Iodine Sufficiency Research Articles

8046 Milk Provision as a Potential Intervention to Improve Iodine Status in a Pregnant Cohort in Northern Ireland (NI), UK: A Randomised Controlled Trial

Abstract Disclosure: L.R. Kayes: None. K.R. Mullan: None. J.V. Woodside: None. Iodine deficiency is the leading cause of reversible mental retardation worldwide. During pregnancy there is ∼50% increase in iodine requirement for foetal neurodevelopment. The most recently studied cohorts of pregnant women across Ireland and UK consistently demonstrated mild iodine deficiency (target median urinary iodine concentration (mUIC) ≥150 µg/L). A recent study in NI has shown that women of child-bearing age provided with three litres of cow’s milk per week had improved iodine status. We wished to explore whether a similar milk intervention might improve iodine status during pregnancy. Pregnant women were recruited at their first antenatal appointment, and all were provided with the British Dietetic Association’s iodine food fact sheet. Participants were randomised to either milk intervention, (four litres/week milk delivered weekly free of charge), or no milk delivery (control group). Patients were stratified based on use of an iodine-containing multivitamin prior to randomisation. Urine was collected at recruitment, after 12-week intervention period, in the third trimester and 6-12 weeks postnatally along with an infant urine sample when possible. A total of 55 urine samples were collected from infants. A total of 118 women were recruited. Participants had a mean age of 32 years, (range 21 - 45) with a mean BMI of 27.5 kg/m2. Mean gestational age was 12 weeks (IQR 12-13 weeks). The mUIC in the whole group women was 53.2 µg/L in the first trimester. In the control group the mUIC at the first study visit (n=59) was 93.4 µg/L (22% achieving iodine sufficiency); at the second visit (n=38), the mUIC was 158.7 µg/L with 34% achieving sufficiency. In the milk group the mUIC at the first study visit (n=59) was 82.0 µg/L with 10% achieving sufficiency (no statistical significance between groups, p=0.08); at the second visit (n=43), mUIC was 154.7 µg/L with 37% achieving sufficiency (no statistical difference between groups p=0.78). The mean change in UIC between the first and second trimesters was 44.5 and 88.1 µg/L in the control and milk arms respectively (p=0.27). In this cohort, 71.4% of women reported taking an iodine-containing multivitamin in the first trimester of pregnancy with no difference between group randomised to milk intervention (p=0.95). In the infants, mUIC was 124.1 µg/L with no statistically difference in the proportion reaching iodine sufficiency according to maternal randomisation (p=0.64) or maternal use of an iodine-containing multivitamin (p=0.95). In this cohort, there was no significant improvement in mUIC in those receiving a milk intervention. Presentation: 6/1/2024

8046 Milk Provision as a Potential Intervention to Improve Iodine Status in a Pregnant Cohort in Northern Ireland (NI), UK: A Randomised Controlled Trial

Abstract Disclosure: L.R. Kayes: None. K.R. Mullan: None. J.V. Woodside: None. Iodine deficiency is the leading cause of reversible mental retardation worldwide. During pregnancy there is ∼50% increase in iodine requirement for foetal neurodevelopment. The most recently studied cohorts of pregnant women across Ireland and UK consistently demonstrated mild iodine deficiency (target median urinary iodine concentration (mUIC) ≥150 µg/L). A recent study in NI has shown that women of child-bearing age provided with three litres of cow’s milk per week had improved iodine status. We wished to explore whether a similar milk intervention might improve iodine status during pregnancy. Pregnant women were recruited at their first antenatal appointment, and all were provided with the British Dietetic Association’s iodine food fact sheet. Participants were randomised to either milk intervention, (four litres/week milk delivered weekly free of charge), or no milk delivery (control group). Patients were stratified based on use of an iodine-containing multivitamin prior to randomisation. Urine was collected at recruitment, after 12-week intervention period, in the third trimester and 6-12 weeks postnatally along with an infant urine sample when possible. A total of 55 urine samples were collected from infants. A total of 118 women were recruited. Participants had a mean age of 32 years, (range 21 - 45) with a mean BMI of 27.5 kg/m2. Mean gestational age was 12 weeks (IQR 12-13 weeks). The mUIC in the whole group women was 53.2 µg/L in the first trimester. In the control group the mUIC at the first study visit (n=59) was 93.4 µg/L (22% achieving iodine sufficiency); at the second visit (n=38), the mUIC was 158.7 µg/L with 34% achieving sufficiency. In the milk group the mUIC at the first study visit (n=59) was 82.0 µg/L with 10% achieving sufficiency (no statistical significance between groups, p=0.08); at the second visit (n=43), mUIC was 154.7 µg/L with 37% achieving sufficiency (no statistical difference between groups p=0.78). The mean change in UIC between the first and second trimesters was 44.5 and 88.1 µg/L in the control and milk arms respectively (p=0.27). In this cohort, 71.4% of women reported taking an iodine-containing multivitamin in the first trimester of pregnancy with no difference between group randomised to milk intervention (p=0.95). In the infants, mUIC was 124.1 µg/L with no statistically difference in the proportion reaching iodine sufficiency according to maternal randomisation (p=0.64) or maternal use of an iodine-containing multivitamin (p=0.95). In this cohort, there was no significant improvement in mUIC in those receiving a milk intervention. Presentation: 6/1/2024

