Thyroid function and morphology in overweight and obese children and adolescents in a Chinese population

Thyroid volume in Turkish school-age children living in an iodine-sufficient region

OBJECTIVES

We aimed to obtain local normative data on thyroid volume evaluated by ultrasonography and iodine status by measuring urine iodine levels in school-age children living in Aydın province.

METHODS

In this cross-sectional study, a sample comprising 1,553 cases was meticulously selected from a total cohort of 170,461 children aged 6-17, drawn from 21 distinct educational institutions located within the Aydın region, as participants in the investigation. Those with a known chronic disease or thyroid disease were excluded from the study. The children underwent physical examinations and ultrasonography imaging of the thyroid gland, and urine samples were collected to measure urinary iodine concentration (UIC).

RESULTS

The median UIC was 189.5 (IQR=134.4) μg/L, which was optimal according to WHO criteria. Thyroid volume was found to be 4.6 (IQR=3.5) mL in girls and 4.2 (IQR=4.0) mL in boys (p=0.883). The thyroid volumes in our study were found to be smaller when compared to the WHO. According to WHO age and body surface area criteria, thyroid volume was over 97 % in 0.9 % (n=15) of cases. Thyroid volume was found to have a positive correlation with age, height, weight, body mass index (BMI), and body surface area (BSA) in both genders (p<0.001). However, there was no significant correlation between thyroid volume and UIC.

CONCLUSIONS

This cross-sectional study provides normative data on thyroid volume and iodine status in school-age children in iodine-sufficient population, revealing a low prevalence of goiter and correlations between thyroid volume and anthropometric measures.

Thyroid axis hormones and anthropometric recovery of children/adolescents with overweight/obesity: A scoping review

Introduction

Thyroid hormones exert multiple physiological effects essential to the maintenance of basal metabolic rate (BMR), adaptive thermogenesis, fat metabolism, growth, and appetite. The links between obesity and the hormones of the thyroid axis, i.e., triiodothyronine (T3), thyroxine (T4), and thyrotropin (TSH), are still controversial, especially when considering children and adolescents. This population has high rates of overweight and obesity and several treatment approaches, including nutritional, psychological, and physical exercise interventions have been used. Understanding the importance of the hormones of the thyroid axis in the recovery from overweight and obesity may help directing measures to the maintenance of a healthy body composition. The present scoping review was carried out to analyze studies evaluating these hormonal levels throughout interventions directed at treating overweight and obesity in children and adolescents. The main purpose was to ascertain whether the hormones levels vary during weight loss.

Methods

We selected for analysis 19 studies published between 1999 and 2022.

Results

Most of the studies showed that changes in different anthropometric indicators, in response to the multidisciplinary interventions, correlated positively with free T3 (fT3), total T3 (TT3), and TSH. With respect to free T4 (fT4) and total T4 (TT4).

Discussion

The most common finding was of unchanged levels and, hence, no significant association with weight loss. Moreover, thyroxine supplementation has failed to affect the response to the interventions. Further studies are necessary to elucidate the relevance of the variations in hormone levels to the establishment of overweight/obesity and to the recovery from these conditions in children/adolescents.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42020203359.

Comparative Analysis of Five Correction Methods for Thyroid Volume by Ultrasound and Their Recommended Reference Values in Chinese Children Aged 8-10 Years

Considering the influence of body's growth and development on thyroid volume (TVOL), whether five existed corrected methods could be applied to correct TVOL remains unclear, in terms of Chinese children's increased growth and development trends. This study aimed to compare the applicability of five correction methods for TVOL: Body Surface Area corrected Volume (BSAV), Body Mass Indicator corrected Volume (BMIV), Weight and Height corrected Volume Indicator (WHVI), Height corrected Volume Indicator 1 (HVI1) and Height corrected Volume Indicator 2 (HVI2); to establish the reference values for correction methods. The data of Iodine Nutrition and Thyroid Function Survey was used to analyse the differences in TVOL between normal and abnormal thyroid function children. Data of National Iodine Deficiency Disorders Survey were used to compare five correction methods and to establish their reference values. The median urinary iodine concentration of children surveyed were 256.1μg/L in 2009 and 192.6μg/L in 2019, respectively. No significant difference was found in TVOL and thyroid goitre rate between children with normal and abnormal thyroid function. In the determination of goitre, HVI1, HVI2, BSAV and BMIV all showed high agreement with TVOL, while the area under the ROC curve (AUC) of WHVI was relatively low for children aged 8(AUC=0.8993) and 9(AUC=0.8866). Most differences of TVOL between light and heavy weight, short and tall height children can be eliminated by BSAV correction. BSAV was the best method of TVOL correction in this research. Reference values were established for corrected thyroid volumes in Chinese children aged 8-10 years by sex.

