Obesity and thyroid cancer: epidemiologic associations and underlying mechanisms

Obesity and thyroid cancer: unraveling the connection through a systematic review and meta-analysis of cohort studies

Background

The relationship between adiposity indicators and thyroid cancer (TC) risk has garnered increasing attention due to the rising prevalence of obesity and its potential impact on cancer incidence. We conducted a comprehensive meta-analysis to investigate this association across various effect measures.

Method

Until July 2022, a comprehensive search of databases was conducted to identify cohort studies that assessed the association between adiposity and the development of TC. Meta-analysis was performed using random effects models. Subgroup analyses were conducted to explore heterogeneity. Publication bias was assessed using Begg's tests.

Results

A systematic literature search identified 27 eligible studies reporting odds ratios (OR), relative risks (RR), or hazard ratios (HR) as effect measures. Pooling the studies irrespective of the effect measure, a significant positive association between adiposity indicators and TC risk was observed, yielding an effect estimate of 1.16 (95% CI 1.12-1.21). The combined effect estimate for OR/RR studies was 1.10 (95%CI 1.04-1.17), while HR studies yielded an effect estimate of 1.20 (95%CI 1.13-1.26). Subgroup analyses revealed associations across different age groups, obesity indices, and regions, with some variations based on effect measure. Meta-regression identified follow-up duration as a confounding factor only in HR studies.

Conclusion

The synthesis of 27 studies with diverse designs and populations underscores a robust positive association between adiposity and TC risk, providing compelling evidence for the potential role of increased adiposity in TC development.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-024-01425-3.

Nonalcoholic Fatty Liver Disease and the Risk of Thyroid Cancer Among Young Adults in South Korea

CONTEXT

Nonalcoholic fatty liver disease (NAFLD) is a hepatic manifestation of metabolic syndrome. Obesity and metabolic syndrome are known risk factors for thyroid cancer.

OBJECTIVE

We investigated the association between NAFLD and thyroid cancer risk in young adults.

METHODS

This nationwide cohort study included 1 135 967 participants aged 20 to 39 years who underwent 4 consecutive health screenings in South Korea. NAFLD was categorized using the fatty liver index (FLI), as follows: ≥60, 30 to 60, and <30. The cumulative FLI points were defined as the number of times participants had a FLI of ≥30 (0-4).

RESULTS

During a median follow-up of 5.2 years, 4126 participants (0.36%) were newly diagnosed with thyroid cancer. Compared with the participants with an FLI of <30, those with an FLI of 30 to 60 (men: hazard ratio [HR] 1.36 [95% CI, 1.22-1.51] and women: HR 1.44 [1.21-1.70]) and those with an FLI of ≥60 (men: HR 1.71 [1.53-1.92] and women: HR 1.81 [1.46-2.25]) had a significantly higher risk of thyroid cancer. Participants with higher cumulative FLI points had a higher risk of thyroid cancer compared to those with a cumulative FLI point of 0 (P < .001). During the follow-up period, the participants with an increased FLI exhibited an increased risk of thyroid cancer.

CONCLUSION

NAFLD was associated with an increased risk of thyroid cancer in young adults. Repeatedly elevated FLI and progression of NAFLD were associated with an increased risk of thyroid cancer in this study.

Epidemiological, Pathophysiological, and Clinical Considerations on the Interplay between Thyroid Disorders and Type 2 Diabetes Mellitus

Thyroid disorders (TD) and diabetes mellitus (DM) are the two endocrinopathies with the highest prevalence in the general population that frequently coexist. Thyroid dysfunction is more common in people with type 2 diabetes mellitus (T2DM) compared to normoglycemic individuals. Untreated TD can impair glycemic control, increasing the risk of diabetes complications. Hyperinsulinemia can affect the morphology of the thyroid gland by promoting the proliferation of thyroid tissue and increasing the size of thyroid nodules. Metformin can confer benefits in both endocrinopathies, while other antidiabetics, such as sulfonylureas, can negatively affect thyroid function. Animal and human observational data suggest an increased risk of medullary thyroid carcinoma after treatment with glucagon-like peptide-1 receptor agonists. However, randomized trials have so far been reassuring. Furthermore, some observational studies suggest an association between thyroid cancer and T2DM, especially in women. This narrative review aims to shed light on the epidemiological, pathophysiological, and clinical aspects of the interplay between TD and T2DM. Taking into account the important clinical implications of the coexistence of T2DM and TD, proper screening and management strategies are needed for both endocrinopathies to ensure optimal patient care.