Correlation of offspring thyroid function and maternal iodine status in iodine deficient-coastal area

Thyroid hormone is vital for children's growth and metabolism, relying on sufficient iodine levels for synthesis. Maternal intake determines iodine supply to fetuses and children under two years old. This study aimed to correlate offspring thyroid function with maternal iodine status in coastal areas. A cohort study was conducted, involving pregnant coastal residents. Maternal urinary iodine levels were measured via the ammonium persulfate method, while offspring thyroid stimulating hormones (TSHs) and free thyroxine hormone (fT4) levels were assessed using electro-chemiluminescence immunoassay (ECLIA). Iodine intake was determined through a semiquantitative food frequency questionnaire (FFQ). The correlation between offspring thyroid function and maternal iodine status was analyzed using Pearson’s correlation test. Differences in TSHs and fT4 levels among iodine status groups were examined using the One way-ANOVA test. Maternal iodine status was insufficient with a median urinary iodine of 125 μg/L, resulting in a 60.8% prevalence of iodine insufficiency. Iodine intake (62.20±43.45 μg/day) fell short of recommended levels (RDA). Offspring TSH was 2.29±1.07 μIU/mL, fT4 was 1.26±0.14 ng/dL. TSH and fT4 concentrations showed no significant inter-group differences (p=0.852, p=0.075). Offspring thyroid function did not correlate with maternal iodine status (TSHs: p=0.314; fT4: p=0.258). Offspring thyroid function did not correlate to maternal iodine status in a population of iodine-insufficient and mercury-contaminated coastal areas.

Midwives and public health nurses’ knowledge and clinical practice in securing sufficient iodine status in relation to pregnancy: A cross-sectional study

Midwives and public health nurses’ knowledge and clinical practice in securing sufficient iodine status in relation to pregnancy: A cross-sectional study

Hipotiroidismo

Hypothyroidism is one of the most prevalent endocrine diseases in routine clinical practice. The most common etiology worldwide is iodine deficiency. In countries with sufficient iodine intake, it is Hashimoto's thyroiditis. In this sense, it is important to take an adequate case history and physical examination for a diagnosis, although confirmation is determined by biochemical analysis. The universal screening protocol consists of the initial TSH measurement and, in case of abnormal values, FT4 measurement. The normal limits for TSH are controversial and continue to be the subject of debate today. They have associated conditioning factors such as pregnancy or the normal limit in the older adult population. Replacement therapy is not always indicated, but when it is, oral levothyroxine is the treatment of choice.