Metabolic syndrome and its components are associated with thyroid volume in adolescents

OBJECTIVE

To explore the association between metabolic syndrome (MetS) and its component and thyroid volume in Chinese adolescents, and to compare the detection rate of MetS under the three different diagnostic criteria.

METHODS

A total of 1097 school students (610 males and 487 females, ages 12-15 years) were enrolled. All the participants underwent physical examination, biochemical test, and thyroid gland ultrasonography. The thyroid volume of normal, overweight and obese group was compared. We also analyzed the association between the number of MetS components and thyroid volume. Linear and multiple linear regression were applied to explore the association between metabolic parameters and thyroid volume.

RESULTS

The thyroid volume of the males in overweight (t = 3.784, P < 0.001) and obese group (t = 5.068, P < 0.001) was significantly larger than that in normal group; the thyroid volume of the females in overweight group (t = 4.627,P < 0.001) was significantly larger than that of normal group. As the number of MetS components increased, the thyroid volume also increased significantly (F = 10.64, P < 0.01). Height, weight, body mass index (BMI), waist circumference, hip circumference, systolic blood pressure, fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), uric acid and triglyceride were all positively associated with thyroid volume in the adolescents (P all < 0.001). Meanwhile, there was a negative association between high-density lipoprotein cholesterol (HDL-C) and thyroid volume (P < 0.001). According to multiple linear regression, waist circumference (β = 0.029, 95 %CI: 0.015 ~ 0.042; P < 0.01) and waist height ratio (β = 3.317, 95 %CI: 1.661 ~ 4.973; P < 0.01) were predict factors of thyroid volume. No statistical difference was found in the detection rates of metabolic syndrome under the three diagnostic criteria.

CONCLUSIONS

Overweight, obesity and metabolic syndrome was associated with adolescent thyroid volume. Central obesity may be an independent risk factor for thyroid enlargement in adolescents.

Obesity and Monitoring Iodine Nutritional Status in Schoolchildren: is Body Mass Index a Factor to Consider?

Background: The frequency of overweight (OW) and obese (OB) children has increased worldwide, particularly in economically developed countries. No studies have been conducted to verify whether the increasing frequency of OW and obesity in schoolchildren may affect the evaluation of iodine nutritional status in populations. The aim of this study was to verify whether urinary iodine concentration (UIC), thyroid volume (TV), and thyroid hypoechoic pattern may be affected by body mass index (BMI) in schoolchildren. Methods: The children included in this study (aged 11-13 years) were a part of the schoolchildren recruited in the second nationwide survey (period 2015-2019) conducted in Italy to monitor by law (Atto di Intesa Stato-Regioni February 26, 2009) the nationwide iodine prophylaxis program. Specifically, 1281 schoolchildren residing in iodine-sufficient areas (IS group) and 384 children residing in a still mildly iodine-deficient area (ID group) were recruited between January and March 2015 in the first-degree secondary state schools. In all the children, spot UIC was measured, thyroid ultrasound was performed to evaluate TV, and hypoechogenicity was assessed to indirectly evaluate iodine-associated thyroid autoimmunity. Results: The frequency of OW, OB, and adequate weight (AW) children was similar in the IS and ID groups at any age. After adjusting for sex and age, the regression analysis showed lower UIC values in OB children than in AW children of the IS group (beta coefficient = -34.09 [95% confidence interval -65.3 to -2.8]), whereas no significant differences were observed in the ID group. In both the IS and ID groups, the distribution of TV in AW children was significantly shifted toward lower values in comparison to the distribution of OB children (p < 0.001 in the IS group; p = 0.012 in the ID group). Furthermore, the frequency of thyroid hypoechogenicity was higher in the ID group than in the IS group (10.9% vs. 6.6%, p = 0.005); however, in both groups, it was significantly lower in AW children than in OB children (p < 0.01). Conclusions: This study for the first time demonstrates that BMI may be a confounding factor in monitoring iodine nutritional status in schoolchildren. Since in Italy as in other Western countries the number of OW and OB children is high, BMI is a factor to consider in monitoring salt iodization programs worldwide.

