Thyroid disorders in mild iodine deficiency

The impact of replacing milk with plant-based alternatives on iodine intake: a dietary modelling study

PURPOSE

Cow's milk is the primary source of iodine in the UK, but consumption of plant-based milk alternatives (PBMA) is increasing and these products are often not fortified with iodine. We evaluated the impact that replacing current milk consumption with PBMA would have on iodine intake.

METHODS

We used data from the National Diet and Nutrition Survey (2016-2019) for children (1.5-10 years), girls 11-18 years, and women of reproductive age (WRA). We used a dietary modelling approach with scenarios using brand-level iodine-fortification data (0, 13, 22.5, 27.4 and 45 µg/100 mL). Relative to usual diet, we calculated change in iodine intake, and the proportion with intake below the Lower Reference Nutrient Intake (LRNI) or above the upper limit.

RESULTS

For all groups, replacement with PBMA, either unfortified or fortified at the lowest concentration, resulted in a meaningful decrease in iodine intake, and increased the proportion with intake < LRNI; compared to usual diet, iodine intake reduced by 58% in children 1.5-3 years (127 vs. 53 µg/day) and the proportion with intake < LRNI increased in girls (11-18 years; 20% to 48%) and WRA (13% to 33%) if an unfortified PBMA was used. Replacement of milk with PBMA fortified at 27.4 µg/100 mL had the lowest impact.

CONCLUSION

Replacing milk with commercially available PBMAs has potential to reduce population iodine intake, depending on the fortification level. PBMAs fortified with ≥ 22.5 and < 45 µg iodine/100 mL would be required to minimize the impact on iodine intake. Research is needed on the impact of total dairy replacement.

Burden and trends of iodine deficiency in Asia from 1990 to 2019

OBJECTIVES

Understanding iodine deficiency (ID) burdens and trends in Asia can help guide effective intervention strategies. This study aims to report the incidence, prevalence, and disability-adjusted life years (DALYs) of ID in 48 Asian countries during the period 1990-2019.

STUDY DESIGN

Data on ID were retrieved from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 and estimated by age, sex, geographical region, and sociodemographic index (SDI).

METHODS

The estimated annual percentage change (EAPC) was calculated to evaluate the changing trend of age-standardized incidence rate (ASIR), age-standardized prevalence rate (ASPR), and age-standardized DALYs rate (ASDR) related to ID during the period 1990-2019.

RESULTS

In Asia, there were 126,983,965.8 cases with 5,466,213.1 new incidence and 1,765,995.5 DALYs of ID in 2019. Between 1999 and 2019, the EAPC in ASIR, ASPR and ASDR were -0.6 (95% confidence interval [CI], -0.8 to -0.4), -0.9 (95% CI, -1.2 to -0.7), and -1.6 (95% CI, -1.8 to -1.5), respectively. Malaysia charted the largest decrease in ASIR, ASPR, and ASDR (82.4%, 85.3%, and 80.9% separately), whereas the Philippines and Pakistan were the only two countries that witnessed an increase in ASIR and ASPR. ID burdens were more pronounced in women, countries located to the south of the Himalayas, and low-middle SDI regions.

CONCLUSIONS

The incidence, prevalence, and DALYs of ID in Asia substantially decreased from 1990 to 2019. Women and low-middle SDI countries have relatively high ID burdens. Governments need to pay constant attention to the implementation and monitoring of universal salt iodization.

Relationship between mild iodine deficiency in pregnant women and thyroid function: A meta-analysis

BACKGROUND

Pregnant women are among the key groups in iodine nutrition evaluation. The purpose of the present study was to summarize the evidence supporting the relationship between mild iodine deficiency (UIC: 100-150 μg/L) in pregnant women and levels of thyroid function tests.

METHODS

This review follows the guidelines for systematic reviews (PRISMA 2020). Three electronic databases (PubMed, Medline, and Embase) were searched for relevant publications in English on the association between mild iodine deficiency in pregnant women and thyroid function. Articles published in Chinese were searched in China's electronic databases (CNKI, WanFang, CBM, and WeiPu). Pooled effects were presented as standardized mean differences (SMDs) and odds ratios (ORs) with 95% confidence intervals (CIs) using fixed or random effect models, respectively. This meta-analysis was registered at www.crd.york.ac.uk/prospero as CRD42019128120.

RESULTS

We summarized the results from 7 articles with 8261 participants. The overall pooled results showed that the levels of FT₃, FT4, and abnormal TgAb (the antibody levels exceeded the upper limit of the reference range) were significantly increased in pregnant women with mild iodine deficiency compared to pregnant women with adequate iodine status (FT₃: SMD=0.854, 95% CI: 0.188, 1.520; FT₄: SMD=0.550, 95% CI: 0.050, 1.051; TgAb: OR=1.292, 95% CI: 1.095; 1.524). Subgroup analysis was carried out on the sample size, ethnicity, country, and gestation of FT₃, FT_4, and TSH, but no plausible factor was found. Egger's tests indicated no publication bias.The increase in FT₃ and FT_4, as well as TgAb levels, in pregnant women is associated with mild iodine deficiency.

CONCLUSION

Mild iodine deficiency is associated with an increase in FT_3，FT₄ and TgAb levels in pregnant women. Mild iodine deficiency may increase the risk of thyroid dysfunction in pregnant women.

Exposure to Novel Brominated Flame Retardants and Organophosphate Esters and Associations with Thyroid Cancer Risk: A Case-Control Study in Eastern China

Novel brominated flame retardant (NBFR) and organophosphate ester (OPE) exposure may engender adverse effects on human health. However, present epidemiological information regarding the effects of such exposure is limited and controversial. In this case-control study, 481 serum samples were collected from patients with thyroid cancer (n = 242) and healthy controls (n = 239) in Shandong Province, eastern China. The levels of NBFRs and OPEs, thyroid hormones, and serum lipid parameters were measured in all the participants. Pentabromotoluene, 2,3-dibromopropyl 2,4,6 tribromophenyl ether, decabromodiphenylethane (DBDPE), tris (2-chloroethyl) phosphate (TCEP), and triphenyl phosphate (TPP) were widely detected (detection frequency > 60%) in all the participants. A significantly high risk association was found between exposure of NBFRs and OPEs (namely 1,2,3,4,5-pentabromobenzene, DBDPE, tri-n-propyl phosphate, tri[(2R)-1-chloro-2-propyl] phosphate, tris (1,3-dichloro-2-propyl) phosphate, and tris (2-butoxyethyl) phosphate) and thyroid cancer in both males and females. In the females of the control group, TCEP levels exhibited a significantly positive association with thyroid-stimulating hormone and a negative association with triiodothyronine (T3), free triiodothyronine (FT3), and free thyroxine (FT4) levels. Weighted quantile sum regression evaluated the mixed effects of the compounds on thyroid hormones levels and thyroid cancer. As a result, TPP accounted for the majority of the T3, thyroxine, and FT3 amounts. Our results suggest that NBFR and OPE exposure contributes to alterations in thyroid function, thereby increasing thyroid cancer risk.

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.

Prevalence and risk factors of untreated thyroid dysfunctions in the older Caucasian adults: Results of PolSenior 2 survey

INTRODUCTION

To determine the prevalence of treated and untreated thyroid dysfunction and to identify factors associated with increased risk of undiagnosed thyroid dysfunction in older adults.