The ongoing quest for worldwide iodine sufficiency

The ongoing quest for worldwide iodine sufficiency

Iodine Metabolism in Urine and Breast Milk among Lactating Women with Adequate Iodine

BackgroundIn lactating women, iodine metabolism is regulated and maintained by the kidneys and mammary glands. Limited research exists on how iodine absorbed by lactating women is distributed between the kidneys and breasts. ObjectivesThis study aimed to accurately evaluate the total iodine intake (TII), urinary iodine excretion (UIE), and breast milk iodine excretion (BMIE) in lactating women and explore the relationship between TII and total iodine excretion (TIE). MethodsA 7-d iodine metabolism study was conducted on 41 lactating women with a mean age of 30 y in Yuncheng and Gaoqing, China, from December 2021 to August 2023. TII and TIE were calculated by measuring the iodine content in food, water, 24-h urine, feces, and breast milk. The urinary iodine excretion rate (UIER), breast milk iodine excretion rate (BMIER), and partitioning of iodine excretion between urine and breast milk were determined. ResultsIodine metabolism studies were performed for 285 d. The median TII and TIE values were 255 and 263 μg/d, respectively. With an increase in TII, UIER, and BMIER, the UIE and BMIE to TII ratio exhibited a downward trend. The median UIER, BMIER, and proportion of iodine excreted in urine and breast milk were 51.5%, 38.5%, 52%, and 37%, respectively. When the TII was <120 μg/d, the BMIER decreased with the increase of the TII (β: −0.90; 95% confidence interval: −1.08, −0.72). ConclusionsWhen maternal iodine intake is low, the proportion in breast milk increases, ensuring sufficient iodine nutrition for infants. In addition, the UIE of lactating women with adequate iodine concentrations is higher than their BMIE.This study was registered at clinicaltrials.gov as NCT04492657.

Pregnant women at risk for iodine deficiency but adequate iodine intake in school-aged children of Zhejiang Province, China

The median urinary iodine concentration (UIC) of school-aged children has been commonly used as a surrogate to assess iodine status of a population including pregnant women. However, pregnant women have higher iodine requirements than children due to increased production of thyroid hormones. The aim of the study was to evaluate the iodine status of pregnant women and children as well as their household salt iodine concentration (SIC) in Quzhou, Zhejiang Province, China. Eligible pregnant women and children from all six counties of Quzhou in 2021 were recruited into the study. They were asked to complete a socio-demographic questionnaire and provide both a spot urine and a household table salt sample for the determination of UIC and SIC. A total of 629 pregnant women (mean age and gestation weeks of 29.6 years and 21.6 weeks, respectively) and 1273 school-aged children (mean age of 9 years and 49.8% of them were females) were included in the study. The overall median UIC of pregnant women and children in our sample was 127 (82, 193) μg/L and 222 (147, 327) μg/L, respectively, indicating sufficient iodine status in children but a risk of mild-to-moderate iodine deficiency in pregnant women. Distribution of iodine nutrition in children varied significantly according to their sex and age (P < 0.05). The rate of adequately household iodised salt samples (18–33 mg/kg) provided by pregnant women and children was 92.4% and 90.6%, respectively. In conclusion, our results indicated a risk of insufficient iodine status in pregnant population of China, but iodine sufficiency in school-aged children. Our data also suggested that median UIC of children may not be used as a surrogate to assess iodine status in pregnant women.

Long-Term Effects of 0.1 mg Recombinant-Human-Thyrotropin-Stimulated Fixed-Dose Radioiodine Therapy in Patients with Recurrent Multinodular Goiter after Surgery.

(1) Background: After thyroid malignancy is ruled out, treatment options for multinodular goiter patients include surgery, levothyroxine suppressive therapy, and 131-I therapy. Surgery effectively reduces goiter size but carries risks of surgical and anesthetic complications. 131-I therapy is the only nonsurgical alternative, but its effectiveness diminishes with goiter size and depends on iodine sufficiency. This study aimed to assess the efficacy and safety of 0.1 mg rhTSH as an adjuvant to a fixed dose of 131-I therapy in patients with a recurrence of large multinodular goiter, several years after the initial thyroidectomy. (2) Methods: 14 patients (13 females and 1 male), aged 59.14 ± 15.44 (range, 35-78 years) received 11mciu of 131-I, 24 h after the administration of 0.1 mg rhTSH. The primary endpoint was the change in thyroid volume (by ultrasound measurements) as well as in the diameter of the predominant nodule during a follow-up period of 10 years. Secondary endpoints were the alterations in thyroid function and potential adverse effects. (3) Results: A significant decrease in the volume of initial thyroid remnants (32.16 ± 16.66 mL) was observed from the first reevaluation (at 4 months, 23.12 ± 11.59 mL) as well as at the end of the follow-up period (10 years, 12.62 ± 8.76 mL), p < 0.01. A significant reduction in the dominant nodule was also observed (from 31.71 ± 10.46 mm in the beginning to 26.67 ± 11.05 mm). (4) Conclusions: Further investigation is needed since this approach could be attractive in terms of minimizing the potential risks of reoperation in these patients.