Uncovering the pathogenesis of obesity complicated with papillary thyroid carcinoma via bioinformatics and experimental validation

This study aimed to investigate the common molecular mechanism between obesity and papillary thyroid cancer (PTC), the most common pathological type of thyroid cancer. In this study, we obtained gene expression datasets for obesity (GSE151839) and PTC (GSE33630) from the Gene Expression Omnibus (GEO). We used the Perl program and R software to identify differentially expressed genes (DEGs) and common genes, perform GO function and KEGG pathway enrichment analysis, construct a protein-protein interaction (PPI) network, identify hub genes, and perform transcription factors (TFs) analysis. After undergoing validation in external datasets and in vitro experiments, common targets for both diseases were ultimately identified. A total of 23 genes that were differentially expressed (DEGs) between obesity and papillary thyroid carcinoma (PTC) were identified in our study. Among these DEGs, 17 genes were up-regulated while 6 genes were down-regulated. Then the top ten key genes were identified from the PPI network using cytoHubba and MCODE plug-in. Further evidence from external datasets revealed that MMP9, MNDA, TNC, and CHIT1 were identified as hub genes for both diseases. The study utilized Transcriptional Regulatory Relationships Unraveled by Sentence-based Text mining (TRRUST) to perform an enrichment analysis of TFs. This analysis identified ELF4 and STAT3 as common TFs for both diseases. Additionally, in vitro experiments were conducted to further analyze the clinical significance and biological functions of these TFs. The identification and investigation of hub genes and their corresponding TFs that regulate abnormalities in obesity and PTC can enhance our comprehension of the underlying connection between these two diseases, thus leading to the development of novel diagnostic approaches.

Polycystic ovary syndrome and thyroid disorder: a comprehensive narrative review of the literature

Background

Published data on the relationship between polycystic ovary syndrome (PCOS) and thyroid dysfunction are sparse and confusing.

Objective

To comprehensively review data available in the literature regarding the relationship between PCOS and the thyroid function, and its abnormalities.

Methods

Nine main areas of interest were identified and analyzed according to the available evidence: 1) Evaluation of thyroid function for PCOS diagnosis; 2) Epidemiology data on thyroid function/disorders in patients with PCOS, and vice versa; 3) Experimental data supporting the relationship between thyroid function/disorders and PCOS; 4) Effects of thyroid function/disorders on PCOS features, and vice versa; 5) Effect of thyroid alterations on the cardiometabolic risk in women with PCOS; 6) Effect of thyroid abnormalities on reproductive outcomes in women with PCOS; 7) Relationship between thyroid function/abnormalities in patients with PCOS who are undergoing fertility treatment; 8) Effect of treatments for thyroid diseases on PCOS; and 9) Effect of treatments for PCOS on thyroid function. An extensive literature search for specific keywords was performed for articles published from 1970 to March 2023 using PubMed and Web of Science. Data were reported in a narrative fashion.

Results

PCOS is a diagnosis of exclusion for which diagnosis is possible only after excluding disorders that mimic the PCOS phenotype, including thyroid dysfunctions. However, the tests and the cutoff values used for this are not specified. Many experimental and clinical data suggest a relationship between perturbations of the thyroid function and PCOS. Direct and unequivocal evidence on the effects of thyroid function/disorders on PCOS features are lacking. High thyroid-stimulating hormone levels and subclinical hypothyroidism may be associated with significant worsening of several intermediate endpoints of cardiometabolic risk in women with PCOS. Thyroid abnormalities may worsen reproductive outcomes, especially in patients undergoing fertility treatment. To date, there are no data demonstrating the efficacy of thyroid medications on fertility and cardiometabolic risk in women with PCOS. Lifestyle modification changes, metformin, and vitamin D seem to improve thyroid function in the general population.

