Ten repeat collections for urinary iodine from spot samples or 24-hour samples are needed to reliably estimate individual iodine status in women

Although the median urinary iodine concentration (UIC) is a good indicator of iodine status in populations, there is no established biomarker for individual iodine status. If the UIC were to be used to assess individuals, it is unclear how many repeat urine collections would be needed and if the collections should be spot samples or 24-h samples. In a prospective, longitudinal, 15-mo study, healthy Swiss women (n = 22) aged 52-77 y collected repeated 24-h urine samples (total n = 341) and corresponding fasting, second-void, morning spot urine samples (n = 177). From the UIC in spot samples, 24-h urinary iodine excretion (UIE) was extrapolated based on the age- and sex-adjusted iodine:creatinine ratio. Measured UIE in 24-h samples, estimated 24-h UIE, and UIC in spot samples were (geometric mean ± SD) 103 ± 28 μg/24 h, 86 ± 33 μg/24 h, and 68 ± 28 μg/L, respectively, with no seasonal differences. Intra-individual variation (mean CV) was comparable for measured UIE (32%) and estimated UIE (33%). The CV tended to be higher for the spot UIC (38%) than for the estimated 24-h UIE (33%) (P = 0.12). In this population, 10 spot urine samples or 24-h urine samples were needed to assess individual iodine status with 20% precision. Spot samples would likely be preferable because of their ease of collection. However, the large number of repeated urine samples needed to estimate individual iodine status is a major limitation and emphasizes the need for further investigation of more practical biomarkers of individual iodine status.     

Day-to-day and within-day variation in urinary iodine excretion.

OBJECTIVE: To examine the day-to-day and within-day variation in urinary iodine excretion and the day-to-day variation in iodine intake. DESIGN: Collection of consecutive 24-h urine samples and casual urine samples over 24h. SETTING: The study population consisted of highly motivated subjects from our Institute. SUBJECTS: Study 1: Ten healthy subjects (seven females and three males) aged 30-46 y. Study 2: Twenty-two healthy subjects (9 males and 13 females) aged 30-55 y. METHODS: Study 1: 24-h urine samples were collected for four consecutive days. Study 2: Each urine voided over 24 h was collected into separate containers. In both studies dietary records were kept. MAIN OUTCOME MEASURES: Twenty-four-hour urinary iodine excretion, 24-h urinary iodine excretion estimated as I/Cr*24 h Cr and as a concentration in casual urine samples. RESULTS: Study 1: Both iodine excreted in 24-h urine and iodine intake varied from day-to-day. Iodine excretion correlated with iodine intake (=-0.46, P=0.01). Iodine intake (mean 89 +/- 6.5 microg/d) was not significantly different from iodine excretion (mean 95 +/- 5.3 microg/d). Study 2: Twenty-four hour iodine excretion estimated as I/Cr*24 h Cr from the morning urine sample was significantly lower than actual 24-h iodine excretion, whereas 24-h iodine excretion estimated as I/Cr*24 h Cr from the first sample after the morning sample and the last sample before the subjects went to bed was not significantly different from actual 24-h iodine excretion. Twenty-four-hour urine excretion estimated as a concentration was lower than actual 24-h iodine excretion in casual urine taken at any time of the day. CONCLUSIONS: For determination of iodine status in an individual, more than one 24-h urine sample must be used. The use of the I/Cr ratio in casual urine samples is a usable measure of iodine status if corrected for the age- and sex-adjusted 24-h creatinine excretion. Further, the study suggests that fasting morning urine samples would underestimate iodine status in this population.     

Iodine deficiency in pregnant women residing in an area with adequate iodine intake

