. Twenty-four-hour urine was collected from 169 participants (91 females and 78 males). Iodine was analysed using the Sandell–Kolthoff reaction on microplates and colorimetric measurement. Information about diet was collected using a short food frequency questionnaire. Iodine intake was calculated from the 24-h iodine excretion. The mean urine volume over 24-h was 1.93 liters (min–max: 0.55–4.0) and the urinary iodine concentration (UIC) varied from 13 to 263 µg/L with a median value of 62.5 µg/L indicating a population with mild iodine deficiency. The median daily iodine intake for the study population was estimated to be 124 μg/day. Mean serum thyroid-stimulating hormone, thyroxine (T4) and triiodothyronine (T3) was 2.1 (SD 1.1) mU/L, 15.0 (SD 2.1) pmol/L, and 5.1 (SD 0.6) pmol/L, respectively. No food groups were associated with iodine intake and neither was gender, age, education level nor length of residence in Norway. In conclusion, this study showed that iodine intake was low, and a considerable proportion of the Somali population studied had sub-optimal iodine status. Monitoring of iodine status should be prioritised and measures to ensure adequate iodine intake, particularly among vulnerable groups initiated.

Iodine deficiency amongst pregnant women in South-West England

INTRODUCTION

Iodine deficiency in pregnancy may impair foetal neurological development. The UK population is generally thought to be iodine sufficient; however, recent studies have questioned this assumption. Our study aimed to explore the prevalence of iodine deficiency in a cohort of pregnant mothers from South-West England.

METHODS

Urine samples were obtained from 308 women participating in a study of breech presentation in late pregnancy. They had no known thyroid disease and a singleton pregnancy at 36-38 weeks' gestation. Samples were analysed for urinary iodine concentrations (UIC). Baseline data included age, parity, smoking status, ethnicity, body mass index (BMI) at booking, prenatal vitamin use and a dietary questionnaire. There was no difference in median UIC between women with (n = 156) or without (n = 152) a breech presentation (P = 0·3), so subsequent analyses were carried out as a combined group.

RESULTS

Participants had a mean (SD) age 31(5) years, median (IQR) BMI 24·4 (22·0, 28·3) kg/m² ; 42% were primiparous, 10% smoked during pregnancy, and 35% took iodine-containing vitamins. Ninety-six per cent were Caucasian. Median (IQR) UIC was 88·0 (54·3, 157·5) μg/l, which is consistent with iodine deficiency by WHO criteria. A total of 224/308 (73%) of women had UIC values <150 μg/l. Increasing milk intake was associated with higher UIC (P = 0·02). There was no difference in median (IQR) UIC between those women who took iodine-containing vitamins (n = 108) and those who did not (n = 200): 88 (54, 168) vs 88 (54, 150) μg/l, P = 0·7.

CONCLUSION

Iodine deficiency in pregnancy is common in South-West England. Measures to develop optimum prevention and treatment strategies are urgently needed.

Canadian Consensus on Female Nutrition: Adolescence, Reproduction, Menopause, and Beyond

OBJECTIVES

To provide health care professionals in Canada with the basic knowledge and tools to provide nutrition guidance to women through their lifecycle.

OUTCOMES

Optimal nutrition through the female lifecycle was evaluated, with specific focus on adolescence, pre-conception, pregnancy, postpartum, menopause, and beyond. The guideline begins with an overview of guidance for all women, followed by chapters that examine the evidence and provide recommendations for the promotion of healthy nutrition and body weight at each life stage. Nutrients of special concern and other considerations unique to each life stage are discussed in each chapter.

EVIDENCE

Published literature, governmental and health agency reports, clinical practice guidelines, grey literature, and textbook sources were used in supporting the recommendations made in this document.

VALUES

The quality of evidence was rated using the criteria described in the report of the Canadian Task Force on Preventive Health Care. CHAPTER 2: GENERAL FEMALE NUTRITION: Summary Statements Recommendations CHAPTER 3: ADOLESCENCE NUTRITION: Summary Statements Recommendations CHAPTER 4: PRE-CONCEPTUAL NUTRITION: Summary Statement Recommendations CHAPTER 5: NUTRITION IN PREGNANCY: Summary Statements Recommendations CHAPTER 6: POSTPARTUM NUTRITION AND LACTATION: Summary Statements Recommendations CHAPTER 7: NUTRITION DURING MENOPAUSE AND BEYOND: Summary Statement Recommendations.

