Development of a dried whole-blood spot thyroglobulin assay and its evaluation as an indicator of thyroid status in goitrous children receiving iodized salt

Clinical use of thyroglobulin: not only thyroid cancer

Thyroglobulin (TG) is a dimeric glycoprotein produced exclusively by mature thyroid tissue and stored within the follicular lumen. It is essential for the organification of iodine and the production of thyroid hormones. The concentration of TG in the bloodstream varies between individuals and depends on factors such as thyroid mass, stimulation of the gland by thyrotropin or autoantibodies, and tissue destruction. TG is essential to monitor patients with differentiated thyroid cancer; however, its use is not limited only to this clinical entity. Measurement of circulating TG can provide better insight into numerous clinical scenarios, such as destructive thyroiditis, presence of ectopic thyroid tissue, thyroid trauma, factitious thyrotoxicosis, or iodine nutrition. Lately, TG has found its new clinical use in immune checkpoint-related thyroid dysfunction. TG measurement should be performed carefully in patients with antithyroglobulin antibodies due to possible laboratory interferences. In this review, we offer a summary of current knowledge about the clinical use of TG and the implications it brings to daily practice.

Rapid diagnosis of malaria by chemometric peak-free LIBS of trace biometals in blood

Laser Induced Breakdown Spectroscopy (LIBS) trace atomic species of diseased biofluids are subtle (peak-free) in complex spectra. Trace analysis requires a considerable push in analytical strategy. Enabling LIBS with chemometrics can help identify, extract, analyze and interpret the trace species' spectral signatures to give an insight on the biophysiological status of the bodies from which the biofluids originate. We report on the trace quantitative performance of peak-free LIBS enabled by chemometrics modelling using principal components analysis (PCA) for direct artificial neural network (ANN)-based analysis of Cu, Zn, Fe and Mg in Plasmodium falciparum-infected blood in the context of rapid spectral diagnosis of malaria utilizing the biometals as the disease biomarkers. Only one standard is required in this method-to delineate the analyte spectral regions (feature selection) and to test for accuracy. Based on the alteration of the biometal levels and their multivariate and correlational patterns in cultured blood, peripheral finger blood drops dried directly on Nucleopore membrane filters was accurately discriminated as either malaria-infected or healthy. Further the morphological evolution of Plasmodium was accurately predicted using spectral features of the biometals wherein high negative correlations between Fe (- 0.775) and Zn (- 0.881) and high positive correlations between Cu (0.892) and Mg (0.805) with parasitemia were observed. During the first 96 h of malaria infection Cu increases profoundly (from 328 to 1999 ppb) while Fe, Zn and Mg decrease (from 1206 to 674 ppb), (from 1523 to 499 ppb) and (from 23,880 to 19,573 ppb) respectively. Compared with healthy, Plasmodium falciparum-infected blood has high Cu but low levels of Fe, Zn and Mg. Cu and Zn are highly (≥ 0.9) positively correlated while Fe and Cu as well as Zn and Cu are highly (≥ 0.9) negatively correlated. Chemometric peak-free LIBS showed the potential for direct rapid malaria diagnostics in blood based on the levels, alterations and multivariate associations of the trace biometals which are used as biomarkers of the disease.

Thyroglobulin levels among iodine deficient pregnant women living in Northern Ireland

BACKGROUND

Iodine deficiency has re-emerged among pregnant cohorts in the UK. Thyroglobulin (Tg) is a protein produced uniquely by the thyroid gland which appears to mount a U-shaped response to extremes of iodine status. Tg has been suggested as an alternative marker for chronic iodine deficiency but the value of Tg in pregnancy has not been fully elucidated. A recent non-European study suggested a median Tg ≤10 µg/L with <3% of values >44 µg/L was indicative of sufficiency in the second trimester of pregnancy.

METHODS

We measured serum Tg levels in each trimester in 241 pregnant women living in Northern Ireland, a population with mild iodine deficiency at all stages of pregnancy as defined by urinary iodine concentration (UIC) and iodine: creatinine ratio (ICR). Women with Tg antibodies (6% in 1st trimester) were excluded.

RESULTS

The median UIC in this cohort was in the deficient range at 73, 94 and 117 µg/L in sequential trimesters (adequacy ≥ 150 µg/L). Corresponding median Tg levels were 19, 16 and 16 µg/L respectively. Median Tg for all samples was 17 μg/L (IQR 11-31) suggestive of iodine deficiency. Tg was >44 μg/L in 14.3%, 9.4% and 12.4% of women in sequential trimesters respectively. Women with either UIC/ICR below the cut-offs 150 µg/L and 150 µg/g creatinine had higher Tg concentrations in 1st and 2nd trimester (p < 0.01; p < 0.001) but not in 3rd trimester.

CONCLUSION

This study adds to the evolving evidence that Tg measurement is of value in reflecting iodine status in pregnancy.

Improving Iodine Status in Lactating Women: What Works?

PURPOSE OF REVIEW

Iodine deficiency is a global concern, and in recent years, there has been a significant improvement in the number of countries identified as being iodine-sufficient. This review considers the best strategies to ensure iodine sufficiency among breastfeeding women and their infants.

RECENT FINDINGS

Fortification strategies to improve iodine intake have been adequate for school-age children (SAC); however, often, iodine deficiency remains for breastfeeding women and their infants. Daily supplementation with iodine is not an ideal strategy to overcome deficiency. Countries defined as iodine-sufficient, but where pregnant and breastfeeding women have inadequate intake, should consider increasing salt iodine concentration, such that the median urinary iodine concentration of SAC can be up to 299 µg/L. This will ensure adequate intake for mothers and infants, without SAC being at risk thyroid dysfunction. Consensus is required for thresholds for iodine adequacy for breastfeeding women and infants.

Iodine nutrition: Disorders, monitoring and policies

Iodine is an essential mineral nutrient and an integral component of thyroid hormones. Iodine deficiency is typically associated with goiter, but can have more serious health implications. Adequate iodine status is important for normal brain development. Iodine deficiency in utero or in early life can cause severe neurological and cognitive impairment. Over the last three decades, global efforts have reduced the prevalence of iodine deficiency disorders (IDD) in many areas of the world with implementation of nutrition policies and programs such as "salt" iodization. However, in a number of areas iodine deficiency is still widespread. Iodine deficiency in remote regions with high poverty will be more difficult to eradicate. Efforts to eliminate IDD in affected areas and sustaining successful iodine programs will be a priority given the substantial public health and economic benefits. A key component will be periodic monitoring of population iodine status to ensure sufficient intakes and the absence of excessive intakes. Median urinary iodine concentration (UIC), a validated biomarker for assessing population iodine status, will facilitate monitoring. Research validating "usual" UIC for use in combination with the Estimated Average Requirement cut-point method will expand its utility and allow accurate determination of the prevalence of inadequate intakes in populations. Further research on the development of biomarkers for assessment of individual iodine status for routine patient care will be important.

Thyroglobulin determination on silane-antibody functionalized interdigitated dielectrode surface to diagnose thyroid tumor

Thyroid cancer appears in endocrine glands and specific to thyroid glands has been reported widely. This work was targeted to identify and quantify thyroglobulin by using antithyroglobulin antibody complexed silane surface on interdigitated electrode (IDE) sensing surface. (3-Aminopropyl)triethoxysilane linker was used to make silane-coupling with antibody and attached on the hydroxylated IDE. This electroanalytical IDE revealed the dose-dependent responses with thyroglobulin concentrations. By getting increments with the thyroglobulin concentrations, the current responses were enhanced concomitantly and the thyroglobulin detection limit was noted as 1 pM on the linear curve [y = 0.1311x + 0.5386; R² = 0.9707] with the sensitivity at lower picomolar range. Moreover, the control experiments with thyroid peroxidase and nonimmune antibody cannot yield any response of current, confirming the specific detection of thyroglobulin. This research set-up is useful to determine and quantify the thyroglobulin and diagnose thyroid cancer.

