Iodine nutrition in the United States. Trends and public health implications: iodine excretion data from National Health and Nutrition Examination Surveys I and III (1971-1974 and 1988-1994)

Associations between urinary iodine concentration and the prevalence of metabolic disorders: a cross-sectional study

Background

Few studies have examined the role of iodine in extrathyroidal function. Recent research has shown an association between iodine and metabolic syndromes (MetS) in Chinese and Korean populations, but the link in the American participants remains unknown.

Purpose

This study aimed to examine the relationship between iodine status and metabolic disorders, including components associated with metabolic syndrome, hypertension, hyperglycemia, central obesity, triglyceride abnormalities, and low HDL.

Methods

The study included 11,545 adults aged ≥ 18 years from the US National Health and Nutrition Examination Survey (2007-2018). Participants were divided into four groups based on their iodine nutritional status(ug/L), as recommended by the World Health Organization: low UIC, < 100; normal UIC, 100-299; high UIC, 300-399; and very high, ≥ 400. The Odds ratio (OR) for MetS basing the UIC group was estimated using logistic regression models for our overall population and subgroups.

Results

Iodine status was positively associated with the prevalence of MetS in US adults. The risk of MetS was significantly higher in those with high UIC than in those with normal UIC [OR: 1.25; 95% confidence intervals (CI),1.016-1.539; p = 0.035). The risk of MetS was lower in the low UIC group (OR,0.82; 95% CI: 0.708-0.946; p = 0.007). There was a significant nonlinear trend between UIC and the risk of MetS, diabetes, and obesity in overall participants. Participants with high UIC had significantly increased TG elevation (OR, 1.24; 95% CI: 1.002-1.533; P = 0.048) and participants with very high UIC had significantly decreased risk of diabetes (OR, 0.83; 95% CI: 0.731-0.945, p = 0.005). Moreover, subgroup analysis revealed an interaction between UIC and MetS in participants aged < 60 years and ≥ 60 years, and no association between UIC and MetS in older participants aged ≥ 60 years.

Conclusion

Our study validated the relationship between UIC and MetS and their components in US adults. This association may provide further dietary control strategies for the management of patients with metabolic disorders.

Iodine contrast exposure and incident COVID-19 infection

Background

Iodine and particularly its oxidated forms have long been recognized for its effective antiseptic properties. Limited in vitro and in vivo data suggest that iodine exposure may rapidly inactivate, reduce transmission, and reduce infectivity of SARS-CoV-2. We hypothesized that iodine exposure may be associated with decreased incident COVID-19 infection.

Methods

A retrospective population-level cohort analysis was performed of the U.S. Veterans Health Administration between 1 March 2020 and 31 December 2020, before the widespread availability of vaccines against SARS-CoV-2. Multivariable logistic regression models estimated the adjusted odds ratios (OR) and 95% confidence intervals (CI) of the associations between iodinated contrast exposure and incident COVID-19 infection, adjusting for age, sex, race/ethnicity, place of residence, socioeconomic status, and insurance status.

Results

530,942 COVID-19 tests from 333,841 Veterans (mean ± SD age, 62.7 ± 15.2 years; 90.2% men; 61.9% non-Hispanic Whites) were analyzed, of whom 9% had received iodinated contrast ≤60 days of a COVID-19 test. Iodine exposure was associated with decreased incident COVID-19 test positivity (OR, 0.75 95% CI, 0.71-0.78). In stratified analyses, the associations between iodinated contrast use and decreased COVID-19 infection risk did not differ by age, sex, and race/ethnicity.

Conclusion

Iodine exposure may be protective against incident COVID-19 infection. Weighed against the risks of supraphysiologic iodine intake, dietary, and supplemental iodine nutrition not to exceed its Tolerable Upper Limit may confer an antimicrobial benefit against SARS-CoV-2. A safe but antimicrobial level of iodine supplementation may be considered in susceptible individuals, particularly in geographic regions where effective COVID-19 vaccines are not yet readily available.

Iodine and Iodine Deficiency: A Comprehensive Review of a Re-Emerging Issue

Iodine is a mineral nutrient essential for the regulation of a variety of key physiological functions including metabolism and brain development and function in children and adults. As such, iodine intake and status within populations is an area of concern and research focus. This paper will review recently published studies that focus on the re-emerging issue of iodine deficiency as a global concern and declining intake among populations in developed countries. Historically, the implementation of salt-iodization programs worldwide has reduced the incidence of iodine deficiency, but 30% of the world’s population is still at risk. Iodine nutrition is a growing issue within industrialized countries including the U.S. as a result of declining iodine intake, in part due to changing dietary patterns and food manufacturing practices. Few countries mandate universal salt iodization policies, and differing agriculture and industry practices and regulations among countries have resulted in inconsistencies in supplementation practices. In the U.S., in spite of salt-iodization policies, mild-to-moderate iodine deficiency is common and appears to be increasing. European countries with the highest incidence of deficiency lack iodization programs. Monitoring the iodine status of at-risk populations and, when appropriate, public health initiatives, appear to be warranted.

Trends in Iodine Status Among U.S. Children and Adults: A Cross-Sectional Analysis of National Health and Nutrition Examination Survey Data from 2001-2004 to 2017-2020

Background: Iodine nutrition is an important public health issue. Trends in iodine status over time among U.S. schoolchildren and adults and factors mediating changes of iodine status were examined. Methods: In this cross-sectional study of National Health and Nutrition Examination Survey (NHANES) data, we estimated trends in the U.S. population using linear regression analyses. Representative samples of U.S. children and adults were enrolled in NHANES 2001-2020. The NHANES cycles were categorized into 5 four-year periods: 2001-2004, 2005-2008, 2009-2012, 2013-2016, and 2017-2020. The final sample sizes of children and adults for analysis were 4288 and 19,661, respectively. The estimated average requirement (EAR) (based on guidelines from the Institute of Medicine), was used to estimate the prevalence rate of inadequate iodine intake. Binary logistic regression analyses were used to investigate the association between iodine status and contributing factors. Results: From 2001-2004 to 2017-2020, among children, urinary iodine concentration (UIC) decreased from 243 to 166 μg/L (p_trend = 0.0057) and prevalence of iodine intake below the EAR rose from 15.4% to 27.6%. In adults, the UIC decreased from 153 to 116 μg/L (p_trend < 0.001) and prevalence of iodine intake below the EAR rose from 15.0% to 17.9%. A higher prevalence rate of iodine intake below the EAR was observed in females compared with males (children, 24.0% vs. 16.5%, p < 0.001; adults, 20.0% vs. 11.1%, p < 0.001). Inadequate iodine intake was less frequent among non-Hispanic White and Hispanic compared with non-Hispanic Black in children and adults. Adults without thyroid problems had a higher prevalence of inadequate iodine intake than those with thyroid problems (16.0% vs. 13.0%, p = 0.001). Inadequate iodine intake was less likely in the children who "sometimes" and "often" consumed milk products compared with children who "never or rarely" consumed milk products (OR = 0.60 [CI 0.30-1.21] and OR = 0.24 [CI 0.13-0.43], respectively). The prevalence of inadequate iodine intake among adults reporting "sometimes" (OR = 0.70 [CI 0.58-0.83]) and "often" consuming milk products was lower than those who "never or rarely" consumed them (OR = 0.36 [CI 0.30-0.44]). Conclusions: In this weighted survey, the prevalence of inadequate iodine intake increased from 2001-2004 to 2017-2020 among U.S. school-age children and adults. Sex, race, thyroid problems, and a decreased intake of milk products were significantly associated with iodine intake below the EAR.

Clinically diagnosed iron and iodine deficiencies and disorders in the entire population of US military service members from 1997 to 2015

OBJECTIVE

Iron and/or iodine deficiencies can have multiple serious adverse health outcomes, but examination of incidence rates of these deficiencies has rarely been conducted in any large population. This study examined incidence rates, temporal trends and demographic factors associated with medically diagnosed iron and iodine deficiencies/disorders in US military service members (SM).

DESIGN

The Defense Medical Epidemiological Database (DMED) was queried for medical visits of active duty SM to obtain specific International Classification of Diseases, Version 9, codes involving clinically diagnosed iron and iodine deficiencies/disorders.

SETTING

Analysis of existing database (DMED).

PARTICIPANTS

Entire population of US military SM from 1997 to 2015 (average n per year = 1 382 266, 15 % women).

RESULTS

Overall incidence rates for iron and iodine were 104 and 36 cases/100 000 person-years, respectively. Over the 19-year period, rates for iron disorders increased steadily (108 % for men, 177 % for women). Rates for iodine disorders also increased steadily for men (91 %), but, for women, there was an initial rise followed by a later decline. Overall, women's rates were 12 and 10 times higher than men's for iron and iodine, respectively. Compared with whites, blacks and those of other races had higher rates of deficiencies of both minerals. Incidence rates for iodine deficiency increased substantially with age.