METHODS

The population of 5987 community-dwelling Polish Caucasian seniors aged 60 years and above who participated in the PolSenior 2 study (2018-2019). Population-based cross-sectional multidisciplinary study in design. Data from structured questionnaires, geriatric tests, and scales were obtained from all study participants who underwent anthropometric and blood pressure measurements during three home visits. Assessment of thyroid function was based on TSH serum measurements.

RESULTS

The prevalence of thyroid dysfunction in the Polish population aged 60 years or above was estimated at 15.5% (21.5% in women and 7.2% in men), with 3.2% of undiagnosed individuals among them. The prevalence of hypothyroidism and hyperthyroidism in the studied group was 13.9% (19.4% in women and 6.3% in men) and 1.6% (2.1% in women and 0.9% in men) respectively, untreated hypothyroidism was revealed in 21.9% (in 160 out of 732 subjects) and untreated hyperthyroidism in 34.2% of subjects (in 41 out of 120 participants). In multiple regression analysis independent risk factors for thyroid disorders being untreated were older age (> 75 years), male sex, a low education level (primary or lower), and low utilization of medical services.

CONCLUSIONS

One-fifth of Polish Caucasian seniors with hypothyroidism and one-third with hyperthyroidism are untreated. Older, poorly educated and rarely utilizing medical services seniors, especially men, are more frequently untreated for thyroid dysfunction and some of them do not benefit from contemporary achievements in medicine.

The Prevalence and Risk Factors Associated with Iodine Deficiency in Canadian Adults

Iodine is a trace micronutrient that is critical for normal thyroid function and human health. Inadequate dietary intake is associated with cognitive impairment, infertility, growth retardation and iodine deficiency disorders in affected populations. Herein, we examined the prevalence of iodine deficiency in adults (median age of 61 years) based on the analysis of 24 h urine samples collected from 800 participants in four clinical sites across Canada in the Prospective Urban and Rural Epidemiological (PURE) study. Urinary iodide together with thiocyanate and nitrate were measured using a validated capillary electrophoresis assay. Protective/risk factors associated with iodine deficiency were identified using a binary logistic regression model, whereas daily urinary iodine concentration (24 h UIC, μg/L) and urinary iodine excretion (24 h UIE, μg/day) were compared using complementary statistical methods with covariate adjustments. Overall, our Canadian adult cohort had adequate iodine status as reflected by a median UIC of 111 μg/L with 11.9% of the population <50 μg/L categorized as having moderate to severe iodine deficiency. Iodine adequacy was also evident with a median 24 h UIE of 226 μg/day as a more robust metric of iodine status with an estimated average requirement (EAR) of 7.1% (< 95 μg/day) and a tolerable upper level (UL) of 1.8% (≥1100 μg/day) based on Canadian dietary reference intake values. Participants taking iodine supplements (OR = 0.18; p = 6.35 × 10−5), had greater 24 h urine volume (OR = 0.69; p = 4.07 × 10−4), excreted higher daily urinary sodium (OR = 0.71; p = 3.03 × 10−5), and/or were prescribed thyroxine (OR = 0.33; p = 1.20 × 10−2) had lower risk for iodine deficiency. Self-reported intake of dairy products was most strongly associated with iodine status (r = 0.24; p = 2.38 × 10−9) after excluding for iodine supplementation and T4 use. Participants residing in Quebec City (OR = 2.58; p = 1.74 × 10−4) and Vancouver (OR = 2.54; p = 3.57 × 10−4) were more susceptible to iodine deficiency than Hamilton or Ottawa. Also, greater exposure to abundant iodine uptake inhibitors from tobacco smoking and intake of specific goitrogenic foods corresponded to elevated urinary thiocyanate and nitrate, which were found for residents from Quebec City as compared to other clinical sites. Recent public health policies that advocate for salt restriction and lower dairy intake may inadvertently reduce iodine nutrition of Canadians, and further exacerbate regional variations in iodine deficiency risk.

The Association Between Circulating Trans Fatty Acids and Thyroid Function Measures in U.S. Adults

BACKGROUND

There has been controversial evidence regarding the effect of trans fatty acids (TFAs) on thyroid function in animal studies, and the epidemiological studies are lacking. We aimed to investigate the potential associations between circulating TFAs and thyroid function biomarkers in a U.S. adult population sample.

METHODS

We performed a cross-sectional survey with 626 adults aged ≥20 years who participated in the National Health and Nutrition Examination Survey (NHANES) 2009-2010. Multivariable linear regression models were constructed to elucidate the relationships between circulating concentrations of TFAs (palmitelaidic acid, vaccenic acid, elaidic acid, linoelaidic acid and the sum of the four TFAs) and a panel of thyroid function measures.

RESULTS

For 626 adults, positive associations were found between palmitelaidic acid, elaidic acid and total thyroxine (TT4), between palmitelaidic acid and total triiodothyronine (TT3), and between linolelaidic acid and thyroid stimulating hormone (TSH), while linolelaidic acid was negatively associated with free thyroxine (FT4) (all P<0.05). Besides, the four TFAs and the sum TFAs were positively associated with free triiodothyronine (FT3). Vaccenic acid, elaidic acid, linoelaidic acid and the sum TFAs were positively associated with FT3/FT4, while the four TFAs and the sum TFAs were negatively associated with FT4/TT4 (all P<0.05). In stratified analysis, the associations between thyroid function measures and the ratios remained significant in female. For men, linolelaidic acid was negatively associated with FT4 and elaidic acid and the sum TFAs were positively associated with FT3. Furthermore, the associations between TFAs and FT3/FT4 remained significant.

CONCLUSION

Our findings revealed that TFAs exposure was associated with serum biomarkers of thyroid function. More researches are needed to evaluate the long-term health outcomes of these findings.

Identifying potential metabolic tissue biomarkers for papillary thyroid cancer in different iodine nutrient regions

PURPOSE

To investigate the applicability of metabolomics to select thyroid cancer-associated biomarkers and discover the effects of iodine on metabolic changes in thyroid cancer.

METHODS

In this study, a total of 33 papillary thyroid cancer (PTC) patients from areas with iodine excess and 32 PTC patients from areas with adequate iodine were recruited, and their cancerous tissue and paracancerous tissue were collected. These specimens were analyzed by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC/QTOF/MS) in conjunction with multivariate statistical analysis.

RESULTS

Good separations were obtained for PTC tissue vs. paracancerous tissue, and 15 metabolites, including L-octanoylcarnitine, N-arachidonoylglycine, and others were found to be disturbed in PTC tissue. Moreover, the metabolic profile presented considerable separation between PTC tissue from different iodine areas, and 15 metabolomic biomarkers were found to be differentially expressed. Among them, 10 metabolites, including arachidonoylcarnitine and LysoPCs, were related to thyroid cancer and excess iodine. These biomarkers play a role in arachidonic acid metabolism pathways and others. In addition, biomarkers such as 3,5-tetradecadiencarnitine and oxidized glutathione were significantly correlated with thyroid function, and biomarkers such as L-octanoylcarnitine and arachidonic acid were significantly correlated with the clinical characteristics of PTC.

CONCLUSIONS

Distinct differences in metabolic profiles were found to exist between PTCs from areas with different levels of iodine nutrition. The identified biomarkers have significant potential for diagnosing PTC and investigating its underlying mechanisms.

