Effects of increased iodine intake on thyroid disorders

Factors associated with inadequate urinary iodine concentration among pregnant women in Mbeya region Tanzania

Background

Insufficient and above WHO-recommended levels of iodine intake during pregnancy can lead to serious health outcomes. This study aimed to assess median urine iodine concentration and its associated risk factors among pregnant women in the Mbeya region, Tanzania.

Method

A cross sectional survey involving 420 pregnant women (n=420) aged 15-49, registered in Reproductive and Child Health Clinics was conducted. Socio-demographic and dietary factors were assessed by structured questionnaire and the urine samples were analyzed using the ammonium persulfate digestion method.

Results

Median urinary iodine concentration (mUIC) was 279.4μg/L and it ranged from 26.1 to 1915μg/L. Insufficient mUIC (below 150μg/L) was observed in 17.14% of participants, sufficient mUIC was 24.29% and 58.57% had mUIC above the recommended level (>250μg/L). Sample women who reported consuming fish in the last 24 hours had an increased risk of insufficient mUIC [Adjusted OR= 2.60 (95%CI 1.31-5.15)] while the risk was lower for those who attended at least primary education [AOR= 0.29 (CI 0.08-0.99)]. Further, sample women resident in Mbarali district, in the oldest age group (35-49) and having a higher socio-economic status were associated with an increased risk of having MUIC above recommended level [AOR=4.09 (CI 1.85-9.010], [AOR=2.51 (CI 0.99-6.330] and, [AOR=2.08 (CI 0.91-4.71) respectively.

Conclusion

This study demonstrated a significant association between geographical, age and socio-economic factors and median urine iodine concentration above the WHO-recommended level. Further, this study found association between inadequate iodine in diet and insufficient median urine iodine concentration. Therefore, educational programs on iodine intake should be strengthened.

Relationship Between Urinary Iodine Concentration and the Prevalence of Thyroid Nodules and Subclinical Hypothyroidism

The aim of the study was to investigate the iodine intake in the resident population in Xi'an and analyze the relationship between iodine nutritional status and the prevalence of subclinical hypothyroidism and thyroid nodules (TNs). A total of 2507 people were enrolled in Xi'an. Venous serum thyroid stimulating hormone (TSH), thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb), urinary iodine concentration (UIC), and thyroid ultrasonography were collected. Patients with abnormal TSH were checked for free thyroxine (FT4) and triiodothyronine (FT3). Adults in Xi'an had median UICs of 220.80 μg/L and 178.56 μg/l, respectively. A sum of 16.78% of people had subclinical hypothyroidism. Both iodine excess and iodine deficit increased the frequency of subclinical hypothyroidism. The lowest was around 15.09% in females with urine iodine levels between 200 and 299 μg/l. With a rate of 10.69%, the lowest prevalence range for males was 100-199 μg/l. In Xi'an, 11.37% of people have TNs. In comparison to other UIC categories, TN occurrences were higher in females (18.5%) and males (12%) when UIC were below 100 μg/l. In conclusion, iodine intake was sufficient in the Xi'an area, while the adults' UIC remains slightly higher than the criteria. Iodine excess or deficiency can lead to an increase in the prevalence of subclinical hypothyroidism. Patients with iodine deficiency are more likely to develop TNs.

Associations of Combined Exposure to Metabolic and Inflammatory Indicators with Thyroid Nodules in Adults: A Nested Case-Control Study

Objective

To explore associations of combined exposure to metabolic/inflammatory indicators with thyroid nodules.

Methods

We reviewed personal data for health screenings from 2020 to 2021. A propensity score matching method was used to match 931 adults recently diagnosed with thyroid nodules in a 1 : 4 ratio based on age and gender. Conditional logistic regression and Bayesian kernel machine regression (BKMR) were used to explore the associations of single metabolic/inflammatory indicators and the mixture with thyroid nodules, respectively.

Results

In the adjusted models, five indicators (ORQ4 vs. Q1: 1.30, 95% CI: 1.07-1.58 for fasting blood glucose; ORQ4 vs. Q1: 1.30, 95% CI: 1.08-1.57 for systolic blood pressure; ORQ4 vs. Q1: 1.26, 95% CI: 1.04-1.53 for diastolic blood pressure; ORQ4 vs. Q1: 1.23, 95% CI: 1.02-1.48 for white blood cell; ORQ4 vs. Q1: 1.28, 95% CI: 1.07-1.55 for neutrophil) were positively associated with the risk of thyroid nodules, while high-density lipoproteins (ORQ3 vs. Q1: 0.75, 95% CI: 0.61-0.91) were negatively associated with the risk of thyroid nodules. Univariate exposure-response functions from BKMR models showed similar results. Moreover, the metabolic and inflammatory mixture exhibited a significant positive association with thyroid nodules in a dose-response pattern, with systolic blood pressure being the greatest contributor within the mixture (conditional posterior inclusion probability of 0.82). No interaction effects were found among the five indicators. These associations were more prominent in males, participants with higher age (≥40 years old), and individuals with abnormal body mass index status.

Conclusions

Levels of the metabolic and inflammatory mixture have a linear dose-response relationship with the risk of developing thyroid nodules, with systolic blood pressure levels being the most important contributor.

Thyroid hormone biosynthesis and its role in brain development and maintenance

Thyroid hormones are critical modulators in the physiological processes necessary to virtually all tissues, with exceptionally fundamental roles in brain development and maintenance. These hormones regulate essential neurodevelopment events, including neuronal migration, synaptogenesis, and myelination. Additionally, thyroid hormones are crucial for maintaining brain homeostasis and cognitive function in adulthood. This chapter aims to offer a comprehensive understanding of thyroid hormone biosynthesis and its intricate role in brain physiology. Here, we described the mechanisms underlying the biosynthesis of thyroid hormones, their influence on various aspects of brain development and ongoing maintenance, and the proteins in the brain that are responsive to these hormones. This chapter was geared towards broadening our understanding of thyroid hormone action in the brain, shedding light on potential therapeutic targets for neurodevelopmental and neurodegenerative disorders.

Relationship between Thyroid CT Density, Volume, and Future TSH Elevation: A 5-Year Follow-Up Study

This study aimed to explore the relationship between thyroid-stimulating hormone (TSH) elevation and the baseline computed tomography (CT) density and volume of the thyroid. We examined 86 cases with new-onset hypothyroidism (TSH > 4.5 IU/mL) and 1071 controls from a medical check-up database over 5 years. A deep learning-based thyroid segmentation method was used to assess CT density and volume. Statistical tests and logistic regression were employed to determine differences and odds ratios. Initially, the case group showed a higher CT density (89.8 vs. 81.7 Hounsfield units (HUs)) and smaller volume (13.0 vs. 15.3 mL) than those in the control group. For every +10 HU in CT density and -3 mL in volume, the odds of developing hypothyroidism increased by 1.40 and 1.35, respectively. Over the course of the study, the case group showed a notable CT density reduction (median: -8.9 HU), whereas the control group had a minor decrease (-2.9 HU). Thyroid volume remained relatively stable for both groups. Higher CT density and smaller thyroid volume at baseline are correlated with future TSH elevation. Over time, there was a substantial and minor decrease in CT density in the case and control groups, respectively. Thyroid volumes remained consistent in both cohorts.

Iodine status and its association with prevalence of thyroid diseases in adults from Jiangxi Province, China

BACKGROUND

Iodine is an essential element for the biosynthesis of thyroid-stimulating hormone (TSH). Both excessive and deficient iodine are major risk factors for thyroid diseases, including thyroid dysfunction, thyroid nodules, and thyroid autoimmunity (TAI). This study aimed to elucidate the relationship between iodine status and the prevalence of thyroid diseases through a national cross-sectional epidemiological survey in Jiangxi province (China).

METHODS

This population-based, cross-sectional study enrolled 2636 Chinese local inhabitants who aged over 18 years old from April to August in 2015. Physical examination was performed and biochemical indices, urinary iodine concentration (UIC), and TSH level were measured. The Chi-square test, nonparametric test, and 4 multivariate logistic regression models adjusted for risk factors were applied to analysis. Spearman correlation coefficients were calculated to investigate the relationship between iodine intake level and the prevalence of thyroid diseases.

RESULTS

The median UIC was 176.4 μg/L, and a significant difference was found in median UIC between men (182.45 μg/L) and women (169.25 μg/L) (P = 0.03). Among these study subjects, 14.4%, 44.5%, 26.1%, and 15.0% had deficient, adequate, more than adequate, and excessive iodine concentrations, respectively. The prevalence rates of hyperthyroidism, subclinical hyperthyroidism, hypothyroidism, subclinical hypothyroidism, thyroid nodules, and TAI were 0.91%, 0.57%, 0.34% and 7.89%, 9.45%, and 12.7%, respectively. Significant differences were found in iodine status, waist circumstance, systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol (TC), TSH, thyroid nodules, and TAI between men and women (P < 0.05). Compared with those with adequate UIC, subjects with excessive UIC had higher prevalence rates of thyroid dysfunction (odds ratio (OR) = 1.74, 95% confidence interval (CI): 1.40-2.54) and thyroid nodules (OR = 3.33, 95%CI 1.32-8.42). In addition, subjects with deficient and excessive UIC were at the higher risk of TAI compared with those with adequate UIC (OR = 1.68, 95%CI: 1.19-2.60; OR = 1.52, 95%CI: 1.04-2.96, respectively). UIC was positively correlated with the prevalence rates of thyroid nodules (r = -0.44, P < 0.01) and TAI (r = -0.055, P < 0.01). On the contrary, UIC was negatively correlated with the risk of thyroid dysfunction (r = -0.24, P > 0.05).