CONCLUSIONS

The overall incidence of clinically diagnosed iron and iodine deficiency among SM was low, but increased over the 19 years examined, and certain demographic groups were at significantly greater risk. Given the unexpected increases in incidence of these mineral disorders, increased surveillance may be appropriate.Clinical Trial Registration No. ISRCTN58987177 (http//:www.isrctn.com/ISRCTN58987177).

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.

Evidence-Based Recommendations for an Optimal Prenatal Supplement for Women in the U.S., Part Two: Minerals

The levels of many essential minerals decrease during pregnancy if un-supplemented, including calcium, iron, magnesium, selenium, zinc, and possibly chromium and iodine. Sub-optimal intake of minerals from preconception through pregnancy increases the risk of many pregnancy complications and infant health problems. In the U.S., dietary intake of minerals is often below the Recommended Dietary Allowance (RDA), especially for iodine and magnesium, and 28% of women develop iron deficiency anemia during their third trimester. The goal of this paper is to propose evidence-based recommendations for the optimal level of prenatal supplementation for each mineral for most women in the United States. Overall, the evidence suggests that optimal mineral supplementation can significantly reduce a wide range of pregnancy complications (including anemia, gestational hypertension, gestational diabetes, hyperthyroidism, miscarriage, and pre-eclampsia) and infant health problems (including anemia, asthma/wheeze, autism, cerebral palsy, hypothyroidism, intellectual disability, low birth weight, neural tube defects, preterm birth, rickets, and wheeze). An evaluation of 180 commercial prenatal supplements found that they varied widely in mineral content, often contained only a subset of essential minerals, and the levels were often below our recommendations. Therefore, there is a need to establish recommendations on the optimal level of mineral supplementation during pregnancy.

Changing patterns of thyroid cancer in different stages of Universal Salt Iodization in Peking Union Medical College Hospital, 1986-2018

Backgrounds

Iodine intake may be associated with increased thyroid cancer, but its effect varied from places to places. Universal salt iodization (USI) has been introduced in China from 1996 to 2012. The effects of increased iodine intake on thyroid cancer needs to be investigated in China.

Methods

From 1986 to 2018, patients who had thyroidectomies in Peking Union Medical College Hospital (PUMCH) were retrospectively studied. The detection rate, constituent ratio, mean age, sex distribution of thyroid cancer and the pattern of papillary thyroid microcarcinoma (PTMC) were compared between different historical periods.

Results

The detection rate of thyroid cancer in thyroid surgery significantly increased from 6.77% to 75.78% post-USI, with papillary thyroid cancer (PTC) being the majority, and that of follicular thyroid cancer (FTC) and medullary thyroid cancer (MTC) showed only minor changes. There was a descending trend of female/male ratio in PTC from 3.7 to 2.8, and a slight decrease of mean age observed in PTC after USI compared with during USI. The percentage of PTMC in PTC decreased from 13.99% to 8.64%, with a lower mean age after USI (44.88±10.37 vs. 46.44±10.42). Prevalence of goiter coexisting with PTMC was also lower after USI than during USI (31% vs. 41%).

Conclusions

With the popularization of iodized salt, PTC has become the major type in surgery for thyroid cancer, and trends in other histological subtypes remained mostly stable over the periods. The increase in PTC cannot be attributed to the increase of PTMC which is smaller than 1 cm, indicating that contributing factors other than diagnostic activities, may play a role in the increase of PTC.

HYPOTHYROIDISM AND GOITER IN A YOUNG MALE WITH SUSPECTED DIETARY IODINE DEFICIENCY FOLLOWED BY THYROTOXICOSIS AFTER IODINE SUPPLEMENTATION

Objective

Iodine deficiency disorders (IDDs) remain a major public health concern in most parts of the world but are extremely rare in North America. We describe a case of goiter in a young male with dietary history and findings suggestive of IDD.

Methods

Laboratory and imaging procedures including thyroid function tests, autoantibodies, urine iodine, thyroid ultrasound, and radioactive iodine (RAI) uptake scan were performed.

Results

On initial presentation, thyroid-stimulating hormone (TSH) was 24.4 mIU/L (normal range is 0.4 to 5.0 mIU/L), free thyroxine was <0.4 ng/dL (normal range is 0.8 to 1.8 ng/dL), and thyroid peroxidase antibody was positive at 43 IU/mL (normal range is <35 IU/mL). He reported consuming strawberries and peanut butter sandwiches with no intake of dairy or seafood due to gastrointestinal issues (abdominal pain, bloating, and nausea). Physical exam revealed a diffusely enlarged, palpable thyroid gland (grade II goiter). Ultrasound of the neck showed an enlarged thyroid gland with no nodules. RAI uptake scan showed diffuse increased uptake (91%). Given his poor diet, a 24-hour urinary iodine excretion test was ordered which was suggestive of very low iodine intake. He was started on multivitamins with 150 μg of iodine daily. On follow up, clinical exam showed grade I goiter and TSH had normalized to 0.7 mIU/L and free thyroxine was 1.2 ng/dL. He continued on iodine supplementation and tolerated iodine-rich foods. Six months later, thyroid function tests showed hyperthyroidism with TSH of <0.002 ng/dL and free thyroxine was elevated to 2.8 ng/dL. Iodine supplements were stopped.

Conclusion

Hypothyroidism and goiter due to IDD should be suspected in the setting of poor dietary intake. IDDs can be rapidly diagnosed in a patient on a restricted diet with multiple urinary iodine determinations and RAI study. Regular thyroid labs should be done to monitor for hyperthyroidism that can develop after iodine supplementation.

Association between urinary sodium levels and iodine status in Korea

BACKGROUND/AIMS

To evaluate the association between the urinary sodium concentration and iodine status in different age groups in Korea.

METHODS

This nationwide, population-based, cross-sectional study used data from the Korean National Health and Nutrition Examination Survey (VI 2-3, 2014 to 2015). We included 3,645 subjects aged 10 to 75 years with normal kidney function and without a history of thyroid disease. Adequate iodine intake was defined as a urinary iodine/creatinine (I/Cr) ratio of 85 to 220 µg/g. The urinary sodium/ creatinine (Na/Cr) ratios were classified as low (< 47 mmol/g), intermediate (47 to 114 mmol/g), or high (> 114 mmol/g).

RESULTS

The median urinary iodine concentration (UIC) was 292 µg/L (interquartile range [IQR], 157 to 672), and the median urinary I/Cr ratio was 195 µg/g (IQR, 104 to 478). Iodine deficiency (< 100 µg/L) and iodine excess (> 300 µg/L) were observed in 11.3% and 49.0% of subjects, respectively. The UIC was significantly associated with the urinary sodium concentration, and the urinary I/Cr ratio was significantly correlated with the urinary Na/Cr ratio (both p < 0.001). The distributions of UIC, urinary I/Cr ratio, and Na/Cr ratio varied among age groups. Low urinary I/Cr and Na/Cr ratios were most common in young adults (age, 19 to 29 years), while high urinary I/Cr and Na/Cr ratios were most common in elderly people (age, 60 to 75 years).

CONCLUSION

Iodine intake was significantly associated with sodium intake in the Korean population. Our study suggested that an adequately low salt intake might be helpful for preventing iodine excess in Korea.

Breast Milk Iodine Concentration Is Associated with Infant Growth, Independent of Maternal Weight

In breastfed infants, human milk provides the primary source of iodine to meet demands during this vulnerable period of growth and development. Iodine is a key micronutrient that plays an essential role in hormone synthesis. Despite the importance of iodine, there is limited understanding of the maternal factors that influence milk iodine content and how milk iodine intake during infancy is related to postnatal growth. We examined breast milk samples from near 2 weeks and 2 months post-partum in a mother-infant dyad cohort of mothers with pre-pregnancy weight status defined by body mass index (BMI). Normal (NW, BMI < 25.0 kg/m2) is compared to overweight/obesity (OW/OB, BMI ≥ 25.0 kg/m2). The milk iodine concentration was determined by inductively coupled plasma mass spectrometry. We evaluated the associations between iodine content at 2 weeks and infant anthropometrics over the first year of life using multivariable linear mixed modeling. Iodine concentrations generally decreased from 2 weeks to 2 months. We observed no significant difference in iodine based on maternal weight. A higher iodine concentration at 2 weeks was associated with a larger increase in infant weight-for-age and weight-for-length Z-score change per month from 2 weeks to 1 year. This pilot study shows that early iodine intake may influence infant growth trajectory independent of maternal pre-pregnancy weight status.