Conclusion

PCOS and thyroid disorders are closely related, and their coexistence may identify patients with a higher reproductive and metabolic risk. Regular screening for thyroid function and thyroid-specific autoantibodies in women with PCOS, particularly before and during pregnancy, is highly recommended.

Thyroid Nodules and Obesity

A widely discussed topic in the pathophysiology of thyroid nodules is the role of obesity, a state that leads to increased systemic inflammatory markers. Leptin plays a vital role in forming thyroid nodules and cancer through several mechanisms. Together with chronic inflammation, there is an augmentation in the secretion of tumor necrosis factor (TNF) and the cytokine interleukin 6 (IL-6), which contributed to cancer development, progression and metastasis. In addition, leptin exerts a modulatory action in the growth, proliferation and invasion of thyroid carcinoma cell lines via activating various signal pathways, such as Janus kinase/signal transducer and activator of transcription, mitogen-activated protein kinase (MAPK) and/or phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt). Through several proposed mechanisms, aberrant endogenous estrogen levels have been suggested to play a vital role in the development of both benign and malignant nodules. Metabolic syndrome triggers the development of thyroid nodules by stimulating thyroid proliferation and angiogenesis due to hyperinsulinemia, hyperglycemia and dyslipidemia. Insulin resistance influences the distribution and structure of the thyroid blood vessels. Insulin growth factor 1 (IGF-1) and insulin affect the regulation of the expression of thyroid genes and the proliferation and differentiation of thyroid cells. TSH can promote the differentiation of pre-adipocytes to mature adipocytes but also, in the presence of insulin, TSH possesses mitogenic properties. This review aims to summarize the underlying mechanisms explaining the role of obesity in the pathophysiology of thyroid nodules and discuss potential clinical implications.

Understanding the effect of obesity on papillary thyroid cancer: is there a need for tailored diagnostic and therapeutic management?

INTRODUCTION

Several studies have focused on the relationship between obesity and differentiated thyroid carcinoma (DTC), particularly papillary histotype (PTC). However, the association of obesity with both incidence and aggressiveness of PTC is still incompletely understood.

AREAS COVERED

We reviewed the mechanisms underlying the cross talk between obesity and thyroid carcinomas and described the most recent evidence evaluating the effect of obesity on the development of PTC, as well as the impact of excessive body weight on the clinicopathologic features and outcome of this type of cancer.

EXPERT OPINION

Available evidence suggests that excessive body weight is linked with a higher risk of getting PTC, while its impact on the aggressiveness of the disease, if present, is still not clear. Therefore, while attention should be paid to discover thyroid cancer in patients with obesity earlier, once diagnosed it should be managed following a conventional workup as in normal weight patients, based on the clinical presentation of the disease and including active surveillance if appropriate, as recommended by referral guidelines.

The Inverse Association of Serum Magnesium with Papillary Thyroid Cancer in Thyroid Nodules: a Cross-Sectional Survey Based on Thyroidectomy Population

Magnesium is considered to play a role in preventing cancer. However, the association between serum magnesium and papillary thyroid cancer (PTC) remains unknown. We retrospectively reviewed records of all patients who underwent thyroidectomy with thyroid nodules confirmed pathologically as benign nodule or PTC at our institution from January 2016 to December 2020. Data including demographic characteristics, laboratory tests, and pathological features were analyzed in 5709 adult patients eventually. The subjects with benign nodules had a higher mean serum magnesium level than those with PTC (P < 0.001), and the proportions of PTCs decreased across quartiles of serum magnesium within the normal range. After adjustment for confounders, patients with the lowest quartile of serum magnesium had a higher prevalence of PTC than those with the highest quartile (OR = 1.421, 95%CI: 1.125-1.795, P for trend = 0.005), and the risk of PTC was 0.863 (95%CI: 0.795-0.936) for a per-SD change in serum magnesium. The contribution of serum magnesium remained in subgroup analysis (P for interaction for all analyses > 0.05). Based on the ROC curve, the cut-off value of serum magnesium used to differentiate benign nodules from PTCs was 935 μmol/L. Combining serum magnesium with other clinical indicators can improve the efficacy of predicting PTC. Our results showed that lower serum magnesium within the normal range was associated with a greater risk of PTC among patients with thyroid nodules considering thyroidectomy. Serum magnesium may be an independent protective factor against PTC and provide additional information on the odds of malignancy in uncertain thyroid nodules in combination with other clinical factors.