OBJECTIVE: To prevent iodine deficiency disorders, the World Health Organization, United Nations Children's Fund, and International Council for the Control of Iodine Deficiency Disorders established that for a given population median urinary iodine concentrations (UIC) must be 100-199 microg/L in clinically healthy subjects and 150-249 microg/L in clinically healthy pregnant women. We evaluated whether in the urban area of Rome, Italy, where a salt iodination program (30 mg/kg) was introduced since 2005, an increased demand of iodine during pregnancy is guaranteed. METHODS: During 2006, 51 pregnant women at first trimester of a physiologic gestation were consecutively enrolled on presentation to evaluate UIC in morning spot urine samples. As controls, 100 age-matched clinically healthy non-pregnant women were evaluated. RESULTS: The median UICs were 182 microg/L (range 85-340 microg/L) and 74 microg/L (range 17-243 microg/L), respectively, in the control and pregnant groups. This difference was highly significant (P < 0.001). In particular, the UIC was found to be lower than adequate in 4% of control women compared with 92% of pregnant women. This difference of occurrences was highly significant (P < 0.001). CONCLUSION: This observational study demonstrated that, despite the adequate supplementation of iodine intake, most pregnant women appear not to be protected against iodine deficiency. If confirmed in larger case studies, this finding claims the attention of relevant professionals to monitor iodine nutrition during gestation, assuming that ordinary supplementation of iodine intake seems to be sufficient only in non-gestational conditions.     

Recommended number of participants in iodine nutrition studies is similar before and after an iodine fortification programme

Background

Iodine fortification programs have been applied in many iodine deficient regions. Iodine excess is also unfavourable, and it is recommended to monitor iodine status by measuring urinary iodine concentration (UIC). The number of samples needed in such monitoring depends on the variation in UIC. However, it is not known if variation in UIC differs according to iodine levels.

Aim and method

We aimed to describe the effect of an iodisation program on the individual and group-based variation in UIC in spot urine samples. Group 1 (G1, n = 16) was studied before, and group 2 (G2, n = 21) was studied after an iodine fortification program was implemented. Individual urine samples were collected monthly for one year, 13 samplings.

Results

G1s (207 samples) median (interquartile range) UIC was 50 (37–67) μg/L, and G2 (265 samples) was 98 (69–139) μg/L. Median individual coefficient of variation (CV) was 38 % in G1 and 40 % in G2 (p = 0.55), whereas the group-based CV was 50 % in G1 and 53 % in G2. No trend was seen between mean UIC and variation in UIC, neither at the individual (p = 0.36) nor at the group level (p = 0.43). Based on data from both groups, approximately 100 samples were needed to reliably estimate the UIC in a population.

Conclusion

In two groups studied before and after an iodine fortification program was implemented and with different UIC levels, variation in UIC was comparable both at the individual level and according to UIC level. When mild iodine deficiency is corrected, the number of samples needed to reliably estimate the UIC in a population is unaffected.     

Reliability of studies of iodine intake and recommendations for number of samples in groups and in individuals

The iodine intake level in a population is determined in cross-sectional studies. Urinary iodine varies considerably and the reliability of studies of iodine nutrition and the number of samples needed is unsettled. We performed a longitudinal study of sixteen healthy men living in an area of mild to moderate iodine deficiency. Iodine and creatinine concentrations were measured in spot urine samples collected monthly for 13 months. From these data we calculated the number of urine samples needed to determine the iodine excretion level for crude urinary iodine and for 24 h iodine excretion estimated from age- and gender-specific creatinine excretions. We found that mean urinary iodine excretion varied from 30 to 87 microg/l (31 to 91 microg/24 h). Sample iodine varied from 10 to 260 microg/l (20 to 161 microg/24 h). Crude urinary iodine varied more than estimated 24 h iodine excretion (population standard deviation 32 v. 26; individual standard deviation 29 v. 21; Bartlett's test, P < 0.01 for both). The number of spot urine samples needed to estimate the iodine level in a population with 95 % confidence within a precision range of +/- 10 % was about 125 (100 when using estimated 24 h iodine excretions), and within a precision range of +/- 5 % was about 500 (400). A precision range of +/- 20 % in an individual required twelve urine samples or more (seven when using estimated 24 h iodine excretions). In conclusion, estimating population iodine excretion requires 100-500 spot urine samples for each group or subgroup. Less than ten urine samples in an individual may be misleading.     

