Prevalence of inadequate and excessive iodine intake in a US pregnancy cohort.

BACKGROUND: US iodine intake, estimated from the median urinary iodine concentration of population representative data, has declined by half since the 1970s, which is problematic because maternal iodine intake is critical for fetal neurodevelopment. Relying on median urinary concentrations to assess iodine intake of populations is standard practice but does not describe the number of individuals with insufficient intake. Prevalence estimates of inadequate and excessive intake are better for informing public health applications but require multiple urine samples per person; such estimates have been generated in pediatric populations but not yet among pregnant women. OBJECTIVE: Our aims were as follows: (1) to assess median urinary iodine concentrations across pregnancy for comparison with national data and (2) to estimate the prevalence of inadequate and excessive iodine intake among pregnant women in mid-Michigan. STUDY DESIGN: Data were collected from 2008 to 2015 as part of a prospective pregnancy cohort in which women were enrolled at their first prenatal clinic visit. Few exclusion criteria (<18 years or non-English speaking) resulted in a sample of women generally representative of the local community, unselected for any specific health conditions. Urine specimens were obtained as close as practicable to at least 1 specimen per trimester during routine prenatal care throughout pregnancy (n=1-6 specimens per woman) and stored at -80°C until urinary iodine was measured to estimate the iodine intake (n=1014 specimens from 464 women). We assessed urinary iodine across pregnancy by each gestational week of pregnancy and by trimester. We used multiple urine specimens per woman, accounted for within-person variability, performed data transformation to approximate normality, and estimated the prevalence of inadequate and excessive iodine intake using a method commonly employed for assessment of nutrient status. RESULTS: Maternal characteristics reflected the local population in racial and ethnic diversity and socioeconomic status as follows: 53% non-Hispanic white, 22% non-Hispanic black, and 16% Hispanic; 48% had less than or equal to high school education and 71% had an annual income of <$25,000. Median urinary iodine concentrations in the first, second, and third trimester-including some women contributing more than 1 specimen per trimester-were 171 µg/L (n=305 specimens), 181 µg/L (n=366 specimens), and 179 µg/L (n=343 specimens), respectively, with no significant difference by trimester (P=.50, Kruskal-Wallis test for equality of medians). The estimated prevalence of inadequate and excessive iodine intake was 23% and <1%, respectively. CONCLUSION: Median urinary iodine concentrations in each trimester were above the World Health Organization cutoff of 150 µg/L, indicating iodine sufficiency at the group level across pregnancy. However, the estimated prevalence of inadequate iodine intake was substantial at 23%, whereas prevalence of excessive intake was <1%, indicating a need for at least some women to increase consumption of iodine during pregnancy. The American Thyroid Association, the Endocrine Society, and the American Academy of Pediatrics recommend that all pregnant and lactating women receive a daily multivitamin or mineral supplement that contains 150 µg of iodine. The data presented here should encourage the collection of similar data from additional US population samples for the purpose of informing the American College of Obstetricians and Gynecologists' own potential recommendations for prenatal iodine supplementation.

Oral Contraceptive Intake and Iodine Status in Young Women.

OBJECTIVE: Similar to pregnant women, women taking an oral contraceptive (OC) might have elevated iodine requirements due to the altered hormonal state. This is the first study aimed at investigating the prevalence of iodine deficiency and possible influences of OC intake on urine creatinine and iodine levels in young women. METHODS: One hundred fifty-five women between the age of 18 and 35 years (62 taking an OC and 93 controls) participated in a cross-sectional pilot study at the Medical University of Vienna, which included a 1-spot urine sample and a questionnaire on OC intake as well as a food questionnaire. RESULTS: The median urinary iodine concentration (UIC) in this study was 68 µg/L (41, 111 µg/L) suggesting an inadequate iodine status in the women according to the WHO guidelines. Median UIC (OC: 89 µg/L, IQR 55-120; control: 59 µg/L, IQR 39-91, p = 0.010) and urine creatinine (OC: median = 99.0 µg/L, IQR 74.9-175.5; control: 77.0 µg/L, IQR 49.6-147.2, p = 0.030) levels were significantly higher in OC women than in the control group. UIC corrected for urine creatinine was comparable between both groups. CONCLUSION: With similar creatinine-corrected UICs in both groups, OC intake might not have a significant impact on iodine status. However, the low median UIC in a vulnerable group of young women potentially conceiving in the following years points at the necessity of optimizing the iodine intake in the Austrian population and reiterates the insufficiency of the current iodine supplementation measures.