Thyroid Cancer in Patients with Metabolic Syndrome or Its Components: A Nationwide Population-Based Cohort Study

The rapidly increasing coincidence of thyroid cancer and metabolic syndrome (MS) in recent decades suggests an association between the two disorders. To investigate this association, we conducted a nationwide study of a large-scale patient cohort. Between 2009 and 2011, data were collected by the Korean National Health Insurance Service for 4,658,473 persons aged 40−70 years without thyroid cancer. During the six-year follow-up period, participants were monitored for the development of thyroid cancer. The relative risks and incidences of thyroid cancer were calculated using multivariate Cox proportional hazards regression analyses after adjusting for age and body mass index. The risk of thyroid cancer was significantly elevated in men and women with MS or MS components, except for hyperglycaemia (p = 0.723) or hypertriglyceridemia (p = 0.211) in men. The incidence of thyroid cancer per 10,000 person-years in individuals with MS was significantly higher in men (6.2, p < 0.001) and women (21.3, p < 0.001) compared to those without MS. Additionally, the risk of thyroid cancer increased significantly with an increasing number of MS components even in individuals with only one or two MS components. MS and its components were significantly associated with increased risk of developing thyroid cancer.

The Endocrine Adipose Organ: A System Playing a Central Role in COVID-19

In the last 30 years the adipose cell has been object of several studies, turning its reputation from an inert cell into the main character involved in the pathophysiology of multiple diseases, including the ongoing COVID-19 pandemic, which has changed the clinical scenario of the last two years. Composed by two types of tissue (white and brown), with opposite roles, the adipose organ is now classified as a real endocrine organ whose dysfunction is involved in different diseases, mainly obesity and type 2 diabetes. In this mini-review we aim to retrace the adipose organ history from physiology to physiopathology, to provide therapeutic perspectives for the prevention and treatment of its two main related diseases (obesity and type 2 diabetes) and to summarize the most recent discoveries linking adipose tissue to COVID-19.

Body Mass Index and Thyroid Cancer Risk: A Pooled Analysis of Half a Million Men and Women in the Asia Cohort Consortium

Background: Although previous meta-analyses have suggested a dose-response relationship between body mass index (BMI) and thyroid cancer risk, limited evidence has been presented about Asian populations. To assess this association among Asian populations, where underweight is more prevalent than in other regions, a pooled analysis from the Asia Cohort Consortium was conducted. Methods: Baseline height and weight were measured in five cohorts and self-reported in eight cohorts. Thyroid cancer incidence was ascertained by linkage to local cancer registries. Cohorts were treated as a stratum in the Cox proportional hazard model to estimate the pooled hazard ratios (HRs) and corresponding confidence intervals (CIs) from the estimates for each cohort. All analyses were stratified by sex. Results: A total of 538,857 men and women from 13 cohorts from mainland China, Korea, Japan, and Singapore were included in the analysis. During a mean of 15.1 years of follow-up, 1132 thyroid cancer cases were ascertained. Using a BMI of 18.5-22.9 kg/m² as a reference, an elevated risk of thyroid cancer was observed for groups with a BMI between 25 and 29.9 kg/m² (HR: 1.31, [CI: 0.95-1.80]) and a BMI of 30 kg/m² and greater (HR: 1.84, [CI: 0.89-3.81]) in men. Thyroid cancer risk was elevated in women with a BMI of 23-24.9 kg/m² (HR: 1.26, [CI: 1.07-1.48]). The HRs for 5-U increment of BMI showed a linear association among men (HR: 1.25, [CI 1.10-1.55]) but not among women (HR: 1.07, [CI: 0.97-1.18]). Although the overall thyroid cancer risk was lower among underweight men and women, the papillary cancer risk may be elevated among underweight men (HR: 2.24, [CI: 0.75-6.66]). Conclusion: While higher BMI is associated with an elevated risk of thyroid cancer in both men and women, the association of underweight BMI may differ by sex and histological subtype.