Iodine status of reproductive age women and their toddlers in northern Ghana improved through household supply of iodized salt and weekly indigenous meal consumption

Iodine deficiency (ID) during pregnancy results in pregnancy losses, intrauterine growth retardation, and lower IQ in the offspring. Even after two decades of universal salt iodization (USI) implementation, the efficacy of USI has not been reported in high risk groups in vulnerable regions in Ghana. We aimed to assess and improve ID status in childbearing age women (all lactating women) and their toddlers in northern Ghana, a geographically and socioeconomically vulnerable region. We provided weekly supply of household iodized salt and community-based feeding of native Hibiscus Sabdariffaa leaves meal (HSM) prepared with iodized salt to women and their toddlers in intervention (n = 60) vs. control group (n = 60). At baseline, ID was prevalent in women (36%) and their toddlers (29%). For women, both median UIC values for intervention (57.4 ug/l) and control group (65.1 ug/l) were below the recommended UIC value of 100 ug/l with no significant differences between the two groups (p = 0.2778). At the endpoint, median UIC for the intervention group (123.6 ug/l) was significantly higher (p = 0.008) than the control group (59.7 ug/l). Our results suggest that weekly supply of iodized salt along with the feeding HSM is an effective channel for improving iodine status of economically disadvantaged groups in communities remote from coastal lands. Furthermore, our results suggest that decreased median UIC among lactating mothers does not necessarily imply lower iodine status for their breastfed toddlers. And finally, the observed median UIC<100 ug/l may point to a non-improvement in iodine status for the past decade for Ghana. There is a need to revisit, assess, and ascertain the challenges in preventing populations from attaining the intended benefits of the USI policy in Ghana.

Iodine Nutrition in Weaning Infants in the United States

BACKGROUND

As iodine is a requisite micronutrient for infant brain development, infants are at risk for iodine deficiency during the weaning period when their diet transitions from milk (breast-milk, infant formula, or follow-on formula) to solid food. Dietary iodine intake during this weaning period is likely minimal, as the iodine content of commercial baby food is not regulated, and the addition of salt to baby food is not recommended. This study reports the current status of iodine nutrition among weaning infants in the United States.

METHODS

Subjects (n = 60; 50% Caucasian, 30% black) were infants <12 months of age who were fed any combination of formula and/or baby food. Samples of all formula and food consumed in the previous 24 hours and a spot urine sample from each infant were obtained for the measurement of iodine. The estimated quantities of ingested formula and baby food were summed from a food diary recorded by the infants' parents.

RESULTS

The mean age of the infants was 6.3 ± 3.5 months. The median urinary iodine concentration (UIC) was 117 μg/L (range 26.9-1302.8 μg/L). Estimated daily iodine intake obtained from the measured iodine content in infant formula/foods was 89 μg (range 0-288 μg). There was a positive correlation between the infants' UIC and the iodine content in the consumed foods (r = 0.4, p < 0.001).

CONCLUSIONS

Although the median UIC of infants fed a combination of infant formula and baby food would meet the criteria for iodine sufficiency in a larger sample, those consuming the lowest quartile of iodine-containing nutritional sources had a median UIC <100 μg/L.

Fluoride Exposure Induces Inhibition of Sodium/Iodide Symporter (NIS) Contributing to Impaired Iodine Absorption and Iodine Deficiency: Molecular Mechanisms of Inhibition and Implications for Public Health

The sodium iodide symporter (NIS) is the plasma membrane glycoprotein that mediates active iodide transport in the thyroid and other tissues, such as the salivary, gastric mucosa, rectal mucosa, bronchial mucosa, placenta and mammary glands. In the thyroid, NIS mediates the uptake and accumulation of iodine and its activity is crucial for the development of the central nervous system and disease prevention. Since the discovery of NIS in 1996, research has further shown that NIS functionality and iodine transport is dependent on the activity of the sodium potassium activated adenosine 5'-triphosphatase pump (Na+, K+-ATPase). In this article, I review the molecular mechanisms by which F inhibits NIS expression and functionality which in turn contributes to impaired iodide absorption, diminished iodide-concentrating ability and iodine deficiency disorders. I discuss how NIS expression and activity is inhibited by thyroglobulin (Tg), tumour necrosis factor alpha (TNF-α), transforming growth factor beta 1 (TGF-β1), interleukin 6 (IL-6) and Interleukin 1 beta (IL-1β), interferon-γ (IFN-γ), insulin like growth factor 1 (IGF-1) and phosphoinositide 3-kinase (PI3K) and how fluoride upregulates expression and activity of these biomarkers. I further describe the crucial role of prolactin and megalin in regulation of NIS expression and iodine homeostasis and the effect of fluoride in down regulating prolactin and megalin expression. Among many other issues, I discuss the potential conflict between public health policies such as water fluoridation and its contribution to iodine deficiency, neurodevelopmental and pathological disorders. Further studies are warranted to examine these associations.

A Review of Iodine Status of Women of Reproductive Age in the USA

Iodine, an essential micronutrient, is required to produce thyroid hormones. Iodine deficiency disorders (IDD) comprise a range of adverse maternal and fetal outcomes, with the most significant irreversible effect resulting from neurodevelopmental deficits in fetal brain caused by deficient iodine status during early pregnancy. The objective of this scoping review was to summarize the studies that assessed iodine status of women of reproductive age in the USA. A systematic review of literature using the PRISMA Extension for Scoping Reviews (PRISMA-ScR) statement was conducted. PubMed, Medline, CINAHL, EMBASE, EBSCOHost, Cochrane, ERIC, Google Scholar, and Web of Science databases were searched, 1652 records were identified. One thousand six hundred forty-one records that did not satisfy the inclusion/exclusion criteria and quality review were excluded, and 11 peer-reviewed articles were determined to be eligible for this scoping review. Despite the USA being considered iodine sufficient for the general population, the US dietary iodine intakes have decreased drastically since the 1970s, with iodine deficiency reemerging in vulnerable groups such as women of reproductive age. Although data to conduct a scoping review of iodine status among women of reproductive age in the USA was scarce, majority of the articles reviewed demonstrate emergent iodine deficiency in this population of women of reproductive age, indicating alarm for a public health concern needing immediate attention.

Consistent Iodine Status Assessment in Chinese Adults by Different Spot Urinary Iodine Concentrations in a Day Together With Corresponding Correction Coefficients

Objective: The aim of this research was to determine the correction coefficients of different spot urinary iodine concentrations (UICs) in a day to predict the early morning UIC, to make the different spot UICs of a day comparable in assessing iodine status in the same population. Methods: In total, 424 participants aged 18 to 28 years were recruited from Tianjin, China. Three spot urine samples were collected from each participant during three periods of the day (6:30-7:00, 10:00-10:30, and 16:00-16:30). A total of 1272 urine samples were collected. A 24-hour dietary record was reported by each participant for 3 consecutive days. Results: Both the UICs at 10:00-10:30 and 16:00-16:30 were higher than that at 6:30-7:00 (181.75 or 198.15μg/L vs 157.69 μg/L; all p < 0.05). Bland-Altman plot showed no good agreements between the other two spot UICs and that at 6:30-7:00 with both Bland-Altman indexes of 7.1%. Correction coefficients used to predict UIC at 6:30-7:00 from the UIC at 10:00-10:30 and 16:00-16:30 were 0.9231 and 0.8592, respectively. The predicted UICs at 6:30-7:00 by using the UIC at 10:00-10:30 and 16:00-16:30 both had no statistically significant difference with the actual UIC at 6:30-7:00 (all p > 0.05). Bland-Altman plot showed good agreements between the predicted UICs and actual UICs at 6:30-7:00 with both Bland-Altman indexes of 4.5%. Conclusions: It was reliable to predict the early morning UIC using correction coefficients of other spot UIC of the day, which gave a new idea for standardizing the methodology of surveys assessing iodine status of a population.

Delayed conception in women with low-urinary iodine concentrations: a population-based prospective cohort study

STUDY QUESTION

Is iodine deficiency associated with decreased fecundability?

SUMMARY ANSWER

Moderate to severe iodine deficiency is associated with a 46% decrease in fecundability.

WHAT IS KNOWN ALREADY

Iodine deficiency is common in women of childbearing age but its effect on fecundability has not been investigated.

STUDY DESIGN, SIZE, DURATION

The LIFE Study, a population-based prospective cohort study, enrolled 501 women who had discontinued contraception within 2 months to become pregnant between 2005 and 2009.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women reported on risk factors for infertility by interview then kept daily journals of relevant information. Women used fertility monitors to time intercourse relative to ovulation then used home digital pregnancy tests to identify pregnancies on the day of expected menstruation. Urine samples for iodine analysis were collected on enrollment.

MAIN RESULTS AND THE ROLE OF CHANCE

Samples were in the deficiency range in 44.3% of participants. The group whose iodine-creatinine ratios were below 50 μg/g (moderate to severe deficiency) had a 46% reduction in fecundity (P = 0.028) compared with the group whose iodine-creatinine ratios were in the adequate range: adjusted fecundability odds ratio of becoming pregnant per cycle, 0.54 (95% confidence interval 0.31-0.94).

LIMITATIONS, REASONS FOR CAUTION

Iodine concentrations vary within individuals over time, so the data must be interpreted by group as we have done; residual confounding is possible.

WIDER IMPLICATIONS OF THE FINDINGS

Significant delays in becoming pregnant occur at iodine concentrations that are common in women in the USA and parts of Europe. Replicating these findings will be important to determine whether improving iodine status could be beneficial in improving fecundability.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, USA. Contracts N01-HD-3-3355; N01-HD-3-3356; N01-HD-3-3358 and HHSN275201100001l/HHSN27500007. None of the authors has any conflict of interest to declare.