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.

Prevalence of Goiter Among School-Aged Children in Ethiopia: Update of Systematic Review and Meta-analysis

Background

Iodine deficiency is a major public health concern throughout the world. Goiter is the most visible sign of iodine deficiency. In Ethiopia, a study finding regarding the prevalence of goiter among school-age children is inconsistent and highly variable.

Objectives

To estimate the pooled prevalence of goiter among school-age children in Ethiopia.

Methods

Three international databases (MEDLINE/Pub-Med, Google Scholar and Science Direct) were systematically searched. Besides, the reference sections of identified articles were searched to increase the chance of detecting missed articles in gray literature. STATA Version 14 statistical software was used to conduct a meta-analysis. The pooled prevalence with a 95% confidence interval was displayed using the forest plot. A random-effect meta-analysis model was used to compute the pooled prevalence, and The Cochrane Q test statistics and I² test were used to assess the heterogeneity of the studies.

Results

A total of 14 studies fulfilled the inclusion criteria and included in this systematic review and Meta-analysis, with a total sample size of 26,282. The finding of this systematic review revealed that the pooled prevalence of goiter among school-age children was 42.9% (95% CI: 38.8–46.9). The highest prevalence of goiter (46.7%) was observed in Oromia region and the lowest (26.3%) was observed in Benishangul-Gumuz region.

Conclusions

This review finding revealed that more than two in five of the school children in Ethiopia suffer from iodine deficiency disorder as manifested by the goiter rate.

Thyroid Diseases Are an Underestimated Risk Factor for Cerebral Venous Sinus Thrombosis

Introduction: Cerebral venous sinus thrombosis (CVST) is a rare disease that generally accounts for just 1% of all strokes. Of the multiple risk factors that have been identified, the most common are genetic or acquired thrombophilia and the use of oral contraceptives, while the less common include local infections and mechanical causes. Thyroid diseases have been described as rare risk factors for CVST (<2% of all cases), without exact knowledge of the underlying pathophysiology. This retrospective study aimed to re-evaluate the relevance of thyroid disease as risk factor for CVST, with particular emphasis on hyperthyroidism.

Patients and Methods: Confirmed cases of CVST were (re-)evaluated in terms of risk factors including thyroid parameters. Results were compared to previous data from the International Study on CVST.

Results: Between 1996 and 2016, 182 patients with confirmed CVST were treated in our hospital with a median age of 44 years and a female proportion of 74.7%. Genetic or acquired thrombophilia along with the use of oral contraceptives were found to be the most common risk factors. Thyroid diseases were present in 20.9% of CVST patients; this included patients with previous (9.9%) and current thyroid dysfunction (11%).

Discussion and Conclusions: Thyroid diseases may represent a more common risk factor for CVST than previously described. This holds true even if patients with current thyroid dysfunction are purely taken into account. However, 58% of patients had more than one additional risk factor, suggesting a multifactorial hypercoagulability.

Clinical Trials Register: Registered at the German Clinical Trials Register: http://www.drks.de, DRKS00017044.

Association Between Thyroid Hormone Status and Trace Elements in Serum of Patients with Nodular Goiter

The present study investigated the status of calcium and magnesium as well as essential trace elements including iodine, selenium, copper, iron, and zinc in adults residing in the Zhytomyr region of Ukraine. In addition, the relative risk of goiter occurrence was evaluated. In this comparative study, 40 adults without goiter (control group) and 16 adults with diagnosed nodular goiter (NG) were examined. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used for the measurements of Mg, Ca, Se, Zn, Cu, and Fe in serum of patients with NG and control group. Patients with nodular goiter had lower serum values of Ca, Mg, Se, Cu, Fe, and Zn than those in the control group. The presence of mild iodine deficiency was evident in both groups with the median urinary iodine excretion (UIE) 80.5 μg/L in the control group and 64.5 μg/L in goiter group. There was a positive association between goiter presence and low concentration of Ca in serum (odds ratio (OR) = 2.29 (1.26-3.55), p < 0.05) in the NG group. High relative risk of goiter was observed at low concentrations of magnesium (OR = 3.33 (1.39-7.62), p < 0.05) and selenium (OR = 1.63, (1.16-1.78), p < 0.05) in comparison with OR values in the control group. Low concentrations of Ca, Mg, Zn, and Se in serum combined with reduced UIE resulted in the highest risk of goiter (OR = 12.5, (2.15-79.42), p < 0.01). This study proved that Thyroglobulin concentration in serum is the reliable indicator of nodular goiter. We also suggest that a combination of low concentrations of Ca, Mg, Zn, Cu, and Se in blood serum, and reduced iodine concentration in urine resulted in the highest risk of nodular goiter development.

Assessment of Dietary Iodine Intake in School Age Children: The Cross-Sectional ANIVA Study

Iodine deficiency is one of the most important health problems in the world. It intervenes in the synthesis of thyroid hormones, which carry out important functions, so that a deficit of this mineral causes alterations of different kinds such as those related to growth. The objective of the present study was to know the prevalence of iodine deficit in the diet of Valencian children from 6 to 8 years old and their relationship with anthropometry. The analysis of the dietary intake was carried out through questionnaires. Thirteen schools participated in the study. The sample studied consists of 661 school children belonging to the Valencian Community, between 6 and 8 years of age: 298 boys and 363 girls. 79.12% of the children did not meet recommended daily iodine intakes. When comparing the groups of girls and boys with an inadequate intake, in general, girls show worse nutritional adequacy. When comparing the groups of girls and boys with sufficient iodine intake, no statistically significant differences were observed. No immediate effects of iodine deficiency on children’s anthropometry were observed. Intake of dairy products, fish and iodized salt is recommended, since they can contribute to the diet the iodine required to avoid a deficiency.

Iodine nutritional status in Asturian schoolchildren

INTRODUCTION

Iodine deficiency is a public health problem, and iodine nutritional status should therefore be regularly measured.

OBJECTIVE

To ascertain iodine nutritional status in Asturias and its relation to use of iodized salt and to other sociodemographic and nutritional parameters.

MATERIAL AND METHODS

A descriptive, observational study was conducted in a random sample of schoolchildren aged 5 to 14 years, in whom urinary iodine levels were measured by high-performance liquid chromatography. Families completed a survey on use of iodized salt, consumption of dairy products and fish, and sociodemographic data.

RESULTS

The study sample consisted of 705 schoolchildren (51.1% females) with a mean age of 9.9 years (SD 2.6). In a total of 620 valid measurements, mean urinary iodine level was 204.1 μg/L (SD 120.6), while the median value was 180.7 μg/L (P₂₅-P₇₅: 124-252.3 μg/L, interquartile range 128.3 μg/L). Urinary iodine levels were <100 μg/L in 16.6% of children, and very low (<20 μg/L) in 0.2%. Iodized salt was used in 69.3% of all households, and in all school canteens. Consumption of dairy products was significantly associated to urinary iodine levels (P<.0005).

CONCLUSION

Iodine nutrition of Asturian schoolchildren is adequate, although the target of use of iodized salt in 90% of households is still far away. Adequate iodine nutrition may be due to other sources, such as dairy products. Public health campaigns are required to promote iodized salt consumption. Regular assessment of iodine nutritional status is also needed.