Association between mild hyperthyrotropinemia and hypercholesterolemia in children with severe obesity

Background Severe obesity is associated with a number of cardiometabolic risk factors. Thyroid-stimulating hormone (TSH) levels are often slightly increased in children with obesity. The clinical significance of the mild elevation in TSH in children with obesity is unclear. Objective To examine the association between TSH and lipids in children with severe obesity. Methods We performed a retrospective analysis of records of children with severe obesity with simultaneous measurements of TSH and lipids. Children with TSH <0.3 mIU/L and ≥10 mIU/L were excluded. The relationship between TSH and lipids was evaluated using univariate/multiple variable linear and logistic regression. Results The study included 834 children (age 13.8 ± 4.1 years, males 46%, body mass index [BMI]: 36.9 ± 7.6 kg/m2; BMI z-score 2.6 ± 0.4). Seventy-four (8.9%) children had TSH between 5 and <10 mIU/L (high TSH [HTSH]). TSH was positively associated with non-high-density lipoprotein (HDL) cholesterol (β: 1.74; 95% confidence interval [CI] 0.29-3.20, p = 0.02). Total cholesterol and non-HDL cholesterol were higher in males with HTSH compared to those with normal TSH (175.5 vs. 163.5 mg/dL, p = 0.02 and 133.7 vs. 121.4 mg/dL, p = 0.02, respectively). The odds of elevated non-HDL cholesterol (≥145 mg/dL) was higher in males with HTSH relative to those with normal TSH (odds ratio [OR]: 2.78; 95% CI 1.35-5.69, p = 0.005). Conclusions TSH levels were positively associated with non-HDL cholesterol in children with severe obesity. Males with mildly elevated TSH had higher total cholesterol and non-HDL cholesterol compared to males with normal TSH. Further studies are warranted to determine if levothyroxine therapy would result in improvement in total cholesterol or non-HDL cholesterol in children with severe obesity with mildly elevated TSH.

Influence of Body Mass Index on the Clinicopathologic Features of Papillary Thyroid Carcinoma

BACKGROUND

Epidemiologic studies have demonstrated an increased risk for papillary thyroid carcinoma (PTC) with increasing body mass index (BMI). However, the relationships between excess weight and the behavior of PTC are inconsistent. The aim of this study was to evaluate the impact of excess weight on clinicopathologic features of PTC and on patient outcomes.

METHODS

Data from 417 patients with PTC who underwent total thyroidectomy with cervical lymph node dissection were retrospectively analyzed. On the basis of World Health Organization standardized categories of BMI, patients were divided into 4 groups: underweight, normal weight, overweight, and obese. Histopathologic tumor features, stage at diagnosis, and disease status were determined by chart review. Logistic regression models were used to define associations between BMI and clinicopathologic features of PTC. Cox proportional-hazards models were used to assess associations between BMI and locoregional recurrence.

RESULTS

Overweight (odds ratio [OR], 3.90; P = .040) and obesity (OR, 9.19; P = .012) were independent predictors of vascular invasion. Furthermore, obesity (OR, 6.14; P = .004) was an independent predictor of extrathyroidal invasion. During follow-up (median, 29 months; range, 5-87 months), 48 patients (11.5%) experienced locoregional recurrence. There were no significant differences in locoregional recurrence of PTC among BMI groups. When adjusted for other confounding factors, extrathyroidal invasion (OR, 8.35; P < .001), vascular invasion (OR, 3.57; P < .001), cervical lymph node metastasis (OR, 3.71; P = .009), and advanced tumor-node-metastasis stage (OR, 3.81; P < .001) were identified as independent factors for locoregional recurrence.

CONCLUSIONS

Higher BMI was associated with extrathyroidal invasion and vascular invasion in patients with PTC, which suggests that excess weight is associated with aggressive clinicopathologic features of PTC. But patients with higher BMI did not have an increased risk for developing postoperative complications and locoregional recurrence.

ASSOCIATIONS OF THYROID VOLUME AND FUNCTION WITH CHILDHOOD OBESITY

Context

The links between obesity and thyroid function or thyroid volume in children are still controversial with limited available data.

Objective

This study aimed to examine thyroid function and volume in obese Turkish school-age children in comparison to normal-weight children.

Design

Cross-sectional study.