CONCLUSION

Adult inhabitants from Jiangxi province in the TIDE study were in the adequate iodine status. Excessive iodine status was noted as a risk factor for thyroid dysfunction and thyroid nodules. In addition, both iodine deficiency and excessive iodine were risk factors for TAI.

Autoimmune thyroid status in subclinical thyroid disorders in patients attending a tertiary care center in Nepal: a hospital-based cross-sectional study

BACKGROUND

Thyroid dysfunction is the leading endocrine disorder worldwide. Iodine deficiency disorders, which were once the major etiology of thyroid dysfunctions, now have been succeeded by autoimmune thyroid diseases with the rise in aberrant salt ionization protocols. This study endeavors to access the level of thyroid autoantibodies viz. anti-thyroid peroxidase (anti-TPO), anti-thyroglobulin (TGA), and anti-thyroid stimulating hormone receptor (TRAb) in individuals with subnormal thyroid profiles.

METHODS

This hospital-based cross-sectional study was conducted at the Department of Clinical Biochemistry, Tribhuvan University for a period of six months. Using non-probability (purposive) sampling method, a total of 60 patients were enrolled with subnormal thyroid profiles to include the population who have not yet started medication. Thyroid hormones (free T3, free T4, TSH) and thyroid antibodies (anti-TPO, TGA, and TRAb) were measured. For non-parametric data, Chi-square test and Kruskal-Wallis test were used. Spearman's correlation was done to determine the association between variables.

RESULTS

Out of 60 participants, the majority of the population between 25 and 44 years were diagnosed with thyroid dysfunction with female preponderance. Among all, 40% (n = 24) had subclinical hyperthyroid states while, 60% (n = 36) had subclinical hypothyroid states, and 75% (n = 45) of the total exhibited positive thyroid antibodies. In subclinical hypothyroid patients with TSH above 10 µIU/ml, anti TPO (58.5%) and TGA (66.7%) positivity were highly prevalent. On the other hand, TRAb was exclusively positive in hyperthyroid condition (50% among the group) which is by far the first of its kind reported in Nepal.

CONCLUSION

The rise in autoimmune thyroid disease among the Nepalese population infers that addressing iodine deficiency simply through salt iodinization may not be adequate to deal with the rising burden of thyroid disorders, especially in iodine-depleted areas. Also, the increasing prevalence of thyroid autoantibodies positivity in subclinical hypothyroidism in the Nepalese population accounts for the arduous screening and monitoring of autoimmune thyroid disorders in Nepal.

Thyroid-Stimulating Hormone Levels within the Trimester-Specific Reference Intervals Are Correlated with Non-High-Density Lipoprotein Cholesterol and Remnant Cholesterol Concentrations in Pregnant Women

OBJECTIVE

Thyroid-stimulating hormone (TSH) levels are associated with serum lipid concentrations in the general nonpregnant population. Here, we aimed to establish trimester-specific reference intervals and to explore the associations of their variations within the specific reference intervals during pregnancy.

METHODS

Trimester-specific reference intervals were established according to the Clinical and Laboratory Standard Institute EP28-A3c guidelines using a direct sampling method based on a large prospective cohort. After making one-to-one matches, correlation analyses between TSH and lipid index levels, especially within the reference intervals, were conducted.

RESULT

A total of 1648 pregnant women for TSH and 2045 subjects for lipids were recruited to establish the trimester-specific reference intervals. The upper reference limit (90% confidence interval) of TSH for pregnant women in the first trimester is 3.95 (3.66-4.29) mIU/L, which is very close to the default value (4.0 mIU/L) recommended by the American Thyroid Association in 2017. Apart from triglyceride and high-density lipoprotein cholesterol, TSH levels were positively associated with the serum concentrations of total cholesterol, low-density lipoprotein cholesterol, non-high-density lipoprotein cholesterol (non-HDL-C), and remnant cholesterol (RC) either in the entire range or within the specific reference intervals. Of note, the positive correlations between TSH and non-HDL-C and RC were, albeit similarly weak (r < 0.25), relatively more robust (P < .001).

CONCLUSION

In this study, we showed positive correlations between TSH and lipid components within trimester-specific reference intervals, highlighting the need for the integrated management of pregnant women over age 35 and with nonoptimal lipid status in China.

Iodine nutrition and papillary thyroid cancer

Thyroid cancer (TC) is the most frequent endocrine malignancy. The incidence of TC, especially papillary thyroid carcinoma (PTC), has continued to rise all over the world during the past few years, for reasons that are not entirely clear. Though the phenomenon of overdiagnosis is occurring, it is not the sole driver of the substantial increase in incidence. Lifestyle, environmental factors, or complications are considered to be potential risk factors. Among these factors, iodine is a micronutrient that is vital to thyroid function. The effect of iodine intake on PTC has been controversial for many years and the epidemiological or experimental studies provided diametrically opposite conclusions. Combining all these studies, we found that iodine nutrition may affect the overall prevalence, distribution of the histological types, and clinicopathological aggressiveness of TC, especially PTC. However, the available evidence is poor due to the impact of various internal and external related factors. Therefore, this article sums up available results from both epidemiological and experimental studies, future studies are also warranted to expound on the relationship between overall PTC prevalence and iodine intake.

Excessive iodine in iodized household salt in Nepal

Iodine is an essential trace element required for the regulation of physiological processes involving the thyroid gland. However, inadequate and excessive intake of iodine are responsible for health problems, such as iodine deficiency disorders, hypothyroidism, hyperthyroidism, thyroiditis, thyroid papillary cancer, and thyrotoxicosis. The Universal Salt Iodization (USI) program has become successful in providing supplemental iodine at the population level globally. Packaging quality, fortification level, and transportation and storage conditions of iodized salt determine the availability of iodine. Previous studies have reported severe health issues caused by excessive iodine intake after the implementation of the USI program. To understand the levels of iodine, we collected 2117 household salt samples from seven districts of Nepal and tested them for iodine content; among them, 98.1% were iodized. Overall median concentration of iodine was 53.9 ppm (range: 43.5-61.4 ppm). The majority (67.2%) of samples had iodine in the range of 45-75 ppm. Approximately 0.9% of samples had inadequate, 13.3% contained adequate, and 83.9% had excessive iodine than the World Health Organization-recommended value. Iodine content varied among the sampling districts and seasons, to some extent. Our study confirmed that iodized salt is widely used in Nepal and is excessively iodized. Excessive intake of iodine through iodized salt requires further attention by policy makers. The iodine level may need adjustment to address the health impact.

Iodine Concentrations in Conventional and Organic Milk in the Northeastern U.S

Milk is a major source of dietary iodine in the United States. Due to a relatively low margin of safety for iodine intake, there are concerns for both deficiency and over-exposure. Iodine concentrations of raw milk samples from farms and retail milk in the Northeastern U.S. region were compared between seasons (winter vs. summer) and farming practices (conventional vs. organic). Overall, mean iodine concentration was 46.2% higher in raw milk from conventional farms vs. organic farms. An interaction effect between season and farming practices was observed. Organic raw milk had higher iodine content in the winter than in the summer (423 ± 54 μg/L vs. 273 ± 24 μg/L), whereas conventional raw milk had higher iodine content in the summer than in the winter (618 ± 75 μg/L vs. 398 ± 27 μg/L). Milk samples from conventional farms had 2.27-fold higher average iodine concentration compared to milk coming from organic farms in the summer but did not differ in the winter. Out of 68 and 98 raw milk samples originating from conventional and organic farms, 22 (32.4%) and 19 (19.4%) respectively, had iodine concentrations > 500 µg/L, reaching as high as 1928 μg/L. In contrast, the overall mean concentration of iodine in retail milk did not differ between conventional and organic milk (345 ± 23 vs. 320 ± 42 μg/L, respectively). The current study confirms dairy milk remains to be a good source of iodine to U.S. consumers. However, dairy farms should be aware of the potential adverse health effects of excess iodine intake. Careful considerations in dairy management may be necessary to not exceed the recommended level of iodine supplementation in both conventional and organic operations at the farm level—to maintain optimal iodine concentrations in retail fluid milk accessible to the consumers.

Secular Trends in the Prevalence of and Disability-Adjusted Life Years Due to Common Micronutrient Deficiencies in China From 1990 to 2019: An Age-Period-Cohort Study and Joinpoint Analysis

Background

Understanding the national burdens and trends of micronutrient deficiencies can help guide effective intervention strategies. However, there is a lack of evidence of secular trends and age and sex differences in China. This study aims to elucidate trends in common micronutrient deficiencies, in particular, dietary iron, iodine and vitamin A deficiencies in China, from 1990 to 2019 using Global Burden of Disease (GBD) 2019 study data.