Iodine status in pregnant women living in Melbourne differs by ethnic group

The iodine status of pregnant women from different ethnic groups in an Australian population was determined by measuring urinary iodine concentration (UIC) from stored spot urine samples. Study subjects were selected from pregnant women participating in a Down Syndrome screening study at Monash Medical Centre in Melbourne, Australia. In total, 263 Vietnamese, 262 Indian/Sri Lankan (ISL) and 277 Caucasian women were included. The median UIC of Caucasian women (52 microg/L) was significantly lower than that of both Vietnamese women (58 microg/L, P <0.01) and ISL women (61 microg/L, P = 0.03). The proportion of women who had a UIC below 50 microg/L was 48.4% of the Caucasian women, 38.4% of the Vietnamese women and 40.8% of the ISL women. These data are consistent with mild iodine deficiency for each of the groups of pregnant women. The evidence for mild iodine deficiency in these groups of pregnant women is consistent with recent Australian studies in pregnant and non-pregnant individuals. The association of ethnicity with iodine status is most likely due to differences in dietary behaviours. Understanding the factors that influence iodine nutrition in a multiethnic population will be important for identifying the most useful approaches to improving iodine status, evaluating different strategies and the development of appropriate monitoring programs. Action to improve iodine status in the Australian population should include consideration of ethnic differences in diet.     

Longitudinal examination of 24-h urinary iodine excretion in schoolchildren as a sensitive, hydration status-independent research tool for studying iodine status

BACKGROUND: Because worldwide iodine status (IS) depends on continuous fortification, the adequacy of IS needs to be regularly monitored. OBJECTIVE: Our study aimed to evaluate IS in a longitudinal sample of healthy schoolchildren who regularly used table salt iodized with 20 microg I/g. DESIGN: Urine osmolality (Uosm) and 24-h urinary excretion rates of iodine (24-h UI), sodium, creatinine, and total urine volume (24-h Uvol) were measured in 1046 specimens that were collected at repeated intervals from 1996 to 2003 in a sample of 358 German children aged 6-12 y. Energy intake and food consumption were calculated from 3-d weighed dietary records that were collected in parallel to the urine samples. RESULTS: During the 4-y period from 1996 to 1999, the median 24-h UI increased from 87 to 93 microg I/d (P = 0.017), whereas urinary iodine concentration (UIC), Uosm, and 24-h Uvol did not change significantly. Thereafter (from 2000 to 2003), UIC stagnated and Uosm decreased (P = 0.004), whereas 24-h Uvol (P = 0.008) and 24-h UI (P = 0.002) increased. The final median 24-h UI reached 120 microg I/d. Milk, fish, egg, and meat intakes and 24-h sodium excretion were all significant predictors of IS, with an almost doubled contribution from milk intake during the second 4-y period. CONCLUSIONS: Our study shows a continuous improvement of IS in a longitudinal sample of German schoolchildren. This improvement was masked when UIC was used as an IS index, especially from 2000 to 2003 because of changes in hydration status. Thus, in research-oriented studies that focus on UIC measurements, hydration status can be a relevant confounder. Longitudinal analyses of 24-h UI in cohort studies may represent an alternative hydration status-independent tool to examine trends in IS and the contribution of relevant foods to IS.     

An assessment of progress toward universal salt iodization in Rajasthan, India, using iodine nutrition indicators in school-aged children and pregnant women from the same households

Background: In Rajasthan, an Indian State with significant salt production, the sale of non-iodized salt for human consumption was banned in 1992. This study explored the relationships between the use of iodized salt in Rajasthan and the iodine status of children and pregnant women living in the area. Methods: In a State-wide survey, 30 clusters were selected proportionate-to-population-size and 40 school children, 6-12 years old, were enrolled by random house-to-house visits in each cluster. Twelve pregnant women from the same households were also sampled. Salt used for cooking and a casual urine sample from each child and pregnant woman were collected. The salt iodine content was measured by titration and the urinary iodine concentration (UIC) by a quality-assured colorimetric method. Results: Salt iodine content was >or=15 mg/kg in 41.9% of the households, and 23.0% used non-iodized salt. Median UIC was 139 microg/L in children and 127 microg/L in pregnant women. In households using non-iodized salt, the median UIC's were 96 microg/L and 100 microg/L in children and women, respectively. Dis-aggregating the UIC distributions by salt iodine levels revealed a consistent, step-wise pattern of UIC in children with increasing salt iodine content. A similar but less steep pattern was observed in pregnant women. The iodine status of both children and pregnant women attained the optimal range only when the salt iodine content was close to 30 mg/kg. Conclusion: For optimum iodine status in the population of Rajasthan, the iodization of household salt should be mandated at a higher level than what is practiced at present.     