Measuring attack on self: The need for field-friendly methods development and research on autoimmunity in human biology

BACKGROUND

Autoimmune and inflammatory disorder (AIID) prevalence appears to be increasing in all but the world's poorest regions and countries. Autoimmune diseases occur when there is a breakdown in processes that regulate inflammation and self-recognition by immune cells. Very few field-based studies have been conducted among Indigenous populations and underserved communities with limited access to medical care. This is due, in part, to the fact that autoimmune diseases are difficult to diagnose, even in clinical settings. In remote field settings these difficulties are compounded by the absence of infrastructure necessary for sample storage and analysis, and the lack of hospital/clinic access for more invasive diagnostic procedures. Because of these limitations, little is known about the prevalence of autoimmunity outside wealthy regions and clinical settings.

AIMS

The present paper discusses why AIID are of critical importance in human biology research and why more work needs to be devoted to validating, testing, and utilizing methods for detecting autoantibodies and other biomarkers related to autoimmunity in field-friendly, minimally invasively-collected samples. This paper reviews some of the methods used to diagnose AIIDs in clinical settings, and highlights methods that have been used in studies within human biology and related fields, emphasizing the invasiveness of specific methods and their feasibility in remote field settings.

DISCUSSION AND CONCLUSIONS

Risk for AIID is affected by several reproductive, dietary, environmental, and genetic factors. Human biologists have unique perspectives that they can bring to autoimmunity research, and more population-based studies on autoimmunity are needed within these and related fields.

Dried Blood Spot in Laboratory: Directions and Prospects

Over the past few years, dried blood spot (DBS) technology has become a convenient tool in both qualitative and quantitative biological analysis. DBS technology consists of a membrane carrier (MC) on the surface of which a biomaterial sample becomes absorbed. Modern analytical, immunological or genomic methods can be employed for analysis after drying the sample. DBS has been described as the most appropriate method for biomaterial sampling due to specific associated inherent advantages, including the small volumes of biomaterials required, the absence of a need for special conditions for samples’ storage and transportation, improved stability of analytes and reduced risk of infection resulting from contaminated samples. This review illustrates information on the current state of DBS technology, which can be useful and helpful for biomedical researchers. The prospects of using this technology to assess the metabolomic profile, assessment, diagnosis of communicable diseases are demonstrated.

Evaluation of median urinary iodine concentration cut-off for defining iodine deficiency in pregnant women after a long term USI in China

Background

The WHO/UNICEF/ICCIDD define iodine deficiency during pregnancy as median urinary iodine concentration (MUIC) ≤ 150 μg/L. China implemented universal salt iodization (USI) in 1995, and recent surveillance showed nationwide elimination of iodine deficiency disorders (IDD). Data from 2014 showed that the MUIC in 19,500 pregnant women was 154.6 μg/L and 145 μg/L in 9000 pregnant women in 2015. However, symptoms of iodine deficiency were absent. Our study sought to evaluate whether MUIC below 150 μg/L affects thyroid function of Chinese pregnant women and their newborns in Chinese context.

Methods

We screened 103 women with normal thyroid function and MUIC lower than 150 μg/L during week 6 of pregnancy at Peking Union Medical College Hospital. Patient demographics and dietary salt intake were recorded. Subjects were followed at 12, 24, and 32 gestational weeks. At each visit, a 3-day dietary record, drinking water samples, and edible salt samples were collected and analyzed for total dietary iodine intake. Additionally, 24-h urine iodine and creatinine were measured. Blood tests assessed thyroid function in both mothers and newborns.

Results

Of 103 pregnant women enrolled, 79 completed all follow-up visits. Most subjects maintained normal thyroid function throughout pregnancy. However, 19 had thyroid dysfunction based on thyroid stimulating hormone and free thyroxine levels. The median serum iodine was 71 μg/L (95% CI: 44, 109). The median thyroglobulin was < 13 μg/L. values above this level indicate iodine deficiency in pregnant women. The median dietary iodine intake during pregnancy, derived from the 3-day record and measures of water and salt, was 231.17 μg/d. Assuming 90% urinary iodine excretion (UIE), 200.11 μg/d UIE means the 222.34 μg iodine loss per day, suggesting that subjects had a positive iodine balance throughout pregnancy. All neonatal blood samples showed TSH levels lower than 10 mIU/L, indicating normal thyroid function. No significant difference was found among gestational weeks for urinary iodine, and the MUIC in subjects who completed 3 follow-up visits was 107.41 μg/L.

Conclusion

Twenty years after implementing USI, expectant Chinese mothers with MUIC of 107.4 μg/L, less than the WHO's 150 μg/L benchmark, maintained thyroid function in both themselves and their newborn babies.

Goiter and its associated factors among primary school children aged 6-12 years in Anchar district, Eastern Ethiopia

BACKGROUND

Goiter is a major public health problem in Ethiopia. Even though there were studies done on goiter in Ethiopia, there was little evidence in the eastern part of the country. Therefore, the aim of this study was to assess the prevalence of goiter and its associated factors among school-age children in Anchar district of Eastern Ethiopia.

METHODS

A school based cross-sectional study was conducted from February 13 to 30, 2017. Multistage sampling method was used to select 418 children aged 6-12 years. Data were collected using a questionnaire. Children were examined for the presence or absence of goiter based on the criteria of the World Health Organization (WHO). Salt samples were tested using a rapid test kit. Data were entered to EpiData version 3.1 and exported to SPSS version 22.0 for analysis. Bivariate and multivariate logistic regression models were fitted; Crude Odds Ratio (COR) and Adjusted Odds Ratio (AOR) with 95% Confidence Interval (CI) were computed. Level of significance was determined at p-value less than 0.05.

RESULTS

The total goiter prevalence rate was 51.8% (CI: 46.9%, 56.8%). Father's education (AOR = 1.87, CI: 1.06, 3.30), type of salt used (AOR = 2.09, CI: 1.13, 3.88), iodine level of salt (AOR = 2.77, CI: 1.11, 6.89), frequency of milk consumption (AOR = 3.65, CI: 1.63, 8.20), frequency of cabbage consumption (AOR = 7.74, CI: 4.48, 13.39), eating status of eggs (AOR = 3.16, CI: 1.54, 6.50), and eating status of dark green vegetables/fruits (AOR = 2.14, CI: 1.17, 3.93) were factors associated with goiter among school-age children.

CONCLUSIONS

The total goiter prevalence rate was very high. Therefore, the health and education sectors of the study area should work hand in hand to improve the awareness of the community about goiter, iodized salt and iodine rich foods.

Excess iodine intake: sources, assessment, and effects on thyroid function

Iodine is essential for thyroid hormone synthesis. High iodine intakes are well tolerated by most healthy individuals, but in some people, excess iodine intakes may precipitate hyperthyroidism, hypothyroidism, goiter, and/or thyroid autoimmunity. Individuals with preexisting thyroid disease or those previously exposed to iodine deficiency may be more susceptible to thyroid disorders due to an increase in iodine intake, in some cases at intakes only slightly above physiological needs. Thyroid dysfunction due to excess iodine intake is usually mild and transient, but iodine-induced hyperthyroidism can be life-threatening in some individuals. At the population level, excess iodine intakes may arise from consumption of overiodized salt, drinking water, animal milk rich in iodine, certain seaweeds, iodine-containing dietary supplements, and from a combination of these sources. The median urinary iodine concentration (UIC) of a population reflects the total iodine intake from all sources and can accurately identify populations with excessive iodine intakes. Our review describes the association between excess iodine intake and thyroid function. We outline potential sources of excess iodine intake and the physiological responses and consequences of excess iodine intakes. We provide guidance on choice of biomarkers to assess iodine intake, with an emphasis on the UIC and thyroglobulin.