Universal Salt Iodization Provides Sufficient Dietary Iodine to Achieve Adequate Iodine Nutrition during the First 1000 Days: A Cross-Sectional Multicenter Study.

Background: Dietary iodine requirements are high during pregnancy, lactation, and infancy, making women and infants vulnerable to iodine deficiency. Universal salt iodization (USI) has been remarkably successful for preventing iodine deficiency in the general population, but it is uncertain if USI provides adequate iodine intakes during the first 1000 d. Objective: We set out to assess if USI provides sufficient dietary iodine to meet the iodine requirements and achieve adequate iodine nutrition in all vulnerable population groups. Methods: We conducted an international, cross-sectional, multicenter study in 3 study sites with mandatory USI legislation. We enrolled 5860 participants from 6 population groups (school-age children, nonpregnant nonlactating women of reproductive age, pregnant women, lactating women, 0-6-mo-old infants, and 7-24-mo-old infants) and assessed iodine status [urinary iodine concentration (UIC)] and thyroid function in Linfen, China (n = 2408), Tuguegarao, the Philippines (n = 2512), and Zagreb, Croatia (n = 940). We analyzed the iodine concentration in household salt, breast milk, drinking water, and cow's milk. Results: The salt iodine concentration was low (<15 mg/kg) in 2.7%, 33.6%, and 3.1%, adequate (15-40 mg/kg) in 96.3%, 48.4%, and 96.4%, and high (>40 mg/kg) in 1.0%, 18.0%, and 0.5% of household salt samples in Linfen (n = 402), Tuguegarao (n = 1003), and Zagreb (n = 195), respectively. The median UIC showed adequate iodine nutrition in all population groups, except for excessive iodine intake in school-age children in the Philippines and borderline low intake in pregnant women in Croatia. Conclusions: Salt iodization at ∼25 mg/kg that covers a high proportion of the total amount of salt consumed supplies sufficient dietary iodine to ensure adequate iodine nutrition in all population groups, although intakes may be borderline low during pregnancy. Large variations in salt iodine concentrations increase the risk for both low and high iodine intakes. Strict monitoring of the national salt iodization program is therefore essential for optimal iodine nutrition. This trial was registered at clinicaltrials.gov as NCT02196337.

Iodine intake as a risk factor for BRAF mutations in papillary thyroid cancer patients from an iodine-replete area.

PURPOSE: Both deficient and excessive iodine intake leads to thyroid disease, which shows U-shaped curves. Our previous study showed that a relatively low [urinary iodine concentration (UIC) <300 µg/L] and extremely excessive (UIC ≥ 2500 µg/L) iodine intake were associated with thyroid cancer in Korea, an iodine-replete area. Papillary thyroid cancer (PTC) accounts for more than 97 % of thyroid cancer and 80% or more PTC cases harbor the BRAF mutation in Korea. We aimed to investigate the relationship between iodine intake and the prevalence of the BRAF mutation in PTC in Korea. METHODS: UIC was measured by inductively coupled plasma mass spectrometry. The BRAF mutation was detected using both allele-specific polymerase chain reaction and mutant enrichment with 3'-modified oligonucleotide sequencing. Risk factors for the occurrence of BRAF mutations in PTC were evaluated using multivariate logistic regression models. RESULTS: The median UIC in all patients with PTC was 287 µg/L (range from 7 to 7, 426 µg/L). Nearly half of the patients (102/215, 47%) belonged to the excessive iodine intake category (UIC ≥ 300 µg/L) according to the WHO iodine recommendations. The frequency of BRAF mutations was lowest in the 300-499 µg/L UIC group; it was significantly different compared to the relatively low (UIC < 300 µg/L) and more than excessive (UIC ≥ 500 µg/L) iodine intake groups. UIC was an independent predictor for BRAF mutations in PTC. The multivariate-adjusted odds ratios (95% confidence intervals) in the relatively low and more than excessive iodine intake groups for the BRAF mutation were 4.761 (1.764-12.850) and 6.240 (2.080-18.726), respectively, compared to the 300-499 µg/L UIC group. CONCLUSION: Relatively low iodine intake and more than excessive iodine intake seem to be significant risk factors for the occurrence of BRAF mutations in the thyroid and, therefore, may be risk factors for the development of PTC in an iodine-replete area.