Urinary Iodine Concentration and Mortality Among U.S. Adults

BACKGROUND

Iodine deficiency has long been recognized as an important public health problem. Global approaches such as salt iodization that aim to overcome iodine deficiency have been successful. Meanwhile, they have led to excessive iodine consumption in some populations, thereby increasing the risks of iodine-induced thyroid dysfunction, as well as the comorbidities and mortality associated with hypothyroidism and hyperthyroidism. This study aimed to elucidate whether iodine intake is associated with mortality among U.S. adults.

METHODS

This was an observational study to estimate mortality risks according to urinary iodine concentration (UIC) utilizing a nationally representative sample of 12,264 adults aged 20-80 years enrolled in the National Health and Nutrition Examination Survey (NHANES) III. Crude and multivariable Cox proportional hazards regression models were employed to investigate the association between UIC (<50, 50-99, 100-299, 300-399, and ≥400 μg/L) and mortalities (all-cause, cardiovascular, and cancer). In sensitivity analyses, the study adjusted for total sodium intake and fat/calorie ratio in addition to other potential confounders. Stratum-specific analyses were also conducted to estimate the effects of UIC on mortality according to age, sex, race/ethnicity, and estimated glomerular filtration rate category.

RESULTS

Over a median follow-up of 19.2 years, there were 3159 deaths from all causes. Participants with excess iodine exposure (UIC ≥400 μg/L) were at higher risk for all-cause mortality compared to those with adequate iodine nutrition (hazard ratio = 1.19 [confidence interval 1.04-1.37]). Elevated hazard ratios of cardiovascular and cancer mortality were also found, but the confidence interval of the effect estimates included the null value for both outcomes. Low UIC was not associated with increased mortality. Restricted cubic spline models showed similar results for all outcomes. The results did not change substantially after adjusting for total sodium intake and fat/calorie ratio. None of the potential interactions were statistically significant on a multiplicative scale.

CONCLUSION

Higher all-cause mortality among those with excess iodine intake compared to individuals with adequate iodine intake highlights the importance of monitoring population iodine status. Further studies with longitudinal measures of iodine status are needed to validate these results and to assess the potential risks excess iodine intake may have on long-term health outcomes.

Re-establishment of normal radioactive iodine uptake reference range in the era of universal salt iodization in the Indian population

Background & objectives:

The reference radioactive iodine uptake (RAIU) values established in the 1970s in the era of widespread iodine deficiency were relatively high. Now, after four decades of successful Universal Salt Iodization (USI) programme in India, there is a need to re-establish these reference ranges. The present study was aimed to quantify the two-hour and 24-h RAIU values in iodine sufficient euthyroid individuals and validate the results in Graves’ and Hashimoto's thyroiditis patients.

Methods:

In this prospective study conducted from April 2012 to September 2013, euthyroid volunteers who consented for the investigations were enrolled in the study. Treatment-naive Graves’ disease and Hashimoto's thyroiditis patients were recruited from the outpatient clinic. The investigations included neck ultrasonography, thyroid function tests, thyroglobulin (Tg), anti-Tg and anti-thyroid peroxidase antibody and urinary iodine concentration.

Results:

Three different groups comprising 110 euthyroid volunteers, 38 Graves’ and 17 Hashimoto's thyroiditis patients were enrolled in the study. The mean 2-h RAIU values for the euthyroid group, Hashimoto's thyroiditis and Graves’ patients were 3.83±2.77, 4.22±3.41 and 32.67±15.93 per cent, and mean 24-h RAIU values were 12.75±5.51, 11.66±9.55 and 61.85±12.9 per cent, respectively. The mean thyroid volumes were 7.63±2.72, 7.81±1.67 and 20.76±12.56 ml for the euthyroid, Hashimoto's thyroiditis and Graves’ disease groups and the mean spot urinary iodine concentrations were 9.0, 7.8 and 13.9 µg/dl in the three groups, respectively. The new reference range (95% confidence interval) for two-hour was 1-7 per cent and 24-h was 7-18 per cent.

Interpretation & conclusions:

Compared to the previous values, there was a considerable decrease in the RAIU values in euthyroid individuals. This was further corroborated with increase in the urinary iodine concentration and decrease in thyroid volume, attributed to successful USI programme. Further studies with a large sample from different parts of India need to be done to confirm these findings.

A Randomized Controlled Multicenter Trial of an Investigational Liquid Nutritional Formula in Women with Cyclic Breast Pain Associated with Fibrocystic Breast Changes

Objective: A randomized, multicenter, controlled double-blind trial was performed in women with cyclic breast pain (mastalgia) associated with fibrocystic breast changes (FBCs) to determine whether a nutritional formula reduced breast pain and/or nodularity.

Study Design: Women were randomized to receive a specifically designed liquid formulation (n = 93) (1 g gamma-linolenic acid [GLA], 750 μg iodine, and 70 μg selenium) or control formula (n = 95) (without GLA, iodine, and selenium) daily for three cycles. Women recorded breast pain, medications, and menstrual signs daily using interactive voice-response system. Nodularity was determined by physical breast examination.

Results: Breast pain scores decreased similarly in the experimental (−32.2%) and control (−33.1%) groups (p = 0.64). Nodularity was reduced in the experimental, but not the control group (p = 0.03). Among women who continued pain medication, the amount was reduced in the experimental group relative to controls (p = 0.02).

Conclusion: Women with FBC using the formula containing GLA, iodine, and selenium experienced reduced nodularity and in those women who took over-the-counter breast pain medication, a decrease in the quantity of pain medication was observed.

Urinary Iodine, Perchlorate, and Thiocyanate Concentrations in U.S. Lactating Women

BACKGROUND

Iodine is an essential micronutrient for thyroid hormone production. Adequate iodine intake and normal thyroid function are important during early development, and breastfed infants rely on maternal iodine excreted in breast milk for their iodine nutrition. The proportion of women in the United States of childbearing age with urinary iodine concentration (UIC) <50 μg/L has been increasing, and a subset of lactating women may have inadequate iodine intake. UIC may also be influenced by environmental exposure to perchlorate and thiocyanate, competitive inhibitors of iodine transport into thyroid, and lactating mammary glands. Data regarding UIC in U.S. lactating women are limited. To adequately assess the iodine sufficiency of lactating women and potential associations with environmental perchlorate and thiocyanate exposure, we conducted a multicenter, cross-sectional study of urinary iodine, perchlorate, and thiocyanate concentrations in healthy U.S. lactating women.

METHODS

Lactating women ≥18 years of age were recruited from three U.S. geographic regions: California, Massachusetts, and Ohio/Illinois from November 2008 to June 2016. Demographic information and multivitamin supplements use were obtained. Iodine, perchlorate, and thiocyanate levels were measured from spot urine samples. Correlations between urinary iodine, perchlorate, and thiocyanate levels were determined using Spearman's rank correlation. Multivariable regression models were used to assess predictors of urinary iodine, perchlorate, and thiocyanate levels, and UIC <100 μg/L.

RESULTS

A total of 376 subjects (≥125 from each geographic region) were included in the final analyses [mean (SD) age 31.1 (5.6) years, 37% white, 31% black, and 11% Hispanic]. Seventy-seven percent used multivitamin supplements, 5% reported active cigarette smoking, and 45% were exclusively breastfeeding. Median urinary iodine, perchlorate, and thiocyanate concentrations were 143 μg/L, 3.1 μg/L, and 514 μg/L, respectively. One-third of women had UIC <100 μg/L. Spot urinary iodine, perchlorate, and thiocyanate levels all significantly positively correlated to each other. No significant predictors of UIC, UIC <100 μg/L, or urinary perchlorate levels were identified. Smoking, race/ethnicity, and marital status were significant predictors of urinary thiocyanate levels.

CONCLUSION

Lactating women in three U.S. geographic regions are iodine sufficient with an overall median UIC of 143 μg/L. Given ubiquitous exposure to perchlorate and thiocyanate, adequate iodine nutrition should be emphasized, along with consideration to decrease these exposures in lactating women to protect developing infants.

Vitamin D deficiency affects thyroid autoimmunity and dysfunction in iodine-replete area: Korea national health and nutrition examination survey

PURPOSE

We evaluated the effects of vitamin D levels and iodine intake on thyroid autoimmunity and dysfunction in the Korean population.

METHODS

In this nationwide population-based study, data were obtained from the Korea National Health and Nutrition Examination Survey VI-1 and 2 (2013 and 2014), which was the first nationwide survey that measured both serum 25-hydroxy vitamin D [25(OH)D] levels and urinary iodine concentrations (UICs) in Korea. A total of 4181 participants who underwent laboratory tests for thyroid function, serum 25(OH)D levels, and UICs were included.

