Iodine-sufficient Populations Research Articles

Normative Values for Thyroid Volume and Tracheal Index in Healthy Turkish Newborns in an Iodine Sufficient Region.

The study aims to determine the normal values of thyroid volume and tracheal index in healthy term newborns born in an iodine-sufficient population. Additionally, we investigated the usability of a handheld device for assessing the tracheal index. Thyroid imaging was performed at 0-2 days and 15-30 days using handheld and portable ultrasound devices. Thyroid volume and tracheal index were calculated using standard formulas. A total of 144 healthy term newborns with a mean birth weight 3230 g were enrolled. The normal thyroid volume for the entire population was 0.66 ± 0.25 ml at 0-2 days, which significantly increased to 1.12 ± 0.33 ml at 15-30 days (p<0.01). There were no significant differences in thyroid volume between genders in either age group (p=0.246 and p=0.879). Thyroid volume correlated with birth weight, length, and head circumference, with the strongest correlation being with birth weight (r=0.404, p<0.001; r=0.252, p=0.002; r=0.223, p=0.007, respectively). The tracheal index at 0-2 days was 1.84±0.30 in girls, 1.82±0.27 in boys, and 1.83±0.29 overall. At 15-30 days, it was 1.99±0.23 in girls, 2.00±0.28 in boys, and 1.99±0.25 overall. Similar to thyroid volume, the tracheal index increased with age (p<0.01), with no significant gender differences in either age group (p=0.593 and p=0.886). Thyroid volume and tracheal index were moderately correlated in both measurements (rho=0.538, p<0.01). Measurements of the trachea, and thyroid lobe widths using portable and handheld ultrasound devices were correlated (r=0.449, p<0.01; r=0.638, p<0.01; r=0.497, p<0.01). There was also a correlation between tracheal index measurements using both devices in both the first and second measurements. This study provides normative data on thyroid volumes and tracheal index in newborns from an iodine-sufficient population. The tracheal index can estimate thyroid size when volume calculation is not feasible and handheld ultrasound devices are effective for this assessment.

Thyroid Function Test in Preterm Neonates: Normative Data.

Initial surge of thyroid-stimulating hormone (TSH) in neonates increases free and total triiodothyronine (T3) and tetraiodothyronine (T4) in 24-36 hours following birth, and the effect then gradually wanes off. As somatic and intellectual development is dependent on normal thyroid function especially in infancy, normative data in these children may be of immense value to diagnose hypothyroidism in this subset of infants. Comprehensive normative values of thyroid function parameters in preterm neonates are scarcely available. The objective of this study was to determine the normative value of thyroid function parameters in preterm neonates. Preterm neonates (n = 102) born at 34 and 35 weeks of gestation of euthyroid mothers from an iodine-sufficient population were evaluated for T3, T4, free thyroxine (FT4) and TSH during 3-7 days after birth and again after 1 month. The expected date of delivery (EDD) and Ballard score were used to identify the duration of gestation. The mean gestational age was 34.7 ± 0.41 weeks. The mean (± SD) for T3 (ng/dl), T4 (μg/dl), FT4 (ng/ml) and TSH (μIU/ml) on days 3-7 following birth was as follows: 156 ± 44.6, 12.8 ± 3.7, 1.50 ± 0.54 and 7.13 ± 6.04, respectively. Around 4 weeks of age, values changed to 104 ± 38.4, 12.1 ± 4.02, 1.46 ± 0.42 and 3.25 ± 2.85, respectively. All parameters changed significantly around 4 weeks, except FT4. None of the parameters were correlated with gestational age or body weight at birth. Normative values for each parameter in percentiles were generated. This study generated the normative values of the thyroid function test during the first week and after around 4 weeks of life for premature neonates (born at 34-35 weeks).

Thyroid volume in Turkish school-age children living in an iodine-sufficient region.