The Urine Iodine to Creatinine as an Optimal Index of Iodine During Pregnancy in an Iodine Adequate Area in China

CONTEXT

Iodine nutrition is a global event, especially for pregnant women.

OBJECTIVE

To develop applicable index of iodine intake for population during pregnancy.

DESIGN, SETTING, AND PARTICIPANTS

From 2012 to 2014, pregnant women at less than 8 weeks of gestation (n = 222) and reproductive-age women (n = 827) participated in this study. The pregnant women were evaluated at follow-up visits at 8, 12, 16, 20, 28, and 36 weeks of gestation and 3 and 6 months postpartum.

MAIN OUTCOME MEASURES

Twenty-four-hour urine samples were collected at weeks 8 of gestation. Urine iodine (UI) and creatinine (Cr) and serum thyroglobulin were measured in all of the subjects. Circulatory iodine was measured using inductively coupled plasma-mass spectrometry at 8, 20, and 36 weeks of gestation and 6 months postpartum.

RESULTS

The median UI concentration decreased from 183.6 to 104.2 μg/L during pregnancy. The serum iodine (SI) changes were similar to the UI to creatinine ratio (UI/Cr). The SI level was lowest at the eighth week of gestation (60.5 μg/L), which rose significantly until 20 weeks (106.5 μg/L) and then began to decline (36 wk, 84.7 μg/L). The 24-hour UI excretion measurement was regarded as the gold standard. The area under the receiver-operating characteristic curve for UI/Cr was 0.92 for iodine deficiency diagnoses and 0.78 for SI. The area for SI was 0.82 for excessive iodine diagnoses and 0.75 for UI/Cr. The areas under these curves were significantly different (P < .001). The areas under the receiver-operating characteristic curve for UI were 0.61 (P = .11) and 0.65 (P = .08) for iodine deficiency and excessive iodine diagnoses, respectively. Additionally, for thyroglobulin, these values were 0.54 (P = .53) and 0.53 (P = .74), respectively.

CONCLUSIONS

Iodine intake, as assessed by spot UI concentration in pregnant women, is inaccurate and increases the prevalence of iodine deficiency. The UI/Cr better reflects the 24-hour iodine excretion and circulating iodine levels during pregnancy and the postpartum period.

Maternal iodine status and the thyroid function of pregnant mothers and their neonates in Jaffna District of Sri Lanka

INTRODUCTION

Iodine status of pregnant women and their newborns have not been studied in Jaffna District, Sri Lanka. This study was planned to assess the maternal iodine status and thyroid function at the third trimester of gestation and the thyrotrophin level of their neonate.

METHODS

Four hundred and seventy-seven pregnant women and their newborns were randomly selected among six Medical Officers of Health Divisions out of 12 in Jaffna District, Sri Lanka. Maternal thyroid stimulating hormone (TSH), free thyroxine (fT4), thyroglobulin (Tg), urinary iodine levels, and the neonatal thyrotrophin (nTSH) level were assessed.

RESULTS

In this study, mean age, weight, height, and gestational age of the mothers were 28.95 (±5.46) years, 63.02 (±11.56) kg, 154.39 (±6.00) cm, and 39.33 (±1.37) weeks, respectively. Maternal median urinary iodine concentration (UIC) was 140.0 μg/L (inter-quartile range 126.0-268.0 μg/L). Median values of the maternal serum TSH, fT4, and Tg were 1.9 mIU/L, 12.6 pmol/L, and 21.4 IU/L, respectively. Among the 477 newborns, 50.5% (n = 239) were males. Mean birth weight of newborn was 3.03 (±0.43) kg, while the mean length was 51.1 (±2.1) cm. Among the newborns, 18% (n = 86) had nTSH level > mIU/L and 37.7% (n = 180) within TSH level > mIU/L. nTSH level had positive but very weak correlations with maternal thyroid parameters, that is, UIC (r = 0.06, P = 0.13), fT4 (r = 0.01, P = 0.05), TSH (r = 0.09, P = 0.05), and Tg (r = 0.12, P = 0.03).

CONCLUSION

On the basis of the World Health Organization criteria, the iodine status of pregnant women was inadequate in this region and also nTSH levels indicate moderate iodine deficiency during pregnancy. Therefore, the continuous education on adequate iodine intake during pregnancy and monitoring of iodine status are useful.

Should All Women Be Screened for Thyroid Dysfunction in Pregnancy?