Methods

Prevalence and DALYs trends of common micronutrient deficiencies from 1990 to 2019 were assessed by joinpoint regression analysis. Age, period and cohort effects on the prevalence of common micronutrient deficiencies were estimated by an age-period-cohort model.

Results

From 1990 to 2019, the age-standardized prevalence rates of iodine, vitamin A and dietary iron deficiencies changed by −0.6% (95% CI: −0.7% to −0.5%), −6.3% (−6.6% to −6.0%), and −3.5% (−3.6% to −3.4%) in males and + 0.8% (+ 0.6% to + 1.0%), −4.5% (−4.8% to −4.2%), and −3.3% (−3.4% to −3.2%) in females, respectively. The average annual percent change (AAPC) in the iodine deficiency prevalence increased in females aged 20 years and older. The relative risk (RR) of iodine deficiency associated with the age effect peaked at 30–34 years of age and then decreased with increasing age. The RR of vitamin A deficiency decreased with age. The age distribution of the RR of iron deficiency differed significantly between sexes. The RRs of vitamin A deficiency and dietary iron deficiency decreased over time, whereas the RR of iodine deficiency substantially increased starting in 2004. The RRs of iodine deficiency and dietary iron deficiency associated with the cohort effect decreased, but the vitamin A deficiency prevalence increased in successive birth cohorts.

Conclusion

Micronutrient deficiency prevalence rates and associated DALYs decreased from 1990 to 2019 in China. Young adults, children aged less than 5 years, and older individuals were disproportionately affected by iodine, vitamin A, and dietary iron deficiencies, respectively. The results of this study may help identify individuals who would benefit from interventions to improve micronutrient deficiency.

Thyroid function disorders

Thyroid function disorders are the most common endocrine disorders in humans. They are frequently diagnosed, with prevalence varying between 2 and 6%, and a female to male ratio of up to 10:1. Disorders of thyroid function in the narrower sense are presented by its hyperactivity or underactivity, although there are conditions that lead to an increased concentration of thyroid hormones, without its increased activity. In iodine-sufficient regions, the most common cause of hyperthyroidism, as well as hypothyroidism, is an autoimmune disease of the thyroid. For hyperthyroidism, it is Graves' disease, with typical symptoms and signs of hypermetabolism. The diagnosis of hyperthyroidism is based on suppressed TSH and elevated fT4 (free, and in the differential diagnosis, elevated TSH-receptor-antibodies are crucial for Graves' disease. Management of Graves' disease relies on three equally potent approaches: medical therapy, ablative treatments with 131I-radiotherapy-RAI, and thyroidectomy. Hashimoto's thyroiditis is the most common cause of hypothyroidism in iodine-sufficient regions. Symptoms and signs of hypothyroidism are non-specific and correspond to the symptoms and signs of hypometabolism. The diagnosis is made based on elevated TSH with decreased fT4. Thyroxine-peroxidaseantibodies and thyroglobuline-antibodies are important in differential diagnosis. Sometimes elevated TRAb is found in Hashimoto's thyroiditis. The treatment of hypothyroidism is levothyroxine replacement therapy.

The relationship between urinary iodine concentration and papillary thyroid cancer: A systematic review and meta-analysis

BACKGROUND

The effect of iodine on papillary thyroid cancer (PTC) has been controversial for many years. Since urinary iodine is an effective indicator of iodine intake, some recent epidemiological studies have described the relationship between urinary iodine concentration (UIC) and PTC.

METHODS

We searched PubMed, Embase, Cochrane Library, and Web of Science for case-control studies about UIC and PTC published before September 2022. Results are presented as the overall odds ratio (OR) and 95% confidence intervals (CI).

RESULTS

According to the analysis of the included studies, excessive iodine intake (UIC≥300ug/L) was positively associated with the occurrence of PTC patients compared with healthy controls (OR4.05, 95%CI 1.64-10.02, P=0.002). Meanwhile, adequate iodine exposure (100≤UIC&lt;200ug/L) may play a protective role in the occurrence of PTC compared with healthy individuals (OR 0.36, 95%CI 0.14-0.91, P=0.03) while the difference in the prevalence of insufficient iodine intake (UIC&lt;100ug/L) and iodine above requirements (200≤UIC&lt;300ug/L) among the two groups were not significant (deficiency: OR 0.38, 95%CI 0.13-1.16, P=0.09; above requirements: OR 0.92, 95%CI 0.40-2.10, P=0.84). After comparing the UIC levels of PTC patients with those of other thyroid diseases, we found that there was also no significant difference in the incidence of different levels of UIC in the two groups (excessive: OR 1.25, 95%CI 0.87-1.80, P=0.22; above requirements: OR 0.93, 95%CI 0.77-1.14, P=0.49; adequate: OR 0.96, 95%CI 0.78-1.17, P=0.67; deficiency: OR 1.02, 95%CI 0.86-1.22, P=0.80). The result of this meta-analysis also did not support the relationship between UIC and the BRAF mutation and lymph node metastasis (LNM) of PTC patients. Besides, we also found that studies on the relationship between urinary iodine and PTC may be influenced by the way UIC was measured.

CONCLUSION

The 10 case-control included studies involved a total of 6,544 participants. The results of this meta-analysis showed excessive iodine intake, that is, UIC≥300ug/L was associated with the occurrence of PTC but not with BRAF mutation and LNM while adequate iodine intake (100≤UIC&lt;200ug/L) may be one of the protective factors for PTC.

Effect of the transition from more than adequate iodine to adequate iodine on national changes in the prevalence of thyroid disorders: repeat national cross-sectional surveys in China

OBJECTIVE

Longitudinal studies have investigated the effects of changing iodine status on thyroid disorders, but the effect of a transition from more than adequate iodine to adequate iodine on national changes in prevalence adjusted for changing risk factors remains unclear.

DESIGN

Two repeat nationwide surveys were conducted from 2009-2010 to 2015-2017 to assess changes in thyroid disorder prevalence and iodine status in China.

METHODS

A multistage stratified random sampling method was used to obtain a nationally representative sample of urban adults aged 18 and older in mainland China in 2009 (n = 14 925) and 2015 (n = 12 553). Changes in thyroid disorder prevalence, urinary iodine concentration (UIC), and thyroid-stimulating hormone (TSH) levels were assessed. Logistic regression models were used to examine changes in prevalence over time.

RESULTS

The median UIC decreased significantly from 219.7 to 175.9 μg/L (P < 0.0001). The weighted prevalence of overt hyperthyroidism, subclinical hyperthyroidism, Graves' disease, and goitre decreased between 2009 and 2015 in the overall population (P < 0.05 for all). Despite no significant changes in subclinical hyperthyroidism or hypothyroidism or anti-thyroid peroxidase or anti-thyroglobulin antibody positivity prevalence, a significant increase in thyroid nodule prevalence (P < 0.0001) was found in the overall population. The 2.5th TSH percentile increased by 0.15 mIU/L (95% CI: 0.01 to 0.30 mIU/L, P = 0.04) from 2009 to 2015.

CONCLUSIONS

With the iodine status transition from more than adequate to adequate, thyroid disorder (except for thyroid nodules) prevalence remained stable or even decreased after adjusting for confounding factors among adults in mainland China between 2009 and 2015. Additional studies are needed to explore the reasons for the increased thyroid nodule prevalence.

Environmental and human iodine and selenium status: lessons from Gilgit-Baltistan, North-East Pakistan

Iodine and selenium deficiencies are common worldwide. We assessed the iodine and selenium status of Gilgit-Baltistan, Pakistan. We determined the elemental composition (ICP-MS) of locally grown crops (n = 281), drinking water (n = 82), urine (n = 451) and salt (n = 76), correcting urinary analytes for hydration (creatinine, specific gravity). We estimated dietary iodine, selenium and salt intake. Median iodine and selenium concentrations were 11.5 (IQR 6.01, 23.2) and 8.81 (IQR 4.03, 27.6) µg/kg in crops and 0.24 (IQR 0.12, 0.72) and 0.27 (IQR 0.11, 0.46) µg/L in water, respectively. Median iodised salt iodine was 4.16 (IQR 2.99, 10.8) mg/kg. Population mean salt intake was 13.0 g/day. Population median urinary iodine (uncorrected 78 µg/L, specific gravity-corrected 83 µg/L) was below WHO guidelines; creatinine-corrected median was 114 µg/L but was unreliable. Daily selenium intake (from urinary selenium concentration) was below the EAR in the majority (46-90%) of individuals. Iodine and selenium concentrations in all crops were low, but no health-related environmental standards exist. Iodine concentration in iodised salt was below WHO-recommended minimum. Estimated population average salt intake was above WHO-recommended daily intake. Locally available food and drinking water together provide an estimated 49% and 72% of EAR for iodine (95 µg/day) and selenium (45 µg/day), respectively. Low environmental and dietary iodine and selenium place Gilgit-Baltistan residents at risk of iodine deficiency disorders despite using iodised salt. Specific gravity correction of urine analysis for hydration is more consistent than using creatinine. Health-relevant environmental standards for iodine and selenium are needed.