Measurement of micronutrient deficiency associated biomarkers in dried blood spots using a multiplexed immunoarray

Simplifying blood collection is often critical when collecting specimens in remote and/or austere settings. The use of dried blood spots (DBS) offers a practical collection method suitable for a wide variety of analytes. A small volume of whole blood can be obtained rapidly through a minimally invasive heel- or finger-stick using a disposable safety lancet. Once dried, the samples require no further processing, are stable for months or longer, pose minimal risk of disease transmission, and are easy to ship. DBS are often used in demographic health surveys to assess infectious disease status in vulnerable populations. These samples can be used to screen biomarkers of micronutrient deficiency (MND) and inflammation. We recently described a multiplexed immunoarray, the Q-plex human micronutrient array, which can simultaneously quantify seven biomarkers related to MND, inflammation and malarial antigenemia using plasma (alpha-1-acid glycoprotein, C-reactive protein, ferritin, histidine-rich protein 2, retinol binding protein, soluble transferrin receptor, and thyroglobulin). In this work, we present a protocol for preparing eluates from DBS samples and their measurement using a modified protocol for this new tool. We evaluated the concordance of analyte concentrations (excluding ferritin) from a panel ninety samples of DBS prepared from anticoagulated venous blood and paired K2-EDTA plasma. The results show high correlation between DBS eluates and wet plasma for five of the six analytes screened, suggesting the Q-plex human micronutrient array can be used with DBS samples, but also highlighting that anticoagulants can have a negative effects on some test components.

Quantitative dried blood spot analysis for metallodrugs by laser ablation-inductively coupled plasma-mass spectrometry

A quantitative dried blood spot (DBS) method based on direct sampling by means of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is presented. Gadolinium-based contrast agents were used as model metallodrugs with a significant relevance for pharmaceutical applications. Challenges regarding the ablation of the complex blood-filter matrix were characterized and successfully addressed by a thorough adaption of the laser ablation conditions. Especially the laser fluence was optimized with respect to the particle size distribution of the generated aerosol as monitored by an optical particle counter. Thus, generation of micrometer-sized particles could be minimized in favor of smaller particles increasing the transport efficiency of the DBS ablation aerosol to the plasma and the recorded signal stability. Inhomogeneous blood drying on the porous filter paper could be compensated by the addition of an internal standard prior to blood spotting. To preserve the advantages of DBS sampling, such as small blood volumes and minimal invasiveness, the combined use of DBS and a capillary blood sampling system is demonstrated. By placing the internal standard into the capillary prior to blood sampling, a simple workflow usable for clinical application was implemented. The applicability of the developed method, achieving limits of detection and quantification in the low μg L^-1 range and covering a linear range of over four orders of magnitude, was demonstrated for blood samples containing different concentrations of the gadolinium contrast agents gadopentetate and gadoterate.

The assessment of iodine status - populations, individuals and limitations

Iodine deficiency is a significant global health concern, and the single greatest cause of preventable cognitive impairment. It is also a growing public health concern in the UK particularly among pregnant women. Biomarkers such as urinary iodine concentration have clear utility in epidemiological studies to investigate population-level iodine status, but determination of iodine status in individuals is much more problematic with current assays. This article reviews the available biomarkers of iodine status and their relative utility at the level of both populations and individuals for the investigation of iodine deficiency and iodine excess.

Contemporary challenges to iodine status and nutrition: the role of foods, dietary recommendations, fortification and supplementation

Iodine deficiency (ID) in women of childbearing age remains a global public health concern, mainly through its impact on fetal and infant neurodevelopment. While iodine status is improving globally, ID is still prevalent in pregnancy, when requirements increase. More than 120 countries have implemented salt iodisation and food fortification, strategies that have been partially successful. Supplementation during pregnancy is recommended in some countries and supported by the WHO when mandatory salt iodisation is not present. The UK is listed as one of the ten countries with the lowest iodine status globally, with approximately 60 % of pregnant women not meeting the WHO recommended intake. Without mandatory iodine fortification or recommendation for supplementation in pregnancy, the UK population depends on dietary sources of iodine. Both women and healthcare professionals have low knowledge and awareness of iodine, its sources or its role for health. Dairy and seafood products are the richest sources of iodine and their consumption is essential to support adequate iodine status. Increasing iodine through the diet might be possible if iodine-rich foods get repositioned in the diet, as they now contribute towards only about 13 % of the average energy intake of adult women. This review examines the use of iodine-rich foods in parallel with other public health strategies, to increase iodine intake and highlights the rare opportunity in the UK for randomised trials, due to the lack of mandatory fortification programmes.

Dried Blood Spot Thyroglobulin as a Biomarker of Iodine Status in Pregnant Women

CONTEXT

Thyroglobulin (Tg) could be a sensitive biomarker of iodine nutrition in pregnant women (PW). A dried blood spot (DBS) assay would simplify collection and transport in field studies.

OBJECTIVES

Our aims were to (1) establish and test a reference range for DBS-Tg in PW; (2) determine whether co-measurement of Tg antibodies (Abs) is necessary to define population iodine status.

DESIGN, SETTING, AND PARTICIPANTS

Standardized cross-sectional studies of 3870 PW from 11 countries. For the DBS-Tg reference range, we included TgAb-negative PW (n = 599) from 3 countries with sufficient iodine intake.

MAIN OUTCOME MEASURES

We measured the urinary iodine concentration and DBS thyroid-stimulating hormone, total thyroxin, Tg, and TgAb.

RESULTS

In the reference population, the median DBS-Tg was 9.2 μg/L (95% confidence interval, 8.7 to 9.8 μg/L) and was not significantly different among trimesters. The reference range was 0.3 to 43.5 μg/L. Over a range of iodine intake, the Tg concentrations were U-shaped. Within countries, the median DBS-Tg and the presence of elevated DBS-Tg did not differ significantly between all PW and PW who were TgAb-negative.

CONCLUSIONS

A median DBS-Tg of ∼10 μg/L with <3% of values ≥44 μg/L indicated population iodine sufficiency. Concurrent measurement of TgAb did not appear necessary to assess the population iodine status.

Urinary iodine concentration identifies pregnant women as iodine deficient yet school-aged children as iodine sufficient in rural Niger

OBJECTIVE

To assess iodine status among pregnant women in rural Zinder, Niger and to compare their status with the iodine status of school-aged children from the same households.

DESIGN

Seventy-three villages in the catchment area of sixteen health centres were randomly selected to participate in the cross-sectional survey.

SETTING

Salt iodization is mandatory in Niger, requiring 20-60 ppm iodine at the retail level.

SUBJECTS

A spot urine sample was collected from randomly selected pregnant women (n 662) and one school-aged child from the same household (n 373). Urinary iodine concentration (UIC) was assessed as an indicator of iodine status in both groups. Dried blood spots (DBS) were collected from venous blood samples of pregnant women and thyroglobulin (Tg), thyroid-stimulating hormone and total thyroxine were measured. Iodine content of household salt samples (n 108) was assessed by titration.

RESULTS

Median iodine content of salt samples was 5·5 ppm (range 0-41 ppm), 98 % had an iodine content 40 µg/l.

CONCLUSIONS

In this region of Niger, most salt is inadequately iodized. UIC in pregnant women indicated iodine deficiency, whereas UIC of school-aged children indicated marginally adequate iodine status. Thus, estimating population iodine status based solely on monitoring of UIC among school-aged children may underestimate the risk of iodine deficiency in pregnant women.