RESULTS

Anti-thyroid peroxidase antibody (TPOAb) positivity was more prevalent in the vitamin D deficient group (9.1%) than the vitamin D insufficient and sufficient groups (5.3% each; P = 0.016). The rate of TPOAb positivity was significantly higher in the iodine deficient group (P = 0.032). Thyroid dysfunction was significantly more prevalent in the iodine excessive group than in the other groups in total (P = 0.016) and TPOAb negative participants (P = 0.007). In the vitamin D deficient group, excessive iodine intake was significantly associated with high prevalence of thyroid dysfunction in total and TPOAb negative participants (P = 0.021 and P = 0.033, respectively). In the vitamin D insufficient and sufficient groups, association between thyroid dysfunction and iodine intake disappeared in total and TPOAb negative participants.

CONCLUSIONS

This nationwide survey revealed a significant association between vitamin D deficiency and high prevalence of thyroid autoimmunity and dysfunction in participants with excessive iodine intake. Our findings might be helpful for elucidating the potential benefit of vitamin D supplements in TPOAb negative patients with excessive iodine intake.

The Impact of Iodine Status on the Recall Rate of the Screening Program for Congenital Hypothyroidism: Findings from Two National Studies in Iran

Back ground: Iodine deficiency is one of the important factors in increasing the recall rate in congenital hypothyroidism (CH) screening programs. The present study assessed whether the iodine status of the general population may predict the recall rate or vice versa.

METHODS

In the current national study, among 1,382,229 live births delivered between March 2010 and March 2011, 1,288,237 neonates were screened for detecting CH by TSH (thyroid stimulating hormone) measurement via heel prick sampling. Simultaneously, a total of 11,280 school-aged children, aged 7-8 years, were selected using random multi-cluster sampling for measurement of urinary iodine.

RESULTS

A negative correlation was found between median urinary iodine (MUI) and the recall rate (r = -0.33, p = 0.03). No correlation was found between MUIC (median urinary iodine concentration) and the incidence rate of CH. Linear regression analysis showed a 0.1% increase in the recall rate for a one unit decrease in MUIC (β = -0.11, 95% CI: -0.2, -0.1, p = 0.03). MUIC, at a cut-off point of 144.7 µg/L, was predictive for a recall rate < 3% (p = 0.05).

CONCLUSION

Frequencies of TSH ≥ 5 mU/L may be a more sensitive indicator for iodine status during pregnancy rather than in the general population. As higher recall rates reflect inadequate iodine nutrition, sufficient iodine supplementation is needed to reduce the recall rate in such communities.

Iodine stimulates estrogen receptor singling and its systemic level is increased in surgical patients due to topical absorption

Iodine is crucial for thyroid hormone production. However, recent epidemiologic studies have shown that breast cancer patients have an elevated risk of developing thyroid cancer and vice versa. A notable finding in this study is that iodine stimulated the transcriptional activity of estrogen receptor-α (ER-α) in breast cancer cells. Iodine stimulated expression of several ER-α regulated gene including PS2, Cathepsin D, CyclinD1, and PR both in vitro and in nude mice, which is consistent with its stimulation of both anchorage-dependent and -independent growth of ER-α positive breast cancer cells and the effect to dampen tumor shrinkage of MCF-7 xenograft in ovariectomized nude mice. Analyses of clinical urine samples from breast cancer patients undergoing surgery demonstrated that urinary iodine levels were significantly higher than that in controls; and this increased level is due to the antiseptic use of iodine during breast surgery. The present study indicates that excess iodine intake may be an unfavorable factor in breast cancer by stimulation of ER-α transcriptional activity.

Worldwide Recall Rate in Newborn Screening Programs for Congenital Hypothyroidism

CONTEXT

Neonatal mass screening program for congenital hypothyroidism provides the best tool for prevention of its devastating effects on mental development. Despite the overall success of the screening programs in detecting congenital hypothyroidism and eliminating its sequelae and new developments made in the program design, high recall rate and false positive results impose a great challenge worldwide. Lower recall rate and false positive results may properly organize project expenses by reducing the unnecessary repeated laboratory tests, increase physicians and parents' assurance and cooperation, as well as reduce the psychological effects in families.

EVIDENCE ACQUISITION

In this review, we assessed the recall rate in different programs and its risk factors worldwide.

METHODS

Publications reporting the results of the CH screening program from 1997 to 2016 focusing on the recall rate have been searched.

RESULTS

Recall rates vary from 0.01% to 13.3% in different programs; this wide range may be due to different protocols of screening (use of T4 or TSH or both), different laboratory techniques, site of sample collection, recall cutoff, iodine status, human error, and even CH incidence as affected by social, cultural, and regional factors of the population.

CONCLUSIONS

It is suggested to implement suitable interventions to reduce the contributing factors by improving the quality of laboratory tests, selecting conservative cut off points, control iodine deficiency, use of iodine free antiseptic during delivery, and use of more specific markers or molecular tests. Applying an age dependent criteria for thyrotropin levels can be helpful in regions with a varied time of discharge after delivery or for preterm babies.

Thyroid Stimulating Hormone Reference Range and Prevalence of Thyroid Dysfunction in the Korean Population: Korea National Health and Nutrition Examination Survey 2013 to 2015

BACKGROUND

No nationwide epidemiological study evaluating the prevalence of subclinical and overt forms of hypothyroidism and hyperthyroidism has yet been conducted in Korea. This study aimed to evaluate the reference range of serum thyroid stimulating hormone (TSH) and the national prevalence of thyroid dysfunctions in Korea.

METHODS

Nation-wide cross-sectional data were analyzed from a representative sample of the civilian, non-institutionalized Korean population (n=6,564) who underwent blood testing for thyroid function and anti-thyroid peroxidase antibody (TPOAb) as part of the Korea National Health and Nutrition Examination Survey VI (2013 to 2015).

RESULTS

The reference interval of serum TSH in the Korean reference population was 0.62 to 6.68 mIU/L. Based on this reference interval, the prevalence of overt and subclinical hypothyroidism was 0.73% (males 0.40%, females 1.10%) and 3.10% (males 2.26%, females 4.04%), respectively. The prevalence of hypothyroidism increased with age until the age group between 50 to 59 years. Positive TPOAb were found in 7.30% of subjects (males 4.33%, females 10.62%). The prevalence of overt and subclinical hypothyroidism TPOAb-positive subjects was 5.16% and 10.88%, respectively. The prevalence of overt and subclinical hyperthyroidism was 0.54% (males 0.30%, females 0.81%) and 2.98% (males 2.43%, females, 3.59%), respectively.

CONCLUSION

The Serum TSH reference levels in the Korean population were higher than the corresponding levels in Western countries. Differences were found in the prevalence of hypothyroidism and hyperthyroidism according to age, sex, and TPOAb positivity. This study provides important baseline information for understanding patterns of thyroid dysfunction and diseases in Korea.

The changing characteristics and molecular profiles of papillary thyroid carcinoma over time: a systematic review

BACKGROUND

The genetic alterations of papillary thyroid carcinoma (PTC) have been reported to change over the past few decades. We performed this systematic review to further examine the trends and modifications of patient demographic, clinicopathological features and molecular profiles of PTC over time.

METHODS

A literature search was performed within six electronic databases to identify relevant articles. The inclusion criteria were published studies investigating BRAF mutations, RET/PTC rearrangements or RAS mutations in PTCs or classical PTCs. Two teams of reviewers independently screened titles and abstracts of all articles. Full texts of potential articles were read and extracted data were listed and stratified into an excel file according to country, city, institution, and surgical time period. Student t test and Pearson Chi-square were used to analyze the trends of demographic and clinicopathological features of PTC patients and the prevalence of each genetic alteration in individual institutions.

RESULTS

From 3139 articles, we included 16 articles for final analysis. Our results showed an increasing trend of BRAF and a decreasing trend of RET/PTC prevalence over time in PTCs and classical PTCs, accompanied by an older age of PTC patients, an increase in proportion of PTMC and less aggressive behaviours of tumours.

CONCLUSIONS

The demographic and clinicopathological characteristics and molecular profile of PTCs have been changing over the past few decades. These modifications suggest changes in etiologies and risk factors of thyroid cancer that influence the tumorigenesis of PTCs.

Multistage carcinogenesis and the incidence of thyroid cancer in the US by sex, race, stage and histology

Background

Thyroid cancer has the fastest growing incidence in the US. However, the underlying causes are still under debate.

Methods

We analyzed thyroid cancer incidence in the SEER-9 registry from 1973-2010 using multistage carcinogenesis and age-period-cohort models. Multistage models were used to investigate differences in initiation, promotion and malignant conversion rates of thyroid tumors by sex, race, stage, and histology. Models were adjusted for period and cohort trends to investigate the contributions of each factor, and determine whether birth- or diagnosis-year better correlate with observed incidence patterns.