Obesity and Thyroid Cancer Risk: An Update

Thyroid cancer (TC) is the most common endocrine malignancy worldwide and its incidence has increased dramatically in recent years. In parallel, the prevalence of overweight and obesity has also increased, suggesting a possible link between these two diseases. Indeed, low-grade chronic inflammation, altered cytokine levels, insulin resistance, oxidative stress, and hormonal changes that occur in obese patients are all factors that contribute to the occurrence and growth of TC. In this review, the most recent evidence supporting the potential role of the mechanisms linking obesity to TC will be discussed.

The prevalence of thyroid nodules and its factors among Chinese adult women: A cross-sectional study

OBJECTIVE

To determine the prevalence of thyroid nodules in Chinese adult women. To analyze the relationships between lifestyle, metabolic syndrome and thyroid nodules.

METHODS

We conducted a retrospective cross-sectional study in the tertiary hospital from 2017 to 2019. Included participants underwent thyroid color Doppler ultrasonography, lipids examination, and dietary evaluation.

RESULTS

Totally 2,784 participants were included, and 933 participants were found to have thyroid nodule(s) by B-ultrasound. The prevalence of thyroid nodules was 33.3%. Women in 50-59 years (OR: 1.746, 95% CI [1.356-2.249]), older than 60 (2.147 [1.540-2.993]) and occupations with mainly manual work (1.780 [1.367-2.317]) were risk factors for thyroid nodules, while moderate dietary diversity (0.624 [0.476-0.817]) and normal triglycerides level (0.739 [0.604-0.905]) were protective factors.

CONCLUSION

Women over 50 and those whose jobs are mainly manual should enhance screening, follow-up and health management of thyroid nodules. Higher dietary diversity is protective measures against thyroid nodules for adult women and should consider dietary balance and the food varieties, not just increased quantities.

Association of Metabolic Health and Central Obesity With the Risk of Thyroid Cancer: Data from the Korean Genome and Epidemiology Study

BACKGROUND

It is unknown whether the risk of thyroid cancer differs among metabolically healthy/unhealthy, normal-weight, or obese women. We aimed to assess the association of metabolic health and obesity with thyroid cancer risk.

METHODS

The Korean Genome and Epidemiology Study is a population-based prospective cohort study. Data were obtained from 173,343 participants (age {greater than or equal to}40 years) enrolled from 2004 to 2013. Obese participants were those with body mass index (BMI) {greater than or equal to}25 kg/m2. Participants with abnormalities in three of these indices were considered metabolically unhealthy: triglycerides, blood pressure, high-density lipoprotein cholesterol (HDL-cholesterol), waist circumference (WC), and fasting glucose levels. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for thyroid cancer risk associated with metabolic health and obesity.

RESULTS

Compared to non-obese women without metabolic abnormalities, metabolically unhealthy women, either normal-weight or obese, had an increased risk of thyroid cancer (HR [95% CI]=1.57[1.02-2.40] and 1.71[1.21-2.41], respectively). Significant association was not observed in men. Thyroid cancer risk was higher among non-obese women with high WC ({greater than or equal to}85 cm; HR [95% CI]=1.62[1.03-2.56]) than in non-obese women with low WC, and in obese women with low HDL-cholesterol (<50 mg/dL; HR[95% CI]=1.75[1.26-2.42]) compared to non-obese women with high HDL-cholesterol.