We aimed to obtain local normative data on thyroid volume evaluated by ultrasonography and iodine status by measuring urine iodine levels in school-age children living in Aydın province. In this cross-sectional study, a sample comprising 1,553 cases was meticulously selected from a total cohort of 170,461 children aged 6-17, drawn from 21 distinct educational institutions located within the Aydın region, as participants in the investigation. Those with a known chronic disease or thyroid disease were excluded from the study. The children underwent physical examinations and ultrasonography imaging of the thyroid gland, and urine samples were collected to measure urinary iodine concentration (UIC). The median UIC was 189.5 (IQR=134.4) μg/L, which was optimal according to WHO criteria. Thyroid volume was found to be 4.6 (IQR=3.5) mL in girls and 4.2 (IQR=4.0) mL in boys (p=0.883). The thyroid volumes in our study were found to be smaller when compared to the WHO. According to WHO age and body surface area criteria, thyroid volume was over 97 % in 0.9 % (n=15) of cases. Thyroid volume was found to have a positive correlation with age, height, weight, body mass index (BMI), and body surface area (BSA) in both genders (p<0.001). However, there was no significant correlation between thyroid volume and UIC. This cross-sectional study provides normative data on thyroid volume and iodine status in school-age children in iodine-sufficient population, revealing a low prevalence of goiter and correlations between thyroid volume and anthropometric measures.

Too Much Too Little: Clarifying the Relationship Between Maternal Iodine Intake and Neurodevelopmental Outcomes

BackgroundIn 2009, the Australian government mandated the fortification of bread salt with iodine. In 2010, pregnant and lactating women were also advised to take an iodine-containing supplement. Our assessment of this policy in an iodine-sufficient population showed that children whose mothers were in the highest and lowest quartiles of iodine intake performed more poorly on early childhood tests of cognition and language than those in the second quartile. However, we did not quantify the iodine intake associated with optimal neurodevelopment. ObjectivesThe aim was to establish the iodine intake range in pregnancy associated with optimal child neurodevelopment. MethodsA prospective cohort study of pregnant women and their young children (n = 699). Iodine intake was assessed by a validated food frequency questionnaire at 16 and 28 wk of gestation. Child neurodevelopment at 18 mo of age was measured using the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III). The relationship between average iodine intake during pregnancy and child neurodevelopment was assessed using linear regression with fractional polynomials and adjustment for confounders. ResultsMean (SD) iodine intake was similar at study entry and 28 wk, 308 (120) μg/d, with 82% of women taking iodine supplements at study entry. The relationship between iodine intake during pregnancy and Bayley-III cognitive and language scores was curvilinear (P = 0.001 and P = 0.004, respectively), with the lowest Bayley-III scores observed at lower and higher iodine intakes. The inflection point that drove the association between lower iodine intake in pregnancy and poorer child neurodevelopment scores was around 185 μg/d; for the higher pregnancy iodine intakes, language and cognitive scores were negatively affected from ∼350 μg/d to 370 μg/d, respectively. Higher iodine intakes were being driven by supplement use. ConclusionsTargeted, not blanket, iodine supplementation may be needed for pregnant women with low-iodine intake from food.

An iodine balance study in Chinese school-age children.

Few iodine balance studies have been conducted in school-age children. This study aimed to conduct an iodine balance study in school-aged children. We measured daily iodine intake, excretion, and retention for three consecutive days without any dietary interventions in school-age children. Linear mixed-effects models were used to fit the relationship between total iodine intake (TII) and iodine retention (IR). 29 children aged 7-12 years (mean age 10.2 ± 1.4 years) with normal thyroid function and thyroid volume (Tvol) were recruited. The zero balance value (iodine intake = iodine excretion, iodine retention = 0 μg/d) shifted with iodine intake in an iodine sufficient population. The zero balance value for school-aged children with an iodine intake of 235 (133, 401) μg/d is 164 μg/d. Children aged 7-12 years with iodine intake >400 μg/d were almost in a positive iodine state. An iodine intake of 235 (133, 401) μg/d for children aged 7-10 years achieved a zero balance value of 164 μg/d. Long-term iodine intake of >400 μg/d is not recommended.

Iodine status of pregnant women in iodine-sufficient regions: A tertiary care unit experience.