Dietary Micronutrients from Zygote to Senility: Updated Review of Minerals' Role and Orchestration in Human Nutrition throughout Life Cycle with Sex Differences

Micronutrients such as selenium, fluoride, zinc, iron, and manganese are minerals that are crucial for many body homeostatic processes supplied at low levels. The importance of these micronutrients starts early in the human life cycle and continues across its different stages. Several studies have emphasized the critical role of a well-balanced micronutrient intake. However, the majority of studies looked into or examined such issues in relation to a specific element or life stage, with the majority merely reporting the effect of either excess or deficiency. Herein, in this review, we will look in depth at the orchestration of the main element requirements across the human life cycle beginning from fertility and pregnancy, passing through infancy, childhood, adolescence, and reaching adulthood and senility, with insight on the interactions among them and underlying action mechanisms. Emphasis is given towards approaches to the role of the different minerals in the life cycle, associated symptoms for under- or overdoses, and typical management for each element, with future perspectives. The effect of sex is also discussed for each micronutrient for each life stage as literature suffice to highlight the different daily requirements and or effects.

Age-specific thyrotropin references decrease over-diagnosis of hypothyroidism in elderly patients in iodine-excessive areas

OBJECTIVE

Acute or chronic exposure to excess iodine has detrimental effects on thyroid physiology; therefore, this study aimed to determine the prevalence of overt hypothyroidism (OH) and subclinical hypothyroidism (SCH) in an elderly population residing in geographical areas with chronic exposure to excess iodine intake and to analyse contributing risk factors.

DESIGN

This cross-sectional study was conducted from 2016 to 2017 in areas of Jiangsu Province that have documented chronic exposure to high iodine intake.

PATIENTS

We enroled 2559 adult participants using a multistage, stratified sampling method.

MEASUREMENTS

Urinary iodine concentration (UIC), serum thyroid-stimulating hormone (TSH) level and other relevant parameters were measured. Demographic information was recorded using a standardized questionnaire. The age-specific TSH references were determined by the National Academy of Clinical Biochemistry guidelines. Univariate and multivariate logistic regression analyses were performed to identify risk factors for hypothyroidism in the study population.

RESULTS

The median UIC of participants was 307.3 µg/L (interquartile range: 200.7, 469.8 μg/L). The prevalence of OH in subjects ≥70 years using laboratory reference ranges was 2.37%; however, it decreased to 1.78% with the use of an age-specific reference range. Similarly, the prevalence of SCH also declined drastically from 29.59% to 2.96% with the application of an age-specific reference range. In both univariate and multivariate models, advanced age, female gender and high UIC were identified as risk factors for hypothyroidism.

CONCLUSIONS

Usage of age-specific TSH reference ranges led to a significantly lower prevalence of OH and SCH in the study population, thus preventing unnecessary over-diagnosis and over-treatment.

Factors influencing the reference interval of thyroid-stimulating hormone in healthy adults: A systematic review and meta-analysis

BACKGROUND

Many studies have reported that the thyroid-stimulating hormone (TSH) reference interval is susceptible to external factors, such as age, sex, race, region and iodine intake. However, no meta-analysis has comprehensively explored the effect of these factors on the TSH reference interval.

METHODS

Articles published from January 1960 to January 2020 were searched in PubMed, Embase, Cochrane, Scopus, Medline English databases and CNKI, WanFang and CQVIP Chinese databases. In total, 19 studies were ultimately included. All data were analysed using Review Manager 5.3, STATA 16.0 software, GraphPad Prism 8.0 and Microsoft Excel 2010 to draw the TSH concentration curve.

RESULTS

The TSH reference interval was significantly influenced by sex and age. The mean of TSH concentration in females was 0.27 mIU/L higher than that in males. Reference interval of TSH is divided into 20-59 years old and >60 years old age groups in males, and 20-39 years old and >40 years old age groups in females. Regardless of sex, TSH concentrations all increase with age. In iodine-deficient areas, TSH reference intervals were generally lower than those in iodine-sufficient or iodine-excessive areas. The TSH reference interval in Asia and North American countries was generally higher than that in most European countries. In the subgroup analyses of sample size, region and assay methods and manufacturers, the between-group differences were significant.

CONCLUSION

The TSH reference interval was significantly influenced by sex, age, iodine intake, sample size, region, and assay methods and manufacturers, but other factors should not be ignored. Therefore, it is necessary for each laboratory to validate an appropriate TSH reference interval based on local conditions.

Association between Iodine Intake, Thyroid Function, and Papillary Thyroid Cancer: A Case-Control Study

BACKGROUND

This study aimed to assess the effects of iodine intake, thyroid function, and their combined effect on the risk of papillary thyroid cancer (PTC) and papillary thyroid microcarcinoma (PTMC).

METHODS

A case-control study was conducted including 500 community-based controls who had undergone a health check-up, and 446 overall PTC cases (209 PTC and 237 PTMC) from the Thyroid Cancer Longitudinal Study. Urinary iodine concentration (UIC), was used as an indicator of iodine intake, and serum for thyroid function. The risk of PTC and PTMC was estimated using unconditional logistic regression.

RESULTS

Excessive iodine intake (UIC ≥220 μg/gCr) was associated with both PTC (odds ratio [OR], 18.13 95% confidence interval [CI], 8.87 to 37.04) and PTMC (OR, 8.02; 95% CI, 4.64 to 13.87), compared to adequate iodine intake (UIC, 85 to 219 μg/gCr). Free thyroxine (T4) levels ≥1.25 ng/dL were associated with PTC (OR, 1.97; 95% CI, 1.36 to 2.87) and PTMC (OR, 2.98; 95% CI, 2.01 to 4.41), compared to free T4 levels of 0.7 to 1.24 ng/dL. Individuals with excessive iodine intake and high free T4 levels had a greatly increased OR of PTC (OR, 43.48; 95% CI, 12.63 to 149.62), and PTMC (OR, 26.96; 95% CI, 10.26 to 70.89), compared to individuals with adequate iodine intake and low free T4 levels.

CONCLUSION

Excessive iodine intake using creatinine-adjusted UIC and high free T4 levels may have a synergistic effect on PTC and PTMC. Considering both iodine intake and thyroid function is important to assess PTC and PTMC risk.

The change in the clinical presentation of Graves' disease: a 30 years retrospective survey in an academic Brazilian tertiary center

Objective

Graves' disease (GD) is the main cause of hyperthyroidism among adults. It is an autoimmune condition classically marked by the Merserburg Triad (goiter, thyrotoxicosis, and orbitopathy), but the change in presentation of GD over time has rarely been studied. To determine changes in the clinical presentation of patients with GD in the last 30 years.

Methods

The study evaluated 475 patients diagnosed with GD between 1986 and 2016 in a single center. Patients were evaluated regarding epidemiological aspects, thyroid function, inflammatory activity of the eyes evaluated by the Clinical Activity Score; CAS, severity evaluated by NOSPECS classification and thyroid volume estimated by ultrasonography.

Results

Patients assessment identified an increase in the mean age of diagnosis of GD (p < 0.02), a reduction in thyroid volume (p < 0.001) and less intense orbital involvement from 2007-2016 compared to 1986-2006 (p = 0.04). The number of smoking patients was smaller from 2007 to 2016 (28.7%) than 1986 to 2006 (42.8% p = 0.001). The TSH and TRAb values did not had significant changes.

Conclusion

GD presentation appears to be changed in the last years compared to the typical initial presentation. There is a less frequent inflammatory involvement of orbital tissue, smaller goiters, a lower number of smokers and diagnosis at older age.

The Iodine Status and Prevalence of Thyroid Disorders Among Women of Childbearing Age in China: National Cross-sectional Study

OBJECTIVE

Mandatory universal salt iodization in China was implemented 20 years ago. However, the current iodine status and prevalence of thyroid disorders among childbearing-age women are unknown.

METHODS

A nationally representative cross-sectional study with 26 166 enrolled participants aged 18 to 49 years from all 31 provincial regions of mainland China was performed. The participants were given a questionnaire and underwent B-mode ultrasonography of the thyroid. The serum concentrations of thyroid hormones and thyroid antibodies and the urinary iodine concentration (UIC) were measured.

RESULTS

The median UIC was 178.7 μg/L, indicative of adequate iodine status. pHowever, 19.04% and 19.87% of the participants were classified as having iodine deficiency and excessive iodine, respectively. The weighted prevalence of thyroid disorders was as follows: 1.08% had overt hyperthyroidism, 0.58% had subclinical hyperthyroidism, 0.76% had Graves disease, 1.28% had overt hypothyroidism, 14.28% had subclinical hypothyroidism, 13.53% were positive for thyroid peroxidase antibodies, and 14.55% were positive for thyroglobulin antibodies. Excessive iodine and overweight were associated with higher odds of subclinical hypothyroidism. A family history of thyroid disorders and an age between 40 and 49 years were significantly associated with higher odds of positivity for thyroid peroxidase antibodies and thyroglobulin antibodies.