Serum thyroglobulin reference intervals in regions with adequate and more than adequate iodine intake

The purpose of this study was to establish normal thyroglobulin (Tg) reference intervals (RIs) in regions with adequate and more than adequate iodine intake according to the National Academy of Clinical Biochemistry (NACB) guidelines and to investigate the relationships between Tg and other factors.A total of 1317 thyroid disease-free adult subjects (578 men, 739 nonpregnant women) from 2 cities (Guangzhou and Nanjing) were enrolled in this retrospective, observational study. Each subject completed a questionnaire and underwent physical and ultrasonic examination. Serum Tg, thyroid-stimulating hormone (TSH), thyroid peroxidase antibody (TPOAb), Tg antibody (TgAb), and urinary iodine concentration (UIC) were measured. Reference groups were established on the basis of TSH levels: 0.5 to 2.0 and 0.27 to 4.2 mIU/L.The Tg RIs for Guangzhou and Nanjing were 1.6 to 30.0 and 1.9 to 25.8 ng/mL, respectively. No significant differences in Tg were found between genders or among different reference groups. Stepwise linear regression analyses showed that TgAb, thyroid volume, goiter, gender, age, and TSH levels were correlated with Tg.In adults from regions with adequate and more than adequate iodine intake, we found that Tg may be a suitable marker of iodine status; gender-specific Tg RI was unnecessary; there was no difference between Tg RIs in regions with adequate and more than adequate iodine intake; and the TSH criterion for selecting the Tg reference population could follow the local TSH reference rather than 0.5 to 2.0 mIU/L.

Development of Standard Reference Materials to support assessment of iodine status for nutritional and public health purposes

The use of urinary iodine as an indicator of iodine status relies in part on the accuracy of the analytical measurement of iodine in urine. Likewise, the use of dietary iodine intake as an indicator of iodine status relies in part on the accuracy of the analytical measurement of iodine in dietary sources, including foods and dietary supplements. Similarly, the use of specific serum biomarkers of thyroid function to screen for both iodine deficiency and iodine excess relies in part on the accuracy of the analytical measurement of those biomarkers. The National Institute of Standards and Technology has been working with the NIH Office of Dietary Supplements for several years to develop higher-order reference measurement procedures and Standard Reference Materials to support the validation of new routine analytical methods for iodine in foods and dietary supplements, for urinary iodine, and for several serum biomarkers of thyroid function including thyroid-stimulating hormone, thyroglobulin, total and free thyroxine, and total and free triiodothyronine. These materials and methods have the potential to improve the assessment of iodine status and thyroid function in observational studies and clinical trials, thereby promoting public health efforts related to iodine nutrition.

Urinary iodine, thyroid function, and thyroglobulin as biomarkers of iodine status

The accurate assessment of population iodine status is necessary to inform public health policies and clinical research on iodine nutrition, particularly the role of iodine adequacy in normal neurodevelopment. Urinary iodine concentration (UIC) directly reflects dietary iodine intake and is the most common indicator used worldwide to assess population iodine status. The CDC established the Ensuring the Quality of Iodine Procedures program in 2001 to provide laboratories that measure urinary iodine with an independent assessment of their analytic performance; this program fosters improvement in the assessment of UIC. Clinical laboratory tests of thyroid function (including serum concentrations of the pituitary hormone thyrotropin and the thyroid hormones thyroxine and triiodothyronine) are sometimes used as indicators of iodine status, although such use is often problematic. Even in severely iodine-deficient regions, there is a great deal of intraindividual variation in the ability of the thyroid to adapt. In most settings and in most population subgroups other than newborns, thyroid function tests are not considered sensitive indicators of population iodine status. However, the thyroid-derived protein thyroglobulin is increasingly being used for this purpose. Thyroglobulin can be measured in either serum or dried blood spot (DBS) samples. The use of DBS samples is advantageous in resource-poor regions. Improved methodologies for ascertaining maternal iodine status are needed to facilitate research on developmental correlates of iodine status. Thyroglobulin may prove to be a useful biomarker for both maternal and neonatal iodine status, but validated assay-specific reference ranges are needed for the determination of iodine sufficiency in both pregnant women and neonates, and trimester-specific ranges are possibly needed for pregnant women. UIC is currently a well-validated population biomarker, but individual biomarkers that could be used for research, patient care, and public health are lacking.

Innovations in health and demographic surveillance systems to establish the causal impacts of HIV policies

PURPOSE OF REVIEW

Health and demographic surveillance systems (HDSS), in conjunction with HIV treatment cohorts, have made important contributions to our understanding of the impact of HIV treatment and treatment-related interventions in sub-Saharan Africa. The purpose of this review is to describe and discuss innovations in data collection and data linkage that will create new opportunities to establish the impacts of HIV treatment, as well as policies affecting the treatment cascade, on population health and economic and social outcomes.

RECENT FINDINGS

Novel approaches to routine collection of biomarkers, behavioural data, spatial data, social network information, migration events and mobile phone records can significantly strengthen the potential of HDSS to generate exposure and outcome data for causal analysis of HIV treatment impact and policies affecting the HIV treatment cascade. Additionally, by linking HDSS data to health service administration, education and welfare service records, researchers can substantially broaden opportunities to establish how HIV treatment affects health and economic outcomes when delivered through public sector health systems and at scale.

SUMMARY

As the HIV treatment scaleup in sub-Saharan Africa enters its second decade, it is becoming increasingly important to understand the long-term causal impacts of large-scale HIV treatment and related policies on broader population health outcomes, such as noncommunicable diseases, as well as on economic and social outcomes, such as family welfare and children's educational attainment. By collecting novel data and linking existing data to public sector records, HDSS can create near-unique opportunities to contribute to this research agenda.

Development and Validation of a New Low-Cost Enzyme-Linked Immunoassay for Serum and Dried Blood Spot Thyroglobulin

BACKGROUND

Thyroglobulin (Tg), a biomarker of iodine nutrition, can be measured on dried blood spots (DBS), which simplifies collection and transport in surveys. The World Health Organization recommends DBS-Tg for monitoring iodine status in children. It could also be a useful iodine biomarker during pregnancy. However, the Tg antibody (Ab) used in earlier DBS-Tg assays is no longer commercially available. The aims of the present study were: (i) to develop a new low-cost serum and DBS-Tg sandwich enzyme-linked immunosorbent assay for assessment of Tg in population studies; (ii) to check the stability of DBS-Tg during long-term storage; and (iii) to assess within-subject variability in DBS-Tg.

METHODS

Serum and DBS samples were measured from healthy pregnant women (n = 424) with the new assays, as well as the Immulite 2000 (Siemens), including TgAb positive (n = 150) and TgAb negative (n = 274) women. DBS-Tg stability was tested over 15 weeks of storage at -20 °C. Within-subject variability was evaluated over four weeks in four healthy adults.

RESULTS

Intra-assay and interassay variability was 4.4-7.3% and 10.1-12.9% for the new serum Tg assay, and 7.6-12.3% and 7.6-16.5% for the DBS-Tg assay. Correlation between the two serum methods was high (r = 0.68, p < 0.01). Assay performance in all women and those TgAb negative was comparable. Correlation between the new serum Tg assay and the DBS-Tg assay was high (r = 0.78, p < 0.01), and agreement expressed as a function of the average Tg concentration for the two methods (X) was 0.59X -4.59 μg/L. DBS-Tg was stable for 15 weeks stored at -20 °C. Within-subject variability in DBS-Tg was 21.1%. Reagents and antibodies costs for the new serum and DBS assays are ∼ US$1.

CONCLUSIONS

These new low-cost serum and DBS-Tg assays perform well over a wide range of Tg concentrations, and the field-friendly DBS assay may be particularly useful in population studies of iodine nutrition.

Urinary iodine excretion and thyroid function status in school age children of hilly and plain regions of Eastern Nepal

BACKGROUND

Iodine deficiency is a major public health problem in many developing countries including Nepal. The present study was designed to investigate the urinary iodine excretion (UIE), thyroid function status and household salt iodine content (SIC) in school-aged children (SAC) and to establish the relationships between these factors.