Assessment of iodine nutritional status and gestational thyroid function reference ranges during the first trimester of pregnancy in Taiwan.

Iodine nutrition is critical for fetal neurodevelopment in the first trimester of pregnancy, a period associated with dramatic changes in thyroid function. The aim of this study was to evaluate iodine nutritional status and thyroid function reference ranges in the first trimester in Taiwan. Pregnant women aged 20 years and above in the first trimester were recruited in Taipei Veterans General Hospital, Taiwan from March 2019 to July 2022. Each participant provided a spot urine sample for measurement of urinary iodine concentration (UIC) and a blood sample for checkup of thyroid function and thyroid autoantibodies. A simple food frequency questionnaire was also completed. A total of 209 women with a mean age of 32.9 ± 4.4 years were enrolled. The median UIC was 160.9 μg/L (interquartile range [IQR]: 105.0-246.2 μg/L), indicating overall iodine sufficiency. The gestational thyroid function reference ranges were: thyroid stimulating hormone (TSH) (median: 0.93 [0.007-2.9] µIU/mL), free T4 (1.3 [0.93-2.2] ng/dL), free T3 (3.0 [2.3-5.0] ng/dL), total T4 (9.9 [6.4-16.9] ng/dL), and total T3 (135 [88-231] ng/dL). If the nonpregnant reference range of serum TSH was used, eight women (4.8%) would be misclassified as having subclinical hyperthyroidism, and two women (1.2%) with subclinical hypothyroidism would be missed. In multivariate analysis, nulliparous (adjusted odds ratio [OR] from model 1-3: 2.02, 2.05, 2.02; 95% CI, 1.08-3.77, 1.10-3.81, 1.11-3.66; p = 0.027, 0.023, 0.022, respectively) and multivitamin nonusers (adjusted OR from model 1-3: 1.86, 1.85, 1.78; 95% CI, 1.04-3.34, 1.03-3.32, 1.004-3.71; p = 0.038, 0.039, 0.049, respectively) had increased odds of having lower UIC levels <150 μg/L. The iodine nutritional status in the first trimester is adequate in Taiwan; however, certain subgroups such as nulliparous and multivitamin nonusers are still at risk for iodine deficiency. Gestational thyroid function reference ranges are needed for correct diagnosis of thyroid dysfunction in pregnancy.

New Reference Values for Thyroid Volume by Ultrasound in German Children and Adolescents from a Population-Based Study.

Reliable reference values for thyroid ultrasound measurements are essential to effectively guide individual diagnostics and direct health care measures at the population level, such as iodine fortification programs. However, the latest reference values for total thyroid volume (Tvol) provided by the WHO in 2004 only apply to the 6 to 12-year-old age group and are limited to countries with a long history of iodine sufficiency, which does not reflect the situation in most European countries, including Germany. The present aims to derive up to date thyroid volume ultrasound reference values in German children and adolescents. Data from the baseline assessment of a nationwide study in German children and adolescents (KiGGS) conducted between 2003 and 2006 were used to determine sex-specific reference values for Tvol in thyroid-healthy participants aged 6 to 17 years by age and body surface area (BSA) according to the Lambda-Mu-Sigma (LMS) method. Data from 5559 participants were available for reference chart construction (girls: 2509 (45.1%)). On average, the 97th percentile is 33.4% and 28.5% higher than the corresponding WHO's reference values for boys and girls, respectively. These findings are consistent with most other studies in German and European children and adolescents at a similar time of investigation. Notably, the sample used for this study was iodine-sufficient according to WHO criteria. The reference values provided by the WHO are overly conservative for this population and could potentially apply to other European countries with a similar history of iodine supply.