Do Helper T Cell Subtypes in Lymphocytic Thyroiditis Play a Role in the Antitumor Effect?

BACKGROUND

Papillary thyroid carcinoma (PTC) is frequently accompanied by lymphocytic thyroiditis (LT). Some reports claim that Hashimoto's thyroiditis (the clinical form of LT) enhances the likelihood of PTC; however, others suggest that LT has antitumor activity. This study was aimed to find out the relationship between the patterns of helper T cell (Th) cytokines in thyroid tissue of PTC with or without LT and the clinicopathological manifestation of PTC.

METHODS

Fresh surgical samples of PTC with (13 cases) or without (10 cases) LT were used. The prognostic parameters (tumor size, extra-thyroidal extension of PTC, and lymph node metastasis) were analyzed. The mRNA levels of two subtypes of Th cytokines, Th1 (tumor necrosis factor α [TNF-α], interferon γ [IFN-γ ], and interleukin [IL] 2) and Th2 (IL-4 and IL-10), were analyzed. Because most PTC cases were microcarcinomas and recent cases without clinical follow-up, negative or faint p27 immunoreactivity was used as a surrogate marker for lymph node metastasis.

RESULTS

PTC with LT cases showed significantly higher expression of TNF-α (p = .043), IFN-γ (p < .010), IL-4 (p = .015) than those without LT cases. Although the data were not statistically significant, all analyzed cytokines (except for IL-4) were highly expressed in the cases with higher expression of p27 surrogate marker.

CONCLUSIONS

These results indicate that mixed Th1 (TNF-α, IFN-γ , and IL-2) and Th2 (IL-10) immunity might play a role in the antitumor effect in terms of lymph node metastasis.

Perchlorate Exposure Through Water and Milk in Istanbul

Perchlorate is a chemical pollutant that inhibits iodide uptake and may possibly impair thyroid function. Our previous study found widespread perchlorate exposure in non-pregnant, non-lactating, healthy women residing in Istanbul. The aim of this study is to assess the relative amounts of perchlorate exposure attributable to consumption of municipal water, bottled water and boxed milk available in Istanbul. Only trace levels of perchlorate were found in treated municipal water (58 % detectable, mean = 0.13 µg/L, maximum = 0.75 µg/L) and bottled water (7.4 % detectable, mean = <LOD, maximum = 0.19 µg/L). Conversely, all 30 boxed milk samples contained measurable levels of perchlorate (mean = 4.53 µg/L; maximum = 6.21 µg/L). Median perchlorate exposure attributable to water and milk (0.007 µg/kg/day) is small compared both to the reference dose (0.7 µg/kg/day) and to total perchlorate exposure (0.13 µg/kg/day) in Istanbul. Therefore, additional studies are needed to identify the major sources of perchlorate exposure in Istanbul.

High prevalence of autoimmune thyroid diseases in patients with prolactinomas: A cross-sectional retrospective study in a single tertiary referral centre

BACKGROUND

Prolactin has been shown to exert potent immunomodulatory activities.

DESIGN

Retrospective cross-sectional study examining the prevalence of autoimmune thyroid diseases (AITD) in patients with prolactinomas. The medical files of 462 patients (367 women and 95 men) followed up at a single tertiary referral centre were analyzed.

RESULTS

The prevalence of AITD among prolactinoma patients was estimated at 21.0% (23.2% in females and 12.6% in males). In 51.5% of the patients, diagnosis of prolactinoma preceded the development of AITD; in 37.2%, both diseases were simultaneously diagnosed and 11.3% of patients were diagnosed first with AITD. Hyperthyroidism was observed in 1.24% of the investigated subjects. Primary hypothyroidism was detected in 15.6% of all patients (16.4% in women; 10.7% in men) with a mean incidence of 24 cases/1000/year.

CONCLUSIONS

Our results demonstrate the high frequency of AITD in patients with prolactinomas. The prevalence rate of hyperthyroidism is comparable with the literature data from community-based studies. In contrast, the prevalence of the spontaneous hypothyroidism due to autoimmune thyroiditis is significantly higher in female and male subgroups of patients with prolactinomas in comparison with the general population. A possible role of supraphysiologically increased prolactin levels in the pathogenesis and the clinical course of AITD in patients with prolactinomas can be suggested. Based on these findings we recommend routine screening for AITD with simple thyroid tests (TSH, TPO-Abs and ultrasound examination) in all patients diagnosed with prolactinoma.

Influence of iodization programmes on the epidemiology of nodular goitre

Iodine is essential for the synthesis of thyroid hormones. Iodine deficiency can affect human health in different ways, and is commonly referred to as iodine deficiency disorders (IDD). These range from defective development of the central nervous system during the fetal-neonatal life, to goitre in the adult. Only a few countries were completely iodine sufficient before 1990. Since then, a major effort has been made to introduce salt iodization to ensure sufficient intake of iodine in deficient areas. Iodine prophylaxis has been shown to exert a pivotal role in abating goitre and other iodine-deficiency disorders, and has also been shown to modulate the pattern of thyroid diseases. An increased frequency of thyroid autoimmunity and of hypothyroidism has been observed after introducing iodization programmes. Nevertheless, available evidence clearly confirms that the benefits of correcting iodine deficiency, consisting mainly of reducing nodular goitre and non-autoimmune hyperthyroidism, far outweigh the risks of iodine supplementation.

Iodine status in Turkish populations and exposure to iodide uptake inhibitors

Perchlorate, nitrate, and thiocyanate are competitive inhibitors of the sodium iodide symporter of the thyroid membrane. These inhibitors can decrease iodine uptake by the symporter into the thyroid gland and may disrupt thyroid function. This study assesses iodine status and exposure to iodide uptake inhibitors of non-pregnant and non-lactating adult women living in three different cities in Turkey (Istanbul, Isparta and Kayseri). We measured iodine and iodide uptake inhibitors in 24-hr urines collected from study participants (N = 255). All three study populations were mildly iodine deficient, with median urinary iodine (UI) levels of 77.5 µg/L in Istanbul, 58.8 µg/L in Isparta, and 69.8 µg/L in Kayseri. Perchlorate doses were higher in the study population (median 0.13 µg/kg/day), compared with a reference population (median 0.059 µg/kg/day), but lower than the U.S. EPA reference dose (0.7 µg/kg/day). Urinary thiocyanate levels increased with increasing exposure to tobacco smoke, with non-smokers (268 µg/L) significantly lower than light smokers (1110 µg/L), who were significantly lower than heavy smokers (2410 µg/L). This pilot study provides novel data indicating that study participants were moderately iodine deficient and had higher intakes of the iodide uptake inhibitor perchlorate compared with a reference population. Further investigation is needed to characterize the thyroid impact resulting from iodine deficiency coupled with exposure to iodide uptake inhibitors such as perchlorate, thiocyanate and nitrate.