Results

Significant increases in thyroid cancer incidence by period or calendar-year were found for all sex, race, stage and histology combinations, particularly for localized cases (a 3- and 4-fold increase from 1973-2010 for females and males, respectively). Multistage analyses suggest that the 3-fold higher incidence in women could be explained by 1.5-fold higher initiation and promotion rates. Analyses by race suggest that the lower incidence in blacks can be attributed to lower promotion rates versus whites. Analysis by histology showed considerable decreases in follicular cancer incidence by birth-cohort since the early 1900s.

Conclusions

Multistage modeling suggests that variations in thyroid cancer initiation and promotion can explain the observed differences in incidence by sex, race and histology. The consistent increases in incidence by calendar-year for all sex-race-histology-stage combinations suggest that the rise may be predominantly due to more intensive screening-diagnostics, although an environmental factor may be also at play. Our analyses constitute a first step towards the development of thyroid cancer natural history models.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-015-2108-4) contains supplementary material, which is available to authorized users.

Effect of a Low Iodine Diet vs. Restricted Iodine Diet on Postsurgical Preparation for Radioiodine Ablation Therapy in Thyroid Carcinoma Patients

PURPOSE

The radioiodine ablation therapy is required for patients who underwent a total thyroidectomy. Through a comparative review of a low iodine diet (LID) and a restricted iodine diet (RID), the study aims to suggest guidelines that are suitable for the conditions of Korea.

MATERIALS AND METHODS

The study was conducted with 101 patients. With 24-hour urine samples from the patients after a 2-week restricted diet and after a 4-week restricted diet, the amount of iodine in the urine was estimated. The consumed radioiodine amounts for 2 hours and 24 hours were calculated.

RESULTS

This study was conducted with 47 LID patients and 54 RID patients. The amounts of iodine in urine, the 2-week case and 4-week case for each group showed no significant differences. The amounts of iodine in urine between the two groups were both included in the range of the criteria for radioiodine ablation therapy. Also, 2 hours and 24 hours radioiodine consumption measured after 4-week restrictive diet did not show statistical differences between two groups.

CONCLUSION

A 2-week RID can be considered as a type of radioiodine ablation therapy after patients undergo a total thyroidectomy.

Iodine intake as a risk factor for thyroid cancer: a comprehensive review of animal and human studies

Thyroid cancer (TC) is the most common endocrine malignancy and in most countries, incidence rates are increasing. Although differences in population iodine intake are a determinant of benign thyroid disorders, the role of iodine intake in TC remains uncertain. We review the evidence linking iodine intake and TC from animal studies, ecological studies of iodine intake and differentiated and undifferentiated TC, iodine intake and mortality from TC and occult TC at autopsy, as well as the case–control and cohort studies of TC and intake of seafood and milk products. We perform a new meta-analysis of pooled measures of effect from case–control studies of total iodine intake and TC. Finally, we examine the post-Chernobyl studies linking iodine status and risk of TC after radiation exposure. The available evidence suggests iodine deficiency is a risk factor for TC, particularly for follicular TC and possibly, for anaplastic TC. This conclusion is based on: a) consistent data showing an increase in TC (mainly follicular) in iodine deficient animals; b) a plausible mechanism (chronic TSH stimulation induced by iodine deficiency); c) consistent data from before and after studies of iodine prophylaxis showing a decrease in follicular TC and anaplastic TC; d) the indirect association between changes in iodine intake and TC mortality in the decade from 2000 to 2010; e) the autopsy studies of occult TC showing higher microcarcinoma rates with lower iodine intakes; and f) the case control studies suggesting lower risk of TC with higher total iodine intakes.

No difference in urinary iodine concentrations between Boston-area breastfed and formula-fed infants

BACKGROUND

Thyroid hormone is essential for normal mental and physical development in infancy and childhood and is dependent on adequate iodine intake. During the first few months of life, infants are reliant on breastmilk and/or infant formula as their sole sources of dietary iodine. The iodine status of U.S. infants has not been well studied.

METHODS

This was a cross-sectional study of 95 breastfed and/or formula-fed infants less than 3 months of age in the Boston area. We measured iodine content from infants' single spot urine samples and assessed associations with infant feeding type as well as maternal demographic data, salt and multivitamin use, smoking status, and diet.

RESULTS

The median infant urine iodine concentration was 197.5 μg/L (range 40-897.5 μg/L). Median infant urine iodine concentrations were similar between infants who were exclusively breastfed (n=39, 203.5 μg/L; range 61.5-395.5 μg/L), formula-fed (n=44, 182.5 μg/L; range 40-897.5 μg/L), and mixed (n=10, 197.8 μg/L; range 123-592.5) (p=0.88). There were no significant correlations of infant urinary iodine with maternal salt or multivitamin use (regularly or in the past 24 hours), active or secondhand cigarette smoke exposures, infant weight, infant length, or recent maternal ingestion of common iodine-containing foods, although the correlations with iodine-containing foods are difficult to accurately determine due to the small sample sizes of these variables.

CONCLUSIONS

Both breastfed and formula-fed infants less than 3 months of age in the Boston area were generally iodine sufficient. Larger studies are needed to confirm these observations among infants nationwide and elucidate other factors that may contribute to infant iodine nutrition.

Comparison of population iodine estimates from 24-hour urine and timed-spot urine samples

BACKGROUND

Median urine iodine concentration (UIC; μg/L) in spot urine samples is recommended for monitoring population iodine status. Other common measures are iodine:creatinine ratio (I/Cr; μg/g) and estimated 24-hour urine iodine excretion (UIE; I/Cr × predicted 24-hour Cr; μg/day). Despite different units, these measures are often used interchangeably, and it is unclear how they compare with the reference standard 24-hour UIE.

METHODS

Volunteers aged 18-39 years collected all their urine samples for 24 hours (n=400). Voids from morning, afternoon, evening, overnight, and a composite 24-hour sample were analyzed for iodine. We calculated median observed 24-hour UIE and 24-hour UIC, and spot UIC, I/Cr, and two measures of estimated UIE calculated using predicted 24-hour Cr from published estimates by Kesteloot and Joosens (varies by age and sex) and published equations by Mage et al. (varies by age, sex, race, and anthropometric measures). We examined mean differences and relative difference across iodine excretion levels using Bland-Altman plots.

RESULTS

Median 24-hour UIE was 173.6 μg/day and 24-hour UIC was 144.8 μg/L. From timed-spot urine samples, estimates were: UIC 147.3-156.2 μg/L; I/Cr 103.6-114.3 μg/g, estimated 24-hour UIE (Kesteloot and Joosens) 145.7-163.3 μg/day; and estimated 24-hour UIE (Mage) 176.5-187.7 μg/day. Iodine measures did not vary consistently by timing of spot urine collection. Compared with observed 24-hour UIE, on average, estimated (Mage) 24-hour UIE was not significantly different, while estimated 24-hour UIE (Kesteloot and Joosens) was significantly different for some ethnicity/sex groups. Compared with 24-hour UIC, on average, spot UIC did not differ.

CONCLUSIONS

Estimates of UIC, I/Cr, and estimated 24-hour UIE (I/Cr × predicted 24-hour Cr) from spot urine samples should not be used interchangeably. Estimated 24-hour UIE, where predicted 24-hour Cr varies by age, sex, ethnicity, and anthropometric measures and was calculated with prediction equations using data from the sample, was more comparable to observed 24-hour UIE than when predicted 24-hour Cr was from published estimates from a different population. However, currently no cutoffs exist to interpret population estimated 24-hour UIE values.

The epidemic of thyroid cancer in the United States: the role of endocrinologists and ultrasounds

BACKGROUND

The incidence of thyroid cancer has increased at an alarming rate in both men and women in the United States. The etiology of this epidemic is unclear. We tested the hypothesis that a significant component of this epidemic is due to increased detection of occult disease. We examined whether the density of endocrinologists and general surgeons as well as employment of cervical ultrasonography were factors associated with this epidemic.

METHODS

Thyroid cancer incidence rates by states were obtained from the United States Cancer Statistics 1999-2009 reported by the National Program of Cancer Registries. The densities of endocrinologists and general surgeons and the employment of cervical ultrasonography were calculated on a statewide basis and correlated with the incidence of thyroid cancer.

RESULTS

Age-standardized incidence rates of thyroid cancer have increased in every state in the United States. Significant regional variations were noted, with the highest incidence rates in the northeast and the lowest in the south. The incidence rates were significantly correlated with the density of endocrinologists (r = 0.58, p<0.0001 for males; r = 0.44, p = 0.0031 for females) and the employment of cervical ultrasonography (r = 0.40, p = 0.0091 for males; r = 0.36, p = 0.0197 for females). Both the density of endocrinologists and general surgeons and employment of cervical ultrasonography could explain 57% of the variability in state-level incidence for males and 49% for females.

CONCLUSIONS

These data offer evidence to suggest that the epidemic of thyroid cancer is due to increased detection of a reservoir of previously occult disease. The increased detection of thyroid cancer results in therapeutic interventions including surgery and radioactive thyroid treatment that may be of limited benefit.