The recommended urinary iodine concentration (UIC) levels in the overall adult population is 100-199 μg/L whereas 150-249 μg/L in pregnant women. The objective is to determine the prevalence and severity of iodine deficiency in pregnant women in Amasya, which is located in the Western Black Sea region in Turkey, where sufficient iodine levels were achieved in the normal population. In this single-center study, we retrospectively searched hospital patient records and identified pregnant women who were assessed for iodine levels between January 2019 and January 2021. A total of 408 pregnant women were found eligible for the study. Thyroid-stimulating hormone (TSH), free triiodothyronine, free thyroxine, antithyroid peroxidase antibodies, and antithyroglobulin antibodies in serum samples and UIC were evaluated and compared between the trimesters. Insufficient iodine intake in pregnancy was defined as UIC <150 μg/L. Median UIC and median TSH levels were 129 (range 45-452) μg/L and 2.98 (range 0.01-71.2) μIU/ml, respectively. 81.1% of pregnant women had UIC <150 μg/L. Iodine intake was adequate in 17.4% of pregnant whereas excessive in 1.5%. Prevalence of iodine deficiency during 1st, 2nd, and 3rd trimesters were 82.1%, 82.4%, and 74.5%, respectively. There was no significant difference in UIC levels between trimesters (P = 0.399). 72.9% of pregnant womens had TSH >2.5 mIU/L in the 1st trimester. Iodine deficiency in pregnancy may exist in an iodine-sufficient population. Appropriate measures must be taken to ensure sufficient iodine levels in these individuals.

Assessment of Iodine Concentration in Human Milk from Donors: Implications for Preterm Infants.

Preterm infants are particularly vulnerable to developing iodine deficiency. Donor human milk (DHM) is the preferred feeding option if the mother’s own milk (MOM) is not available, but information on DHM iodine concentration (DHMIC) is lacking. Hence, we aimed to assess DHMIC to further evaluate the adequacy of iodine provision in preterm infants. Finally, associations that might influence DHMIC were studied. In 113 donors, we measured iodine intake by evaluating dietary records for five consecutive days with the DIAL® Software. From the second day of dietary record, donors provided human milk samples (at least one per day) for four consecutive days. Daily human milk samples were analyzed for DHMIC. A DHMIC ≥ 200 µg/L was considered an adequate iodine content for preterm infants. DHMIC and urine iodine concentration (UIC) were determined using ICP-MS. In our study, 83.2% of donors had a full-term infant. Breastfeeding time range was 1.5–49.4 months. During the dietary record, 55.8% took iodine-containing supplements, providing 40–200 µg/day of iodine. The medians (p25, p75) UIC and DHMIC were 112.4 (75.8, 160.1) and 148.5 (97.6, 206.1) µg/L, respectively. In this iodine-sufficient population, 70% had a DHMIC of <200 µg/L. Donors’ intake of iodine-containing supplements was associated with higher DHMIC.

Neonatal TSH as a marker of iodine nutrition status. Effect of maternal ioduria and thyroid function on neonatal TSH

IntroductionNeonatal thyroid stimulating hormone (nTSH) is a marker of iodine nutrition status in the population. The WHO considers a prevalence of less than 3% of nTSH levels greater than 5 mIU/L in samples obtained within 72h from birth indicative of iodine sufficiency. The aim of this study was to determine the prevalence of nTSH levels greater than 5 mIU/L in an iodine-sufficient population and its association with maternal, neonatal and obstetric factors. Materials and methodsA total of 243 pregnant women were recruited between May and June 2017 in our health area. A questionnaire of iodine intake was administered, in addition to determination of ioduria, thyroid function and autoimmunity in the first trimester of gestation. We analysed nTSH levels in samples collected between 48 and 72h post birth and other obstetric and neonatal factors. ResultsThe mean nTSH level (standard deviation) was 2.43 (1.68 mIU/L), with 7.8% of neonates having levels greater than 5 mIU/L. The highest nTSH levels corresponded to neonates of mothers with insufficient ioduria (P = 0.021) or TSH levels greater than 2.5 mIU/L, in both the case of negative (P = 0.049) and positive (P = 0.006) thyroid autoimmunity results. Maternal ioduria less than 150 μg/L was a risk factor for nTSH levels greater than 5 mIU/L (3.70 [1.06−14.60]; P = 0.046), while a neonatal weight of 2500 g or greater was a protective factor (0.14 [0.02−1.00]; P = 0.038). ConclusionsThe prevalence of nTSH levels greater than 5 mIU/L in our health area was high based on the WHO recommendations. Maternal iodine deficiency was associated with a higher risk of nTSH levels greater than 5 mIU/L. Given that nTSH is currently measured before 72h post birth, we need new cut-off points to keep on using nTSH as a marker of iodine nutritional status.