The effect of iodine in production of broiler chickens and selected quality indicators of breast muscles

Due to the different effects on the human health it is necessary to avoid excessive or insufficient consumption of iodine. Iodine deficiency weakens the synthesis of the thyroid hormones, causes hypothyroidism and can lead to various developmental and functional disturbances known as the disorders from iodine deficiency. The latest literary knowledge about the use of iodine in the broiler chickens identifies the concentration of iodine 5 mg per kg feed as safe for a given group of the animals. Working Group on Additives and Products or Substances used in Animal Feed of  Panel on Additives and Products or Substances used in Animal Feed notes that the maximum authorized limit of iodine in the feed of the broiler chickens 10 mg per kg does not represent a health risk. The aim of our research was an observation and assessment of the effect of feed mixtures with iodized oil on production quality of the line hybrid chickens Cobb 500 and selected indicators of breast muscle. For comparison, a control group consists of the chickens, which were fed the feed mixtures without iodized oil. Dietary iodine in the form of potassium iodide was applied to sunflower oil. The mixture was heated at 70 °C with continuous stirring until dissolution of potassium iodide. The content of iodine in iodine suplement was 0.04  mg per g per 1 kg of feed mixture of starter, growth and the finisher was used 5 g of iodine supplement. The oil mixture was mixed into kibbled grain of corn and carefully homogenized with other components of  the feed mixtures. To meet the aim of research, we realized an experiment, where body weight of the chickens was observed at the end of the experiment, the breast muscle weight and chemical analysis was made from selected indicators of breast muscle. A body weight of broiler chickens at the beginning and the end of the experiment and a breast muscle weight were observed by weighing on the Kern ECB 20K20 type scale with an accuracy of d = 0,1 g. The breast muscles were analyzed for selected indicators according to the methodology for analytical laboratories (2009). The data were evaluated according to the basic statistical characteristics. The differences in the values of indicators between groups were evaluated by the SAS system program by t-test. The broiler chickens that were included in the experiment were first grade with a balanced average weight of 42 g. Statistical evaluation   of body weight of the broiler chickens at the beginning of the experiment results in not significant difference between the control group and the experimental group – iodine supplement. Average body weight of the chickens was 2183.06 g at end of experiment in the group with the addition of iodine compared to 2145.21 g in control group with a statistically not significant difference (P>0.05). Average weight of the breast muscles was 426.83 g in the group with the addition of iodine compared to 412.11 g in control group with a statistically not significant difference (P>0.05). Average dry matter content    in the breast muscles was 26.13 g per 100 g in the group with the addition of iodine compared to 26.25 g per 100 g in control group with a statistically not significant difference (P>0.05). Average protein contents in breast muscles was 23.63 g per 100 g in the group with the addition of iodine compared to 23.31 g per 100 g in control group with a statistically not significant difference (P>0.05). Average fat contents in breast muscles was 1.05 g per 100 g in the group with the addition of iodine compared to 0.88 g per 100 gin control group with a statistically significant difference (P<0.05). The results of the experiment indicated some tendency of the positive effect of the feed mixtures with iodized oil on the quality of production of broiler chickens. Based on results, further research was recommended.

Essential genes in thyroid cancers: focus on fascin

Although thyroid cancers are not among common malignancies, they rank as the first prevalent endocrine cancers in human. According to the results of published studies it has been shown the gradual progress from normal to the neoplastic cell in the process of tumor formation is the result of sequential genetic events. Among them we may point the mutations and rearrangements occurred in a group of proto-oncogenes, transcription factors and metastasis elements such as P53, RAS,RET,BRAF, PPARγ and Fascin. In the present article,we reviewed the most important essential genes in thyroid cancers, the role of epithelial mesenchymal transition and Fascin has been highlighted in this paper.

MicroRNAs networks in thyroid cancers: focus on miRNAs related to the fascin

miRNAs are non coding ribonucleic acids which are protected with respect to evolution, and have a length of 18–25 nucleotides. microRNAs control the gene expression after transcription, through mRNA destruction or translation processing, and therefore participate in arrangement of the physiologic and pathologic cellular processes; They also may act as oncogene or tumor suppressors. Altered expression of a number of microRNAs is reported in process of progression and metastasis of thyroid cancers. Therefore, identification of these microRNAs may shed a light to oncogenesis pathway of thyroid cancers and their metastasis. In addition, microRNAs might apply as potential biological markers in diagnosis and treatment of thyroid cancers. The changes made in miRNAs profile of thyroid cancers are reviewed in this paper.

The effects of iodine level and source on iodine carry-over in eggs and body tissues of laying hens

In the presented study the effect of different iodine (I) levels and sources in hen feed on the iodine concentration of different tissues, blood serum, and eggs of laying hens was studied. For this purpose, two experiments were conducted with 30 laying hens each. In these experiments feed was enriched with KI and Ca(IO(3))(2), respectively, at 0 (Control), 0.25, 0.5, 2.5 and 5 mg I/kg feed, resulting a analysed iodine level from 0.44 to 4.20 mg/kg feed. After four weeks experimental feeding the iodine concentrations of thyroid glands, blood, meat, liver, abdominal fat and eggs were measured with inductively coupled plasma mass spectrometry. The experimental treatment did not affect hen performance. The iodine supplementation significantly increased the iodine concentration of eggs (144-1304 μg/kg), thyroid glands (3367-5975 μg/g), blood serum (16-67 μg/kg) and liver (13-43 μg/kg). Meat (about 14 μg I/kg) and abdominal fat (about 12 μg I/kg) were not significantly affected by iodine treatment. Comparative regression analyses showed that at a similar iodine intake, the supply via KI resulted in significantly higher iodine deposition into eggs than Ca(IO(3))(2). Due to the high carry-over of iodine into eggs, eggs may considerably contribute to the iodine supply of the consumers.

Fortification of bread with iodized salt corrected iodine deficiency in school-aged children, but not in their mothers: a national cross-sectional survey in Belgium

BACKGROUND

In the years 1985-1998, it was noted that mild iodine deficiency (MID) was a public health problem in Belgium. Therefore, an agreement was signed in 2009 between the bakery sector and the Ministry of Health, to fortify bread with iodized salt. We tested the hypothesis that the iodine status of Belgian children improved after the introduction of bread fortified with iodized salt. Since the dietary habits of children and adults may differ, we also investigated whether the median urinary iodine concentration (UIC) among the children in this study reflected the iodine status of their mothers.

METHODS

The study was cross-sectional. In a van, equipped with an ultrasound device, the thyroid volumes (Tvol) of children were measured and household salt samples and urine samples were collected from the children and their mothers. From across Belgium, 60 schools were selected and 1541 children participated in the study.

RESULTS

The median UIC in children was 113.1 and 84.4 μg/L among their mothers. The median UIC among children was substantially greater compared to more than 10 years ago (80 μg/L; p<0.001). The median UIC in school-aged children was lower in Wallonia than in Flanders (p<0.001) and was higher in boys than in girls (p<0.001). The percentage of children with goiter was 7.2%. Of the 904 salt samples received, 63.2% did not contain iodine.

CONCLUSIONS

Fortification of bread with iodized salt corrected iodine deficiency in Belgian children, but not in their mothers. To provide these women with an adequate iodine intake, the use of both iodized salt in bread and iodized instead of noniodized household salt needs to increase. Our findings suggest that the median UIC in children may not be an adequate surrogate of adults' iodine status. Therefore, monitoring iodine status should not be limited to children, but should be extended to women of child-bearing age.

Thyroid cancer incidence by histological type and related variants in a mildly iodine-deficient area of Northern Italy, 1998 to 2009

BACKGROUND

The incidence of thyroid cancer is increasing in several countries. However, the issue of whether this applies to all different histological types and related variants is poorly addressed.