Standardizing Normal Reference Value for Thyroid Uptake of Technetium-99m Pertechnetate in Nepalese Population.

Objective Changes in normal reference values of thyroid uptake for iodine have been reported due to geographical and chronological fluctuations in dietary iodine intake in different populations. Nepal is a country with mixed ethnicity, with access to dietary iodine in the form of successful universal salt iodination program by the government of Nepal since 1973. The aim of this study was to establish the normal reference values for thyroid uptake of technetium-99m (Tc-99m) pertechnetate in the Nepalese population in iodine sufficiency era. Methods We prospectively evaluated 52 clinically and biochemically euthyroid participants (46 females and 6 males) with age range from 20 to 71 years who underwent a thyroid Tc-99m pertechnetate scan and uptake between December 2019 to November 2023 in the Department of Nuclear Medicine, Chitwan Medical College fulfilling inclusion/exclusion criteria. Biochemical thyroid function tests were reviewed and Tc-99m pertechnetate thyroid uptake values were determined for each patient. Blood was withdrawn for thyroid hormone assessment. Euthyroid participants were then administered 3.5 to 4.5 mCi of Tc-99m pertechnetate intravenously and their percentage thyroid uptake was calculated after 20 minutes. Results The mean and median uptake of Tc-99m pertechnetate in euthyroid patients were 1.26 and 0.85%, respectively, and the interquartile range was 0.7 to 1.7%. The normal reference uptake value for Tc-99m pertechnetate in the studied population ranged between 0.3 and 3.6%. The fifth and 95th percentiles for pertechnetate uptake were 0.5 and 2.9%, respectively. Conclusion The normal reference range for Tc-99m pertechnetate thyroid uptake in Nepalese population was 0.5 to 2.9% that is lower than the currently accepted international standard of 0.75 to 4.5%. Uptake also increased with increasing age. This study highlights the importance of periodically redefining the geographic location specific normal thyroid uptake reference values.

A grain of salt – a cross-sectional study on the consumption of foods containing iodine and sodium among adults from Croatia

Salt is the main dietary source of two important nutrients: iodine and sodium. Deficiency and excess of both minerals results in a number of adverse health effects. However, social media is full of misinformation regarding iodine’s role in thyroid diseases. The aim of this cross-sectional study was to determine the types of salt consumed and the consumption of foods naturally containing iodine in adults (19 to 69 years old), both genders, in charge of food shopping and/or meal preparation (N=220), in regard to their health status. Only women reported being diagnosed with Hashimoto’s thyroiditis (14.1 %) and having infertility issues (16.8 %). Sea salt is the most commonly used (62.7 %), followed by table salt (45.5 %) and Himalaya salt (29.5 %), with many using two or more types of salt simultaneously. Women diagnosed with thyroid disease were most likely to use only Himalaya salt. Foods naturally containing iodine cannot provide sufficient iodine due to low consumption; milk and dairy are consumed once a day, cheese 4 times a week, eggs 1.9 times a week, and saltwater fish 1.2 times a week. Seaweed, as the natural source with the highest content of iodine, is consumed by 5.9 % of the study participants (one has Hashimoto’s thyroiditis). Participants reported high consumption of salt-containing seasonings, and pre-packed, ready-to-eat meals, which contribute significantly to daily sodium intake. Consumption of foods naturally containing iodine is low, but some types of salt could significantly alter iodine’s consumption. More studies are needed to determine the exact dietary iodine consumption, especially in vulnerable populations.

Iodine status, including breastmilk iodine content, of lactating mothers and their infants aged 0 to 6 months in Vhembe and Mopani districts of the Limpopo province, South Africa.