CONCLUSIONS

Metabolically unhealthy women or women with central adiposity may be at an increased thyroid cancer risk despite normal BMI.

IMPACT

This study suggests that women with central obesity and metabolically abnormality despite normal BMI may constitute a target group for thyroid cancer prevention and control programs.

Gender Differences in Obesity-Related Cancers

PURPOSE OF REVIEW

In this review, we summarize the role of obesity in carcinogenesis, providing details on specific cancer sites. Special emphasis is given to gender differences in obesity-related cancers and on the effect of bariatric surgery on cancer risk.

RECENT FINDINGS

Accumulating evidence has highlighted the detrimental role of overweight/obesity in cancer, with almost 55% of cancers diagnosed in women and 24% diagnosed in men considered overweight- and obesity-related cancers. Sufficient data have shown that higher BMI is associated with risk of gynecologic malignancies (mainly breast and endometrial cancers) as well as cancers in sites such as the esophagus (adenocarcinoma), gastric cardia, colon, rectum, liver, gallbladder, pancreas, kidney, thyroid gland, and multiple myeloma. The main mechanisms underlying this relationship include the insulin/IGF1 system, the effect of sex hormones, and adipocytokines. Marked differences may be seen in specific cancer sites when comparing men to women. There is a higher overall incidence of obesity-related cancers among females (endometrial, ovarian, and postmenopausal female breast cancers), whereas cancers that concern both sexes show a higher incidence in males, particularly esophageal adenocarcinoma (male to female ratio: 9: 1 in the USA). Additionally, bariatric surgery has provided evidence of lowering overall cancer risk in patients with morbid obesity. Interestingly, bariatric surgery may lower overall cancer risk in women within the first 5 years after surgery due to the reduced risk of breast and endometrial cancer, and non-Hodgkin lymphoma. Obesity constitutes the base for marked metabolic, hormonal, and inflammatory alterations, including increased cancer risk in both men and women. Implementation of early obesity prevention strategies could ameliorate the continuously increasing incidence of cancer attributed to obesity.

Serum Follistatin Is Increased in Thyroid Cancer and Is Associated With Adverse Tumor Characteristics in Humans

CONTEXT

Obesity and classical growth factors are associated with thyroid cancer (TC). However, less is known regarding novel hormones such as follistatins and activins. We hypothesized that serum follistatin but not activins would be increased in TC.

OBJECTIVE

This work aimed to assess circulating levels of follistatins, activins, and growth factors in patients with a history of TC vs patients with nonmalignant thyroid diseases.

METHODS

A hospital-based, unmatched case-control study was conducted with 170 thyroidectomized patients due to well-differentiated TC and 106 thyroidectomized patients without history of malignancy. Anthropometric, biochemical, and histological parameters were recorded. Serum samples were collected in the steady state 45 days after surgery. Multivariate models were used to adjust for baseline differences of the unmatched variables. Serum levels of follistatin (FST), follistatin like-3, activin A, activin B, bioactive insulin-like growth factor-1, and stanniocalcin-2 were assayed with novel, highly specific ELISA kits.

RESULTS

In unmatched univariate models, TC patients had higher FST serum levels compared to cancer-free individuals, independently of histological subtype. In multivariate models adjusting for covariates, individuals in the highest tertile of FST levels were associated with an increased risk for the presence of any type of TC or specific histological subtypes, including papillary, follicular and Hürthle-cell carcinoma, and medullary TC. Higher postoperative FST concentrations were found in patients with vascular invasion and distant metastases and associated with TNM staging at diagnosis.

CONCLUSION

FST serum levels are increased in TC patients and correlate with advanced tumor aggressiveness. Future longitudinal studies are needed to confirm and extend our observations.