METHODS

All incident thyroid cancers diagnosed between 1998 and 2009 in a mildly iodine-deficient area in northern Italy were derived from a population-based tumor registry. Stage of disease, size of the tumor, focality, and histological variants were recorded from a review of pathology reports and slides. The mean annual increase (MAI) of the standardized incidence rate was calculated over the entire 12-year period of observation and a standardized rate ratio was evaluated to compare the mean standardized incidence between 2 periods of 6 years each (1998-2003 vs 2004-2009).

RESULTS

In total, 980 cases were considered. An increase in the incidence trend for all thyroid tumors was demonstrated; the increase was found to be continuous from 1998 to 2002 but not afterward. The cancer incidence increased in both male and female subjects. Papillary thyroid carcinoma (PTC), the follicular variant of PTC, the tall cell variant of PTC (TCV-PTC), and Hurthle cell carcinoma (HC) showed the most relevant changes in incidence whereas follicular carcinoma was not found to be significantly affected. TCV-PTC was the only histological type to demonstrated a significant (P < .01) proportional increase in the second 6-year period of observation. Only TCV-PTC and HC were found to display a significant MAI after 2002.

CONCLUSIONS

The incidence of thyroid cancer has increased within the last decade, an increase that is accounted for mostly by differentiated tumors. The most significant increases were documented for aggressive variants of basic histotypes.

Simulation of total dietary iodine intake in Flemish preschool children

The aim of the present study was to calculate the distribution of total iodine intake among Flemish preschoolers and to identify the major sources contributing to iodine intake. A simulation model using a combination of deterministic and probabilistic techniques was utilised. Scenario analyses were performed to assess iodine intake via dairy products, industrially added iodised salt in bread and discretionarily added iodised household salt. Relevant data from 3-d estimated dietary records of 696 preschoolers 2·5–6·5 years old were used. Usual iodine intakes were calculated using the Iowa State University method. With a more generalised utilisation of iodised salt in bread (44 % of the bakers in 2011 instead of 12 % in 2002), mean iodine intake increased from 159 to 164 μg/d using the McCance and Widdowson's food composition table and from 104 to 109 μg/d using the German food composition table. The percentage of preschoolers with an iodine intake below the estimated average requirement (65 μg/d) decreased from 5–12 to 4–9 %, while the percentage of preschoolers with an iodine intake above the tolerable upper intake level (300 μg/d) remained constant (0·3–4 %). Mean iodine intake via food supplements was 4·2 μg/d (total population) and 16·9 μg/d (consumers only). Both in 2002 and 2011, sugared dairy products, milk and iodised salt (21·4, 13·1, and 8·7 %, respectively in 2011) were the main contributors to total iodine intake. In conclusion, dietary iodine intake could still be improved in Flemish preschoolers. The use of adequately iodised household salt and the more generalised use of iodised salt by bakers should be further encouraged.

Does a small difference in iodine status among children in two regions of Belgium translate into a different prevalence of thyroid nodular diseases in adults?

PURPOSE

To explore whether there are regional differences in iodine status and in prevalence of thyroid diseases in the two main regions of Belgium.

METHODS

A national survey of iodine status among children was performed in 1998. The raw data of this survey were reanalyzed to explore regional differences. The total number of thyroidectomies, carried out for multinodular goiter or solitary nodules, was obtained from the Minimal Clinical Summary hospital discharge database. Percentage of people with thyroid diseases going to the general practitioner or the specialist was assessed by means of data about the number of adults using anti-thyroid medications. Food consumption patterns were explored using national food consumption data.

RESULTS

In Flanders, median urinary iodine concentration (UIC) was higher than in Wallonia, 84 μg/L (n = 1,316) and 78 μg/L (n = 1,268), respectively (p < 0.001). There were no differences in goiter prevalence and thyroid volume between the regions among children. Data from the food consumption survey showed a significant higher consumption of seafood in Flanders compared to Wallonia. Further, it was observed that the number of thyroidectomies, carried out for MNG or solitary nodules, and the use of anti-thyroid medication were significantly higher in Wallonia than in Flanders.

CONCLUSION

Iodine status in children was found slightly different in both regions of the country. This finding is in agreement with a higher incidence of thyroidectomies and more extensive use of anti-thyroid medications in the adult population in the region with the lowest iodine excretion.

The effect of various iodine supplementations and two different iodine sources on performance and iodine concentrations in different tissues of broilers

1. The objective of this study was to determine the influence of iodine (I) supplementation of feed, within the range of the European guidelines, on the performance of broiler chickens and I transfer into different organs and tissues, especially meat. The main emphasis was to assess whether broiler meat could be enriched and used as an I source in human nutrition. 2. Two experiments were performed, one with KI and the other with Ca(IO(3))(2). For each experiment, 288 d-old broiler chicks were divided into 4 groups (72 birds/group) and fed on diets with supplementations between 0 and 5 mg I/kg feed. The birds were reared to 35 d of age under standard conditions. Six birds per group were slaughtered at 35 d and samples of blood, thyroid gland, liver, pectoral and thigh meat taken. 3. Iodine treatment did not significantly affect the growth and slaughter performance of the broiler chickens. In all investigated parameters, I concentrations increased significantly with increasing I intake of the animals. The lowest I concentrations were measured in the meat, but they were considerably higher in blood serum, liver and thyroid gland. Since the I content of meat was still low in the highest supplemented group (highest median concentration: 67·8 µg I/kg thigh meat), there is no evidence that this could substantially improve I supply in human nutrition.

Optimization of iodine intake in Belgium

Mild iodine deficiency (MID) is a long-standing problem in Belgium and was recognized only recently as public health issue by the Ministry of Health (MOH). The main MID-related health problems in Belgium are a high prevalence of thyroid nodules and multinodular goiter. The economic cost of thyroid nodular disease only in Belgium was estimated at about €40 millions per year. The Belgian health authorities adopted a selective strategy to optimize iodine intake through the fortification of bread with iodized salt. A progressive, step-by-step increase of the iodine content of salt was chosen in order to minimize the incidence of hyperthyroidism. MOH monitors this strategy by assessing periodically the urinary iodine concentration in school-aged children and pregnant women, as well as by a yearly follow-up of TSH concentrations in all Belgian newborns. Although the implementation of this strategy was an important step, the main drawback of the current situation is the absence of a legal framework to support the strategy. The utilization of iodized salt in bread on a voluntary basis was endorsed by the bakery industry and MOH. However a legal framework is required to assure the effectiveness and continuity of the program and to avoid a higher than optimal iodine intake in the population.