Subjects and Methods

One hundred obese children (47 boys, 53 girls; mean age 10.34±2.79 years) with a body mass index (BMI) above 95th percentile, and 100 normal-weight children (42 boys, 58 girls; 10.34±2.79 years) were included. The study parameters were BMI z score (Z-BMI), body surface area (BSA), thyroid volume, free thyroxine (fT4) and thyroid stimulating hormone (TSH) levels.

Results

The mean TSH and fT4 levels did not show a significant difference between obese and normal-weight children (p>0.05). The mean thyroid volume was higher in obese children (6.46±5.84 and 4.64±1.44, respectively; p=0.043). fT4 correlated negatively with Z-BMI in both normal-weight and obese children (r=-0.285, p=0.004 and r=-0.289, p=0.004, respectively). Thyroid volume, on the other hand, correlated positively with Z-BMI, again in both normal-weight and obese children (r=0.657, p<0.001 and r=0.444, p<0.001, respectively). Similar associations were found for BSA.

Conclusions

Thyroid volume correlated positively and fT4 correlated negatively with Z-BMI and BSA, in both obese and normal-weight school-age children, whereas TSH appears to be independent of these parameters.

Correlation analysis of metabolic syndrome and its components with thyroid nodules

OBJECTIVE

This study aimed to analyze the relationship between the metabolic syndrome (MetS) and its components with the occurrence of thyroid nodules.

METHODS

A total of 2719 volunteers from some areas of Gansu Province, China, who participated in the national survey of thyroid diseases and iodine nutrition status (Tide) and diabetes prevalence, were selected. Their height, weight, waist circumference (WC), systolic blood pressure (SBP), and diastolic blood pressure were recorded. The fasting plasma glucose (FPG), 2-h plasma postprandial glucose (2hPG), total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and glycosylated hemoglobin (HbA1C) levels were measured. The prevalence of MetS and thyroid nodules was evaluated, and the correlation between each component of MetS and thyroid nodules was studied.

RESULTS

The prevalence of MetS and thyroid nodules was 15.4% and 17.2%, respectively. WC, SBP, body mass index, FPG, 2hPG, TG, TC, and thyroid-stimulating hormone levels were significantly higher in the thyroid nodule group. The prevalence of thyroid nodules was significantly higher in the MetS group. A positive correlation was found between the degree of metabolic disorder and the occurrence of thyroid nodules. WC was found to be a risk factor for the occurrence of thyroid nodules. For WC≥90 cm, an increase in the independent variables led to a significant rise in the incidence of thyroid nodules.

CONCLUSION

The prevalence of thyroid nodules was higher in the MetS group. The WC of the MetS components might be an independent risk factor for the occurrence of thyroid nodules.

Waist Circumference and Subclinical Thyroid Dysfunction in a Large Cohort of Chinese Men and Women

OBJECTIVE

The association between subclinical thyroid dysfunction and waist circumference (WC) is still controversial, especially from the perspective of sex differences. We aimed to explore the impact of sex on this relationship in a large Chinese cohort.

METHODS

This cross-sectional study recruited 13,505 healthy participants (8,346 males, 5,159 females) who were enrolled in a health check program. Clinical data were collected. The association between subclinical thyroid dysfunction and WC of both sexes was analyzed separately after dividing WC into quartiles. Odds ratios (ORs) were calculated by binary logistic regression models, and linear regression analysis was also performed.

RESULTS

The prevalence rates of subclinical hyper-and hypothyroidism were significantly lower in males. Binary logistic regression models showed that WC in females with subclinical hypothyroidism had a detrimental effect with an OR of 1.011, but the effect disappeared when we included other covariates. The other ORs indicated no significant effects. The weak negative relationship between WC and thyrotropin was also indicated by linear regression analyses with very low R² values.

CONCLUSION

The current research did not show WC as a risk factor for subclinical thyroid dysfunction in either sex. Regional and ancestral origin differences may account for the variations with other studies.

ABBREVIATIONS

ALT = alanine aminotransferase; BMI = body mass index; FT3 = free triiodothyronine; FT4 = free thyroxine; TG = triglycerides; TSH = thyroid-stimulating hormone; UA = uric acid; WC = waist circumference.

Association of thyroid nodules with adiposity: a community-based cross-sectional study in China

BACKGROUND

The association between thyroid nodules and adiposity remains controversial. We performed a cross-sectional, community-based study to examine whether thyroid nodules are associated with overweight and obesity, as defined with body mass index (BMI) and waist circumference.