CONCLUSION

Iodine deficiency, excessive iodine, subclinical hypothyroidism, and positivity for thyroid autoantibodies remain prevalent among women of childbearing age in China. Women of childbearing age who are relatively older, are overweight, or have a family history of thyroid disorders are encouraged to undergo active screening of their UIC and thyroid function when planning a pregnancy.

Serum T3 Level and Duration of Minimum Maintenance Dose Therapy Predict Relapse n Methimazole-Treated Graves Disease

Background

Methimazole (MMI) has been advocated as a preferred option for most Graves disease (GD) patients. However, long-term remission after a course of MMI treatment is achieved in only 20% to 40% of patients, depending on the duration of follow-up.

Objective

To evaluate clinical factors for predicting relapse of GD in Thai patients after MMI treatment.

Methods

A retrospective analysis was performed of newly diagnosed patients with GD who achieved remission of hyperthyroid GD after at least 12 months of MMI treatment. Long-term outcomes were assessed and predictive factors of early and late relapse were evaluated.

Results

A total of 443 patients with newly diagnosed GD who were treated with MMI for at least 12 months from 1985 to 2019, and were able to discontinue medication, were studied. The mean age at diagnosis was 37.0 ± 11.4 years and 81.7% were female. Of the 320 patients (72.2%) who achieved initial remission after MMI treatment for 23 months, 106 patients (33.1%) experienced late relapse during the mean follow-up duration of 9.7 years after MMI withdrawal. The remission rates decreased from 36.4% at the first year after stopping MMI to only 20.7% at 10 years. High initial serum triiodothyronine (T3) level and duration of minimum maintenance dose therapy (MMDT) of <6 months were associated with late disease relapse after remission.

Conclusion

The long-term remission rate of Graves hyperthyroidism was achieved in one-fifth of MMI-treated Thai patients. Predictive markers for late relapse included high initial serum T3 level and a duration of MMDT of <6 months.

Association between Urinary Iodine Concentration and Thyroid Nodules in Adults: A Cross-Sectional Study in China

Background

Associations between iodine intake and thyroid nodules (TNs) were not consistent. We aimed to illustrate the relationship between urinary iodine concentration (UIC) and TNs.

Methods

A total of 12,698 participants were enrolled in analysis. All of the participants filled out questionnaires and underwent physical examinations, laboratory tests, and thyroid ultrasonography. UIC, serum thyrotropin (TSH), thyroid peroxidase antibodies (TPOAb), and thyroglobulin antibodies (TgAb) were measured in the central laboratory.

Results

The prevalence of TNs was 16.00%, and the median UIC was 206.1 μg/L. TNs and UIC were negatively related when UIC was less than 527 μg/L (adjusted OR = 0.87; 95% CI, 0.80, 0.94), and the relationship between UIC and TNs was not statistically significant when UIC was greater than 527 μg/L (adjusted OR = 1.25; 95% CI, 0.98, 1.60). In women, UIC was negatively associated with risk for TNs (adjusted OR 0.95; 95% CI, 0.91, 0.99).

Conclusion

The relationship between TNs and UIC differed between men and women. The risk of TNs decreased with the elevation of UIC in men when UIC was lower than 527 μg/L, while UIC and the presence of TNs were negatively correlated in women. In the future, cohort studies or other studies that can explain causality must be conducted to explore the relationship between iodine status and TNs.

An Inverse Relationship Between Iodine Intake and Thyroid Antibodies: A National Cross-Sectional Survey in Mainland China

Background: Iodine intake is associated with thyroid autoimmunity. In this study, we evaluated the changes in thyroid autoimmunity after 20 years of universal salt iodization (USI) in China. Methods: A total of 78,470 subjects (18 years or older) from 31 provincial regions of mainland China participated in the study. Serum thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TgAb), TSH receptor antibody, thyrotropin (TSH), and urinary iodine concentration (UIC) were measured. Results: Positive TPOAb and TgAb were detected in 10.19% [CI 9.80-10.59] and 9.70% [CI 9.28-10.13] of the subjects, respectively. The prevalence of positive isolated TPOAb (i-TPOAb), positive isolated TgAb (i-TgAb), and double positive TPOAb and TgAb (d-Ab) was 4.52%, 4.16%, and 5.94%, respectively. The prevalence of thyroid antibody positivity was the highest in the iodine-deficient (UIC <100 μg/L) groups. The prevalence of i-TPOAb was inversely associated with more than adequate iodine intake (MAI) and excessive iodine intake (EI); the odds ratio (OR) was 0.89 [CI 0.81-0.98] for MAI and 0.90 [CI 0.81-0.99] for EI. We observed that i-TgAb, like i-TPOAb, was a high-risk factor for subnormal TSH levels (OR = 3.64 [CI 2.62-5.05]) and elevated TSH levels (OR = 1.62 [CI 1.49-1.77]). The prevalence of thyroid antibody positivity varied among five ethnic groups. Conclusions: After two decades of USI, the prevalence of thyroid antibody positivity has remained low. MAI and EI had an inverse relationship with TPOAb positivity, which reveals that UIC between 100 and 299 μg/L is optimal and safe for thyroid autoimmunity. These conclusions need to be confirmed in a follow-up study because this study was a cross-sectional study.

The Diverse Upper Reference Limits of Serum Thyroid-Stimulating Hormone on the Same Platform for Pregnant Women in China

OBJECTIVE

To describe the diverse upper reference limits of serum thyroid stimulating hormone on the same platform for pregnant women in China.

METHODS

The trimester-specific and population-specific TSH reference intervals for pregnant women were established, and then 5 reference intervals on the same platform in China were compared with the reference intervals derived from the present study and the manufacturer.

RESULTS

The most striking difference in the upper reference limits of TSH among 5 reference intervals on the same platform was shown at the first trimester of pregnancy. The calculated regional prevalence rates of subclinical thyroid diseases varied using the data derived from 30,771 pregnant women who visited the largest obstetric center in our district from 2008 to 2018.

CONCLUSION

We reported differences among 7 reference intervals of TSH on the same platform and showed the changing population factors significantly affected them.

High prevalence of TPO-Abs and subclinical hypothyroidism in iodine-sufficient pregnant women in Northern Algeria

BACKGROUND

Iodine is a trace element whose adequate intakes are essential during gestation to promote the correct growth and development of the fetus. Historically, endemic goiter and cretinism affected northern regions of Algeria, and iodized salt was introduced in 1990. However, there has been no national study of iodine nutrition in Algeria since 1994. The aim of this study was to assess the iodine status and thyroid function of women of reproductive age (WRA) and pregnant women (PW) in northern Algeria.

METHODS

Healthy WRA and PW were recruited from an urban area (Algiers) and healthy WRA from a rural area (Tizi-Ouzou). Spot urine and venous blood samples were collected to assess iodine status (urinary iodine concentration, UIC) and serum thyroid hormones (TSH, FT4), thyroglobulin (Tg), and anti-thyroid peroxidase antibodies (TPO-Ab) concentrations.

RESULTS

The median UIC in WRA was 256 μg/L (IQR: 166-354 μg/L; n = 151) in Algiers and 253 μg/L (167-341 μg/L; n = 150) in Tizi-Ouzou. The median UIC for the PW in Algiers was 233 μg/L (IQR: 157-326 μg/L; n = 173).Thirty-five percent of WRA and 30% of PW had an UIC > 300 μg/L. Median TSH, FT4 and Tg concentrations were within reference ranges in all groups of women. Among PW, 72.7%, 75.4% and 75.5% in the first, second and third trimester were TPO-Ab+. Among TPO-Ab + PW in the first, second and third trimesters, 18.7%, 13% and 10.3% had subclinical hypothyroidism.

CONCLUSION

In northern Algeria, median UICs in PW indicate iodine sufficiency, and in WRA indicate more than adequate intakes. About 75% of PW are TPO-Ab + and the prevalence of subclinical hypothyroidism is high. Monitoring and surveillance of iodine fortification programs is vital to avoid both iodine deficiency and excess. There is an urgent need for a comprehensive national iodine status survey including school-age children and other vulnerable population groups in Algeria.