TSH neonatal como marcador del estado de nutrición de yodo. Influencia de la yoduria y la función tiroidea maternas sobre la TSH neonatal

IntroductionNeonatal thyroid stimulating hormone (nTSH) is a marker of iodine nutrition status in the population. The WHO considers a prevalence of less than 3% of nTSH levels greater than 5mIU/L in samples obtained within 72h from birth indicative of iodine sufficiency. The aim of this study was to determine the prevalence of nTSH levels greater than 5mIU/L in an iodine-sufficient population and its association with maternal, neonatal and obstetric factors. Materials and methodsA total of 243 pregnant women were recruited between May and June 2017 in our health area. A questionnaire of iodine intake was administered, in addition to determination of ioduria, thyroid function and autoimmunity in the first trimester of gestation. We analysed nTSH levels in samples collected between 48 and 72h post birth and other obstetric and neonatal factors. ResultsThe mean nTSH level (standard deviation) was 2.43 (1.68mIU/L), with 7.8% of neonates having levels greater than 5mIU/L. The highest nTSH levels corresponded to neonates of mothers with insufficient ioduria (p=.021) or TSH levels greater than 2.5mIU/L, in both the case of negative (p=0.049) and positive (p=0.006) thyroid autoimmunity results. Maternal ioduria greater than 150μg/L was a risk factor for nTSH levels greater than 5mIU/L (3.70 [1.06–14.60]; p=0.046), while a neonatal weight of 2500g or greater was a protective factor (0.14 [0.02–1.00]; p=0.038). ConclusionsThe prevalence of nTSH levels greater than 5mIU/L in our health area was high based on the WHO recommendations. Maternal iodine deficiency was associated with a higher risk of nTSH levels less than 5mIU/L. Given that nTSH is currently measured before 72h post birth, we need new cut-off points to keep on using nTSH as a marker of iodine nutritional status.

New Reference Values for Thyroid Volume and a Comprehensive Assessment for Influencing Factors in Chinese Adults with Iodine Sufficiency

Objectives: The reference values for thyroid volume (Tvol) determined by ultrasound require supportive data of normal Tvol from local iodine-sufficient populations. This study aimed to explore new reference values for Tvol in Chinese adults and comprehensively evaluate the factors associated with enlarged Tvol. Methods: A cross-sectional study was conducted in Tianjin, China. Tvol was measured by ultrasound in adults with long-term iodine sufficiency. Blood and urine samples were collected to evaluate biochemical indexes, thyroid function, and iodine status. Results: A total of 1,991 adults from the urban and suburban areas were analysed. The trend of Tvol increasing with age was observed in men under age 40 years and in women under age 52 years. In the quantile regression analyses, we found that body surface area (BSA) (β = 7.22, 95% CI: 5.33, 9.12), thyroid-stimulating hormone (TSH) (β = −1.48, 95% CI: −2.39, −0.57), thyroid nodules (TNs) (β = 6.70, 95% CI: 2.19, 11.22), and metabolic syndrome (MetS) (β = 1.40, 95% CI: 0.63, 2.17) had a strong effect on Tvol at higher percentiles in males. The dominant factors influencing Tvol were BSA (β = 9.64, 95% CI: 2.66, 16.61), TSH (β = −0.78, 95% CI: −1.16, −0.39), and TNs (β = 1.11, 95% CI: 0.43, 1.79) in females. The largest reference values for Tvol based on BSA were 20.18 (17.79, 24.32) mL in males and 15.31 (14.05, 16.70) mL in females. Conclusions: Quantile regression analyses showed that a high BSA index, a decreased TSH level, and the prevalence of TNs were essential factors associated with the enlargement of the thyroid gland. Our findings reported the new reference values for Tvol determined by ultrasound based on gender and BSA in Chinese adults.