The subject of universal thyroid screening in pregnancy generates impassioned debate. Thyroid dysfunction is common, has significant adverse implications for fetal and maternal well-being, is readily detectable and can be effectively and inexpensively treated. Furthermore, the currently recommended case-finding strategy does not identify a substantially proportion of women with thyroid dysfunction thus favoring universal screening. On the other hand subclinical thyroid dysfunction forms the bulk of gestational thyroid disorders and the paucity of high-level evidence to support correction of these asymptomatic biochemical abnormalities weighs against universal screening. This review critically appraises the literature, examines the pros and cons of universal thyroid screening in pregnancy, highlighting the now strong case for implementing universal screening and explores strategies for its implementation.

Iodine status from childhood to adulthood in females living in North-East Italy: Iodine deficiency is still an issue

PURPOSE

This survey aimed to assess iodine status in a female population at different ages, also investigating their eating habits.

METHODS

We measured urinary iodine concentrations (UIC) in: 634 females at puberty and 361 fertile women in 246 of whom were considered also their children (134 daughters and 120 sons). All subjects completed a food frequency questionnaire.

RESULTS

Median UIC decreased from childhood to adulthood (median UIC 107, 77 and 55 μg/l in the young girls, females at puberty and fertile women, respectively). Though using iodized salt improved iodine status in all groups, a significantly higher UIC was only noted in females at puberty. Milk consumption significantly increased UIC at all ages. In mother-child (both daughters and sons) pairs, the children's median UIC was nearly twice as high as their mothers' (UIC 115 vs. 57 μg/l). Milk consumption varied significantly: 56% of the mothers and 76% of their children drank milk regularly. The children (both daughters and sons) and mothers who drank milk had UIC ≥100 μg/l in 59 and 34% of cases, respectively, among the pairs who did not drink milk, 44% of the children and 19% of the mothers had UIC ≥100 μg/l. On statistical regression, 3.6% of the variability in the children's UIC depended on that of their mothers.

CONCLUSIONS

Dietary iodine status declines from childhood to adulthood in females due to different eating habits. A mild iodine deficiency emerged in women of child-bearing age that could have consequences during pregnancy and lactation.

Iodine deficiency in pregnant women in Austria

BACKGROUND/OBJECTIVES

In Austria, iodine deficiency has been considered to be eliminated owing to table salt fortification with iodine, but whether this also applies to pregnant women is unclear. Even mild iodine deficiency during gestation may lead to neurocognitive sequelae in the offspring.

SUBJECTS/METHODS

This is a cross-sectional investigation of urinary iodine excretion in 246 pregnant women (first trimester n=2, second trimester n=53, third trimester n=191, gestational diabetes mellitus n=115, no gestational diabetes mellitus n=131). The iodine content of morning spot urine samples was determined using inductively coupled plasma mass spectrometry.

RESULTS

Pregnant women in the Vienna area had a median urinary iodine concentration (UIC) of 87 μg/l. Only 13.8% of the cohort were in the recommended range of 150-249 μg/l, whereas 21.5% had a UIC of 0-49 μg/l, 40.2% had a UIC of 50-99 μg/l and 19.5% had a UIC of 100-149 μg/l. In all, 4.9% had a UIC over 250 μg/l. A total of 137 women of foreign origin had a significantly higher iodine excretion compared with Austrian-born women. Maternal or gestational age had no influence on UIC. Although 79 women on iodine supplementation had a significantly higher iodine concentration compared with women without iodine supplementation (97.3 vs 80.1 μg/l, P=0,006), their UIC was below the recommended range, indicating that doses of 100-150 μg per day are not sufficient to normalize iodine excretion. Sodium and iodine concentrations in the urine were tightly correlated (R=0.539, n=61), suggesting that low intake of iodized salt might contribute to insufficient iodine supply.

CONCLUSIONS

This study shows that pregnant women in the Vienna area have a potentially clinically significant iodine deficiency and that currently recommended doses of iodine supplementation may not be sufficient.