A Case Report of Post-Operative Jöd-Basedow Phenomennon Following Oral and IV Iodine Contrast Administration

This is a case of thyrotoxicosis, due to the Jöd-Basedow phenomenon following administration of oral and IV iodinated contrast in a patient with history of gastrointestinal stromal tumor (GIST) and small bowel obstruction. The patient developed atrial fibrillation and had an extended stay in the intensive care unit. Given the aging population with possible subclinical hyperthyroidism, multinodular goiter, and the rise in contrast administration for routine diagnostic studies, this case serves to raise awareness of the risks of “routine” tests administered to our aging patient population.

Intakes of dairy products and dietary supplements are positively associated with iodine status among U.S. children

Although pregnant women and some groups of reproductive-age women in the US may be at risk of iodine deficiency, data also suggest that iodine intake among many U.S. children may be above requirements. Our objective was to describe the association of iodine sources with iodine status among children. We analyzed 2007-2010 NHANES data of urine iodine concentration (UIC) spot tests for children aged 6-12 y (n = 1553) and used WHO criteria for iodine status (median UIC: 100-199 μg/L = adequate; 200-299 μg/L = above requirements; ≥300 μg/L = excess). The overall median UIC was above requirements for children aged 6-12 y [211 μg/L (95% CI: 194, 228 μg/L)]. Median UIC increased by quartile of previous day dairy intake, ranging from adequate in the lowest quartile [157 μg/L (95% CI: 141, 170 μg/L)] to above requirements in the highest quartile [278 μg/L (95% CI: 252, 336 μg/L)]. Median UIC was 303 μg/L (95% CI: 238, 345 μg/L) among the 17% of children who had taken a dietary supplement containing iodine the previous day, compared with 198 μg/L (95% CI: 182, 214 μg/L) among those who had not. In adjusted regression analyses, recent dairy intake and recent supplement use were significantly positively associated with UIC levels, whereas recent grain intake was negatively associated. Adding salt to food at the table was not associated with UIC. Iodine-containing supplements are likely not needed by most schoolchildren in the US because dietary iodine intake is adequate in this age group.

Thyroid cancer incidence patterns in Sao Paulo, Brazil, and the U.S. SEER program, 1997-2008

BACKGROUND

Thyroid cancer incidence has risen steadily over the last few decades in most of the developed world, but information on incidence trends in developing countries is limited. Sao Paulo, Brazil, has one of the highest rates of thyroid cancer worldwide, higher than in the United States. We examined thyroid cancer incidence patterns using data from the Sao Paulo Cancer Registry (SPCR) in Brazil and the National Cancer Institute's Surveillance Epidemiology End Results (SEER) program in the United States.

METHODS

Data on thyroid cancer cases diagnosed during 1997-2008 were obtained from SPCR (n=15,892) and SEER (n=42,717). Age-adjusted and age-specific rates were calculated by sex and histology and temporal patterns were compared between the two populations.

RESULTS

Overall incidence rates increased over time in both populations and were higher in Sao Paulo than in the United States among females (SPCR/SEER incidence rate ratio [IRR]=1.65) and males (IRR=1.23). Papillary was the most common histology in both populations, followed by follicular and medullary carcinomas. Incidence rates by histology were consistently higher in Sao Paulo than in the United States, with the greatest differences for follicular (IRR=2.44) and medullary (IRR=3.29) carcinomas among females. The overall female/male IRR was higher in Sao Paulo (IRR=4.17) than in SEER (IRR=3.10) and did not change over time. Papillary rates rose over time more rapidly in Sao Paulo (annual percentage change=10.3% among females and 9.6% among males) than in the United States (6.9% and 5.7%, respectively). Regardless of sex, rates rose faster among younger people (<50 years) in Sao Paulo, but among older people (≥50 years) in the United States. The papillary to follicular carcinoma ratio rose from <3 to >8 among both Sao Paulo males and females, in contrast to increases from 9 to 12 and from 6 to 7 among U.S.males and females, respectively.

CONCLUSIONS

Increased diagnostic activity may be contributing to the notable rise in incidence, mainly for papillary type, in both populations, but it is not likely to be the only reason. Differences in iodine nutrition status between Sao Paulo and the U.S. SEER population might have affected the observed incidence patterns.

Race-ethnicity is related to biomarkers of iron and iodine status after adjusting for sociodemographic and lifestyle variables in NHANES 2003-2006

The NHANES 2003-2006 has assessed iron and iodine status, 2 trace element nutrients of continued public health interest, in the U.S. population. We investigated associations of sociodemographic (age, sex, race-ethnicity, education, income) and lifestyle (smoking, alcohol consumption, BMI, physical activity, dietary supplement use) variables with the iron status indicators serum ferritin, soluble transferrin receptor (sTfR), and body iron in women aged 20-49 y (n = 2539, 2513, and 2509, respectively) and with urine iodine, a biomarker of iodine intake, in adults aged ≥ 20 y (n = 3066). Significant correlations between the study variables and biomarkers were weak (|r| ≤ 0.24). Urine creatinine (uCr) was moderately significantly correlated with urine iodine (r = 0.52). The individual variables explained ≤ 5% of the variability in biomarker concentrations in bivariate analysis. In multiple regression models, sociodemographic and lifestyle variables together explained 4-13% of the variability in iron indicators and 41% of the variability in urine iodine (uCr in the model). The adjusted estimated body iron was ≈ 1 unit (mg/kg) lower in non-Hispanic black vs. non-Hispanic white women and ≈ 1 unit higher in women who smoked vs. those who did not and in women consuming 1 vs. 0 alcoholic drinks/d. The adjusted estimated urine iodine concentration (uCr in the model) was 34% lower in non-Hispanic blacks vs. non-Hispanic whites, 22% higher in supplement users vs. nonusers, and 11% higher with every 10-y increase in age. In summary, after adjusting for sociodemographic and lifestyle variables (and uCr in the iodine model), race-ethnicity retained a strong association with sTfR, body iron, and urine iodine; smoking and alcohol consumption with iron biomarkers; and supplement use and age with urine iodine.

The prevalence of using iodine-containing supplements is low among reproductive-age women, NHANES 1999-2006

During pregnancy, the iodine requirement rises to meet demands for neurological development and fetal growth. If these requirements are not met, irreversible pathological cognitive and behavioral changes to the fetus may ensue. This study estimated the prevalence of iodine-containing dietary supplement (DS) use and intakes of iodine from DSs among pregnant women and nonpregnant women of reproductive age (15-39 y) who were interviewed and examined in NHANES 1999-2006 (n = 6404). Although 77.5% of pregnant women reported taking one or more DSs in the past 30 d, only 22.3% consumed an iodine-containing supplement. Most pregnant women reported using one DS and reported taking this product daily. The vast majority of iodine-containing DSs reported by pregnant women claimed an iodine content of 150 μg iodine/serving on the label. Pregnant women using at least one DS containing iodine had a mean daily iodine intake of 122 μg/d from supplements; the median value was 144 μg/d. Median urinary iodine concentrations (UICs) were similar for pregnant and nonpregnant women in the population aged 15-39 y. The median UIC was 148 μg/L for pregnant women and 133 μg/L for nonpregnant women. The WHO has established a cutoff for insufficient iodine intake at <150 μg/L for pregnant women and <100 mg/L for those who are not pregnant. This suggests that as a population, we may not be meeting adequate intakes of iodine for pregnant women. More research is needed on the iodine intakes of pregnant women and women of reproductive age on their total iodine intake from all sources, not just DSs.

Assessment of iodine nutrition in pregnant north Indian subjects in three trimesters

OBJECTIVE

The cross-sectional study was carried out to assess the iodine status of pregnant women, using median urinary iodine concentration (MUI) as the measure of outcome, to document the impact of advancing gestation on the MUI in normal pregnancy.

MATERIALS AND METHODS

The present study assessed the MUI in casual urine samples from 50 pregnant subjects of each trimester and 50 age-matched non-pregnant controls.

RESULTS

The median (range) of urinary iodine concentration (UIC) in pregnant women was 304 (102-859) μg/L and only 2% of the subjects had prevalence of values under 150 μg/L (iodine insufficiency). With regard to the study cohort, median (range) UIC in the first, second, and third trimesters was 285 (102-457), 318 (102-805), and 304 (172-859) μg/L, respectively. Differences between the first, second, and third trimesters were not statistically significant. The MUI in the controls (305 μg/L) was not statistically different from the study cohort.

CONCLUSION

The pregnant women had no iodine deficiency, rather had high median urinary iodine concentrations indicating more than adequate iodine intake. Larger community-based studies are required in iodine-sufficient populations, to establish gestation-appropriate reference ranges for UIC in pregnancy.