Reference Intervals for Serum Thyroid-Stimulating Hormone Based on a Recent Nationwide Cross-Sectional Study and Meta-Analysis.

ObjectiveThe aim of our study was to compare the reference intervals (RIs) [median (2.5th-97.5th percentiles)] for thyroid-stimulating hormone (TSH) between subgroups stratified by ethnicity and iodine status in a global context.Design and MethodsPrimary data were derived from a recently published cross-sectional study in mainland China. Secondary data were obtained from online databases. The RIs for TSH were calculated in the reference population according to the National Academy of Clinical Biochemistry (NACB) standard and in the disease-free population. A meta-analysis of ethnicity- and iodine status-specific TSH RIs was performed.ResultsThe primary data showed that the TSH RI (mU/L) in the disease-free population was 2.33 (0.67, 7.87), which is wider than the published RI [2.28 (0.74, 7.04)] in the reference population. The meta-analysis showed that whether in the reference or disease-free population, the RIs in Yellows were much higher than those in Caucasians. In the reference population, the median and 2.5th percentile in the iodine-sufficient subgroup were both lower than the iodine-deficient or more-than-adequate subgroup, while the 97.5th percentile showed a positive trend with increasing sufficiency of iodine. However, in the disease-free population, the iodine-sufficient subgroup had a lower median and 97.5th percentile but higher 2.5th percentile than the iodine-deficient subgroup.ConclusionYellows have a higher TSH RI than Caucasians. In the reference population, both the median and 2.5th percentile TSH in the iodine-sufficient population were the lowest among the different iodine status subgroups, while the 97.5th percentile of TSH showed an upward trend with increasing iodine sufficiency.

Association Between Newborn Thyroid-Stimulating-Hormone Concentration and Neurodevelopment and Growth: a Systematic Review.

Iodine nutrition during pregnancy can affect newborn thyroid-stimulating-hormone concentration (TSH). Associations of newborn TSH with the neurodevelopment and growth of children are inconsistent. The aim of the study was to systematically review the literature on the associations between newborn TSH and childhood neurodevelopment and growth. Databases including PubMed, Scopus, CINAHL, Embase, PsycINFO, WHO, and Iodine Global Network were searched for eligible studies. Seventeen studies were included. Neurodevelopment was assessed using different tools in children aged 1-12 years of age. The associations between newborn TSH and cognitive development were negative in studies from iodine deficient populations, while a nullassociation was found in studies from iodine sufficient populations. A nullassociation between TSH and psychomotor development was observed regardless of iodine status of the study populations. There was no evidence of an association between newborn TSH and child anthropometry, but evidence of negative association was found between newborn TSH and birthweight. Although the associations between newborn TSH and neurodevelopment may differ based on the iodine status of populations, most of the included studies did not adjust for the key confounders and had a small sample size. Quality data-linkage studies that utilize newborn TSH data from newborn screening with adequate adjustment for potential confounders are warranted to better understand the relationship between newborn TSH and neurodevelopment and growth in children. CRD42020152878.

Consequences of Iodine Deficiency and Excess in Pregnancy and Neonatal Outcomes: A Prospective Cohort Study in Rio de Janeiro, Brazil.