Systematic review using meta-analyses to estimate dose-response relationships between iodine intake and biomarkers of iodine status in different population groups

The objective of this systematic review was to identify studies investigating iodine intake and biomarkers of iodine status, to assess the data of the selected studies, and to estimate dose-response relationships using meta-analysis. All randomized controlled trials, prospective cohort studies, nested case-control studies, and cross-sectional studies that supplied or measured dietary iodine and measured iodine biomarkers were included. The overall pooled regression coefficient (β) and the standard error of β were calculated by random-effects meta-analysis on a double-log scale, using the calculated intake-status regression coefficient (β) for each individual study. The results of pooled randomized controlled trials indicated that the doubling of dietary iodine intake increased urinary iodine concentrations by 14% in children and adolescents, by 57% in adults and the elderly, and by 81% in pregnant women. The dose-response relationship between iodine intake and biomarkers of iodine status indicated a 12% decrease in thyroid-stimulating hormone and a 31% decrease in thyroglobulin in pregnant women. The model of dose-response quantification used to describe the relationship between iodine intake and biomarkers of iodine status may be useful for providing complementary evidence to support recommendations for iodine intake in different population groups.

Subclinical Iodine Deficiency among Pregnant Women in Haramaya District, Eastern Ethiopia: A Community-Based Study

Background. Iodine deficiency in pregnancy is a worldwide problem. This study aimed to assess prevalence and predictors of subclinical iodine deficiency among pregnant women in Haramaya district, eastern Ethiopia. Methods. A cross-sectional, community-based study was conducted on 435 pregnant women existing in ten randomly selected rural kebeles (kebele is the smallest administrative unit in Ethiopia). Data on the study subjects' background characteristics, dietary habits, and gynecological/obstetric histories were collected via a structured questionnaire. UIC of <150 μg/L defined subclinical iodine deficiency. Data were analyzed by Stata 11. A multivariable logistic regression was used to identify the predictors of subclinical iodine deficiency. Results. The median urinary iodine concentration (MUIC) was 58.1 μg/L and 82.8% of the women who had subclinical iodine deficiency. The risk of subclinical iodine deficiency was reduced by the use of iodized salt (AOR = 0.13) and by intake of milk twice a month or more (AOR = 0.50), but it was increased by maternal illiteracy (AOR = 3.52). Conclusion. Iodine nutritional status of the pregnant women was poor. This shows that women and their children are exposed to iodine deficiency and its adverse effects. Thus, they need urgent supplementation with iodine and improved access to and intake of iodized salt and milk during pregnancy.

Low-level seaweed supplementation improves iodine status in iodine-insufficient women

Iodine insufficiency is now a prominent issue in the UK and other European countries due to low intakes of dairy products and seafood (especially where iodine fortification is not in place). In the present study, we tested a commercially available encapsulated edible seaweed (Napiers Hebridean Seagreens® Ascophyllum nodosum species) for its acceptability to consumers and iodine bioavailability and investigated the impact of a 2-week daily seaweed supplementation on iodine concentrations and thyroid function. Healthy non-pregnant women of childbearing age, self-reporting low dairy product and seafood consumption, with no history of thyroid or gastrointestinal disease were recruited. Seaweed iodine (712 μg, in 1 g seaweed) was modestly bioavailable at 33 (interquartile range (IQR) 28-46) % of the ingested iodine dose compared with 59 (IQR 46-74) % of iodine from the KI supplement (n 22). After supplement ingestion (2 weeks, 0·5 g seaweed daily, n 42), urinary iodine excretion increased from 78 (IQR 39-114) to 140 (IQR 103-195) μg/l (P< 0·001). The concentrations of thyroid-stimulating hormone increased from 1·5 (IQR 1·2-2·2) to 2·1 (IQR 1·3-2·9) mIU/l (P< 0·001), with two participants having concentrations exceeding the normal range after supplement ingestion (but normal free thyroxine concentrations). There was no change in the concentrations of other thyroid hormones after supplement ingestion. The seaweed was palatable and acceptable to consumers as a whole food or as a food ingredient and effective as a source of iodine in an iodine-insufficient population. In conclusion, seaweed inclusion in staple foods would serve as an alternative to fortification of salt or other foods with KI.

Iodine status during pregnancy in India and related neonatal and infant outcomes

OBJECTIVE

To document iodine status in Indian pregnancies, associations with maternal diet and demographics, and offspring developmental measures.

DESIGN

Longitudinal study following mothers through pregnancy and offspring up to 24 months.

SETTING

Rural health-care centre (Vadu) and urban antenatal clinic (Pune) in the Maharashtra region of India.

SUBJECTS

Pregnant mothers at 17 (n 132) and 34 weeks' (n 151) gestation and their infants from birth to the age of 24 months.