Age- and sex-adjusted iodine/creatinine ratio. A new standard in epidemiological surveys? Evaluation of three different estimates of iodine excretion based on casual urine samples and comparison to 24 h values

OBJECTIVE: The most accurate way to measure urinary iodine excretion in epidemiological surveys is still debated. We propose a new principle of estimating iodine excretion based on casual urine samples. MATERIAL AND METHODS: A total of 123 24 h urine samples and corresponding casual urine samples were collected from 31 subjects. Iodine excretion was expressed as 24 h iodine excretion and three different estimates: iodine concentration in the casual sample, iodine/gram creatinine in the casual sample, and the new principle-iodine/creatinine ratio in the casual sample, adjusted for expected creatinine excretion of the individual. RESULTS: All three estimates based on casual urine samples correlated significantly to 24 h values with a r (Pearson) of 0.37 for iodine concentration, 0. 61 for iodine/creatinine ratio and 0.62 for the age- and sex-adjusted iodine/creatinine ratio. The median iodine excretion in the entire group was 143 microg/day in 24 h samples, 87 microg/l as iodine concentration, 77 microg/g creatinine as iodine/creatinine ratio and 126 microg/day as age- and sex-adjusted iodine/creatinine ratio. CONCLUSION: Age- and sex-adjusted iodine/creatinine ratio is a more accurate and unbiased estimate of iodine excretion in epidemiological surveys of adults than the two most frequently used estimated: iodine concentration and iodine/gram creatinine, as these two estimates may introduce a bias depending on the composition of the investigated group. The adjusted iodine/creatinine ratio is superior to the other estimates, especially when individual estimates of 24 h iodine excretion is required or cohorts of selected groups are investigated. Sponsorship: This work was supported by grants from the Medical Research Foundation Region Greater Copenhagen, Faroe Islands and Greenland; the Wedell-Wedellsborg Foundation; Musikforlaeggerne Agnes and Knut Morks Foundation.     

Swiss pilot study of individual seasonal fluctuations of urinary iodine concentration over two years: is age-dependency linked to the major source of dietary iodine?

OBJECTIVE: Because of known significant seasonal fluctuations of iodine concentration in cow's milk (ICM) in Switzerland (winter/summer (w/s) ICM ratio averages 5.6), we looked for seasonal variations and familial aspects in urinary iodine and sodium concentrations (UIC, UNaC). DESIGN:: Prospective sequential cohort investigation. SETTING: University hospital. SUBJECTS: Thirteen children (six girls, seven boys) aged 3-10 y and their parents (n=9) aged 30-47 y. INTERVENTIONS: The volunteers collected 1729 spot urine samples (5.1996-5.1998). UIC data from winter (UIC(w): December-February) and summer seasons (UIC(s): July-September) were compared with UNaC and average milk consumption. Iodine intakes from milk and salt were modelized. RESULTS: Highest seasonal fluctuations of UIC were found in six pre-school children (w/s UIC group average=1.56, significant), followed by seven school children (w/s UIC group average=1.24, N.S.); none existed in adults. UIC/UNaC showed corresponding seasonal fluctuations in children, but not in adults. Winter milk was an important iodine source for children, as proven indirectly by similar seasonal fluctuations of ICM, UIC, UIC/UNaC and an important part within UIC due to milk. CONCLUSIONS: Contribution to UIC from milk intake during winter was high in children (40-50%) and lower in adults (about 20%). Compared with children, dietary habits of adults are more complex and their iodine supply depends mainly on iodized salt and not on milk, so the effect of seasonal ICM variations on UIC is less marked. Because of significant seasonal UIC fluctuations in consumers of fresh milk products in Switzerland, results of future UIC studies conducted during summer and winter seasons should be compared cautiously, especially in young children. Furthermore, consumption of milk is to be promoted, since, besides calcium and vitamins, it is an essential source of iodine. UNaC determination should be included in epidemiologic studies if the dietary source of iodine is questioned.     