METHODS

A community-based cross sectional study was conducted in selected schools of two districts, Tehrathum and Morang, lying in the hill and plain region of eastern Nepal respectively. A total of 640 SAC, (Tehrathum n = 274 and Morang n = 366) aged 6-11 years, were assessed for UIE and household SIC. Among the 640 children, 155 consented to blood samples (Tehrathum n = 78 and Morang n = 77) to test for serum thyroglobulin (Tg), thyroid stimulating hormone (TSH), free triiodothyronine (fT3) and free thyroxine (fT4). UIE was measured by ammonium persulfate digestion method. SIC was measured by iodometric titration method and Tg, TSH, fT4 and fT3 were measured by immunoassay based kit method.

RESULTS

In Tehrathum and Morang, 9.5 and 7.7% of SAC had UIE values of UIE <100 µg/L while 59.5 and 41% had iodine nutrition values of >299 µg/L, with median UIE of 345.65 and 270.36 µg/L respectively. The overall medians were as follows, Tg 14.29 µg/L, fT3 3.94 pmol/L, fT4 16.25 pmol/L and TSH 3.61 mIU/L. There was a negative correlation between UIE and Tg (r = -0.236, p = 0.003) and a positive correlation between UIE and SIC (r = 0.349, p < 0.0001). We found 19.5%, n = 15 and 16.7%, n = 13 subclinical hypothyroid cases in Morang and Tehrathum respectively. Iodometric titration showed only 6.4% (n = 41) of the samples had household SIC <15 ppm. Multivariate analysis revealed that use of packaged salt by SAC of Tehrathum district correlated with higher UIE values.

CONCLUSIONS

Our focused data suggests that collaborative universal salt iodization (USI) programs are improving the health of children in the Tehrathum and Morang districts of Nepal. We also found that excessive iodine in a large portion of the study groups is a substantial concern and iodine intervention programs need to deal with both deficient and excessive iodine scenarios that can both be present simultaneously in study populations.

Subclinical Hypothyroidism and Elevated Thyroglobulin in Infants with Chronic Excess Iodine Intake

BACKGROUND

Acute iodine excess in newborns can cause hypothyroidism, but there are limited data on the effects of iodine excess on thyroid function in older infants. The aim of this study was to measure the effects of chronic excess iodine intake on thyroid function in 6-24-month-old infants.

METHODS

In this cross-sectional study, infants (n=696) in eastern Nepal were studied. Spot urine samples, venous blood samples, and household salt samples were collected, and urinary iodine concentration (UIC), serum free thyroxine (fT4), thyrotropin (TSH), thyroglobulin (Tg), and titrated household salt iodine concentration (SIC) were measured. Daily iodine intake was calculated from UIC based on estimates of urine volume at this age.

RESULTS

Median (25th-75th percentile) household SIC was 89 (70-149) ppm, while national legislation stipulates a fortification level of 50 ppm. Median UIC was 407 (312-491) μg/L; 76% of infants had a UIC >300 μg/L, suggesting iodine excess. Calculated mean iodine intake in 12-24-month-old infants was 220 μg/day, exceeding the recommended safe upper limit for iodine at this age (200 μg/day). Among the infants, 15.8% had an elevated Tg, 7.4% had subclinical hypothyroidism, but <1% had overt hypothyroidism. UIC was not a significant predictor of thyroid function, thyroid hormones, or Tg.

CONCLUSION

In 6-24-month-old infants exposed to excessive iodine intake, ∼7% have subclinical hypothyroidism but <1% have overt hypothyroidism. These findings suggest the thyroid in late infancy is already able to adapt to high iodine intakes and, in most cases, maintain euthyroidism.

Systematic review using meta-analyses to estimate dose-response relationships between iodine intake and biomarkers of iodine status in different population groups

The objective of this systematic review was to identify studies investigating iodine intake and biomarkers of iodine status, to assess the data of the selected studies, and to estimate dose-response relationships using meta-analysis. All randomized controlled trials, prospective cohort studies, nested case-control studies, and cross-sectional studies that supplied or measured dietary iodine and measured iodine biomarkers were included. The overall pooled regression coefficient (β) and the standard error of β were calculated by random-effects meta-analysis on a double-log scale, using the calculated intake-status regression coefficient (β) for each individual study. The results of pooled randomized controlled trials indicated that the doubling of dietary iodine intake increased urinary iodine concentrations by 14% in children and adolescents, by 57% in adults and the elderly, and by 81% in pregnant women. The dose-response relationship between iodine intake and biomarkers of iodine status indicated a 12% decrease in thyroid-stimulating hormone and a 31% decrease in thyroglobulin in pregnant women. The model of dose-response quantification used to describe the relationship between iodine intake and biomarkers of iodine status may be useful for providing complementary evidence to support recommendations for iodine intake in different population groups.

Sensitive quantification of IGF-1 and its synthetic analogs in dried blood spots

Background: Dried blood spot sample collection could improve detection of the misuse of IGF-1, its analogs and growth hormone. An LC–MS/MS method was developed to measure two IGF-1 peptides and one analog peptide after trypsin digestion. In addition to standard method validation parameters, the effect of hematocrit on cysteine alkylation, trypsin digestion and the selection of internal standard were evaluated. Results: Quantification of IGF-1 peptides was possible with an LLOQ of 25 ng/ml and imprecision of less than 15%. Conclusion: While the effects of hematocrit must be evaluated empirically for each method, dried blood spots are a suitable matrix for the measurement of IGF-1 and its analogs by MS.

Thyroglobulin as a biomarker of iodine deficiency: a review

BACKGROUND

Thyroglobulin, produced exclusively by the thyroid gland, has been proposed to be a more sensitive biomarker of iodine status than thyrotropin or the thyroid hormones triiodothyronine and thyroxine. However, evidence on the usefulness of thyroglobulin (Tg) to assess iodine status has not been extensively reviewed, particularly in pregnant women and adults.

SUMMARY

An electronic literature search was conducted using the Cochrane CENTRAL, Web of Science, PubMed, and Medline to locate relevant studies on Tg as a biomarker of iodine status. Since urinary iodine concentration (UIC) is the recommended method to assess iodine status in populations, only studies that clearly reported both Tg and UIC were included. For the purpose of this review, a median Tg <13 μg/L and a median UIC ≥100 μg/L (UIC ≥150 μg/L for pregnant women) were used to indicate adequate iodine status. We excluded studies conducted in subjects with either known thyroid disease or those with thyroglobulin antibodies. The search strategy and selection criteria yielded 34 articles of which nine were intervention studies. The majority of studies (six of eight) reported that iodine-deficient pregnant women had a median Tg ≥13 μg/L. However, large observational studies of pregnant women, including women with adequate and inadequate iodine status, as well as well-designed intervention trials that include both Tg and UIC, are needed. In adults, the results were equivocal because iodine-deficient adults were reported to have median Tg values of either <13 or ≥13 μg/L. Only studies in school-aged children showed that iodine-sufficient children typically had a median Tg <13 μg/L. Some of the inconsistent results may be partially explained by the use of different methodological assays and failure to assess assay accuracy using a certified reference material.

CONCLUSIONS

These data suggest that Tg does hold promise as a biomarker of iodine deficiency. However, it is associated with limitations. A median Tg cutoff of 13 μg/L warrants further investigation, particularly in adults or pregnant women, as there is a lack of both observational and intervention studies in these groups.

Current and future use of "dried blood spot" analyses in clinical chemistry

The analysis of blood spotted and dried on a matrix (i.e., "dried blood spot" or DBS) has been used since the 1960s in clinical chemistry; mostly for neonatal screening. Since then, many clinical analytes, including nucleic acids, small molecules and lipids, have been successfully measured using DBS. Although this pre-analytical approach represents an interesting alternative to classical venous blood sampling, its routine use is limited. Here, we review the application of DBS technology in clinical chemistry, and evaluate its future role supported by new analytical methods such as mass spectrometry.