Background: Insufficient or excessive iodine intake during gestation may compromise adaptive mechanisms in maternal thyroid function and lead to adverse pregnancy outcomes. In this context, we aimed to study the effects of maternal iodine status in the first and third trimesters of gestation on obstetric and neonatal outcomes in an iodine-sufficient population in Rio de Janeiro, Brazil. Methods: A total of 214 pregnant women in the first trimester of gestation were enrolled and prospectively followed until delivery between 2014 and 2017. All participants were ≥18 and ≤35 years, had a spontaneous single pregnancy, and had no history of thyroid or other chronic diseases, nor were they taking iodine-containing supplements at enrollment. In the first trimester, we obtained clinical information and determined thyroid function and the urinary iodine concentration (UIC) of the participants. Thyroid function and UIC were reassessed in the third trimester. Iodine status was determined by the median of UIC obtained from six urine spot samples by the inductively coupled plasma mass spectrometry method. Pregnancy and neonatal outcomes and delivery information were obtained from medical records. Results: The median UIC in the whole population was 219.7 μg/L. The prevalence of UIC <150 μg/L was 17.2%, and 38.7% had UIC ≥250 μg/L. Gestational diabetes (GDM) was higher in the group with UIC 250-499 μg/L (n = 77) compared with the group with UIC 150-249 μg/L (n = 94) (20.3% vs. 9.7%, p < 0.05). Ultimately, UIC ≥250 μg/L was an independent risk factors for GDM (relative risk [RR] = 2.9 [confidence interval, CI = 1.1-7.46], p = 0.027) and hypertensive disorders of pregnancy (HDP) (RR = 4.6 [CI = 1.1-18.0], p = 0.029). Among 196 live-born newborns, lower birth length was observed in infants whose mothers had UIC <150μg/L (n = 37) in the first trimester compared with those with UIC 150-249 μg/L (n = 86) (median interquartile range: 48.0 [2.2] vs. 49.0 [4.0] cm, p = 0.01). Maternal UIC <150 μg/L was negatively associated with birth length of newborns (Exp (B) = 0.33 [CI = 0.1-0.9], p = 0.03). Conclusions: In a population whose median iodine intake is sufficient, extensive individual variation occurs. Such abnormalities are associated with increased GDM and HDP when UIC is ≥250 μg/L, and lower infant birth length when UIC is <150 μg/L.

Long-Term Variations of Antithyroperoxidase Antibodies and its Clinical Significance.

Various cut-offs have been proposed for thyroid peroxidase antibodies (TPOAb) positivity. Considering that the long-term trend of TPOAb levels and its positivity incidence is not clearly understood, we conducted the current study to determine the longitudinal variations of TPOAb in a population-based cohort study. We followed 5783 individuals of Tehran Thyroid cohort Study (TTS) for 10 years (4 phases). After exclusions, data of 3493 euthyroid participants remained for analyses. The baseline prevalence rates of TPOAb positivity were 19.8, 17, and 11.4% and the annual incidence rates (95% CI) of TPOAb positivity were 8.53 (8.29-8.77), 7.59 (7.37-7.80) and 6.79 (6.60-6.98) per 1000 persons for the 3 proposed cut-offs of 14.77, 18.38, and 40 U/l; respectively. Although a slightly increasing trend was observed for TPOAb levels (p=0.001) and its conventional positivity (TPOAb>40U/l), the recently proposed cut-offs of 14.77 and 18.38 U/l showed constant TPOAb positivity over 10 years. The time trends of the TPOAb levels among younger participants were significantly different from older participants (time×age effect p=0.004), with the former having an increasing trend and the latter, a relatively decreasing trend. Although the prevalence of TPOAb positivity was significantly (p<0.001) higher among women as compared to men, the longitudinal changes of TPOAb were similar in men and women. TPOAb positivity along with TSH values between 2.5 and 5.0 mU/l or free T4 values between 0.93 and 1.7 ng/dl exerted a significantly increased risk of subclinical or overt hypothyroidism. In an iodine sufficient population, an increasing trend in TPOAb levels was observed in line with the increasing incidence of subclinical and overt hypothyroidism.

Association Between Maternal Iodine Intake in Pregnancy and Childhood Neurodevelopment at Age 18 Months.