天津市售食品碘含量及部分大学学生碘营养状况的研究

目的了解当前市售食品碘含量,部分大学生膳食碘营养状况,碘盐对膳食摄入碘的补充作用,以及尿碘测定结果对膳食碘的反映程度。方法分层随机采集日常市售食物278份,采用砷铈接触法测定食品碘含量,膳食记录法调查学生的7日膳食情况,砷铈催化分光光度法测定尿碘。结果47种、278份食物样品的检测表明,动物性食品的含碘量（7．8ug／100g～30．8ug／100g）高于植物性食品的含碘量（1．8ug／100g～16．1ug／100g）。膳食调查显示该类学生中以素食为主的占70．19％,以食物碘含量的实测值和膳食调查结果计算出由食物中摄入碘的量为（111．67±53．18）ug/d,而从碘盐中补充碘量（230．27±45．55）ug／d,那么从膳食中共可以摄入碘（341．95±89．58）ug/d。经尿肌酐校正后每克肌酐尿中碘含量中位数为271．28ug／gCr。经尿肌酐校正后的尿含碘量与膳食摄碘量呈正相关关系（0=0．463,P〈0．01）。结论这部分学生多数来自低收入家庭且膳食以素食食物为主,每日从膳食中摄入的碘量低于碘的推荐供给量（RDA）150ug,但是从加碘食盐中可以获得碘230．27ug,从而弥补膳食摄碘量的不足。     

不同浓度碘盐对人群碘营养状况影响的现场试验研究

目的观察不同浓度碘盐对人群碘营养状况影响,寻找适合当地居民食用的盐碘浓度。方法采用流行病学的现场群组干预试验研究方法,对南昌市399户城乡居民共1099人,随机分配4个组,分别提供含碘浓度为(6±2)mg/kg、(15±2)mg/kg、(24±2)mg/kg、(34±2)mg/kg的碘盐,并将其家中原有的碘盐换回。采用单盲法进行31天的干预试验。采集受试者干预前及干预后第27- 31天的一次随机尿样检测尿碘浓度,并进行膳食调查,同时采集干预前受试者实际食用碘盐检测碘含量;采集当地水源水样8份,检测水碘含量。结果当地水碘含量中位数3.05μg/L,干预前盐碘浓度为(36.4±5.4)mg/kg,碘盐合格率98.8%;干预前城区居民尿碘中位数为293.6 μg/L,农村居民尿碘中位数为508.8 μg/L。干预后第27、28、29、30、31天各组人群尿碘中位数不同日期之间的差异无统计学意义(P>0.05)。干预后第28天4个干预组的尿碘中位数:城区分别为97.2、198.6、249.4和330.7μg/L,农村分别为100.5、193.0、246.3和308.3 μg/L。结论当地属于缺碘地区,居民普遍食用合格碘盐,尿碘水平偏高;适宜当地居民食用的碘盐含碘浓度为15-25 mg/kg。     

An evaluation of salt intake and iodine nutrition in a rural and urban area of the C?te d'Ivoire.

OBJECTIVE: To evaluate the habitual salt intake of individuals living in the C?te d'Ivoire, and to monitor the iodine nutrition of adults, schoolchildren and pregnant women one year after implementation of a universal salt iodisation programme. DESIGN: A three day weighed food records with estimation of food intake from a shared bowl based on changes on body weight, determination of sodium and iodine concentrations in 24 h (24 h) urine samples from adults, and determination of urinary iodine in spot urines from schoolchildren and pregnant women. SETTING: A large coastal city (Abidjan) and a cluster of inland villages in the northern savannah region of the C?te d'Ivoire. SUBJECTS: For the food records: 188 subjects (children and adults) in the northern villages; for the 24 h urine collections: 52 adults in Abidjan and 51 adults in the northern villages; for the spot urine collections: 110 children and 72 pregnant women in Abidjan and 104 children and 66 pregnant women in the north. MAIN RESULTS: From the food survey data in the north, the total mean salt intake (s.d.) of all age groups and the adults was estimated to be 5.7 g/d (+/- 3.0), and 6.8 g/d (+/- 3.2), respectively. In the 24 h urine samples from adults, the mean sodium excretion was 2.9 g/d (+/- 1.9) in the north and 3.0 g/d (+/- 1.3) in Abidjan, corresponding to an intake of 7.3-7.5 g/d of sodium chloride. In the north the median 24 h urinary iodine excretion in adults was 163 microg/d, and the median urinary iodine in spot urines from children and pregnant women was 263 microg/l and 133 microg/l, respectively. In contrast, in Abidjan the median 24 h urinary iodine was 442 microg/d, with 40% of the subjects excreting > 500 microg/d, and the median urinary iodine in spot urines from children and pregnant women was 488 microg/l and 364 microg/l, respectively. Nearly half of the children in Abidjan and 32% of the pregnant women were excreting > 500 microg/l. CONCLUSION: Based on the estimates of salt intake in this study, an optimal iodine level for salt (at the point of consumption) would be 30 ppm. Therefore the current goals for the iodised salt programme--30-50 ppm iodine appear to be appropriate. However, in adults, children and pregnant women from Abidjan, high urinary iodine levels--levels potentially associated with increased risk of iodine-induced hyperthyroidism--are common. These results suggest an urgent need for improved monitoring and surveillance of the current salt iodisation programme in the C?te d'Ivoire.     