Iodine status in pre-school children prior to mandatory iodine fortification in Australia

The iodine status of children between the ages of 5 and 15 years has been routinely assessed in many countries, but few studies have examined iodine status in pre-school children. We conducted a cross-sectional study of pre-school children living in Adelaide, South Australia, between 2005 and 2007. Children 1-5 years old were identified using a unique sampling strategy to ensure that the study population was representative. A 3-day weighed diet record, a blood sample and a urine sample were obtained from each child. The median urinary iodine concentration (UIC) of the children (n = 279) was 129 µg L(-1), indicating iodine sufficiency (normal range: 100-199 µg L(-1)), but 35% of the children had a UIC < 100 µg L(-1). The median thyroglobulin concentration of children (n = 217) was 24 µg L(-1) and thyroglobulin concentration declined with increasing age (P = 0.024). The mean daily iodine intake was 76 µg. The intake of iodine was lower than expected and highlights difficulties in accurately assessing iodine intakes. Further studies are needed to monitor dietary changes and iodine status in this age group since the implementation of mandatory fortification of bread with iodised salt in Australia in 2009.

Iodine nutritional status and risk factors for goitre among schoolchildren in South Tajikistan

BACKGROUND

Iodine deficiency affects nearly 1.9 billion people worldwide, but it can be prevented by salt iodization. This cross-sectional survey assessed current iodine status, iodized salt coverage and risk factors for goitre among schoolchildren in South Tajikistan.

METHODS

Ten primary schools in four districts in South Tajikistan were randomly selected. In schoolchildren aged 7 to 11 years, a spot urine sample was collected for measurement of urinary iodine, dried blood spots were collected for measurement of thyroglobulin, and goitre was assessed by palpation. Iodine content of salt samples and local selling points was determined by coloration using rapid test kits and titration method.

RESULTS

Of 623 schoolchildren enrolled, complete data was obtained from 589. The overall median urinary iodine concentration (UIC) was 51.2 μg/L indicating mild-to-moderate iodine deficiency. Among all children, 46.6% (95% Confidence Interval (CI) = 42.4%-50.6%) of children were found to be goitrous (grade 1 goitre: 30.6%, 95% CI = 26.9%-34.5%; grade 2 goitre: 16.0%, 95% CI = 13.1%-19.2%). The risk factor for goitre remaining significant in the multivariable logistic regression model was 'buying salt once a month' (OR = 2.89, 95% CI = 1.01-8.22) and 'buying salt once every six months' (OR = 2.26, 95% CI = 1.01-5.04) compared to 'buying salt every one or two weeks'. The overall median thyroglobulin concentration was elevated at 13.9 μg/L. Of the salt samples from households and selling points, one third were adequately iodised, one third insufficiently and one third were not iodised.

CONCLUSION

Iodine deficiency remains a serious health issue among children in southern Tajikistan. There is a persisting high prevalence of goitre, elevated thyroglobulin and low UIC despite interventions implemented by Tajikistan and international partners. Quality control of salt iodine content needs to be improved. Continued efforts to raise awareness of the health effects of iodine deficiency are needed to increase consumer demand for iodised salt.

Associations of noniodized salt and thyroid nodule among the Chinese population: a large cross-sectional study

BACKGROUND

The controversy that iodized salt may increase the risk of thyroid disorders has arisen in China during the past several years.

OBJECTIVE

This study aimed to explore whether iodized salt increased the risk of thyroid nodule among a Chinese population.

DESIGN

A cross-sectional study was conducted in Hangzhou, China, in 2010. Iodized salt intake, urinary iodine concentration (UIC), and thyroid nodule (by ultrasonography) were measured in 9412 adults. The associations of iodized salt with thyroid nodule were evaluated by using multiple mixed logistic regression models.

RESULTS

The prevalence of thyroid nodule among men and women was 24.1% and 34.7%, respectively. Adults consuming noniodized salt had an increased risk of thyroid nodule (OR: 1.36; 95% CI: 1.01, 1.83). Similarly, compared with moderate salt appetite, mild salt appetite was associated with an increased risk of thyroid nodule among all adults (OR: 1.19; 95% CI: 1.03, 1.37) and among women (OR: 1.23; 95% CI: 1.03, 1.46). Furthermore, those who consumed neither iodized salt nor milk had a higher risk of thyroid nodule (OR: 1.72; 95% CI: 1.21, 2.43) than did those who consumed both iodized salt and milk. In addition, an increased risk of thyroid nodule (OR: 1.25; 95% CI: 1.07, 1.45) was observed among both pooled samples and women with low UIC.

CONCLUSIONS

These findings indicate that low iodine intake may increase the risk of thyroid nodule in a Chinese population, particularly in women. Hence, the Universal Salt Iodization program may be indispensable for a coastal Chinese population such as that living in Hangzhou. This trial was registered at clinicaltrials.gov as NCT01838629.

Translational research in pediatrics II: blood collection, processing, shipping, and storage

Translational research often involves tissue sampling and analysis. Blood is by far the most common tissue collected. Due to the many difficulties encountered with blood procurement from children, it is imperative to maximize the quality and stability of the collected samples to optimize research results. Collected blood can remain whole or be fractionated into serum, plasma, or cell concentrates such as red blood cells, leukocytes, or platelets. Serum and plasma can be used for analyte studies, including proteins, lipids, and small molecules, and as a source of cell-free nucleic acids. Cell concentrates are used in functional studies, flow cytometry, culture experiments, or as a source for cellular nucleic acids. Before initiating studies on blood, a thorough evaluation of practices that may influence analyte and/or cellular integrity is required. Thus, it is imperative that child health researchers working with human blood are aware of how experimental results can be altered by blood sampling methods, times to processing, container tubes, presence or absence of additives, shipping and storage variables, and freeze-thaw cycles. The authors of this review, in an effort to encourage and optimize translational research using blood from pediatric patients, outline best practices for blood collection, processing, shipment, and storage.

Thyroglobulin is a sensitive measure of both deficient and excess iodine intakes in children and indicates no adverse effects on thyroid function in the UIC range of 100-299 μg/L: a UNICEF/ICCIDD study group report

CONTEXT

The median urinary iodine concentration (UIC) is a biomarker of iodine intake. According to the World Health Organization, a median UIC in the range 100-199 μg/L indicates adequate and 200-299 μg/L more than adequate intake. Thyroglobulin (Tg) may be a promising functional biomarker of both iodine deficiency and excess.

OBJECTIVES

Using a standardized dried blood spots-Tg assay in children, we evaluated the Tg response to both low- and high-iodine intake and estimated the population cutoff point for iodine deficiency or excess. Also, we compared thyroid functions within the UIC ranges of 100-199 vs 200-299 μg/L.

DESIGN AND SETTING

We conducted a cross-sectional study in primary schools in 12 countries.

SUBJECTS

SUBJECTS were 6 to 12 years old (n = 2512).

MAIN OUTCOME MEASURES

We measured UIC, TSH, total T4, Tg, and thyroid antibodies.

RESULTS

Over a range of iodine intakes from severely deficient to excessive, Tg concentrations showed a clear U-shaped curve. Compared with iodine-sufficient children, there was a significantly higher prevalence of elevated Tg values in children with iodine deficiency (UIC <100 μg/L) and iodine excess (UIC >300 μg/L). There was no significant change in the prevalence of elevated Tg, TSH, T4, or thyroid antibodies comparing children within the UIC ranges of 100-199 vs 200-299 μg/L.

CONCLUSIONS

In school-aged children, 1) Tg is a sensitive indicator of both low and excess iodine intake; 2) a median Tg of <13 μg/L and/or <3% of Tg values >40 μg/L indicates iodine sufficiency in the population; 3) the acceptable range of median UIC in monitoring iodized salt programs could be widened to a single category of sufficient iodine intake from 100 to 299 μg/L.