RESULTS

Median urinary iodine concentration (UIC) was 203 and 211 μg/l at 17 and 34 weeks of pregnancy, respectively (range 26-800 μg/l). Using the UIC distribution adjusted for within-person variation, extreme UIC quartiles were compared for predictors and outcomes. There was no correlation between UIC at 17 and 34 weeks, but 24 % of those with UIC in the lowest quartile at 17 weeks had UIC in the same lowest quartile at 34 weeks. Maternal educational, socio-economic status and milk products consumption (frequency) were different between the lowest and highest quartile of UIC at 34 weeks. Selected offspring developmental outcomes differed between the lowest and highest UIC quartiles (abdominal circumference at 24 months, subscapular and triceps skinfolds at 12 and 24 months). However, UIC was only a weak predictor of subscapular skinfold at 12 months and of triceps skinfold at 24 months.

CONCLUSIONS

Median UIC in this pregnant population suggested adequate dietary provision at both gestational stages studied. Occasional high results found in spot samples may indicate intermittent consumption of iodine-rich foods. Maternal UIC had limited influence on offspring developmental outcomes.

Iodine deficiency in pregnant women living in the South East of the UK: the influence of diet and nutritional supplements on iodine status

Iodine is a key component of the thyroid hormones which are crucial for brain development. Adequate intake of iodine in pregnancy is important as in utero deficiency may have lifelong consequences for the offspring. Data on the iodine status of UK pregnant women are sparse, and there are no such data for pregnant women in the South East of the UK. A total of 100 pregnant women were recruited to a cross-sectional study carried out at the Royal Surrey County Hospital, Guildford, at their first-trimester visit for an ultrasound scan. The participants provided a spot-urine sample (for the measurement of urinary iodine concentration (UIC) and creatinine concentration) and 24 h iodine excretion was estimated from the urinary iodine:creatinine ratio. Women completed a general questionnaire and a FFQ. The median UIC (85·3 μg/l) indicated that the group was iodine deficient by World Health Organisation criteria. The median values of the iodine:creatinine ratio (122·9 μg/g) and of the estimated 24 h iodine excretion (151·2 μg/d) were also suggestive of iodine deficiency. UIC was significantly higher in women taking an iodine-containing prenatal supplement (n 42) than in those not taking such a supplement (P< 0·001). In the adjusted analyses, milk intake, maternal age and iodine-containing prenatal supplement use were positively associated with the estimated 24 h urinary iodine excretion. Our finding of iodine deficiency in these women gives cause for concern. We suggest that women of childbearing age and pregnant women should be given advice on how to improve their iodine status through dietary means. A national survey of iodine status in UK pregnant women is required.

Therapy of endocrine disease: Impact of iodine supplementation in mild-to-moderate iodine deficiency: systematic review and meta-analysis

BACKGROUND

Although the detrimental effects of severe iodine deficiency are well recognised, the benefits of correcting mild-to-moderate iodine deficiency are uncertain.

OBJECTIVES

We undertook a systematic review of the impact of iodine supplementation in populations with mild-to-moderate iodine deficiency.

METHODS

We searched Medline and the Cochrane library for relevant articles published between January 1966 and April 2013, which investigated the effect of iodine supplementation on maternal and newborn thyroid function, infant neurodevelopment and cognitive performance in school-age children. The quality of studies was graded and eligible trials were evaluated in the meta-analysis.

RESULTS

Nine randomised controlled trials (RCTs) and eight observational studies met the inclusion criteria. Controlled trials on infant neurodevelopment were lacking; gestational iodine supplementation reduced maternal thyroid volume and serum thyroglobulin and in some studies prevented a rise in serum thyroid-stimulating hormone. None of the intervention trials recorded an excess frequency of thyroid dysfunction in contrast to observational studies. A pooled analysis of two RCTs which measured cognitive function in school-age children showed modest benefits of iodine supplementation on perceptual reasoning (standardised mean difference (SMD) 0.55; 95% CI 0.05, 1.04; P=0.03) and global cognitive index (SMD 0.27; 95% CI 0.10, 0.44; P=0.002) with significant heterogeneity between studies.

CONCLUSION

Iodine supplementation improves some maternal thyroid indices and may benefit aspects of cognitive function in school-age children, even in marginally iodine-deficient areas. Further large prospective controlled studies are urgently required to clarify these findings and quantify the risk/benefits of iodine supplementation in regions previously believed to be iodine sufficient such as the UK.