Pilot study of urinary iodine concentration and of biochemical thyroid parameters before and after cautious public health intervention on salt iodide content: the Swiss longitudinal 1996-2000 iodine study

OBJECTIVE AND DESIGN: Iodide concentration (IC) in salt was cautiously increased in Switzerland (15 --> 20 ppm iodide). We evaluated the dynamics of the effect of this intervention on urinary iodine concentration (UIC, microg/l) and on thyroid parameters. SETTING: University Hospital in Bern, Switzerland. SUBJECTS: A cohort of 36 subjects (12 children, 11 women, 13 men) out of 44 were recruited. INTERVENTIONS: During the study periods PRE (May 1996-May 1998) and POST (October 1998-December 2000, subdivided into equal subperiods POST1 and POST2), that is, before and after the increase of IC in salt, subjects collected 6248 urine spots for analysis of UIC. Thyroid volumes (n=2/subject) and serum thyroid parameters (n=8/subject) were sequentially evaluated. METHODS: Average PRE-POST data were compared (multiple regression analysis). RESULTS: UIC increased overall by 5.1% (P=0.0003). Increase of UIC was highest in children (11.3%, P<0.0001), significant in women (8%, P=0.0016), but not significant in men (P=0.143). Comparison between periods POST1 and POST2 showed that UIC changed more gradually in women than in children. Thyroid volumes were normal, no nonphysiological change occurred. TSH indicated euthyroidism; it decreased in children (1.98 ==> 1.74 mU/l, P=0.04) and increased in men (1.65 ==> 1.91mU/l, P=0.025). FT3 decreased in children (P<0.004) and FT4 decreased in men (P=0.017), both within normal ranges. TSH, FT3 and FT4 were unchanged in women. FT3/FT4 ratios were stable. Anti-TPO-Ab titers were stable (P=0.9). Anti-Tg-Ab titers decreased (P=0.009). CONCLUSION: The significant UIC effects were of uncertain metabolic relevance. No pathological side effects occurred. Differential delays and penetrances of UIC increase in children and adults were hitherto unknown. The unspectacular stepwise policy seems to be safe. Our pilot results in a population with moderate iodine deficiency in women should be confirmed in population-based cluster studies. SPONSORSHIP: This work was supported by grants from the University Hospital in Bern, the Swiss Federal Office of Public Health (SFOPH), the 'Swiss National Foundation for Scientific Research' (32-49424.96), the 'Fondation Genevoise de Bienfaisance Valerie Rossi di Montelera', the 'Schweizerische Lebensversicherungs- und Rentenanstalt' and the 'Schüpbach Foundation of the University of Bern'.     

Median Urinary Iodine Concentrations Are Indicative of Adequate Iodine Status among Women of Reproductive Age in Prey Veng,Cambodia

Iodine deficiency disorders are estimated to affect over 1.9 million people worldwide. Iodine deficiency is especially serious for women during pregnancy and lactation because of the negative consequences for both mother and infant. The aim of this cross-sectional study was to determine the median urinary iodine concentration (UIC) as a population-level indicator of iodine status among rural women farmers of reproductive age (18–45 years) in the province of Prey Veng, Cambodia. A total of 450 women provided a spot morning urine sample in 2012. Of those women, 93% (n = 420) were non-pregnant and 7% (n = 30) were pregnant at the time of collection. UIC was quantified using the Sandell-Kolthoff reaction with modifications. The median UIC of non-pregnant (139 μg/L) and pregnant women (157 μg/L) were indicative of adequate iodine status using the WHO/UNICEF/ICCIDD epidemiological criteria for both groups (median UIC between 100–199 and 150–249 μg/L, respectively). We conclude that non-pregnant and pregnant women in rural Prey Veng, Cambodia had adequate iodine status based on single spot morning urine samples collected in 2012. More research is warranted to investigate iodine status among larger and more representative populations of women in Cambodia, especially in light of recent policy changes to the national program for universal salt iodization.     