Thyroglobulin level at week 16 of pregnancy is superior to urinary iodine concentration in revealing preconceptual and first trimester iodine supply.

Pregnant women are prone to iodine deficiency due to the increased need for iodine during gestation. Progress has recently occurred in establishing serum thyroglobulin (Tg) as an iodine status biomarker, but there is no accepted reference range for iodine sufficiency during pregnancy. An observational study was conducted in 164 pregnant women. At week 16 of gestation urinary iodine concentration (UIC), serum Tg, and thyroid functions were measured, and information on the type of iodine supplementation and smoking were recorded. The parameters of those who started iodine supplementation (≥150 µg/day) at least 4 weeks before pregnancy (n = 27), who started at the detection of pregnancy (n = 51), and who had no iodine supplementation (n = 74) were compared. Sufficient iodine supply was found in the studied population based on median UIC (162 µg/L). Iodine supplementation ≥150 µg/day resulted in higher median UIC regardless of its duration (nonusers: 130 µg/L vs. prepregnancy iodine starters: 240 µg/L, and pregnancy iodine starters: 205 µg/L, p < .001, and p = .023, respectively). Median Tg value of pregnancy starters was identical to that of nonusers (14.5 vs. 14.6 µg/L), whereas prepregnancy starters had lower median Tg (9.1 µg/L, p = .018). Serum Tg concentration at week 16 of pregnancy showed negative relationship (p = .010) with duration of iodine supplementation and positive relationship (p = .008) with smoking, a known interfering factor of iodine metabolism, by multiple regression analysis. Serum Tg at week 16 of pregnancy may be a promising biomarker of preconceptual and first trimester maternal iodine status, the critical early phase of foetal brain development.

Reliability of thyroglobulin in serum compared with urinary iodine when assessing individual and population iodine nutrition status.

The occurrence of thyroid disorders relies on I nutrition and monitoring of all populations is recommended. Measuring I in urine is standard but thyroglobulin in serum is an alternative. This led us to assess the reliability of studies using serum thyroglobulin compared with urinary I to assess the I nutrition level and calculate the number of participants needed in a study with repeated data sampling in the same individuals for 1 year. Diet, supplement use and life style factors were assessed by questionnaires. We measured thyroglobulin and thyroglobulin antibodies in serum and I in urine. Participants were thirty-three Caucasians and sixty-four Inuit living in Greenland aged 30-49 years. Serum thyroglobulin decreased with rising I excretion (Kendall's τ -0·29, P=0·005) and did not differ with ethnicity. Variation in individuals was lower for serum-thyroglobulin than for urinary I (mean individual CV: 15·1 v. 46·1 %; P<0·01). It required 245 urine samples to be 95 % certain of having a urinary I excretion within 10 % of the true mean of the population. For serum-thyroglobulin the same precision required 206 samples. In an individual ten times more samples were needed to depict I deficiency when using urinary I excretion compared with serum-thyroglobulin. In conclusion, more participants are need to portray I deficiency in a population when using urinary I compared with serum-thyroglobulin, and about ten times more samples are needed in an individual. Adding serum-thyroglobulin to urinary I may inform surveys of I nutrition by allowing subgroup analysis with similar reliability.

Iodine intakes and status in Irish adults: is there cause for concern?

I is an important mineral for health, required for the production of key thyroid hormones, which are essential for cellular metabolism, growth and physical development. Hence, adequate I is crucial at all stages of life, but imperative during pregnancy for fetal brain development and during a child's early life for neurodevelopment. Within Ireland, limited information exists on population I intakes and status. Therefore, the purposes of the present analysis were to estimate dietary I intakes and to analyse urinary iodine (UI) status using the cross-sectional National Adult Nutrition Survey 2008-2010 and the most recent Irish Total Diet Study. Median I intakes in the total population (n 1106) were adequate with only 26 % of the population being classified as below the estimated average requirement (EAR). Milk consumption was the major source of I in the diet, contributing 45 % to total intake. Likewise, median UI concentrations (107 µg/l) indicated 'optimal' I nutrition according to the WHO cut-off points. In our cohort, 77 % of women of childbearing age (18-50 years) did not meet the EAR recommendation set for pregnant women. Although I is deemed to be sufficient in the majority of adult populations resident in Ireland, any changes to the current dairy practices could significantly impact intake and status. Continued monitoring should be of priority to ensure that all subgroups of the population are I sufficient.