Effect of hypothyroxinemia on thyroid hormone responsiveness and action during rat postnatal neocortical development

Neurological deficits due to maternal and neonatal hypothyroxinemia under mild-moderate iodine deficiency are a major preventable health problem worldwide. The present study assesses the impact of hypothyroxinemia on postnatal neocortical development and also compares it to the known effects of severe hypothyroidism. Our results strongly suggest that even within elevated circulating triiodothyronine (T3) levels, hypothyroxinemia significantly impairs thyroid hormone responsiveness in developing rat neocortex. The significant compensatory alteration in deiodinase levels with unaltered monocarboxylate transporter 8 (MCT8) and thyroid hormone receptors (TRs), although found to be similar in hypothyroxinemic and hypothyroid condition, is more pronounced under later condition. The resultant downregulation of nuclear myelin binding protein (MBP) and mitochondrial transcripts Cytochrome oxidase III (Cox III) as well as significantly enhanced mitochondrial localization of Bax and reduced Bcl-2 and Bcl-xL accompanied by enhanced release of Cytochrome c and Smac with activation of caspase-3 indicates pronounced apoptosis leading to compromised cellular survival. The similarities of this responsiveness albeit with difference in degree under hypothyroidism and hypothyroxinemic state with adequate availability of T3 are suggestive of an independent role of thyroxine in neocortex development. Taken together, this study brings forth the neurophysiological aspects of hypothyroxinemia and underscores the importance of adequate iodine nutrition along with mandatory thyroxin monitoring during pregnancy and after birth.

Natural history of the transition from euthyroidism to overt autoimmune hypo- or hyperthyroidism: a prospective study

OBJECTIVE

To evaluate the progression in time from euthyroidism to overt autoimmune hypothyroidism or to overt autoimmune hyperthyroidism.

SUBJECTS AND METHODS

The design is that of a nested case-control study within the prospective Amsterdam autoimmune thyroid disease (AITD) cohort study in which 790 healthy euthyroid women with at least one first or second degree relative with documented AITD were followed for 5 years. Thyroid function tests were assessed annually. Contrast between cases (overt hypothyroidism - TSH>5.7 mU/l and free thyroxine (FT(4))<9.3 pmol/l and overt hyperthyroidism - TSH<0.4 mU/l and FT(4)>20.1 pmol/l, also referred to as events) and controls (matched for age and duration of follow-up).

RESULTS

At baseline, the 38 hypothyroid cases had already higher TSH and lower FT(4) concentrations than their 76 controls, and the difference between both the groups persisted 1 year before occurrence of the event. In contrast, neither TSH nor FT(4) values differed between the 13 hyperthyroid cases and their 26 controls at baseline or 1 year before the event. The prevalence of thyroid peroxidase-Ab was higher in both hypothyroid and hyperthyroid cases than in controls. At the time of event, hypothyroid cases were less common among current smokers (P=0.083) and more common in the postpartum period (P=0.006) than their controls, whereas hyperthyroid cases were pregnant more frequently (P=0.063).

CONCLUSIONS

The data suggest that progression toward overt autoimmune hypothyroidism is a gradual process taking several years, but in contrast overt autoimmune hyperthyroidism develops faster in terms of months.

Projected reduction in healthcare costs in Belgium after optimization of iodine intake: impact on costs related to thyroid nodular disease

BACKGROUND

Several surveys in the last 50 years have repeatedly indicated that Belgium is affected by mild iodine deficiency. Within the framework of the national food and health plan in Belgium, a selective, progressive, and monitored strategy was proposed in 2009 to optimize iodine intake. The objective of the present study was to perform a health economic evaluation of the consequences of inadequate iodine intake in Belgium, focusing on undisputed and measurable health outcomes such as thyroid nodular disease and its associated morbidity (hyperthyroidism).

METHODS

For the estimation of direct, indirect, medical, and nonmedical costs related to thyroid nodular diseases in Belgium, data from the Federal Public Service of Public Health, Food Chain Safety and Environment, the National Institute for Disease and Disability Insurance (RIZIV/INAMI), the Information Network about the prescription of reimbursable medicines (FARMANET), Intercontinental Marketing Services, and expert opinions were used. These costs translate into savings after implementation of the iodization program and are defined as costs due to thyroid nodular disease throughout the article. Costs related to the iodization program are referred to as program costs. Only figures dating from before the start of the intervention were exploited. Only adult and elderly people (≥18 years) were taken into account in this study because thyroid nodular diseases predominantly affect this age group.

RESULTS

The yearly costs due to thyroid nodular diseases caused by mild iodine deficiency in the Belgian adult population are ∼€38 million. It is expected that the iodization program will result in additional costs of ∼€54,000 per year and decrease the prevalence of thyroid nodular diseases by 38% after a 4-5-year period. The net savings after establishment of the program are therefore estimated to be at least €14 million a year.

CONCLUSIONS

Optimization of iodine intake in Belgium should be quite cost effective, if only considering its impact on nodular thyroid disease. There are likely added benefits relating to more optimal thyroid hormone influenced brain development that are more difficult to estimate but may be even more important.

Interaction of copper with iron, iodine, and thyroid hormone status in goitrous patients

In many developing countries, men and women are at high risk of goiter and iron deficiency. The aim of the recent study is to assess the interaction of (Cu), with iron (Fe), iodine/iodide (I), and thyroid hormones in goitrous patients. Sixty goitrous male (GMPs) and 72 female patients (GFPs) were evaluated for the Cu, Fe, I, and thyroid hormones status in biological samples (serum and urine), and compared to non-goitrous subjects of both genders (M = 106, F = 120). The biological samples were analyzed for Cu and Fe concentration using atomic absorption spectrometer, while I was measured by the potentiometric method, prior to microwave-assisted acid digestion (MD). Quality control for the method was established with certified samples. Significantly higher mean values of Cu in serum, and urine samples of GMPs and GFPs, while lower value of Fe and I were observed as compared to control subjects (p < 0.015), respectively. The mean values of free triiodothyronine (FT3) and free thyroxin (FT4) were found to be lower in goitrous patients of both genders than in the age-matched healthy controls (p < 0.006 and 0.002), respectively, in contrast high mean values of thyroid-stimulating hormone (TSH) were detected in patients (p < 0.009), as compared to non-goitrous subjects. It was observed that the deficiencies of Fe, I, and thyroid hormone in goitrous patients could be influenced by efficiency of Cu.

The nature of the compensatory response to low thyroid hormone in the developing brain

Thyroid hormone is essential for normal brain development, although the degree to which the developing brain is sensitive to small perturbations in serum thyroxin is not clear. An important concept related to this is that the developing brain possesses potent mechanisms to compensate for low serum thyroid hormone, and this concept is routinely employed in discussions concerning clinical treatments or public health. However, experimental studies have not directly tested whether (or the degree to which) putative compensatory mechanisms can ameliorate the consequences of small reductions in serum thyroxin (T(4)). To formally test this concept, we employed a model of graded T(4) reductions using doses of propylthiouracil (PTU) that were 200- to 67-fold lower than the dose traditionally used to produce hypothyroidism in rats. PTU produced a stepwise decrease in serum total T(4), and a stepwise increase in serum thyroid-stimulating hormone (TSH), in type 2 deiodinase mRNA expression and enzyme activity in the brain, and in the expression of the mRNA encoding the tri-iodothyronine (T(3)) transporter MCT8 in the postnatal day (P) 15 cortex. However, the mRNA encoding RC3/neurogranin, a direct target of T(3) action, exhibited a strong negative linear correlation with serum total T(4) despite these adaptive responses. In addition, single-cell analysis of RC3 mRNA levels in cortical neurones demonstrated that the co-expression of MCT8 did not alter the relationship between RC3 mRNA and serum T(4). These findings do not support the currently envisioned concept of the developing brain being capable of compensating for low T(4).