METHODS

The study included 1482 subjects (≥20 years of age; residing in Nanjing, China) receiving questionnaire interview, anthropometric measurements, laboratory tests and thyroid ultrasonography in 2009-2010. Overweight and obesity were defined as BMI ≥24 and ≥28 kg/m², respectively. Central obesity was defined as waist circumference at ≥90 cm in men and ≥80 cm in women. A sensitivity analysis was conducted using the American Diabetes Association (ADA) criteria for overweight and obesity (BMI ≥ 23 and ≥25 kg/m²).

RESULTS

Thyroid nodules were identified in 12.6% of the subjects. A greater proportion of the subjects with thyroid nodules had a BMI at ≥24 kg/m² (51.9% vs. 40.5% in those without thyroid nodules, P = 0.003) and central obesity (43.3% vs. 24.2%, P < 0.001). After adjustment for other confounders, central obesity was still associated with significantly elevated risk of thyroid nodules (OR 1.62, 95%CI 1.14-2.28), whereas obesity/overweight based on BMI was not in both the main analysis and sensitivity analysis with the alternative criteria. In the subgroup analysis, BMI ≥24 kg/m² (OR 1.61, 95%CI 1.01-2.54), as well as BMI ≥25 kg/m² (OR 1.95, 95%CI 1.14-3.34), was significantly associated with higher risk of thyroid nodules among women. Using the ADA criteria, overweight and obesity were associated with thyroid nodules (OR 5.59, 95%CI 1.39-22.51 and 5.15, 95%CI 1.30-20.37) in thyroid-stimulating hormone (TSH) > 4.2 mIU/L subgroup. Central obesity correlated with higher risk of thyroid nodules regardless of age (< 50 years: OR 1.87, 95%CI 1.05-3.32: ≥50 years: OR 1.54, 95%CI 1.00-2.37) and in the following subgroups: men (OR 1.91, 95%CI 1.14-3.20), TSH > 4.2 mIU/L (OR 3.05, 95%CI 1.01-9.22), and urine iodine ≥200 µg/L (OR 1.79, 95%CI 1.14-2.81).

CONCLUSION

Waist circumference is superior to BMI for assessing risk of thyroid nodules in Chinese subjects.

The Association of Triiodothyronine-to-Thyroxine Ratio with Body Mass Index in Obese Nigerian Children and Adolescents

The interest in the relationship between thyroid dysfunction and obesity is on the increase. This study compares the triiodothyronine-to-thyroxine (T3/T4) ratio in obese and lean children and adolescents, and correlates thyroid hormones with body mass index (BMI) in obese Nigerian children. It is a retrospective study of records of 76 obese children and adolescents with a BMI of 31.7 ± 0.1 kg/m² (26 males aged 10.9 ± 0.35 years, and 50 females aged 10.8 ± 0.4 years) that were referred to the laboratory for thyroid hormone evaluation because of their obese status. The controls were 20 age-matched non-obese apparently healthy subjects, with a mean age of 11.0 ± 0.47 years and a BMI of 20.2 ± 0.2 kg/m². Serum T3, T4, and thyroid stimulating hormone (TSH) were determined using ELECSYS 1010 auto-analyzer (Roche Diagnostics, Penzberg, Germany). The BMI (p < 0.001), T3 (p < 0.01), TSH (p < 0.001) and T3/T4 ratio (p < 0.001) were significantly higher in obese than non-obese children and adolescents. Triiodothyronine (r = 0.230; p < 0.05), TSH (r = 0.272; p < 0.02), and T3/T4 ratio (r = 0.232; p < 0.05) correlated positively with BMI in obese children and adolescents. The T3/T4 ratio (p < 0.005) was significantly higher in obese boys than obese girls. Serum T3, TSH, and T3/T4 ratio correlated positive with BMI in obese Nigerian children and adolescents. Since thyroid dysfunction represents a continuum from asymptomatic to clinical symptomatic disease, it is suggested that obese children be counseled on the need to maintain ideal BMI in order to avoid the risks associated with obesity.

Association between lifestyle and anthropometric parameters and thyroid nodule features

PURPOSE

Thyroid nodularity has been associated with obesity, but data regarding associations of body composition parameters with specific ultrasound features of thyroid nodules are lacking. The aim of the present study was to assess associations between thyroid nodule ultrasound characteristics, lifestyle, and anthropometric parameters.