Lebanese children are iodine deficient and urinary sodium and fluoride excretion are weak positive predictors of urinary iodine.

PURPOSE: To assess iodine and fluoride status among Lebanese children. METHODS: A nationally representative cross-sectional study of 6- to 10-year-old schoolchildren was conducted using multistage cluster sampling. Spot urine samples were collected from 1403 children, and urinary iodine, fluoride, creatinine and sodium levels were measured. Salt samples from markets (n = 30) were tested for iodine concentration by titration. RESULTS: Median urinary iodine concentration was 66.0 µg/l, indicating mild deficiency, and almost 75 % of Lebanese children had a urinary iodine concentration (UIC) <100 µg/l. UIC was higher among children from private schools and in areas of higher socioeconomic status. Most salt samples were fortified at levels far below the legislated requirement, and 56 % of samples contained less than 15 ppm iodine. Fluoride-to-creatinine ratio (F/Cr) was 0.250 (0.159-0.448) mg/g. There were weak positive correlations between UIC and urinary sodium (r 2 = 0.039, P value <0.001) and UIC and urinary fluoride (r 2 = 0.009, P value <0.001). CONCLUSIONS: Lebanese elementary school children are iodine deficient due to inadequately iodized salt. The weak correlation between UIC and urinary sodium suggests most dietary iodine does not come from iodized salt. The poor correlation between UIC and urinary fluoride suggests that fluoride intake is not affecting iodine metabolism. Efforts are needed in Lebanon to improve industry compliance with salt fortification through improved monitoring and enforcement of legislation.

Is low iodine a risk factor for cardiovascular disease in Americans without thyroid dysfunction? Findings from NHANES.

BACKGROUND AND AIMS: Low body iodine levels are associated with cardiovascular disease, in part through alterations in thyroid function. While this association suggested from animal studies, it lacks supportive evidence in humans. This study examined the association between urine iodine levels and presence of coronary artery disease (CAD) and stroke in adults without thyroid dysfunction. METHODS AND RESULTS: This cross-sectional study included 2440 adults (representing a weighted n = 91,713,183) aged ≥40 years without thyroid dysfunction in the nationally-representative 2007-2012 National Health and Nutrition Examination Survey. The age and sex-adjusted urine iodine/creatinine ratio (aICR) was categorized into low (aICR<116 µg/day), medium (116 µg/day ≤ aICR < 370µg/day), and high (aICR ≥ 370µg/day) based on lowest/highest quintiles. Stroke and CAD were from self-reported physician diagnoses. We examined the association between low urine aICR and CAD or stroke using multivariable logistic regression modeling. The mean age of this population was 56.0 years, 47% were women, and three quarters were non-Hispanic whites. Compared with high urine iodine levels, multivariable adjusted odds ratios aOR (95% confidence intervals) for CAD were statistically significant for low, aOR = 1.97 (1.08-3.59), but not medium, aOR = 1.26 (0.75-2.13) urine iodine levels. There was no association between stroke and low, aOR = 1.12 (0.52-2.44) or medium, aOR = 1.48 (0.88-2.48) urine iodine levels. CONCLUSION: The association between low urine iodine levels and CAD should be confirmed in a prospective study with serial measures of urine iodine. If low iodine levels precede CAD, then this potential and modifiable new CAD risk factor might have therapeutic implications.

Iodine status and thyroid function among Spanish schoolchildren aged 6-7 years: the Tirokid study.