Iodine status in Melbourne adults in the early 1990s and 2007-08

Objective: To investigate the iodine status of Melbourne adults in 1992–94 and 2007–08, and to assess dietary iodine intake to enable comparison with recommended Nutrient Reference Values. Method: A cross‐sectional study utilising 24‐hr urine samples collected at two time points in a random sample of the Melbourne Collaborative Cohort Study. Two hundred and fifty seven adults (128 males, 129 females) in 1992–94, with a mean age of 56 years, and 265 adults (132 males, 133 females) in 2007–08, with a mean age of 68 years, were assessed, all being Melbourne residents. Urinary iodine concentration (UIC) was determined and daily urinary iodine excretion and daily iodine intake were assessed. Results: In 1992–94, the median UIC was 27 μg/L and 84% had UIC <50 μg/L. The median daily iodine intake was 51 μg/d, and 83% of participants had dietary iodine intakes below the Estimated Average Requirement of 100 μg/d. In 2007–08, the median UIC was 49 μg/L, 51% had UIC <50 μg/L and the median daily iodine intake was 98 μg/d, with 52% of intakes below the EAR. Conclusion: Melbourne adults were moderately iodine deficient in 1992–94, and borderline moderately deficient in 2007–08. Implications: While iodine status appears to have improved, it remains below an adequate level for much of the adult population of Victoria. Adequate monitoring is fundamental to assess whether the mandatory use of iodised salt in bread is effective in reducing iodine deficiency across all population groups.     

Naturally occurring iodine in humic substances in drinking water in Denmark is bioavailable and determines population iodine intake

Iodine intake is important for thyroid function. Iodine content of natural waters is high in some areas and occurs bound in humic substances. Tap water is a major dietary source but bioavailability of organically bound iodine may be impaired. The objective was to assess if naturally occurring iodine bound in humic substances is bioavailable. Tap water was collected at Randers and Skagen waterworks and spot urine samples were collected from 430 long-term Randers and Skagen dwellers, who filled in a questionnaire. Tap water contained 2 microg/l elemental iodine in Randers and 140 microg/l iodine bound in humic substances in Skagen. Median (25; 75 percentile) urinary iodine excretion among Randers and Skagen dwellers not using iodine-containing supplements was 50 (37; 83) microg/24 h and 177 (137; 219) microg/24 h respectively (P < 0.001). The fraction of samples with iodine below 100 microg/24 h was 85.0 % in Randers and 6.5 % in Skagen (P < 0.001). Use of iodine-containing supplements increased urinary iodine by 60 microg/24 h (P < 0.001). This decreased the number of samples with iodine below 100 microg/24 h to 67.3 % and 5.0 % respectively, but increased the number of samples with iodine above 300 microg/24 h to 2.4 % and 16.1 %. Bioavailability of iodine in humic substances in Skagen tap water was about 85 %. Iodine in natural waters may be elemental or found in humic substances. The fraction available suggests an importance of drinking water supply for population iodine intake, although this may not be adequate to estimate population iodine intake.     

Iodine Status of 6–12-Year-Old Children in Russia over the Past 10 Years: A Scoping Review

Iodine is an essential element for growth and development of children. Ensuring adequate iodine intake and monitoring iodine intake are important public health concerns. According to the World Health Organization, a population-based assessment of iodine status is often done by measuring urine iodine concentration (UIC) in children aged 6–12 years. National data for large countries may hide regional differences in the UIC. Currently, there is limited data on the iodine status of children in Russia. We summarized the evidence on the iodine status of children in Russia using both international and local literature in accordance with the PRISMA guidelines. A total of 2164 studies were identified, 12 of which met the selection criteria and covered 10 of 85 federal subjects. For most of the Russian regions there was no information on UIC. A range of methodologies were used to determine UIC. The median UIC ranged from 46 μg/L in the mountainous areas in the Republic of Kabardino-Balkaria, which corresponds to a moderate iodine deficiency (ID), to 719 μg/L in the town of Turinsk (Sverdlovsk region) indicating excessive of iodine intake. Nationwide monitoring should be implemented in Russia and public health measures should be adjusted to regional and local conditions to ensure adequate iodine nutrition for all citizens.     