Background. Both iodine deficiency and excess may affect lactating women and their infants. In Limpopo Province, South Africa (SA), there are no data on the iodine status of individuals in these vulnerable groups.Objective. To determine the iodine status, including breastmilk iodine content, of lactating mothers and their infants aged 0 - 6 months in Vhembe and Mopani districts, Limpopo, SA.Methods. A cross-sectional descriptive study in the quantitative domain was undertaken in Vhembe and Mopani districts. Mother-infant pairs were randomly selected. Breastmilk iodine content (BMIC), urinary iodine content (UIC) of infants, UIC of mothers, household (HH) salt iodine content (SIC) and water iodine content (WIC). The iodine nutrition knowledge of mothers was determined.Results. The median (interquartile range (IQR)) of BMIC among lactating mothers in Vhembe and Mopani was 102 (62 - 179.7) μg/Land 150.4 (89.4 - 201.7) μg/L, respectively. The median (IQR) UIC of mothers in Vhembe and Mopani was 96.3 (54.8 - 154.8) μg/L and137.9 (72 - 212.4) μg/L, respectively. The median UIC of infants was 217.7 (107.1 - 409.9) and 339.8 (162.9 - 490.3) μg/L in Vhembe andMopani, respectively. There was a significant difference between SIC of coarse and fine salt in both districts. Lactating mothers in both areas had limited iodine nutrition knowledge.Conclusion. The results suggest that iodised salt is a major contributor to iodine status in lactating mothers and their infants. Our results also show that the salt iodisation programme in SA supplies sufficient iodine for children, women of reproductive age, lactating mothers and breastfed infants.

Fifteen Years of Iodine Prophylaxis in Italy: Results of a Nationwide Surveillance (Period 2015-2019).

In 2005, a nationwide program of iodine prophylaxis on a voluntary basis was implemented in Italy by law. However, recent data on iodine status are lacking. The aim of this study was to evaluate efficiency, effectiveness, and possible adverse effects (increased occurrence of thyroid autoimmunity and hyperthyroidism) of the Italian iodine prophylaxis program. From 2015 to 2019, a nationwide survey was performed. The use of iodized salt was evaluated in a sample of 164 593 adults and in 998 school canteens. A sample of 4233 schoolchildren (aged 11-13 years) was recruited to assess urinary iodine concentration, prevalence of goiter, and thyroid hypoechogenicity on ultrasound, with the latter being an indirect indicator of thyroid autoimmunity. Neonatal TSH values of 197 677 infants screened in regions representative of Northern, Central, and Southern Italy were analyzed to investigate the percentage of TSH values >5.0 mIU/L. Data on methimazole prescriptions were analyzed as indirect indicators of new cases of hyperthyroidism. The prevalence of the use of iodized salt was 71.5% in adult population and 78% in school canteens. A median urinary iodine concentration of 124 μg/L, a prevalence of goiter of 2.2%, and a prevalence of thyroid hypoechogenicity of 5.7% were observed in schoolchildren. The percentage of neonatal TSH values >5.0 mIU/L resulted still higher (5.1%) than the World Health Organization threshold of 3.0%, whereas the prescriptions of methimazole showed a reduction of 13.5%. Fifteen years of iodine prophylaxis have led to iodine sufficiency in Italy, although there still is concern about iodine nutritional status during pregnancy.

FRI484 Assessment Of Early-trimester Maternal Thyroid Function And Iodine Nutritional Status Of Pregnant Women In Northern Taiwan