I deficiency is still a worldwide public health problem, with children being especially vulnerable. No nationwide study had been conducted to assess the I status of Spanish children, and thus an observational, multicentre and cross-sectional study was conducted in Spain to assess the I status and thyroid function in schoolchildren aged 6-7 years. The median urinary I (UI) and thyroid-stimulating hormone (TSH) levels in whole blood were used to assess the I status and thyroid function, respectively. A FFQ was used to determine the consumption of I-rich foods. A total of 1981 schoolchildren (52 % male) were included. The median UI was 173 µg/l, and 17·9 % of children showed UI<100 µg/l. The median UI was higher in males (180·8 v. 153·6 µg/l; P<0·001). Iodised salt (IS) intake at home was 69·8 %. IS consumption and intakes of ≥2 glasses of milk or 1 cup of yogurt/d were associated with significantly higher median UI. Median TSH was 0·90 mU/l and was higher in females (0·98 v. 0·83; P<0·001). In total, 0·5 % of children had known hypothyroidism (derived from the questionnaire) and 7·6 % had TSH levels above reference values. Median TSH was higher in schoolchildren with family history of hypothyroidism. I intake was adequate in Spanish schoolchildren. However, no correlation was found between TSH and median UI in any geographical area. The prevalence of TSH above reference values was high and its association with thyroid autoimmunity should be determined. Further assessment of thyroid autoimmunity in Spanish schoolchildren is desirable.

INCREASED LEVELS OF MEDIAN URINARY IODINE EXCRETION OF PRIMARY SCHOOL CHILDREN IN THE SUBURBAN AREA, KHON KAEN, THAILAND.

Iodine deficiency disorder (IDD) is associated with a low IQ in children and is an important public health problem in northeastern Thailand. Despite campaigns to reduce IDD in northeastern Thailand, studies showed people in this region continue to have the lowest median urinary iodine (UI) excretion and Intelligence Quotient scores. We conducted a cross sectional study of median urinary iodine excretion among primary school children in suburban Khon Kaen Province, in northeastern Thailand, during December 2012 to evaluate the current status of IDD in this population. We studied 377 school children. Urine samples were collected and measured for UI using a simple microplate method. The median UI level was 229.0 µg/l (range 15.0-1,124.1). Forty school children (10.6%) had UI levels less than 100 µg/l and 10 children (2.7%) had UI levels less than 50 µg/l. One hundred nine children (28.9%) had UI levels greater than 300 µg/l. Our study shows that there are still children in the study population and study area with inadequate UI levels. Programs to prevent IDD need to include this population in this area.

Iodine status of young Burkinabe children receiving small-quantity lipid-based nutrient supplements and iodised salt: a cluster-randomised trial.

The objective of the present study was to assess the impact of providing small-quantity lipid-based nutrient supplements (SQ-LNS) on the I status of young Burkinabe children. In total, thirty-four communities were assigned to intervention (IC) or non-intervention cohorts (NIC). IC children were randomly assigned to receive 20 g lipid-based nutrient supplements (LNS)/d containing 90 µg I with 0 or 10 mg Zn from 9 to 18 months of age, and NIC children received no SQ-LNS. All the children were exposed to iodised salt through the national salt iodization programme. Spot urinary iodine (UI), thyroid-stimulating hormone (TSH) and total thyroxine (T4) in dried blood spots as well as plasma thyroglobulin (Tg) concentrations were assessed at 9 and 18 months of age among 123 IC and fifty-six NIC children. At baseline and at 18 months, UI, TSH and T4 did not differ between cohorts. Tg concentration was higher in the NIC v. IC at baseline, but this difference did not persist at 18 months of age. In both cohorts combined, the geometric mean of UI was 339·2 (95% CI 298·6, 385·2) µg/l, TSH 0·8 (95% CI 0·7, 0·8) mU/l, T4 118 (95 % CI 114, 122) nmol/l and Tg 26·0 (95% CI 24·3, 27·7) µg/l at 18 months of age. None of the children had elevated TSH at 18 months of age. Marginally more children in NIC (8·9%) had low T4 (15 ppm). A reduction of SQ-LNS I content could be considered in settings with similarly successful salt iodisation programmes.

Development and validation of an iodine-specific FFQ to estimate iodine intake in Australian pregnant women.