There are limited and inconsistent data suggesting that mild iodine deficiency in pregnancy might be associated with poorer developmental outcomes in children. Between 2011 and 2015, we conducted a prospective cohort study in Australia examining the relationship between maternal iodine intake in pregnancy and childhood neurodevelopment, assessed using Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III), in 699 children at 18 months. Maternal iodine intake and urinary iodine concentration (UIC) were assessed at study entry (<20 weeks' gestation) and at 28 weeks' gestation. Maternal iodine intake in the lowest (<220 μg/day) or highest (≥391 μg/day) quartile was associated with lower cognitive, language, and motor scores (mean differences ranged from 2.4 (95% confidence interval (CI): 0.01, 4.8) to 7.0 (95% CI: 2.8, 11.1) points lower) and higher odds (odds ratios ranged from 2.7 (95% CI: 1.3, 5.6) to 2.8 (95% CI: 1.3, 5.7)) of cognitive developmental delay (Bayley-III score <1 SD) compared with mothers with an iodine intake in the middle quartiles. There was no association between UIC in pregnancy and Bayley-III outcomes regardless of whether UIC and the outcomes were analyzed as continuous or categorical variables. Both low and high iodine intakes in pregnancy were associated with poorer childhood neurodevelopment in this iodine-sufficient population.

Breast Milk Iodine Concentration Is a More Accurate Biomarker of Iodine Status Than Urinary Iodine Concentration in Exclusively Breastfeeding Women

BackgroundIodine status in populations is usually assessed by the median urinary iodine concentration (UIC). However, iodine is also excreted in breast milk during lactation; thus, breast milk iodine concentration (BMIC) may be a promising biomarker of iodine nutrition in lactating women. Whether the mammary gland can vary fractional uptake of circulating iodine in response to changes in dietary intake is unclear. ObjectiveWe evaluated UIC and BMIC as biomarkers for iodine status in lactating women with a wide range of iodine intakes. MethodsWe recruited 866 pairs of lactating mothers and exclusively breastfed infants from 3 iodine-sufficient study sites: Linfen, China (n = 386); Tuguegarao, Philippines (n = 371); and Zagreb, Croatia (n = 109). We also recruited iodine-deficient lactating women from Amizmiz, Morocco (n = 117). We collected urine and breast milk samples and measured UIC and BMIC. ResultsIn the 3 iodine-sufficient sites, a pooled regression analysis of the estimated iodine excretion revealed higher fractional iodine excretion in breast milk than in urine at borderline low iodine intakes. In contrast, in the iodine-deficient site in Morocco, a constant proportion (∼33%) of total iodine was excreted into breast milk. ConclusionsIn iodine-sufficient populations, when iodine intake in lactating women is low, there is increased partitioning of iodine into breast milk. For this reason, maternal UIC alone may not reflect iodine status, and BMIC should also be measured to assess iodine status in lactating women. Our data suggest a BMIC reference range (2.5th and 97.5th percentiles) of 60–465 μg/kg in exclusively breastfeeding women. This trial was registered at clinicaltrials.gov as NCT02196337.

Status of Iodine Nutrition among Pregnant Women Attending Antenatal Clinic of a Secondary Care Hospital: A Cross-sectional Study from Northern India.

Background:Daily requirement of iodine increases during pregnancy making pregnant women a high-risk group for iodine deficiency disorders. The limited available literature shows that even in iodine sufficient population, pregnant women are iodine deficient.Objective:The objective of this study is to assess the current iodine nutrition status among pregnant women in Ballabgarh, district Faridabad, Haryana.Materials and Methods:Pregnant women were recruited from antenatal clinic (ANC) of subdistrict hospital (SDH), Ballabgarh, Haryana. Consecutive sampling strategy was followed to recruit pregnant women, and women of all trimesters were included in the study. Urinary iodine estimation was done using simple microplate method, and salt iodine was estimated using iodometric titration. The study was approved by Institute Ethics Committee, All India Institute of Medical Sciences (AIIMS), New Delhi.Results:Out of the total 1031 pregnant women, 90.9% were using adequately iodized salt. Median (interquartile range [IQR]) salt consumption by the pregnant women was 8.3 (6.7, 11.1) g/day. Median (IQR) urinary iodine concentration (UIC) for the pregnant women was 260 (199, 323) μg/L. Only 13.5% of pregnant women had insufficient iodine intake (UIC <150 μg/L). There was no significant difference in median UIC values by household salt iodine content and across three trimesters of pregnancy.Conclusion:Iodine nutrition status of the pregnant women attending ANC clinic of SDH Ballabgarh was adequate with attainment of universal salt iodization goal of >90% adequately iodized salt coverage in the study population.