SUBJECTS AND METHODS

This was a cross-sectional study in the general apparently healthy population of Northern Greece. Thyroid ultrasound data together with medical history, demographic, and anthropometric characteristics were individually recorded. Body composition was evaluated using bioelectrical impedance.

RESULTS

Three hundred and six subjects [215 females (70.3%), aged 20-83 years] were included. Ultrasound revealed one or more thyroid nodules in 168 subjects (54.9%). Subjects with thyroid nodules were more frequently females (p = 0.033), older (p < 0.001) and had higher fat mass (p = 0.011), total body fat percentage (p < 0.001) and waist circumference (p = 0.045) than subjects without nodules. In logistic regression analyses, age and female gender were the only independent predictors of presence of thyroid nodules, as well as specific sonographic features. Additionally, total body fat percentage was positively correlated with nodule size (rho = 0.210, p = 0.006) and was the only independent predictor of hypoechoic thyroid nodule(s) and peripheral vascularity, while lack of exercise was predictive of internal vascularity.

CONCLUSIONS

Body fat accumulation and lack of exercise, used as surrogate markers of sedentary lifestyle, influence thyroid nodule size and could predict some ultrasonographic characteristics, like hypoechoicity and internal vascularity. Therefore, routine thyroid examination of obese patients and promotion of active lifestyle may be warranted to prevent thyroid nodule formation and possibly progression to malignancy.

Thyroid Function and Thyroid Autoimmunity in Relation to Weight Status and Cardiovascular Risk Factors in Children and Adolescents: A Population-Based Study

OBJECTIVE

In obese subjects, slight increases have been observed in thyrotropin [thyroid-stimulating hormone (TSH)] levels, but data in children are scarce. The aim of this study was to evaluate whether thyroid function and autoimmunity vary with weight status in a healthy population of children and adolescents and to determine whether hyperthyrotropinemia is associated with any cardiovascular risk factor.

METHODS

This cross-sectional epidemiological study was conducted in Almería (Spain) on a representative sample of 1317 healthy subjects aged 2-16 years. Thyroid function, thyroid autoimmunity and cardiovascular risk factors were measured. Chi-square test, analysis of variance and multiple linear regression were used in the statistical analyses.

RESULTS

The obese children and adolescents had thyrotropin levels (mean ± standard deviation) of 3.12±2.44 mU/L. These levels were higher than those of overweight subjects (2.79±1.51 mU/L) and of normal weight subjects (2.73±1.30 mU/L) (p=0.02). Levels of free thyroxine and urinary iodine did not differ significantly between the groups. The prevalence (95% confidence interval) of thyroid autoimmunity was lower in the individuals with normal weight (2.9%; 2.0-4.2) than in the overweight (6.3%; 3.9-9.9) and obese subjects (5.6%, 2.5-11.3) (p=0.02). TSH levels were associated with obesity (β=0.36; p<0.001) and thyroid autoimmunity (β=1.10; p<0.001). They were not associated with any cardiovascular risk factor.

CONCLUSION

Obese children and adolescents had higher levels of thyrotropin than those who were overweight and of normal weight. The differences among the groups were of very little clinical significance and could possibly be linked to the higher prevalence of thyroid autoimmunity in obese subjects. The hyperthyrotropinemia in these subjects was not associated with any cardiovascular risk factor.

2,3',4,4',5-Pentachlorobiphenyl Induces Inflammatory Responses in the Thyroid Through JNK and Aryl Hydrocarbon Receptor-Mediated Pathway

Polychlorinated biphenyls (PCBs) are durable and widely distributed environmental contaminants that can compromise the normal functions of multiple organs and systems; one important mechanism is the induction of inflammatory disorders. In this study, we explored the influences of 2,3',4,4',5-pentachlorobiphenyl (PCB118) on inflammatory responses and its underlying mechanisms in the thyroid. Wistar rats were administered PCB118 intraperitoneally at 0, 10, 100, and 1000 μg/kg/d, 5 days a week for 13 weeks; rat thyroid FRTL-5 cells were treated with PCB118 (0, 0.25, 2.5, and 25 nM) for indicated time. Results revealed that PCB118 promoted the generation of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and intercellular adhesion molecule-1 (ICAM-1) in a time- and dose-related manner and decreased sodium/iodide symporter (NIS) protein expression. Moreover, stimulation with PCB118 resulted in the upregulation of the aryl hydrocarbon receptor (AhR)-responsive gene cytochrome P450 1A1 in FRTL-5 cells; whereas pretreatment with the AhR inhibitor α-naphthoflavone or AhR small interfering RNA (siRNA) suppressed AhR, CYP1A1, IL-6, and ICAM-1 and restored NIS expression. In vivo and in vitro studies also suggested that the c-Jun N-terminal kinase (JNK) pathway was activated on PCB118 exposure, and the experiments using siRNA for JNK partially blocked PCB118-induced upregulation of IL-6 and ICAM-1 and downregulation of NIS. Altogether, PCB118 stimulates production of IL-6, TNF-α, and ICAM-1 in the thyroid through AhR and JNK activations and subsequently interferes with NIS expression, resulting in the disruption of thyroid structure and function.