Adequate iodine is important during pregnancy to ensure optimal growth and development of the offspring. We validated an iodine-specific FFQ (I-FFQ) for use in Australian pregnant women. A forty-four-item I-FFQ was developed to assess iodine intake from food and was administered to 122 pregnant women at 28 weeks gestation. Iodine supplement use was captured separately at 28 weeks gestation. Correlation between iodine intake from food estimated using the I-FFQ and a 4 d weighed food record as well as correlation between total iodine intake and 24 h urinary iodine excretion (UIE), 24 h urinary iodine concentration (UIC), spot UIC and thyroid function were assessed at 28 weeks gestation. A moderate correlation between the two dietary methods was shown (r 0·349, P< 0·001), and it was strengthened with the addition of iodine supplements (r 0·876, P<0·001). There was a fair agreement (k= 0·28, P<0·001) between the two dietary measures in the classification of women as receiving adequate (≥160 µg/d) or inadequate (<160 µg/d) iodine intake from food, but the limits of agreement from the Bland-Altman plot were large. Total iodine intake was associated with 24 h UIE (ß = 0·488, P<0·001) but not with spot UIC. Iodine intake from food using the I-FFQ was assessed at study entry (<20 weeks gestation) in addition to 28 weeks gestation, and there was a strong correlation in iodine intake at the two time points (r 0·622, P<0·001), which indicated good reproducibility. In conclusion, the I-FFQ provides a valid tool for estimating iodine intake in pregnant women and can be used to screen women who are at risk of inadequate intake.

Iodine-deficiency disorders in the Aseer region, south-western Saudi Arabia: 20 years after the national survey and universal salt iodization.

OBJECTIVE: To study (i) the current prevalence of iodine-deficiency disorders among schoolchildren in south-western Saudi Arabia after universal salt iodization and (ii) the iodine content of table salts and water. DESIGN: Cross-sectional study on a stratified proportional allocation sample of children. Thyroid gland enlargement was assessed clinically and by ultrasound scanning. Urine, table salt and water samples were taken to measure iodine content. Settings The Aseer region, south-western Saudi Arabia. SUBJECTS: Schoolchildren aged 8-10 years. RESULTS: The study included 3046 schoolchildren. The total goitre rate amounted to 24·0 %. Prevalence of enlarged thyroid by ultrasound was 22·7 %. The median urinary iodine concentration of the study sample amounted to 17·0 µg/l. The iodine content of table salt ranged from 0 to 112 mg/kg; 22·5 % of the table salt samples were below the recommended iodine content (15 mg/kg) set by WHO. The total goitre rate increased significantly from 19·8 % among children using table salt with iodine content ≥15 mg/kg to reach 48·5 % among children using table salt with 0 mg iodine/kg. Analysis of water samples taken from schools showed that the majority of water samples (78·8 %) had an iodine content of 0 µg/l. CONCLUSIONS: The study documented that 18 years after the national study, and after more than a decade of universal salt iodization in Saudi Arabia, the problem of iodine-deficiency disorders is still endemic in the Aseer region. Efforts should focus on fostering advocacy and communication and ensuring the availability of adequately iodized salt.

Iodine deficiency during pregnancy: a national cross-sectional survey in Latvia.

OBJECTIVE: Low iodine intake during pregnancy may cause thyroid dysfunction, which results in inadequate fetal brain development. In the absence of a universal salt iodization programme, we conducted a nationwide survey of iodine deficiency in pregnant women in Latvia. DESIGN: A countrywide twenty-cluster survey, with at least twenty women per cluster. Participants completed a questionnaire on dietary habits concerning iodine intake (n 739). Thyroid function (thyroid-stimulating hormone, free thyroxine and thyroperoxidase antibodies) was measured (n 550). Urinary iodine was measured using the ammonium persulfate method (n 696). SETTING: The survey was performed in all regions of Latvia during the spring and autumn seasons in 2013. SUBJECTS: Pregnant women (n 829). RESULTS: The median creatinine (Cr)-standardized urinary iodine concentration (UIC) was 80·8 (interquartile range (IQR) 46·1-130·6) µg/g Cr or 69·4 (IQR 53·9-92·6) µg/l during pregnancy, and 81% of pregnant women had UIC levels below the WHO recommended range of 150-250 µg/g Cr. The UIC was lowest during the first trimester of pregnancy, 56·0 (IQR 36·4-100·6) µg/g Cr, reaching higher concentrations of 87·5 (IQR 46·4-141·7) µg/g Cr and 86·9 (IQR 53·8-140·6) µg/g Cr in the second and third trimesters, respectively. Women taking supplements containing ≥150 µg iodine (6·8% of respondents) had non-significantly higher UIC than did women without supplementation (96·2 v. 80·3 µg/g Cr, respectively, P=NS). Thyroperoxidase antibody concentration did not correlate significantly with UIC: Spearman's ρ=-0·012, P=0·78. CONCLUSIONS: The median UIC indicates iodine deficiency in pregnant women in Latvia. Iodine supplementation (150 µg daily) and regular UIC monitoring should be suggested to overcome iodine deficiency and to reach the recommended levels without inducing autoimmune processes.