Urinary iodine concentrations of pregnant women in Ukraine

BACKGROUND

Iodine requirements increase during pregnancy and previous studies have reported the inadequate iodine status of pregnant women in areas that have achieved iodine sufficiency in the general population. We examined the urinary iodine (UI) concentrations of pregnant women in Ukraine, where the iodine status is showing improvement among the general population.

METHODS

We enrolled 148 pregnant women<16 weeks pregnant and 80 healthy women as a control group living in Zhitomir, Ukraine. UI concentration, thyroid-stimulating hormone (TSH), antithyroglobulin antibodies (TGAb), and antithyroid peroxidase antibodies (TPOAb) were measured.

RESULTS

The median UI concentrations were significantly lower in pregnant women than in control women [13.0 (ND–51.0) μg/L vs. 62.0 (35.3–108.5) μg/L, p<0.001]. TSH concentrations were significantly lower in pregnant women than in control women [1.7 (1.2–2.7) IU/L vs. 2.2 (1.4–3.1) IU/L, p=0.011], but this difference disappeared when adjusted for age (2.1±0.1 IU/L vs. 2.4±0.2 IU/L, p=0.097). The frequency of TSH over 6.2 IU/L and the frequency of positive TGAb and/or TPOAb were not statistically different between groups (p=0.70 and p=0.48, respectively). The UI concentrations of 142 pregnant women (95.9%) were <150 μg/L indicating insufficient iodine intake.

CONCLUSIONS

The UI concentration of pregnant women in Ukraine revealed severe iodine deficiency. Regular monitoring and appropriate nutrition education are essential because iodine deficiency can be easily prevented by adequate iodine intake. The risk of iodine deprivation during pregnancy needs to be assessed locally over time because it may occur in areas that are not globally recognized as being iodine-deficient.

Gestational changes of thyroid function and urinary iodine in thyroid antibody-negative Japanese women

Iodine is an essential nutrient for thyroid hormone synthesis, and iodine deficiency especially in pregnant and lactating women results in serious damage to their infants. To characterize iodine nutrition throughout gestation by using a food frequency questionnaire (FFQ) and urinary iodine concentration (UIC) measurement, and to establish appropriate gestational age-specific reference ranges for serum TSH and FT₄ in thyroid autoantibody (ThAb) negative euthyroid Japanese women, a total number of 563 pregnant women including 422 subjects with negative ThAbs, 105 postpartum women and their 297 newborn infants were included in the study. Dietary iodine intake (DII) was evaluated by FFQ. Serum TSH, FT₄ and UIC were sequentially determined in the three trimesters of pregnancy and at the 31st postpartum day. The overall median UICs throughout pregnancy and in the postpartum period were 224.0 and 135.0 μg/L, respectively, suggesting sufficient iodine nutrition. The median DII was 842.4 μg/day in pregnant women. The median UIC in the first trimester (215.9 μg/L) significantly decreased in the second trimester (136.0 μg/L). The prevalence of pregnant women with a UIC below 150 μg/L was 31.6% and that in lactating women with a UIC below 100 μg/L was 33.3%. The pattern of gestational change in serum TSH and FT₄ was comparable to that in iodine-sufficient areas. A substantial percentage of women might be at risk for iodine deficiency if there is a restriction of iodine-rich foods. However, iodine supplementation for pregnant women must be carefully balanced against the risk of iodine excess particularly in Japan. Further research in larger samples is needed.

Iodine intake in the adult population. Di@bet.es study

BACKGROUND & AIMS

To date no nation-wide study has yet been undertaken in Spain to estimate the iodine deficiency. The aim was to evaluate iodine intake and its conditioning factors in a representative sample of the whole adult population.

METHODS

The Di@bet.es Study is a national, cross-sectional, population-based survey conducted in 2009-2010 in Spain.

RESULTS

The median urinary iodine (UI) was 117.2 μg/L. Iodized salt (IS) was consumed by 43.9% of the population. The median UI in those who consumed IS and in those who did not consume IS was 131.1 and 110.8 μg/L respectively (p<0.0001). The likelihood of having UI levels above 100 μg/L was significantly associated with the intake of IS (OR=1.47) and milk at least once a day (OR=1.22). Within each individual autonomous communities, the median UI levels in those who consumed IS correlated significantly with the median levels of those who did not consume IS (r=0.76, p=0.001).

CONCLUSIONS

Though strictly speaking, Spain should be considered within the category of a country having an adequate iodine intake, the current value is too close to the cut point and does not guarantee that those groups with a greater need for iodine will have the required intake of iodine.