Hashimoto's thyroiditis: celebrating the centennial through the lens of the Johns Hopkins hospital surgical pathology records

Hashimoto's thyroiditis is now considered the most prevalent autoimmune disease, as well as the most common endocrine disorder. It was initially described in 1912, but only rarely reported until the early 1950s. To celebrate this centennial, we reviewed the surgical pathology archives of the Johns Hopkins hospital for cases of Hashimoto's thyroiditis, spanning the period from May 1889 to October 2012. Approximately 15,000 thyroidectomies were performed at this hospital over 124 years. The first surgical case was reported in 1942, 30 years after the original description. Then, 867 cases of Hashimoto's thyroiditis were seen from 1942 to 2012, representing 6% of all thyroidectomies. Hashimoto's thyroiditis was the sole pathological finding in 462 cases; it accompanied other thyroid pathologies in the remaining 405 cases. The most commonly associated pathology was papillary thyroid cancer, an association that increased significantly during the last two decades. The most common indication for thyroidectomy was a thyroid nodule that was cytologically suspicious for malignancy. Hashimoto's thyroiditis remains a widespread, intriguing, and multifaceted disease of unknown etiology one century after its description. Advances in the understanding of its pathogenesis and preoperative diagnosis will improve recognition and treatment of this disorder, and may one day lead to its prevention.

History of U.S. iodine fortification and supplementation

Iodine is a micronutrient required for thyroid hormone production. This review highlights the history of the discovery of iodine and its uses, discusses the sources of iodine nutrition, and summarizes the current recommendations for iodine intake with a focus on women of childbearing age.

Environmental perchlorate and thiocyanate exposures and infant serum thyroid function

BACKGROUND

Breastfed infants rely on maternal iodine for thyroid hormone production required for neurodevelopment. Dietary iodine among women of childbearing age in the United States may be insufficient. Perchlorate (competitive inhibitor of the sodium/iodide symporter [NIS]) exposure is ubiquitous. Thiocyanate, from cigarettes and diet, is a weaker NIS inhibitor. Environmental perchlorate and thiocyanate exposures could decrease breast milk iodine by competitively inhibiting NIS in lactating breasts (thus impairing infants' iodine availability), and/or infants' thyroidal NIS to directly decrease infant thyroid function. The current study assessed the relationships between environmental perchlorate and thiocyanate exposures and infant serum thyroid function.

METHODS

Iodine, perchlorate, and thiocyanate in breast milk, maternal and infant urine, and infant serum thyroid function tests were cross-sectionally measured in Boston-area women and their 1-3 month-old breastfed infants. Univariate and multivariable analyses assessed relationships between iodine, perchlorate, thiocyanate, thyroid-stimulating hormone (TSH), and free thyroxine (FT4) levels.

RESULTS

In 64 mothers and infants, median (range) iodine levels were 45.6 μg/L (4.3-1080) in breast milk, 101.9 μg/L (27-570) in maternal urine, and 197.5 μg/L (40-785) in infant urine. Median perchlorate concentrations were 4.4 μg/L (0.5-29.5) in breast milk, 3.1 μg/L (0.2-22.4) in maternal urine, and 4.7 μg/L (0.3-25.3) in infant urine. There were no correlations between infant TSH or FT4 and iodine, perchlorate, and thiocyanate levels in breast milk, maternal urine, and infant urine. In multivariable analyses, perchlorate and thiocyanate levels in breast milk, maternal urine, and infant urine were not significant predictors of infant TSH or FT4.

CONCLUSIONS

Boston-area mothers and their breastfed infants are generally iodine sufficient. Although environmental perchlorate and thiocyanate are ubiquitous, these results do not support the concern that maternal and infant environmental perchlorate and thiocyanate exposures affect infant thyroid function.

Geriatric thyroidology: An update

Thyroid anatomy and physiology change in the elderly with age-related fibrosis and atrophy in the thyroid gland and changes in thyroid hormones. The incidence of thyroid nodules increases with age, making the thyroid more nodular. Hypothyroidism is common in the elderly and, if untreated, is associated with significant morbidity. Elderly patients are sensitive to iatrogenic hyperthyroidism, especially with preexisting cardiac disease. Hence, treatment of hypothyroidism should be individualized and should be started with low doses and titrated according to response. Hyperthyroidism, although less common in the elderly if present, is associated with significant cardiac morbidity and mortality. Radioiodine therapy is considered a safe primary treatment in the elderly with hyperthyroidism. Management of subclinical hypo- and hyperthyroidism is still controversial. The incidence of thyroid tumors increase with age. Thyroid malignancy in the elderly is considered as a more advanced disease compared with the young, and aggressive management is recommended.

Summary of an NIH workshop to identify research needs to improve the monitoring of iodine status in the United States and to inform the DRI

The Office of Dietary Supplements (ODS) at the NIH sponsored a workshop on May 12-13, 2011, to bring together representatives from various NIH institutes and centers as a first step in developing an NIH iodine research initiative. The workshop also provided an opportunity to identify research needs that would inform the dietary reference intakes for iodine, which were last revised in 2001. Iodine is required throughout the life cycle, but pregnant women and infants are the populations most at risk of deficiency, because iodine is required for normal brain development and growth. The CDC monitors iodine status of the population on a regular basis, but the status of the most vulnerable populations remains uncertain. The NIH funds very little investigator-initiated research relevant to iodine and human nutrition, but the ODS has worked for several years with a number of other U.S. government agencies to develop many of the resources needed to conduct iodine research of high quality (e.g., validated analytical methods and reference materials for multiple types of samples). Iodine experts, scientists from several U.S. government agencies, and NIH representatives met for 2 d to identify iodine research needs appropriate to the NIH mission.

The changing epidemiology of iodine deficiency

Globally, about 2 thousand million people are affected by iodine deficiency. Although endemic goitre is the most visible sign of iodine deficiency, its most devastating consequence is brain damage causing mental retardation in children. The relationship between iodine deficiency and brain damage was not clearly established until the 1980s when the term iodine deficiency disorders (IDDs), which encompass a spectrum of conditions caused by iodine deficiency, was introduced. This paradigm shift in the understanding of the clinical consequences of iodine deficiency led to a change in iodine deficiency assessment. The median urinary iodine excretion level has been recommended as the preferred indicator for monitoring population iodine deficiency status since 2001. The 2007 WHO urinary iodine data in schoolchildren from 130 countries revealed that iodine intake is still insufficient in 47 countries. Furthermore, about one-third of countries lack national estimates of the prevalence of iodine deficiency. The picture that has emerged from available data worldwide over the past two decades is that IDDs are not confined to remote, mountainous areas in developing countries, but are a global public health problem that affects most countries, including developed countries and island nations. The recognition of the universality of iodine deficiency highlights the need to develop and apply new strategies to establish and maintain sustainable IDD elimination and strengthen regular monitoring programmes.

Iodine nutrition in pregnancy and lactation

Adequate iodine intake is required for the synthesis of thyroid hormones that are important for normal fetal and infant neurodevelopment. In this review, we discuss iodine physiology during pregnancy and lactation, methods to assess iodine sufficiency, the importance of adequate iodine nutrition, studies of iodine supplementation during pregnancy and lactation, the consequences of hypothyroidism during pregnancy, the current status of iodine nutrition in the United States, the global efforts toward achieving universal iodine sufficiency, and substances that may interfere with iodine use.

Iodine status and thyroid function of Boston-area vegetarians and vegans

CONTEXT

Adequate dietary iodine is required for normal thyroid function. The iodine status and thyroid function of U.S. vegetarians and vegans have not been previously studied. Environmental perchlorate and thiocyanate (inhibitors of thyroid iodine uptake) exposures may adversely affect thyroid function.

OBJECTIVE

The objective of the study was to assess the iodine status and thyroid function of U.S. vegetarians (consume plant based products, eggs, milk; abstain from meat, poultry, fish, shellfish) and vegans (avoid all animal products) and whether these may be affected by environmental perchlorate and thiocyanate exposures.

DESIGN AND SETTING

This was a cross-sectional assessment of urinary iodine, perchlorate, and thiocyanate concentrations and serum thyroid function in Boston-area vegetarians and vegans.

SUBJECTS

One hundred forty-one subjects (78 vegetarians, 63 vegans) were recruited; one vegan was excluded.

RESULTS

Median urinary iodine concentration of vegans (78.5 μg/liter; range 6.8-964.7 μg/liter) was lower than vegetarians (147.0 μg/liter; range 9.3-778.6 μg/liter) (P < 0.01). Adjusted for cigarette smoking (confirmed by urinary cotinine levels) and thiocyanate-rich food consumption, median urinary thiocyanate concentration of vegans (630 μg/liter; range 108-3085 μg/liter) was higher than vegetarians (341 μg/liter; range 31-1963 μg/liter) (P < 0.01). There were no between-group differences in urinary perchlorate concentrations (P = 0.75), TSH (P = 0.46), and free T(4) (P = 0.77). Urinary iodine, perchlorate, and thiocyanate levels were not associated with TSH (P = 0.59) or free T(4) (P = 0.14), even when adjusted for multiple variables.

CONCLUSIONS

U.S. vegetarians are iodine sufficient. U.S. vegans may be at risk for low iodine intake, and vegan women of child-bearing age should supplement with 150 μg iodine daily. Environmental perchlorate and thiocyanate exposures are not associated with thyroid dysfunction in these groups.