Iodine intake and status of UK women of childbearing age recruited at the University of Surrey in the winter.

As intra-thyroidal iodine stores should be maximised before conception to facilitate the increased thyroid hormone production during pregnancy, women who are planning to become pregnant should ideally consume 150 µg iodine/d (US RDA). As few UK data exist for this population group, a cross-sectional study was carried out at the University of Surrey to assess the iodine intake and status of women of childbearing age. Total iodine excretion was measured from 24 h urine samples in fifty-seven women; iodine intake was estimated by assuming that 90 % of ingested iodine was excreted. The average iodine intake was also estimated from 48 h food diaries that the participants completed. The median urinary iodine concentration value (63·1 µg/l) indicated the group to be mildly iodine deficient by WHO criteria. By contrast, the median 24 h urinary iodine excretion value (149·8 µg/24 h) indicated a relatively low risk of iodine deficiency. The median estimated iodine intake, extrapolated from urinary excretion, was 167 µg/d, whereas it was lower, at 123 µg/d, when estimated from the 48 h food diaries. Iodine intake estimated from the food diaries and 24 h urinary iodine excretion were strongly correlated (r 0·75, P< 0·001). The intake of milk, eggs and dairy products was positively associated with iodine status. The iodine status of this UK cohort is probably a best-case scenario as the women were mostly nutrition students and were recruited in the winter when milk-iodine content is at its highest; further study in more representative cohorts of UK women is required. The present study highlights the need for revised cut-off values for iodine deficiency that are method- and age group-specific.

Status of iodine deficiency among pregnant mothers in Himachal Pradesh, India.

OBJECTIVE: Iodine is an essential micronutrient needed for the production of thyroid hormones. Pregnant mothers who are deficient in iodine provide less iodine to the fetal thyroid. This results in low production of thyroid hormones by the fetal thyroid, thereby leading to compromised mental and physical development of the fetus. The current study aimed to assess the current status of iodine nutrition among pregnant mothers in Himachal Pradesh, India, a known endemic region for iodine deficiency. DESIGN: Three districts, namely Kangra, Kullu and Solan, were selected. SETTING: In each district, thirty clusters (villages) were identified by utilizing the population-proportional-to-size cluster sampling methodology. In each cluster, seventeen pregnant mothers attending the antenatal clinics were included. SUBJECTS: A total of 1711 pregnant mothers (647 from Kangra, 551 from Kullu and 513 from Solan) were studied. Clinical examination of the thyroid of each pregnant mother was conducted. Spot urine samples were collected from ten pregnant mothers in each cluster. Similarly, salt samples were collected from eleven pregnant mothers in each cluster. RESULTS: Total goitre rate was 42·2 % (Kangra), 42·0 % (Kullu) and 19·9 % (Solan). The median urinary iodine concentration was 200 µg/l (Kangra), 149 µg/l (Kullu) and 130 µg/l (Solan). The percentage of pregnant mothers consuming adequately iodized salt (iodine content of 15 ppm and more) was found to be 68·3 % (Kangra), 60·3 % (Kullu) and 48·5 % (Solan). CONCLUSION: Pregnant mothers in Kullu and Solan districts had iodine deficiency as indicated by a median urinary iodine concentration less than 150 µg/l.

Marginal biotin deficiency can be induced experimentally in humans using a cost-effective outpatient design.