Iodine intake as a determinant of thyroid disorders in populations

Depending on the availability of iodine, the thyroid gland is able to enhance or limit the use of iodine for thyroid hormone production. When compensation fails, as in severely iodine-deficient populations, hypothyroidism and developmental brain damage will be the dominating disorders. This is, out of all comparison, the most serious association between disease and the level of iodine intake in a population. In less severe iodine deficiency, the normal thyroid gland is able to adapt and keep thyroid hormone production within the normal range. However, the prolonged thyroid hyperactivity associated with such adaptation leads to thyroid growth, and during follicular cell proliferation there is a tendency to mutations leading to multifocal autonomous growth and function. In populations with mild and moderate iodine deficiency, such multifocal autonomous thyroid function is a common cause of hyperthyroidism in elderly people, and the prevalence of thyroid enlargement and nodularity is high. The average serum TSH tends to decrease with age in such populations caused by the high frequency of autonomous thyroid hormone production. On the other hand, epidemiological studies have shown that hypothyroidism is more prevalent in populations with a high iodine intake. Probably, this is also a complication to thyroid adaptation to iodine intake. Many thyroid processes are inhibited when iodine intake becomes high, and the frequency of apoptosis of follicular cells becomes higher. Abnormal inhibition of thyroid function by high levels of iodine is especially common in people affected by thyroid autoimmunity (Hashimoto's thyroiditis). In populations with high iodine intake, the average serum thyroid-stimulating hormone (TSH) tends to increase with age. This phenomenon is especially pronounced in Caucasian populations with a genetically determined high tendency to thyroid autoimmunity. A small tendency to higher serum TSH may be observed already when iodine intake is brought from mildly deficient to adequate, but there is at present no evidence that slightly elevated serum TSH in elderly people leads to an increase in morbidity and mortality.

CONCLUSION

Even minor differences in iodine intake between populations are associated with differences in the occurrence of thyroid disorders. Both iodine intake levels below and above the recommended interval are associated with an increase in the risk of disease in the population. Optimally, iodine intake of a population should be kept within a relatively narrow interval where iodine deficiency disorders are prevented, but not higher. Monitoring and adjusting of iodine intake in a population is an important part of preventive medicine.

Prenatal induced chronic dietary hypothyroidism delays but does not block adult-type Leydig cell development

Transient hypothyroidism induced by propyl-2-thiouracyl blocks postpartum Leydig cell development. In the present study, the effects of chronic hypothyroidism on the formation of this adult-type Leydig cell population were investigated, using a more physiological approach. Before mating, dams were put on a diet consisting of an iodide-poor feed supplemented with a low dose of perchlorate and, with their offspring, were kept on this diet until death. In the pups at day 12 postpartum, plasma thyroid-stimulating hormone levels were increased by 20-fold, whereas thyroxine and free tri-iodothyronine levels were severely depressed, confirming a hypothyroid condition. Adult-type progenitor Leydig cell formation and proliferation were reduced by 40-60% on days 16 and 28 postpartum. This was followed by increased Leydig cell proliferation at later ages, suggesting a possible slower developmental onset of the adult-type Leydig cell population under hypothyroid conditions. Testosterone levels were increased 2- to 10-fold in the hypothyroid animals between days 21 and 42 postpartum compared with the age-matched controls. Combined with the decreased presence of 5alpha-reductase, this implicates a lower production capacity of 5alpha-reduced androgens. In 84-day-old rats, after correction for body weight-to-testis weight ratio, plasma insulin-like factor-3 levels were 35% lower in the hypothyroid animals, suggestive of a reduced Leydig cell population. This is confirmed by a 37% reduction in the Sertoli cell-to-Leydig cell ratio in hypothyroid rats. In conclusion, we show that dietary-induced hypothyroidism delays but, unlike propyl-2-thiouracyl, does not block the development of the adult-type Leydig cell population.

Frequency and characteristics of TBII-seronegative patients in a population with untreated Graves' hyperthyroidism: a prospective study

OBJECTIVE

It is claimed that second generation thyrotropin-binding inhibitory immunoglobulin (TBII) assays have a very high sensitivity for the diagnosis of Graves' hyperthyroidism (GH). However, studies evaluating the accuracy of TBII have been retrospective in nature and/or GH had not been diagnosed independently of TBII. The aim of the present study, therefore, was to prospectively evaluate the frequency and characteristics of TBII-seronegative patients in a population of untreated GH diagnosed independent of serum TBII.

DESIGN

Prospective multicentre observational study.

PATIENTS

A total of 259 consecutive untreated patients with a first episode of GH, diagnosed independent of serum TBII. TBII levels were measured by second generation assay and correlated to thyroid function, clinical characteristics and exposure to environmental factors.

RESULTS

Serum TBII was positive in 245 (94.6%) patients and negative (< 2 IU/l) in 14 (5.4%) patients. TBII-seronegative patients had lower fT4 (median 42.5 vs. 53.9 pmol/l, P = 0.02), T3 (median 3.55 vs. 4.90 nmol/l, P < 0.01) and fT3-index (median 4.30 vs. 6.27, P < 0.01) compared to TBII-seropositive patients. None of the TBII-seronegative patients had TSH-receptor activating mutations, Graves' orbitopathy or pretibial myxedema. Serum TBII was positively correlated to free T3 (fT3)-index and free T4 (fT4)-index (P < 0.01), goitre size (P < 0.01) and the prevalence of Graves' orbitopathy (P < 0.01). There were no significant differences between TBII-seropositive and TBII-seronegative patients in environmental factors.

CONCLUSION

The prevalence of TBII-seronegativity in untreated patients with GH is 5.4% using a second generation assay. TBII-seronegative patients have biochemically less severe thyrotoxicosis and no Graves' orbitopathy. TBII-seronegative and TBII-seropositive patients apparently belong to the same population of GH, albeit the severity of the autoimmune attack is less in TBII-seronegative patients.

Relevance of iodine intake as a reputed predisposing factor for thyroid cancer

Iodine is a trace element that is essential for the synthesis of thyroid hormone. Both chronic iodine deficiency and iodine excess have been associated with hypertrophy and hyperplasia of follicular cells, attributed to excessive secretion of TSH. This may be associated to thyroid cancer risk, particularly in women. Experimental studies have documented thyroid cancer induction by elevation of endogenous TSH, although in a small number of animals. Iodine deficiency associated with carcinogenic agents and chemical mutagens will result in a higher incidence of thyroid malignancy. Inadequate low iodine intake will result in increased TSH stimulation, increased thyroid cell responsiveness to TSH, increased thyroid cell EGF-induced proliferation, decreased TGFbeta 1 production and increased angiogenesis, all phenomena related to promotion of tumor growth. Epidemiological studies associating iodine intake and thyroid cancer led to controversial and conflicting results. There is no doubt that introduction of universal iodine prophylaxis in population previously in chronic iodine-deficiency leads to a changing pattern of more prevalent papillary thyroid cancer and declining of follicular thyroid cancer. Also anaplastic thyroid cancer is practically not seen after years of iodine supplementation. Iodine excess has also been indicated as a possible nutritional factor in the prevalence of differentiated thyroid cancer in Iceland, Hawaii and, more recently, in China.

IN CONCLUSION

available evidence from animal experiments, epidemiological studies and iodine prophylaxis has demonstrated a shift towards a rise in papillary carcinoma, but no clear relationship between overall thyroid cancer incidence and iodine intake.