MANAGEMENT OF ENDOCRINE DISEASE: Isolated maternal hypothyroxinemia during pregnancy: knowns and unknowns.

Isolated maternal hypothyroxinemia (IMH) during pregnancy is defined as a low maternal T4 in the absence of TSH elevation. As IMH is common, with a prevalence of 1-2% in iodine-sufficient populations, and early research has suggested adverse effects on fetal neurodevelopment, it has been the focus of many studies in the last decade. In the current review, we first discuss the significance of IMH based on data from animal models and recent discoveries regarding the role of thyroid hormone on neurodevelopment. We address issues surrounding the definition and prevalence of this entity and discuss new insights into the etiologies, clinical consequences and management of IMH. A number of large cohort studies have investigated the effects of IMH on the risk of various pregnancy complications and child neurodevelopment. We review these studies in detail and describe their limitations. We discuss the available research on management of IMH, including two recent randomized controlled trials (RCTs). Finally, we delineate the remaining uncertainties in this field and emphasize the need for a sufficiently powered, placebo-controlled RCT on the treatment of IMH early in the first trimester of pregnancy.

Sex- and Age-Specific Reference Values and Cutoff Points for TPOAb: Tehran Thyroid Study.

Current guidelines used for establishing reference intervals for thyroid peroxidase antibodies (TPOAb), recommended by the National Academy of Clinical Biochemistry, have been a matter of controversy. The present study sought to determine TPOAb reference intervals for different age and sex groups, as well as the TPOAb cutoff points for subclinical and overt hypothyroidism in an iodine-sufficient population. This cross-sectional study was conducted within the framework of the prospective Tehran Thyroid Study (TTS), in which 4174 healthy euthyroid individuals were followed for 10 years. Thyroid function tests and TPOAb were assessed. The mean age ± standard deviation of participants was 39.3 ± 15.2 years. Estimated reference intervals for TPOAb corresponding to the 2.5th and 97.5th percentiles were 1.5-32.8 and 2.1-35 IU/mL in males and females, respectively. There were no significant variations in the different age groups in either sex. The optimal cutoff points for TPOAb were 18.38 and 14.77 IU/mL for predicting clinical and subclinical hypothyroidism, respectively. This study establishes the reference intervals and the optimal cutoff points for TPOAb in an iodine-sufficient population.

Larger Thyroid Volume and Adequate Iodine Nutrition in Chinese Schoolchildren: Local Normative Reference Values Compared with WHO/IGN.

Objective. Thyroid volume measured by ultrasound to define goiter needs reliable local thyroid volume reference from iodine-sufficient populations. The aim of this study is to explore the reference interval for normal thyroid volume in schoolchildren aged 8–10 years from Zhejiang Province, China. Methods. A probability-proportionate-to-size sampling method was applied to select a representative sample of 1213 children aged 8–10 years in Zhejiang Province to detect the thyroid volume, salt iodine, and urine iodine. Results. Median urinary iodine concentration in involved schoolchildren was 178.30 (125.00) μg l−1, with the percentage of samples less than 100 μg l−1 as 12.69% and more than 300 μg l−1 as 15.25%. Thyroid volume was significantly correlated with age and anthropometric measurements independently of each other. The 97th percentile of thyroid volume in our study was larger generally than the new international reference. Conclusions. The iodine nutritional status in Zhejiang Province was at an adequate level. Despite some limitations in this study, we initially established the reference values for thyroid volume in 8–10-year-old schoolchildren in Zhejiang Province, China, as a local reference to be used for monitoring iodine deficiency disorders.