To date, marginal, asymptomatic biotin deficiency has been successfully induced experimentally by the use of labor-intensive inpatient designs requiring rigorous dietary control. We sought to determine if marginal biotin deficiency could be induced in humans in a less expensive outpatient design incorporating a self-selected, mixed general diet. We sought to examine the efficacy of three outpatient study designs: two based on oral avidin dosing and one based on a diet high in undenatured egg white for a period of 28 d. In study design 1, participants (n = 4; 3 women) received avidin in capsules with a biotin binding capacity of 7 times the estimated dietary biotin intake of a typical self-selected diet. In study design 2, participants (n = 2; 2 women) received double the amount of avidin capsules (14 times the estimated dietary biotin intake). In study design 3, participants (n = 5; 3 women) consumed egg-white beverages containing avidin with a biotin binding capacity of 7 times the estimated dietary biotin intake. Established indices of biotin status [lymphocyte propionyl-CoA carboxylase activity; urinary excretion of 3-hydroxyisovaleric acid, 3-hydroxyisovaleryl carnitine (3HIA-carnitine), and biotin; and plasma concentration of 3HIA-carnitine] indicated that study designs 1 and 2 were not effective in inducing marginal biotin deficiency, but study design 3 was as effective as previous inpatient study designs that induced deficiency by egg-white beverage. Marginal biotin deficiency can be induced experimentally by using a cost-effective outpatient design by avidin delivery in egg-white beverages. This design should be useful to the broader nutritional research community.

Measurement of acylcarnitine substrate to product ratios specific to biotin-dependent carboxylases offers a combination of indicators of biotin status in humans.

This work describes a novel liquid chromatography tandem MS (LC-MS/MS) method for the determination of ratios of acylcarnitines arising from acyl-CoA substrates and products that reflect metabolic disturbances caused by marginal biotin deficiency. The urinary ratios reflecting reduced activities of biotin-dependent enzymes include the following: 1) the ratio of 3-hydroxyisovalerylcarnitine : 3-methylglutarylcarnitine (3HIAc : MGc) for methylcrotonyl-CoA carboxylase; 2) the ratio of propionylcarnitine:methylmalonylcarnitine (Pc : MMc) for propionyl-CoA carboxylase (PCC); and 3) the ratio of acetylcarnitine : malonylcarnitine (Ac : Mc) for acetyl-CoA carboxylase. To demonstrate the suitability of the LC-MS/MS method for biomonitoring, we measured the 3 ratios for 7 healthy adults at various time points (d 0, 14, and 28) during the induction of marginal biotin through the consumption of egg white. The mean change in the Pc : MMc ratio relative to d 0 was 5.3-fold by d 14 (P = 0.0049) and 8.5-fold by d 28 (P = 0.0042). The mean change in the 3HIAc : MGc ratio was 2.8-fold by d 14 (P = 0.0022) and 3.8-fold by d 28 (P = 0.0001). The mean change in the Ac : Mc ratio was 2.9-fold by d 14 (P = 0.03) and 4.7-fold by d 28 (P = 0.02). The results suggest that simultaneous assessment of ratios of multiple biotin-dependent pathways offers insight into the complex metabolic disturbances caused by marginal biotin deficiency. We hypothesize that one or a combination of the ratios might be more sensitive or robust with respect to other nutrient deficiencies or confounding metabolic processes.

Estimating the iodine supplementation level to recommend for pregnant and breastfeeding women in Australia.

OBJECTIVE: To identify a level of iodine supplementation to recommend for pregnant and breastfeeding women in Australia. DESIGN, SETTING AND PARTICIPANTS: Dietary modelling indicated that mandatory fortification of bread with iodine by replacing salt with iodised salt would still leave a gap in iodine intakes in pregnant and breastfeeding women in Australia. Iodine shortfall was estimated by two separate methods: (i) analysis of data from published studies reporting mean urinary iodine concentrations in populations of Australian women who were pregnant or had given birth in the past 6 months; and (ii) modelling based on the postmandatory fortification iodine intake estimates calculated by Food Standards Australia New Zealand using food consumption reported by women aged 19-44 years who participated in the 1995 National Nutrition Survey. MAIN OUTCOME MEASURE: Estimated level of daily supplementation required to provide sufficient iodine to result in a low proportion of pregnant and breastfeeding women having inadequate iodine intakes. RESULTS: Estimations from both data sources indicate that a supplement of 100-150 µg/day would increase iodine intakes to a suitable extent in pregnant and breastfeeding women in Australia. CONCLUSIONS: The final level of supplementation we recommend should be based on these calculations and other factors. There will be population subgroups for whom our general recommendation is not appropriate.