Abstract Disclosure: G. Su: None. C. Yeh: None. C. Yang: None. C. Hwu: None. H. Chen: None. F. Wang: None. C. Huang: None. Background: The American Thyroid Association (ATA) has proposed to lower the early-trimester upper limit of the TSH reference interval to become 0.5 mIU/L less than the non-pregnant value. The local-regional reference intervals in Taiwan is unknown. The aim of the study is to evaluate the early-trimester thyroid function and iodine nutritional status of pregnant women in Taiwan. Methods: Women aged ≥20 years-old and in gestation 8 to 15 weeks were recruited in Taipei Veterans General Hospital from March 2019 to July 2022. Thyroid function and antibodies, including TSH, free T4, free T3, total T4, total T3, anti-thyroglobulin antibody (aTG) and anti-thyroidperoxidase antibody (aTPO), TSH receptor antibody, were measured. The gestation-specific thyroid function reference range was derived from the 2.5th and 97.5th percentiles of the studied women. Random spot urine sample was collected and urinary iodine concentration was checked by inductively coupled plasma mass spectrometry. A simple food frequency questionnaire was also completed. Results: A total of 211 women were enrolled and the derived early-trimester upper limit of serum TSH (median: 0.92 [0.007-3.08] uIU/mL) was lower than the value provided by the manufacturer (0.27-4.2 uIU/mL), while the upper limit of free T4 (median: 1.28 [0.93-2.15] ng/dL) and free T3 (3.00 [2.30-5.10]ng/dL) were both higher than the non-pregnant value (0.93-1.7 ng/dL and 2.0-4.4 ng/dL, respectively). The range of total T4 (median: 9.90 [6.39-15.36] ng/dL) and total T3 (median: 136 [89.50-223.20] ng/dL) in the studied women were similar to the non-pregnant range (5.1-14.1 ng/dL and 80-200 ng/dL, respectively). The positivity rate of aTG &amp; aTPO were 8.6%. Two patients with mild Graves’ disease and three patients with subclinical hypothyroidism were incidentally detected and treated. The positive predictive value for detecting thyroid dysfunction using the non-pregnant reference interval was only 15.9% because subclinical hyperthyroidism (18.2%, n=37) would be over-diagnosed and subclinical hypothyroidism (1.0%, n=2) would be under-diagnosed. The overall median UIC was 160.9 μg/L, indicating a sufficient iodine status. Dairy products were the most commonly consumed iodine-containing food type with 71.8% of the pregnant women ingesting dairy products ≥3 days/week. The median intake frequency for seaweed, fish, and seafood were one day per week. Approximately 34.0% of the women took multivitamin every day, but 58.4% of the women never took multivitamin. Conclusion: Our results indicate that the iodine nutritional status in the early trimester of pregnancy is adequate and that the upper limit of serum TSH was approximately 1.12 uIU/mL lower than the upper limit provided by the manufacturer. Gestation-specific thyroid function reference intervals are needed for correct diagnosis of thyroid dysfunction in pregnancy. Presentation: Friday, June 16, 2023

Iodized Salt May Not Be Sufficient to Guarantee an Adequate Iodine Intake in Pregnant Women.

Adequate iodine intake is of crucial importance in pregnancy to meet the thyroid hormone needs of both mother and fetus. In the present study, undertaken as a part of the surveillance actions following the introduction in Italy of a national salt iodination program in 2005, the iodine intake was investigated in 123 pregnant women and 49 control women living in the same area of central Italy. All the participants were screened for urinary iodine concentration (UIC), serum level of thyrotropin, free-thyroxine, free-triiodothyronine, and thyroid volume. Moreover, they were provided with a questionnaire on the use of iodine-containing salt or supplements. Control women had a median UIC of 102 µg/L, consistent with an iodine sufficiency, while in pregnant women the median UIC value was 108 µg/L, lower than the endorsed UIC of 150 µg/L. In addition, pregnant women showed a significantly increased median thyroid volume compared to controls. Interestingly, the median UIC did not differ between pregnant women not using iodine-containing salt or supplements and those regularly consuming iodized salt alone, while pregnant women with a daily intake of iodine-containing supplements had an adequate median UIC (168 µg/L). In conclusion, the data reported here showed that pregnant women and their fetuses are still exposed to the detrimental effects of iodine deficiency and that the consumption of iodine-containing supplements should be recommended in pregnancy.