Assessment of iodine nutrition in populations: past, present, and future

Iodine status has been historically assessed by palpation of the thyroid and reported as goiter rates. Goiter is a functional biomarker that can be applied to both individuals and populations, but it is subjective. Iodine status is now assessed using an objective biomarker of exposure, i.e., urinary iodine concentrations (UICs) in spot samples and comparison of the median UIC to UIC cut-offs to categorize population status. This has improved standardization, but inappropriate use of the crude proportion of UICs below the cut-off level of 100 µg/L to estimate the number of iodine-deficient children has led to an overestimation of the prevalence of iodine deficiency. In this review, a new approach is proposed in which UIC data are extrapolated to iodine intakes, adjusted for intraindividual variation, and then interpreted using the estimated average requirement cut-point model. This may allow national programs to define the prevalence of iodine deficiency in the population and to quantify the necessary increase in iodine intakes to ensure sufficiency. In addition, thyroglobulin can be measured on dried blood spots to provide an additional sensitive functional biomarker of iodine status.

A comprehensive assessment of urinary iodine concentration and thyroid hormones in New Zealand schoolchildren: a cross-sectional study

Background

Insufficient iodine in children’s diets is of concern because thyroid hormones are needed for normal growth and development, particularly of the brain. This study aimed to carry out a comprehensive assessment of the iodine status of New Zealand schoolchildren using a range of biochemical indices suitable for populations (i.e. urinary iodine concentration) and individuals (i.e. thyroid hormones).

Methods

The New Zealand National Children’s Nutrition Survey was a cross­‒sectional survey of a representative sample of schoolchildren aged 5­‒14 years. Children were asked to provide a casual urine sample for the determination of urinary iodine concentration (UIC) and a blood sample for the determination of thyroglobulin (Tg), Thyroid Stimulating Hormone (TSH), free thyroxine (fT4) and free triiodothyronine (fT3).

Results

The median UIC was 68 μg/L (n = 1153), which falls between 50­‒99 μg/L indicative of mild iodine deficiency. Furthermore, 29% of children had an UIC <50 μg/L and 82% had an UIC <100 μg/L. The median Tg concentration was 12.9 μg/L, which also falls between 10.0­‒19.9 μg/L indicative of mild iodine deficiency. The Tg concentration of children with an UIC <100 μg/L was 13.9 μg/L, higher than the 10.3 μg/L in children with an UIC >100 μg/L (P = 0.001). The mean TSH (1.7 mU/L), fT4 (14.9 pmol/L), and fT3 (6.0 pmol/L) concentrations for these mildly iodine deficient New Zealand children fell within normal reference ranges.

Conclusions

The UIC and Tg concentration indicate that New Zealand schoolchildren were mildly iodine deficient according to WHO/UNICEF/ICCIDD, and both are suitable indices to assess iodine status in populations or groups. The normal concentrations of TSH, fT4 and fT3 of these children suggest that these thyroid hormones are not useful indices of mild iodine deficiency.

Iodine deficiency in pregnancy, infancy and childhood and its consequences for brain development

Iodine deficiency during foetal development and early childhood is associated with cognitive impairment. Randomised clinical studies in school-aged children encountered in the literature indicate that cognitive performance can be improved by iodine supplementation, but most studies suffer from methodological constraints. Tests to assess cognitive performance in the domains that are potentially affected by iodine deficiency need to be refined. Maternal iodine supplementation in areas of mild-to-moderate iodine deficiency may improve cognitive performance of the offspring, but randomised controlled studies with long-term outcomes are lacking. Studies in infants or young children have not been conducted. The best indicators for iodine deficiency in children are thyroid-stimulating hormone (TSH) in newborns and thyroglobulin (Tg) in older children. Urinary iodine may also be useful but only at the population level. Adequate salt iodisation will cover the requirements of infants and children as well as pregnant women. However, close monitoring remains essential.

Iodine in enteral and parenteral nutrition

Iodine deficiency (ID) has multiple adverse effects on growth and development due to inadequate thyroid hormone production. Methods for assessment of iodine nutrition in individuals include the urinary iodine concentration (UI), thyroid size and thyroid function tests. The UI measured in several repeat 24-h urine samples can detect inadequate iodine intake in individuals receiving enteral or parenteral nutrition (PN) and allow for iodine supplementation before the onset of hypothyroidism. A daily dose of 1 microg iodine/kg body weight is currently recommended for children receiving PN, but this is far below their requirements. Daily iodine requirements in adults receiving enteral nutrition or PN are estimated to be 70-150 microg, but most PN formulations do not contain iodine. Despite this, ID has been unlikely because absorption from iodine-containing skin antiseptics and other adventitious sources can provide sufficient iodine. However, if chlorhexidine replaces iodine-containing antiseptics for catheter care, ID may occur during long-term PN, and periodic testing of UI and thyroid function may be prudent. Infants may be particularly vulnerable to ID because of their small thyroidal iodine store. In this review, we describe three recent patients (an infant, a child and an adult) who developed ID and thyroid hypofunction during PN.

Epidemiology of iodine deficiency: Salt iodisation and iodine status

Universal salt iodisation (USI) and iodine supplementation are highly effective strategies for preventing and controlling iodine deficiency. USI is now implemented in nearly all countries worldwide, and two-thirds of the world's population is covered by iodised salt. The number of countries with iodine deficiency as a national public health problem has decreased from 110 in 1993 to 47 in 2007. Still one-third of households lack access to adequately iodised salt. Iodine deficiency remains a major threat to the health and development of populations around the world, particularly in children and pregnant women in low-income countries. Data on iodine status are available from 130 countries and approximately one-third of the global population is estimated to have a low iodine intake based on urinary iodine (UI) concentrations. Insufficient control of iodine fortification levels has led to excessive iodine intakes in 34 countries. The challenges ahead lie in ensuring higher coverage of adequately iodised salt, strengthening regular monitoring of salt iodisation and iodine status in the population, together with targeted interventions for vulnerable population groups.

Selenium and iodine supplementation: effect on thyroid function of older New Zealanders

BACKGROUND

The New Zealand population has both marginal selenium status and mild iodine deficiency. Adequate intakes of iodine and selenium are required for optimal thyroid function.

OBJECTIVE

The aim of the study was to determine whether low selenium and iodine status compromises thyroid function in an older New Zealand population.

DESIGN

We investigated the effects of selenium and iodine supplementation in a double-blind, randomized, placebo-controlled trial in 100 Dunedin volunteers aged 60-80 y. Participants received 100 microg Se/d as l-selenomethionine, 80 microg I, 100 microg Se + 80 microg I, or placebo for 3 mo. Thyroid-stimulating hormone (TSH), free triiodothyronine (T(3)), free thyroxine (T(4)), thyroglobulin, plasma selenium, whole-blood glutathione peroxidase (GPx) activity, and urinary iodine concentrations (UICs) were measured.

RESULTS

Plasma selenium (P < 0.0001) and whole-blood GPx activity (P<0.0001) increased from baseline to week 12 in the selenium and selenium plus iodine groups in comparison with the placebo group. Median UIC at baseline was 48 microg/L (interquartile range: 31-79 microg/L), which is indicative of moderate iodine deficiency. UIC increased in the iodine and selenium plus iodine groups and was significant only for the iodine group (P = 0.0014). Thyroglobulin concentration decreased by 24% and 13% of baseline in the iodine and selenium plus iodine groups in comparison with the placebo group (P = 0.009 and P = 0.108, respectively). No significant treatment effects were found for TSH, free T(3), free T(4), or ratio of T(3) to T(4).

CONCLUSIONS

Additional selenium improved GPx activity but not the thyroid hormone status of older New Zealanders. Iodine supplementation alleviated the moderate iodine deficiency and reduced elevated thyroglobulin concentrations. No synergistic action of selenium and iodine was observed. The trial was registered at www.anzctr.org.au/registry/ as ACTRN012605000368639.