Efficacy and Safety of Long-Term Universal Salt Iodization on Thyroid Disorders: Epidemiological Evidence from 31 Provinces of Mainland China

Background: Mandatory universal salt iodization (USI) has been implemented in China for 20 years. Although iodine deficiency disorders are effectively controlled, the risk of excess iodine have been debated. Methods: A nationally representative cross-sectional study with 78,470 enrolled participants, aged 18 years or older, from all 31 provincial regions of mainland China was performed. The participants were given a questionnaire and underwent B-mode ultrasonography of the thyroid. Serum concentrations of thyroid hormones, thyroid antibodies, and urine iodine concentration (UIC) were measured. Results: The median UIC of the adult population was 177.89 μg/L. The weighted prevalence of thyroid disorders in adults were as follows: 0.78% of overt hyperthyroidism, 0.44% of subclinical hyperthyroidism, 0.53% of Graves' disease, 1.02% of overt hypothyroidism, 12.93% of subclinical hypothyroidism, 14.19% of positive thyroid antibodies, 10.19% of positive thyroid peroxidase antibodies, 9.70% of positive thyroglobulin antibodies, 1.17% of goiter, and 20.43% of thyroid nodules. Iodine excess was only associated with higher odds of overt hyperthyroidism and subclinical hypothyroidism, while iodine deficiency was significantly associated with higher odds of most thyroid disorders. In addition, increased iodine intake was significantly associated with elevated serum thyrotropin levels but was inversely associated with thyroid antibodies and thyroid nodules. Conclusions: The long-term mandatory USI program with timely adjustments is successful in preventing iodine deficiency disorders, and it appears to be safe. The benefits outweigh the risks in a population with a stable median iodine intake level of up to 300 μg/L.

Association between urinary sodium levels and iodine status in Korea

BACKGROUND/AIMS

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

METHODS

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

RESULTS

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

CONCLUSION

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

Relationship of gender and age on thyroid hormone parameters in a large Chinese population

Objective This study aimed to present the impact of age and gender on thyroid hormone levels in a large Chinese population with sufficient iodine intake. Subjects and methods A total of 83643 individuals were included and were stratified by age and gender. The median, 2.5th and 97.5th of thyrotropin (TSH), free triiodothyronine (FT3), free thyroxine (FT4) and FT3/FT4 ratio were calculated for both genders for every decade from 18 to over 80 years. TSH, FT3, FT4, FT3/FT4 distribution in each age group was evaluated for females and males using smoothing splines in the generalized additive models (GAM). TSH concentrations were compared in the different age groups in gender. Results In the over 80s age group, the TSH level (median: 2.57 mIU/L, 2.5th-97.5th: 0.86-7.56 mIU/L) was significantly higher than other age groups, irrespective to gender (P<0.001). Females had a higher TSH value than males in all age groups (P<0.001). Results of the smoothing curves showed that TSH increased with age, FT3 concentration was higher in males than in females and the tendency of the FT3/FT4 ratio was basically similar to that of FT3. TSH concentration in the 50s age group (median 2.48 mIU/L for females versus 2.00 mIU/L for males) was significantly higher than that in the 30s age group (median 2.18 mIU/L for females versus median 1.85 mIU/L for males). Conclusions In accord with increasing TSH values during aging, females and older adults have lower FT3 values and lower FT3/FT4 ratios, while the FT4 values remain stable.

Advanced Ultrasound Application - Impact on Presurgical Risk Stratification of the Thyroid Nodules

AIM

Current major guidelines recommend risk stratification of the thyroid nodules, after each diagnostic evaluation, in order to focus attention on potentially risky nodules. The main aim of our study was to evaluate the performance of combined advanced ultrasound techniques in this process, compared with conventional stratification models, in order to reduce unnecessary fine-needle biopsies, respectively, surgery.

MATERIAL AND METHODS

We evaluated 261 cases (261 nodules) using conventional ultrasound (2B), real-time Doppler evaluation (4D) respectively, real-time elastography, using a linear multifrequency probe and a linear volumetric probe (Hitachi Prerius Machine, Hitachi Inc, Japan). All the nodules were classified using a risk stratification model comprising seven conventional US characteristics, two 4 D characteristics and a color map RTE aspect. The results were compared with the pathology results, considered the golden standard diagnosis.

RESULTS

The prevalence of malignant nodules was 21.83% (57 cases). Conventional risk classification generated: 106 low-risk cases, 113 intermediate-risk and 42 high-risk cases. Our proposed risk classification changes the conventional risk classification with a risk upgrade in 27 cases and with a risk downgrade in 69 cases. The diagnostic quality of the combined risk stratification model was better, considering a low-risk category predictive for benignancy and a high category predictive for malignancy: Sensitivity: 80.88% versus 49.01%, respectively, Specificity: 91.22% versus 54.38. The diagnostic power differences were observed regardless of the nodule size.

CONCLUSION

Advanced ultrasound techniques did add diagnostic value in the presurgical risk assessment of the thyroid nodules.

A cross-sectional research of iodine status of pregnant women in Chongqing, south-west China

OBJECTIVE

To investigate whether implementation of a universal salt iodization (USI) programme has sufficient effects on pregnant women in Chongqing, the present study evaluated the iodine nutritional status of pregnant women living in Chongqing by spot urinary iodine concentration (UIC), to provide scientific suggestions to better meet the specific iodine needs of this vulnerable group.

DESIGN

Cross-sectional design.

SETTING

A random spot urine sample and household table salt sample were provided by each participant.

PARTICIPANTS

A total of 2607 pregnant women from twenty-six of thirty-nine districts/counties in Chongqing participated.

RESULTS

The overall median UIC of pregnant women was 171·80 μg/l (interquartile range (IQR) = 113·85-247·00 μg/l) and 40·97 % (n 1057) of participants were iodine insufficient. The median iodine in table salt samples was 25·40 mg/kg (IQR = 23·10-28·30 mg/kg); 93·26 % (n 2406) of samples examined were found to be adequately iodized. Iodine nutritional status was not significantly different according to table salt iodization category. Trimester was identified to be statistically associated with UIC (P < 0·01). Seven districts/counties had median UIC below 150 μg/l and one district had median UIC of 277·40 μg/l.

CONCLUSIONS

The USI programme in Chongqing prevents iodine deficiency generally, but does not maintain iodine status within adequate and recommended ranges throughout pregnancy. Usage of non-iodized or unqualified iodized salt and the slight change of dietary habits of iodized salt in Chongqing may present a substantial challenge to fight iodine-deficiency disorders; more efforts are needed to ensure adequate iodine intake during pregnancy besides the USI programme.

Association between Iodine Nutrition Status and Thyroid Disease-Related Hormone in Korean Adults: Korean National Health and Nutrition Examination Survey VI (2013-2015)

This study aimed to observe the relationship between iodine nutrition status (dietary iodine intake and estimated iodine intake based on urinary iodine concentration (UIC)) and thyroid disease-related hormones. This study involved 6090 subjects >19 years old with valid UIC, assessed between 2013 and 2015 by the Korean National Health and Nutrition Examination Survey, using a stratified, multistage, clustered probability-sampling design. The estimated iodine intake in participants was measured using UIC and urine creatinine. To examine the effect of iodine intake on thyroid disease, the iodine intake was divided into Korean Dietary Reference Intakes groups, and logistic regression analysis was performed via the surveylogistic procedure to obtain odds ratios (ORs) and 95% confidence intervals (CIs). The estimated iodine intake showed a significant positive correlation with dietary iodine intake (r = 0.021, p < 0.001), UIC (r = 0.918, p < 0.001), and thyroid-stimulating hormone (TSH) (r = 0.043, p < 0.001), but a significant negative correlation with free thyroxine (FT4) (r = -0.037, p < 0.001). Additionally, as the estimated iodine intake increased, age, TSH, and UIC increased, but FT4 decreased (p for trend < 0.0001). The risk of thyroid disease was higher in the "≥tolerable upper intake level (UL ≥ 2400 µg/day)" group than in the " Collapse

Key Words

• Korean
• epidemiologic studies
• iodine nutrition status
• thyroid disease
• thyrotropin
• urine iodine

Collapse

MESH Headings

• Adult
• Female
• Health Surveys
• Humans
• Iodine/administration & dosage
• Male
• Nutritional Status
• Republic of Korea/epidemiology
• Thyroid Diseases/epidemiology
• Thyroid Diseases/metabolism
• Thyroid Hormones
• Young Adult

Collapse

Grants Collapse

Affiliation(s)

Sohye Kim Department of Medical Nutrition, Graduate School of East-West Medical Science, Kyung Hee University, Yongin 17104, Korea; Nutrition Care Services, Seoul National University of Bundang Hospital, Seongnam 13620, Korea
Yong Seok Kwon F&D Communication, Gyeonggi 10433, Korea;
Ju Young Kim Department of Family Medicine, Seoul National University of Bundang Hospital, Seongnam 13620, Korea;
Kyung Hee Hong Department of Food Science and Nutrition, Dongseo University, Pusan 47011, Korea;
Yoo Kyoung Park Department of Medical Nutrition, Graduate School of East-West Medical Science, Kyung Hee University, Yongin 17104, Korea;

Collapse

Analytical evaluation of the new Seal Autoanalyzer 3 High Resolution for urinary iodine determination

Introduction

The aim of the study was to evaluate the analytical performance of the new colorimetric, automatic analyser, Seal AutoAnalyzer 3 High Resolution (Seal AA3 HR) (Seal Analytical, Wisconsin, USA) for urinary iodine measurement.

Materials and methods

This study included testing of several analytical features of the method involving: imprecision (within-run %CVr, between-run %CVb and total laboratory precision %CVl), measurement uncertainty, carryover, linearity and method comparison, with 70 urine samples including the measuring range (20 - 700 µg/L).