Iodine Nutrition in Children ≤2 years of Age in Norway

BackgroundAs a component of the thyroid hormones (THs), iodine is vital for normal neurodevelopment during early life. However, both deficient and excess iodine may affect TH production, and data on iodine status in young children are scarce. ObjectivesTo describe iodine nutrition (iodine status and intake) in children ≤2 y of age in Innlandet County (Norway) and to describe the associations with maternal iodine nutrition. MethodsA cross-sectional study was performed in a representative sample of mother–child pairs selected from 30 municipalities from November 2020 until October 2021. Iodine status [child urinary iodine concentration (UIC), maternal UIC, and breast milk iodine concentration (BMIC)] was measured. Child’s iodine intake was estimated using 2 24-h dietary recalls (24-HR) and a food frequency questionnaire. The Multiple Source Method was used to estimate the usual iodine intake distributions from the 24-HR assessments. ResultsThe median UIC in 333 children was 145 μg/L, indicating adequate iodine status according to the WHO cutoff (100 μg/L). The median usual iodine intake was 83 μg/d. Furthermore, 35% had suboptimal usual iodine intakes [below the proposed Estimated average requirement (72 μg/d)], whereas <1% had excessive usual iodine intakes [above the Upper intake level (200 μg/d)]. There was a positive correlation between children’s iodine intake and BMIC (Spearman rank correlation coefficient r = 0.67, P < 0.001), and between children’s UIC and BMIC (r = 0.43, P < 0.001), maternal UIC (r = 0.23, P = 0.001), and maternal iodine intake (r = 0.20, P = 0.004). ConclusionDespite a median UIC above the cutoff for iodine sufficiency, more than a third of the children had suboptimal usual iodine intakes. Our findings suggest that many children will benefit from iodine fortification and that risk of iodine excess in this age group is low.

The use of breast milk iodine concentration in the first week of lactation as a biomarker of iodine status in breast-feeding women.

Breast milk iodine concentration (BMIC) is a promising indicator of iodine status in lactating women. However, there are limited data on its usefulness to reflect maternal iodine deficiency. Therefore, the aim of our study was to assess iodine concentration in breast milk and urine samples in exclusively breast-feeding women. Eligible pregnant women undergoing routine antenatal care in a large hospital in Shaanxi Province, China, were followed up from the third trimester of pregnancy until the first week of lactation. Urine samples (20 ml) were collected during pregnancy and lactation. Iodine concentration in samples was measured based on Sandell-Kolthoff reaction. Breast milk samples (5 ml) were provided during lactation. A receiver operating curve (ROC) was constructed to determine the diagnostic performance of BMIC. An iodine-specific FFQ was completed twice during pregnancy and lactation. A total of 200 women completed the study. The overall median BMIC was 89 μg/l, indicating iodine sufficiency (i.e. BMIC reference range between 60 and 465 μg/l). Women reported similar median urinary iodine concentration (UIC) during pregnancy and lactation (112 and 113 μg/l, respectively), but their iodine status differed - mild-to-moderate iodine deficiency during pregnancy and iodine sufficiency during lactation. The ROC for BMIC using UIC as a reference standard was 0·755 (95 % CI: 0·644, 0·866). In conclusion, this study demonstrated that women were iodine sufficient in the first week of lactation as assessed by UIC, which was consistent with BMIC. These findings suggested that BMIC is a useful biomarker to assess iodine status in lactating women.

Iodine and plant-based diets: a narrative review and calculation of iodine content.

An increasing number of food-based recommendations promote a plant-based diet to address health concerns and environmental sustainability in global food systems. As the main sources of iodine in many countries are fish, eggs and dairy products, it is unclear whether plant-based diets, such as the EAT-Lancet reference diet, would provide sufficient iodine. This is important as iodine, through the thyroid hormones, is required for growth and brain development; adequate iodine intake is especially important before, and during, pregnancy. In this narrative review, we evaluated the current literature and estimated iodine provision from the EAT-Lancet reference diet. There is evidence that those following a strict plant-based diet, such as vegans, cannot reach the recommended iodine intake from food alone and are reliant on iodine supplements. Using the EAT-Lancet reference diet intake recommendations in combination with iodine values from UK food tables, we calculated that the diet would provide 128 μg/d (85 % of the adult recommendation of 150 μg/d and 51–64 % of the pregnancy recommendation of 200–250 μg/d). However, if milk is replaced with unfortified plant-based alternatives, total iodine provision would be just 54 μg/d (34 % and 22–27 % of the recommendations for adults and pregnancy, respectively). Plant-based dietary recommendations might place consumers at risk of iodine deficiency in countries without a fortification programme and where animal products provide the majority of iodine intake, such as the UK and Norway. It is essential that those following a predominantly plant-based diet are given appropriate dietary advice to ensure adequate iodine intake.