Iodine Status of Women of Reproductive Age in Sierra Leone and Its Association with Household Coverage with Adequately Iodized Salt

Salt iodization programs are a public health success in tackling iodine deficiency. Yet, a large proportion of the world’s population remains at risk for iodine deficiency. In a nationally representative cross-sectional survey in Sierra Leone, household salt samples and women’s urine samples were quantitatively analyzed for iodine content. Salt was collected from 1123 households, and urine samples from 817 non-pregnant and 154 pregnant women. Household coverage with adequately iodized salt (≥15 mg/kg iodine) was 80.7%. The median urinary iodine concentration (UIC) of pregnant women was 175.8 µg/L and of non-pregnant women 190.8 µg/L. Women living in households with adequately iodized salt had higher median UIC (for pregnant women: 180.6 µg/L vs. 100.8 µg/L, respectively, p < 0.05; and for non-pregnant women: 211.3 µg/L vs. 97.8 µg/L, p < 0.001). Differences in UIC by residence, region, household wealth, and women’s education were much smaller in women living in households with adequately iodized salt than in households without. Despite the high household coverage of iodized salt in Sierra Leone, it is important to reach the 20% of households not consuming adequately iodized salt. Salt iodization has the potential for increasing equity in iodine status even with the persistence of other risk factors for deficiency.     

Changes in iodine metabolism during late pregnancy and lactation: a longitudinal study among Sudanese women

OBJECTIVE: To elucidate the persistence, or otherwise, of the pregnancy-related changes in the iodine metabolism and thyroid function in a population residing in an area of mild iodine deficiency in the Sudan. DESIGN: A longitudinal prospective cohort study involving pregnant women who were recruited during their third trimester of pregnancy and were followed up for up to nine months after delivery. SETTING: The study was conducted among Sudanese women residing in the Omdurman area in Khartoum, an area with a total goitre rate of 17.5%. Subjects: Forty-seven pregnant women were recruited during their third trimester of pregnancy. Their mean age and weight were 29+/-4.6 y and 62.4+/-8.7 kg, respectively. Age matched healthy non-pregnant women living in the same area (n=40) served as a control group. METHODS: Serum levels of thyrotropin (TSH), thyroxine (T4), triiodothyronine (T3), thyroglobulin (Tg) and the urinary iodine concentration (UIC) were determined during the third trimester (first occasion), and subsequently at three months (second occasion), six months (third occasion) and nine months after delivery (fourth occasion). Control subjects provided corresponding samples on one occasion. Main outcomes measures: UIC, TSH, Tg, FT4 and T3. RESULTS: During the third trimester of pregnancy the median UIC and the free T4 (FT4) were lower than in the control group (P<0. 0001, P<0.0001, respectively), while the median Tg was higher than in the controls (P<0.03). Three months post-partum maximum thyroidal stimulation was evident, with elevated serum levels of TSH and Tg (P<0.0001, P<0.03) and reduced UIC and serum T3 and FT4 (P<0.0004, P<0.0005, P<0.0001), compared with the control group. Nine months post-partum the thyroid function was restored to the pre-pregnancy state, and the median values of TSH, Tg, T3, FT4 and UIC did not differ significantly from those in the control group. CONCLUSIONS: Our study suggests that the reversibility of the pregnancy-induced changes in the iodine status and thyroid function to the pre-pregnancy levels may depend on the iodine status of the mother during and after pregnancy. The thyroidal stress during the first three months of the post-partum period, which is partially due to the iodine loss in the breast milk, justifies further detailed studies to assess the iodine content of the breast milk and the role of breast milk as a vehicle for iodine supply of infants in situations of iodine deficiency. SPONSORSHIP: This study was supported by a grant from the Swedish Agency for Research Co-operation with Developing Countries.