Results

Within-run, %CVb and %CVl of two control levels were 2.03% and 3.04%, 0.51% and 2.61%, and 2.09% and 4.01%, respectively. Carryover effect was less than 1%. The linearity was good in the range of urinary iodine values between 60 and 500 µg/L (R² = 0.99). Good agreement of urinary iodine values was found between manual technique and Seal AA3 HR, using Passing-Bablok regression (y = 7.84 (- 3.00 to 15.29) + 0.95 (0.90 to 1.00) x) and Blant-Altman test. Cusum test for linearity indicates that there is no significant deviation from linearity (P > 0.1).

Conclusions

The obtained results proved excellent precision, reproducibility and linearity, comparable to the already used, manual method. The New Seal AA3 HR automatic analyser is acceptable for urinary iodine measurement with very good analytical characteristics and can be used for urinary iodine epidemiological studies of the Croatian population.

Increased Incidence Rate of Hypothyroidism After Iodine Fortification in Denmark: A 20-Year Prospective Population-Based Study

OBJECTIVE

To monitor the impact of a cautious iodine fortification (IF) on the incidence of overt hypothyroidism in two subpopulations with different levels of preexisting iodine deficiency (ID).

DESIGN

A 20-year (1997 to 2016) prospective population-based study identified all new cases of diagnosed overt biochemical hypothyroidism in two open cohorts: a western cohort with moderate ID (n = 309,434; 1 January 1997) and an eastern cohort with mild ID (n = 224,535; 1 January 1997). A diagnostic algorithm was applied to all thyroid function tests performed within the study areas, and possible new cases were verified individually. Mandatory IF of salt was initiated in mid-2000 (13 ppm). The current study is a part of the DanThyr study.

RESULTS

At baseline, standardized incidence rates (SIRs) of hypothyroidism were 32.9 and 47.3/100.000/y in the cohorts with moderate and mild ID, respectively. The SIR of hypothyroidism increased significantly in both cohorts after implementing mandatory IF, with peak values of 150% in 2014 to 2016 for the moderate ID cohort and 130% in 2004 to 2005 for the mild ID cohort. Significant increases in SIR were seen among the young and middle-aged participants of both cohorts, whereas no changes were seen among the elderly participants (≥60 years). The follow-up period for the mildly iodine-deficient cohort was restricted up to and including 2008.

CONCLUSION

The cautious initiation of the IF program in Denmark caused a sustained increase in hypothyroidism incidence among subjects residing in areas of moderate and mild ID but only among the young and middle-aged participants.

Sex differences in the association between thyroid-stimulating hormone levels and depressive symptoms among the general population with normal free T4 levels

BACKGROUND

Overt and subclinical thyroid dysfunction has been reported to be related to depression. Thyroid diseases have been known to occur more frequently in women. However, scarce data are available on effects and sex differences of changes in thyroid-stimulating hormone (TSH) levels, with a normal range of thyroid hormones, on depression. This study aimed to investigate the association between TSH levels and depressive symptoms, according to sex, in individuals from the general population with free thyroxine (fT4) values within the normal range.

METHODS

Data from the 2014 Korea National Health and Nutritional Examination Survey were used for this study. The study population of 1651 Korean adults was categorized by tertiles of TSH levels. The presence of depressive symptoms was determined using a cut-off score of 5 in the Patient Health Questionnaire-9.

RESULTS

The highest TSH tertile group was 1.92 times more likely to have depressive symptoms in men after adjustment for covariates than the lowest TSH tertile (adjusted odds ratio: 1.92, 95% confidence interval: 1.11-3.31, P = 0.019). Contrastingly, the highest TSH tertile was associated with an approximately 35% lower prevalence of depressive symptoms in women (adjusted odds ratio: 0.65, 95% confidence interval: 0.43-0.97, P = 0.034).

LIMITATIONS

Cross-sectional design and unrecognized confounding factors, are the main limitations of our study.

CONCLUSIONS

Sex may play a substantial role in the relationship between TSH and depressive symptoms. Sex differences might be associated with differences in thyroid response, TSH blunting, thyroid autoimmunity, and sex hormone levels.

Association Between Thyroid Nodules and Volume and Metabolic Syndrome in an Iodine-Adequate Area: A Large Community-Based Population Study

Background: Given its high incidence, thyroid nodule (TN) warrants public attention. Thyroid volume (TV) has also been associated with multiple factors, such as iodine deficiency and supply and body mass index. It is well known that metabolic syndrome (MetS) comprises many metabolic disturbances, with insulin resistance being its major component. Materials and Methods: The aim of this study was to investigate the relationship between TN and TV and MetS and its components in an iodine-adequate area in Asia. All participants were asked to complete a questionnaire. After excluding 938 individuals based on the exclusion criteria, we reviewed data from 927 of 1865 participants. Adopting MetS diagnostic criteria, we found 437 subjects to be MetS positive [MetS(+)] and 490 subjects to be MetS negative [MetS(-)], respectively. Multivariate linear regression was used to assess the relationship between TNs and MetS. Moreover, univariate binary logistic regression analyses were used to calculate odds ratios (ORs), and 95% confidence intervals (CIs) were used to estimate the associations between different variables and TNs. Results: A total of 232 females and 205 males were MetS(+), as diagnosed using the International Diabetes Federation criteria. However, there were 330 females and 160 males in the group of MetS(-) individuals. The prevalence of TNs was 38.29% in the MetS(+) group and 17.79% in the MetS(-) group. After adjusting for systolic blood pressure, diastolic blood pressure, and gender, only high-density lipoprotein, waist circumference (WC), and age were related to TNs (OR = 0.45, 95% CI 0.27-0.75, P = 0.0023; OR = 1.04, 95% CI 1.02-1.06, P = 0.0036). The TV of all participants was 13.98 (11.24, 17.01) mL; 13.26 (10.62, 16.17) mL for females and 14.96 (11.83, 18.01) mL for males. It was found that only WC was related to TV, after controlling for sex and age (P = 0.02). Conclusions: The morbidity among TN patients in the MetS(+) group was higher than that among the MetS(-) group. High-density lipoprotein cholesterol emerged as a protective factor, and WC was a risk factor for TN. Moreover, TV was related to MetS, and WC was an independent risk factor for TV.

The effect of intake of sausages fortified with β-CD-I2 complex on iodine status and thyroid function: A preliminary study

The present study evaluated influence of boiled sausages consumption fortified with β-CD-I₂ on the urinary iodine excretion (UIE) level of volunteers. Median urinary UIE level was increased from 58.02 (24.0-175.4) μg/L to 110.6 (20.5-231.6) μg/L during 10 days. Thyroid stimulating hormone (TSH) and free thyroxine (FT4) levels were determined by radio immunoassay analysis. As it was expected, intake of sausages fortified with β-CD-I₂ resulted in rise of FT4 level from 1.1 (0.95-1.25) to 1.23 (1.07-1.63) ng/dL, whereas TSH level decreased from 1.53 (0.47-3.37) mIU/L to 1.1 (0.51-3.17) mIU/L. A dynamic gastrointestinal model in vitro was used in order to determine possibility of 3,5-diiodotyrosine (DIT) formation during consumption of the fortified sausages. The DIT concentration was determined by HPLC-MS method and was found to be 0.38 ng/mL in sausage dialyzate. These findings indicate that β-CD-I₂ introduction as an iodine carrier in boiled sausages may help to improve iodine status and to control organic iodine species concentration.

Reference intervals of thyroid hormones in a previously iodine-deficient area in Darfur, Sudan

BACKGROUND

Thyroid-stimulating hormone (TSH), thyroxin (T4) and T3 levels are varied in the different settings with disorders of thyroid homeostasis. It is recommended that every setting has to establish its own reference intervals (RIs) for these hormones.

METHODS

A multi-stage stratified sampling method was used to select a representative sample of a Sudanese adult (>20 years of age) in Nyala in western Sudan in the Darfur region during the period between January and June 2016 to establish RIs of thyroid-related hormones (TSH, T4 and T3).In this study, 1753 serum samples (male and female) with different age groups were investigated. A radioimmunoassay gamma counter was used to measure the level of these hormones.

RESULTS

The median (95% intervals) of serum TSH, T4 and T3 levels was 1.2 (0.50-3.0) mIU/l, 111.0 (72.0-161.0) nmol/l and 1.5 (0.8-2.8) nmol/l respectively.While the level of TSH was significantly higher in the age group between 31 and 40 years, both T4 and T3 levels have shown a progressive increase with age. There was no significant difference in the TSH, T4 and T3 level when the RIs were compared between males and females.

CONCLUSION

The RIs for TSH, T4 and T3 in this setting were different from the levels provided by the manufacturers. The RIs were different in the different age groups.