Thyroglobulin as a marker of iodine nutrition status in the general population

OBJECTIVE

The iodine status of a population is traditionally evaluated by either urinary iodine (UI) excretion or by some measure of thyroid volume and the prevalence of goitre. In this prospective study of a mandatory iodization programme, we aimed to evaluate serum thyroglobulin (Tg) as a marker of iodine status in the population.

METHODS

Two identical cross-sectional studies were performed before (1997-1998, n=4649) and after (2004-2005, n=3570) the initiation of the Danish iodization programme in two areas with mild and moderate iodine deficiency. Serum Tg was measured from blood samples. Thyroid volume was measured by ultrasonography.

RESULTS

Before iodization, the median serum Tg was considerably higher in moderate than in mild iodine deficiency. Iodization led to a lower serum Tg in all examined age groups. The marked pre-iodization difference in Tg level between the regions was eliminated. The prevalence of Tg above the suggested reference limit (40 microg/l) decreased from 11.3 to 3.7% (P<0.0001). Using bootstrapping, we demonstrated a higher efficacy of Tg than of thyroid volume to show a difference between pre- and post-iodization values.

CONCLUSION

We found serum Tg to be a suitable marker of iodine nutrition status in the population. The results may suggest that the Danish iodization programme has led to a sufficient iodine intake, even if the median UI excretion is still marginally low according to WHO criteria.

Methods of assessment of iodine status in humans: a systematic review

BACKGROUND

Biomarkers of iodine status are required to study iodine deficiency disorders in different parts of the world and to evaluate the effects of fortification strategies.

OBJECTIVE

The objective was to assess the usefulness of biomarkers of iodine status in humans by systematically reviewing intervention studies that altered iodine status.

DESIGN

We performed a structured search for iodine intervention studies on Ovid MEDLINE, EMBASE (Ovid), and the Cochrane Library. Studies were assessed for inclusion and validity, with independent duplication. A random-effects meta-analysis was performed.

RESULTS

Twenty-one intervention studies (12 randomized controlled trials, 3 controlled clinical trials, and 6 before-after studies) were included in the review. Urinary iodine (in children and adolescents and in those with low and moderate baseline iodine status), thyroglobulin (in children and adolescents but not in pregnant and lactating women), serum thyroxine (in children and adolescents, adults, women, and those with moderate baseline thyroxine status but not in pregnant and lactating women), and serum thyroid-stimulating hormone (in pregnant and lactating women but not in children and adolescents or those at moderate baseline status), but not triiodothyronine, proved to be useful biomarkers of iodine status.

CONCLUSIONS

Despite the high risk of bias of many of the included studies, the results suggested that urinary iodine, thyroglobin, serum thyroxine, and thyroid-stimulating hormone are useful biomarkers of iodine status, at least in some groups. High-quality controlled studies measuring relevant long-term outcomes are needed to address which biomarker is the most appropriate for assessing iodine intake in some population groups and settings.

Iodine deficiency

Iodine deficiency has multiple adverse effects in humans, termed iodine deficiency disorders, due to inadequate thyroid hormone production. Globally, it is estimated that 2 billion individuals have an insufficient iodine intake, and South Asia and sub-Saharan Africa are particularly affected. However, about 50% of Europe remains mildly iodine deficient, and iodine intakes in other industrialized countries, including the United States and Australia, have fallen in recent years. Iodine deficiency during pregnancy and infancy may impair growth and neurodevelopment of the offspring and increase infant mortality. Deficiency during childhood reduces somatic growth and cognitive and motor function. Assessment methods include urinary iodine concentration, goiter, newborn TSH, and blood thyroglobulin. But assessment of iodine status in pregnancy is difficult, and it remains unclear whether iodine intakes are sufficient in this group, leading to calls for iodine supplementation during pregnancy in several industrialized countries. In most countries, the best strategy to control iodine deficiency in populations is carefully monitored universal salt iodization, one of the most cost-effective ways to contribute to economic and social development. Achieving optimal iodine intakes from iodized salt (in the range of 150-250 microg/d for adults) may minimize the amount of thyroid dysfunction in populations. Ensuring adequate iodine status during parenteral nutrition has become important, particularly in preterm infants, as the use of povidone-iodine disinfectants has declined. Introduction of iodized salt to regions of chronic iodine deficiency may transiently increase the incidence of thyroid disorders, but overall, the relatively small risks of iodine excess are far outweighed by the substantial risks of iodine deficiency.

Methods to assess iron and iodine status

Four methods are recommended for assessment of iodine nutrition: urinary iodine concentration, the goitre rate, and blood concentrations of thyroid stimulating hormone and thyroglobulin. These indicators are complementary, in that urinary iodine is a sensitive indicator of recent iodine intake (days) and thyroglobulin shows an intermediate response (weeks to months), whereas changes in the goitre rate reflect long-term iodine nutrition (months to years). Spot urinary iodine concentrations are highly variable from day-to-day and should not be used to classify iodine status of individuals. International reference criteria for thyroid volume in children have recently been published and can be used for identifying even small goitres using thyroid ultrasound. Recent development of a dried blood spot thyroglobulin assay makes sample collection practical even in remote areas. Thyroid stimulating hormone is a useful indicator of iodine nutrition in the newborn, but not in other age groups. For assessing iron status, haemoglobin measurement alone has low specificity and sensitivity. Serum ferritin remains the best indicator of iron stores in the absence of inflammation. Measures of iron-deficient erythropoiesis include transferrin iron saturation and erythrocyte zinc protoporphyrin, but these often do not distinguish anaemia due to iron deficiency from the anaemia of chronic disease. The serum transferrin receptor is useful in this setting, but the assay requires standardization. In the absence of inflammation, a sensitive method to assess iron status is to combine the use of serum ferritin as a measure of iron stores and the serum transferrin receptor as a measure of tissue iron deficiency.

What a drop can do: dried blood spots as a minimally invasive method for integrating biomarkers into population-based research

Logistical constraints associated with the collection and analysis of biological samples in community-based settings have been a significant impediment to integrative, multilevel bio-demographic and biobehavioral research. However recent methodological developments have overcome many of these constraints and have also expanded the options for incorporating biomarkers into population-based health research in international as well as domestic contexts. In particular using dried blood spot (DBS) samples-drops of whole blood collected on filter paper from a simple finger prick-provides a minimally invasive method for collecting blood samples in nonclinical settings. After a brief discussion of biomarkers more generally, we review procedures for collecting, handling, and analyzing DBS samples. Advantages of using DBS samples-compared with venipuncture include the relative ease and low cost of sample collection, transport, and storage. Disadvantages include requirements for assay development and validation as well as the relatively small volumes of sample. We present the results of a comprehensive literature review of published protocols for analysis of DBS samples, and we provide more detailed analysis of protocols for 45 analytes likely to be of particular relevance to population-level health research. Our objective is to provide investigators with the information they need to make informed decisions regarding the appropriateness of blood spot methods for their research interests.

Iodine requirements and the risks and benefits of correcting iodine deficiency in populations

Iodine deficiency has multiple adverse effects on growth and development due to inadequate thyroid hormone production that are termed the iodine deficiency disorders (IDD). IDD remains the most common cause of preventable mental impairment worldwide. IDD assessment methods include urinary iodine concentration, goiter, thyroglobulin and newborn thyrotropin. In nearly all iodine-deficient countries, the best strategy to control IDD is salt iodization, one of the most cost-effective ways to contribute to economic and social development. When salt iodization is not possible, iodine supplements can be targeted to vulnerable groups. Introduction of iodized salt to regions of chronic IDD may transiently increase the incidence of thyroid disorders, and programs should include monitoring for both iodine deficiency and excess. Although more data on the epidemiology of thyroid disorders caused by differences in iodine intake are needed, overall, the relatively small risks of iodine excess are far outweighed by the substantial risks of iodine deficiency.