Thyroid hormonal status among children with obesity

BACKGROUND

It is presumed that free T4 and thyroid-stimulating hormone (TSH) levels are related to obesity, but the findings are inconsistent. In this study we evaluated T4 and TSH concentrations between normal children and those with obesity and possible correlations between body mass index (BMI) and these markers.

METHODS

In this prospective study, 190 children who were overweight and obese and 133 children without obesity of the same age and sex were evaluated. Thyroid function tests (TSH, total T4, free T4 and free T3) were measured in all subjects in both groups. Thyroid antibodies (thyroid peroxidase and thyroglobulin) were determined among those with elevated TSH levels.

RESULTS

Levels of TSH and total T4 were significantly higher in children with obesity compared with the control group. Subclinical hypothyroidism was significantly higher in children with obesity (14.7%) compared with normal subjects (6.8%, p = 0.02). Among children with obesity and increased TSH levels, 10.7% had positive thyroid peroxidase and thyroglobulin antibodies. There was significantly positive correlation between BMI z score and TSH level (r = 0.198, p < 0.001) and T4 level (r = 0.18, p = 0.001).

CONCLUSION

TSH and total T4 levels are increased in children who are overweight or obese and are a common finding in these children, but the incidence of thyroid antibodies is low in these patients and so could not be accounted for by thyroid autoimmunity. Due to these findings it is possible that increased TSH and total T4 levels are a consequence of obesity and could be reduced by decreasing BMI.

Increased waist circumference is independently associated with hypothyroidism in Mexican Americans: replicative evidence from two large, population-based studies

BACKGROUND

Mexican Americans are at an increased risk of both thyroid dysfunction and metabolic syndrome (MS). Thus it is conceivable that some components of the MS may be associated with the risk of thyroid dysfunction in these individuals. Our objective was to investigate and replicate the potential association of MS traits with thyroid dysfunction in Mexican Americans.

METHODS

We conducted association testing for 18 MS traits in two large studies on Mexican Americans - the San Antonio Family Heart Study (SAFHS) and the National Health and Nutrition Examination Survey (NHANES) 2007-10. A total of 907 participants from 42 families in SAFHS and 1633 unrelated participants from NHANES 2007-10 were included in this study. The outcome measures were prevalence of clinical and subclinical hypothyroidism and thyroid function index (TFI) - a measure of thyroid function. For the SAFHS, we used polygenic regression analyses with multiple covariates to test associations in setting of family studies. For the NHANES 2007-10, we corrected for the survey design variables as needed for association analyses in survey data. In both datasets, we corrected for age, sex and their linear and quadratic interactions.

RESULTS

TFI was an accurate indicator of clinical thyroid status (area under the receiver-operating-characteristic curve to detect clinical hypothyroidism, 0.98) in both SAFHS and NHANES 2007-10. Of the 18 MS traits, waist circumference (WC) showed the most consistent association with TFI in both studies independently of age, sex and body mass index (BMI). In the SAFHS and NHANES 2007-10 datasets, each standard deviation increase in WC was associated with 0.13 (p < 0.001) and 0.11 (p < 0.001) unit increase in the TFI, respectively. In a series of polygenic and linear regression models, central obesity (defined as WC ≥ 102 cm in men and ≥88 cm in women) was associated with clinical and subclinical hypothyroidism independent of age, sex, BMI and type 2 diabetes in both datasets. Estimated prevalence of hypothyroidism was consistently high in those with central obesity, especially below 45y of age.

CONCLUSIONS

WC independently associates with increased risk of thyroid dysfunction. Use of WC to identify Mexican American subjects at high risk of thyroid dysfunction should be investigated in future studies.