Iodine Deficiency in Zhejiang Pregnant Women in the Context of Universal Salt Iodization Programme

Zhejiang introduced universal salt iodization (USI) programme in 1995 and has achieved the goal of elimination of iodine deficiency disorders (IDD) since 2011. However, no systematical data of iodine nutritional status in population in pregnancy is available. In this cross-sectional study, pregnant women were interviewed to complete questionnaires in addition to handing in samples of urine and household table salt between March 2016 to February 2017. Date of birth, age of pregnancy, ethnicity and dietary iodine habits were recorded. The overall median urinary iodine concentration in 8561 pregnant women was 130.47 µg/L, which was lower than the cut-off value of iodine sufficiency of 150 µg/L recommended by the WHO. Participants using non-iodized salt, taking non-iodine-containing supplements, in coastal and in Han group were independently associated with iodine deficiency. The current USI programme did not supply Zhejiang pregnant women with sufficient iodine intake. They are generally iodine deficient, which have great public health importance since even mild IDD in pregnancy have adverse effects on fetal neurodevelopment. We strongly recommend urgent measures to improve iodine intake in pregnancy.

Age- and gender-specific reference intervals of TSH and free T4 in an iodine-replete area: Data from Korean National Health and Nutrition Examination Survey IV (2013-2015)

BACKGROUND

Establishment of the reference interval of thyroid-stimulating hormone (TSH) is critical in the diagnosis of thyroid dysfunction and is affected by age, gender, iodine nutrition, and ethnicity. The aim of this study was to determine the reference intervals of TSH and free thyroxin (FT4) from a large, nationwide data of Korea where iodine intake is more than adequate.

METHODS

We analyzed data from the Korea National Health and Nutrition Examination Survey VI that measured serum TSH, FT4, and thyroid peroxidase antibody from 7,061 individuals (urinary iodine measurement in 6,565). Age- and gender-specific reference intervals were established from 95% confidence limits from the 2.5 to 97.5 percentile of TSH (log-transformed) and FT4 in reference populations.

RESULTS

The geometric mean of TSH was 2.16 ± 0.01 mIU/L, with the lowest value found in the middle aged group (2.04 ± 0.02 mIU/L) and higher values noted in age groups of 10-19 and over 70 years (2.38 ± 0.02 and 2.32 ± 0.07 mIU/L, respectively). The association of TSH and age was U-shaped. The overall reference interval of TSH was 0.59-7.03 mIU/L. Mean FT4 was 1.25 ± 0.003 ng/dL (16.09 ± 0.039 pmol/L), and it showed a small but continuous decrease after 20 years of age (P < 0.001). There was a significant positive correlation between TSH and urine iodine concentration (r = 0.154, P < 0.001).

CONCLUSIONS

The reference interval of TSH in Korea, where iodine intake is above the requirement, was 0.59-7.03 mIU/L and showed U-shaped change with age, which was a similar pattern to iodine intake. The reference interval of FT4 was 0.92-1.60 ng/dL. The geometric mean and upper limit of TSH were higher than those of Western populations, reflecting the paramount importance of iodine intake on thyroid function.

Associations between thyroid dysfunction and developmental status in children with excessive iodine status

Background and objective

Adequate iodine status and normal thyroid hormone synthesis are important for optimal child development. In this study, we explored whether young children’s developmental status is associated with thyroid dysfunction in an area of chronic excessive iodine exposure.

Methods

We included 298 children between 18 and 48 months of age residing in Algerian refugee camps. Early child development was measured using the Ages and Stages Questionnaires, third edition (ASQ-3), consisting of five domains: Communication, Gross Motor, Fine Motor, Problem Solving and Personal-Social. Due to poor discriminatory ability in the Gross Motor domain, the total ASQ-3 scores were calculated both including and excluding this domain. Urinary iodine concentration (UIC), thyroid hormones (TSH, FT3 and FT4), thyroid antibodies and serum thyroglobulin (Tg) were measured.

Results

The median UIC was 451.6 μg/L, and approximately 72% of the children had a UIC above 300 μg/L. Furthermore, 14% had thyroid disturbances, of whom 10% had TSH outside the reference range. Children with thyroid disturbances and TSH outside the reference ranges had lower odds of being among the 66% highest total ASQ scores, with adjusted odds ratios (95% CI) of 0.46 (0.23, 0.93) and 0.42 (0.19, 0.94), respectively.

Conclusion

We found an association between thyroid dysfunction and poorer developmental status among children with excessive iodine intake. The high iodine intake may have caused the thyroid dysfunction and hence the delayed developmental status; however, other influential factors cannot be excluded. Optimal child development is important for a sustainable future. With iodine excess being an increasing problem globally, this subject should be further explored.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Age-specific reference interval of serum TSH levels is high in adolescence in an iodine excess area: Korea national health and nutrition examination survey data

PURPOSE

Serum thyroid-stimulating hormone level was influenced by several factors, including age, gender, thyroid auto-antibodies, race, and intake of dietary iodine. We evaluated age-specific reference interval of serum thyroid-stimulating hormone levels in Korea, an iodine excess area.

METHODS

This nationwide population-based cross-sectional study included representative civilian, non-institutional population (n = 6564) who underwent thyroid function tests from Korea National Health and Nutrition Examination Survey VI (2013-2015). The reference interval of serum thyroid-stimulating hormone levels was defined between the 2.5th and 97.5th percentiles in the reference population.

RESULTS

The geometric mean of serum thyroid-stimulating hormone levels in the reference population was 2.17 mIU/L with a reference interval of 0.62-6.84 mIU/L. In the reference population, the geometric mean of serum TSH levels in each age group of 10-18, 19-29, 30-39, 40-49, 50-59, 60-69, and equal or older than 70 years was 2.47, 2.20, 2.07, 2.04, 2.23, 2.12, and 2.27 mIU/L, with a reference interval of 0.74-7.35, 0.67-6.42, 0.63-6.04, 0.62-6.20, 0.56-7.37, 0.57-6.90, and 0.42-6.58 mIU/L, respectively. In the reference population, the urinary iodine concentrations were consistently high in all age groups (median 298.5 μg/L). Subjects aged 10-18 years had the highest urinary iodine concentrations.

CONCLUSIONS

There was no shift toward higher levels with age in the distribution of serum thyroid-stimulating hormone levels. The reference interval of serum thyroid-stimulating hormone levels was consistently high in all age group, especially from adolescence 10-18 years in a Korean population who had excessive intake of dietary iodine.

Metabolic syndrome is associated with an increased incidence of subclinical hypothyroidism - A Cohort Study

Prior cross-sectional analyses have demonstrated an association between subclinical hypothyroidism and metabolic syndrome and selected components. However, the temporal relation between metabolic syndrome and declining thyroid function remains unclear. In a prospective study, an unselected cohort of 66,822 participants with and without metabolic syndrome were followed. A proportional hazards regression model was used to estimate hazard ratios (HRs) and 95% CIs for hypothyroidism. Exploratory analyses for the relation between components of metabolic syndrome and declining thyroid function were also undertaken. During an average follow-up of 4.2 years, the incident rates for subclinical hypothyroidism were substantially higher in participants who began the study with metabolic syndrome compared with metabolically normal controls. After controlling for risk factors, patients with metabolic syndrome were at a 21% excess risk of developing subclinical hypothyroidism (adjusted HR 1.21; 95% CI 1.03–1.42). When individual components were analyzed, an increased risk of subclinical hypothyroidism was associated with high blood pressure (1.24; 1.04–1.48) and high serum triglycerides (1.18; 1.00–1.39), with a trend of increasing risk as participants had additional more components. Individuals with metabolic syndrome are at a greater risk for developing subclinical hypothyroidism, while its mechanisms and temporal consequences of this observation remain to be determined.

Excessive Iodine Intake and Thyrotropin Reference Interval: Data from the Korean National Health and Nutrition Examination Survey

BACKGROUND

Iodine intake is associated with various thyroid diseases and serum thyrotropin (TSH) levels. The aim of this study was to investigate iodine intake and its impact on the distribution of serum TSH levels using nationwide data from Korea, a country known to be iodine replete.

METHODS

The sixth Korean National Health and Nutrition Examination Survey (2013-2015) is a nationwide, cross-sectional survey of the Korean general population. Participants were selected using two-stage stratified cluster sampling of the population and housing census data. A total of 6564 participants aged ≥10 years who underwent thyroid function tests and urinary iodine level measurements during the survey were included in this study.

RESULTS

The median urinary iodine concentration (UIC) was 299.3 μg/L (interquartile range 158.8-699.8), suggesting more than adequate iodine intake in Korea. With high-iodine intake in all age groups and in both females and males, the TSH reference interval in the Korean reference population was right-shifted at 0.62-6.84 mIU/L. The prevalence of overt and subclinical hypothyroidism in Korea according to this reference interval was 0.73% and 3.12%, respectively, and was significantly associated with nutritional iodine status (p = 0.011 and p < 0.001, respectively).

CONCLUSIONS

This first nationwide survey demonstrates more than adequate iodine intake and a right-shifted distribution of serum TSH levels in the Korean general population. Nutritional iodine status is important for determining serum TSH levels and is associated with a high prevalence of hypothyroidism. Nutritional iodine status might need to be considered when establishing TSH reference intervals of populations in iodine-replete areas.