Value and pitfalls in iodine fortification and supplementation in the 21st century

Although the number of iodine-deficient countries has been reduced by almost 50 % over the last decade, it still remains a frequently misunderstood health problem. The most devastating effects of iodine deficiency occur during fetal development and childhood, periods in which sufficient iodine delivery remains critical. Besides the determination of thyroid size, the concentration of urinary iodine, serum thyroid-stimulating hormone and serum thyroglobulin are useful biomarkers to assess iodine status. Severe iodine deficiency is associated with neurological complications, cretinism, endemic goitre development, hypothyroidism, decreased fertility and increased infant mortality. The recommended iodine supplementation strategies are based on correction of iodine deficiency, close monitoring and evaluation of iodine administration, cooperation of the salt industry, training of local health care professionals and education of the population. Besides the multiple beneficial effects of supplementation, we present in this review a critical look at the possible side effects.

Iodine status of UK schoolgirls: a cross-sectional survey

BACKGROUND

Iodine deficiency is the most common cause of preventable mental impairment worldwide. It is defined by WHO as mild if the population median urinary iodine excretion is 50-99 μg/L, moderate if 20-49 μg/L, and severe if less than 20 μg/L. No contemporary data are available for the UK, which has no programme of food or salt iodination. We aimed to assess the current iodine status of the UK population.

METHODS

In this cross-sectional survey, we systematically assessed iodine status in schoolgirls aged 14-15 years attending secondary school in nine UK centres. Urinary iodine concentrations and tap water iodine concentrations were measured in June-July, 2009, and November-December, 2009. Ethnic origin, postcode, and a validated diet questionnaire assessing sources of iodine were recorded.

FINDINGS

810 participants provided 737 urine samples. Data for dietary habits and iodine status were available for 664 participants. Median urinary iodine excretion was 80·1 μg/L (IQR 56·9-109·0). Urinary iodine measurements indicative of mild iodine deficiency were present in 51% (n=379) of participants, moderate deficiency in 16% (n=120), and severe deficiency in 1% (n=8). Prevalence of iodine deficiency was highest in Belfast (85%, n=135). Tap water iodine concentrations were low or undetectable and were not positively associated with urinary iodine concentrations. Multivariable general linear model analysis confirmed independent associations between low urinary iodine excretion and sampling in summer (p<0·0001), UK geographical location (p<0·0001), low intake of milk (p=0·03), and high intake of eggs (p=0·02).

INTERPRETATION

Our findings suggest that the UK is iodine deficient. Since developing fetuses are the most susceptible to adverse effects of iodine deficiency and even mild perturbations of maternal and fetal thyroid function have an effect on neurodevelopment, these findings are of potential major public health importance. This study has drawn attention to an urgent need for a comprehensive investigation of UK iodine status and implementation of evidence-based recommendations for iodine supplementation.

FUNDING

Clinical Endocrinology Trust.

Iodine sources and iodine levels in pregnant women from an area without known iodine deficiency

OBJECTIVE

An adequate iodine intake during pregnancy is essential for normal development of the foetus. The World Health Organization (WHO) recommends that the median urinary iodine concentration (UIC) in a population of pregnant women should range between 150 and 249 microg/l. The aim of this study was to evaluate iodine status and to examine the main sources of iodine in pregnant women from an apparently iodine-sufficient area.

METHODS

Six hundred pregnant women in the third trimester completed a food frequency questionnaire, and iodine was measured in urine samples. Urinary iodine concentrations were described in the whole population and in subgroups according to their frequency of intake of milk, fish, eggs, bread and iodized salt, as iodine supplements.

RESULTS

The median UIC was 104 microg/l (n = 600), however, the median was higher among women who had a high milk intake (117 microg/l), used iodized salt (117 microg/l) or who were supplemented with iodine (141 microg/l). Women receiving iodine supplementation who also consumed more than one cup of milk per day had median UIC higher than 150 microg/l. In multivariate models, women with moderate and high milk intake had lower risk of having UIC below 150 microg/l [OR (95% CI): 0.42 (0.22-0.82) and 0.29 (0.15-0.55) respectively], after adjustment for potential confounders.

CONCLUSIONS

On the basis of WHO criteria, the iodine status of pregnant women was inadequate in this area. Milk was the most important dietary source of iodine, and iodine supplementation was also an important source of iodine, although not enough to reach the current recommendations.