Evaluation of the relationship between previous statin use and thyroid cancer using Korean National Health Insurance Service-Health Screening Cohort data

The association of thyroid cancer with statin use is controversial. This study aimed to investigate the association of previous statin use with thyroid cancer in the ≥ 40-year-old population in the Korean National Health Insurance Service-Health Screening Cohort. The 5501 patients in the thyroid cancer group were matched with the 22,004 patients in the non-thyroid cancer group for age, sex, income, and region of residence. Previous statin use during the 2 years before the diagnosis of thyroid cancer was examined. The odds ratios (ORs) with 95% confidence intervals (CIs) of previous statin use for thyroid cancer were estimated using conditional logistic regression analyses. Additionally, subgroup analyses were conducted. The thyroid cancer group showed more days of previous statin use than the non-thyroid cancer group (72.3, standard deviation [SD] = 181.2 days vs. 64.3, SD = 174.4 days, P = 0.003). Although the odds of previous statin use for thyroid cancer were high in the crude model (OR = 1.10, 95% CI 1.04–1.17, P = 0.002), they were low in the fully adjusted model (OR = 0.89, 95% CI 0.82–0.95, P = 0.001). According to age and sex subgroups, the younger (< 60 years old) male group showed lower odds for thyroid cancer according to previous statin use (adjusted OR = 0.70, 95% CI 0.55–0.88, P = 0.003), but this finding was not observed in other subgroups of older men or in any groups of women. Thyroid cancer was negatively associated with statin use in the previous 2 years in the adjusted model.

Adiponectin and Thyroid Cancer: Insight into the Association between Adiponectin and Obesity

In recent decades, the incidence and diagnosis of thyroid cancer have risen dramatically, and thyroid cancer has now become the most common endocrine cancer in the world. The onset of thyroid cancer is insidious, and its progression is slow and difficult to detect. Therefore, early prevention and treatment have important strategic significance. Moreover, an in-depth exploration of the pathogenesis of thyroid cancer is key to early prevention and treatment. Substantial evidence supports obesity as an independent risk factor for thyroid cancer. Adipose tissue dysfunction in the obese state is accompanied by dysregulation of a variety of adipocytokines. Adiponectin (APN) is one of the most pivotal adipocytokines, and its connection with obesity and obesity-related disease has gradually become a hot topic in research. Recently, the association between APN and thyroid cancer has received increasing attention. The purpose of this review is to systematically review previous studies, give prominence to APN, focus on the relationship between APN, obesity and thyroid cancer, and uncover the underlying pathogenic mechanisms.

Association Between Aggressive Clinicopathologic Features of Papillary Thyroid Carcinoma and Body Mass Index: A Systematic Review and Meta-Analysis

BACKGROUND

The association between adiposity and papillary thyroid carcinoma (PTC) has been reported in several studies, but its association with aggressive clinicopathologic features is not well-recognized. Our aim is to systematically review the literature to identify whether adiposity, expressed through Body Mass Index (BMI), is related to aggressive clinicopathologic features such as tumor-node-metastasis (TNM) stage, extrathyroidal extension (ETE), lymph node (LN) metastasis and multifocality in patients with PTC.

METHODS

A systematic search for articles was performed using the PubMed, EBSCO, and Cochrane Library for all articles published in English until December 2020. Specific keywords such as "papillary thyroid carcinoma", "Body Mass Index", "clinicopathologic features" were used in the search strategy. Two independent reviewers screened all retrieved articles based on predefined inclusion and exclusion criteria. Meta-analysis was performed in the studies that reported crude and adjusted odds ratios (OR). The methodological quality was assessed using the Newcastle-Ottawa Scale.

RESULTS

A total of 11 retrospective cohort studies involving 26,196 participants included. Our findings showed that elevated BMI was significantly associated with ETE in both overweight (OR 1.26, 95% CI: 1.09-1.44) and obesity group (OR 1.45, 95% CI:1.26-1.64). Elevated BMI was also significantly associated with multifocality in overweight patients (OR 1.17, 95% CI:1.10-1.24) and obese patients (OR 1.45, 95% CI:1.29-1.62). Also, obesity was significantly associated with increased tumor size (OR 1.77, 95% CI:1.52-2.03) and with LN metastasis (OR 1.28, 95% CI: 1.12-1.44), whereas being overweight was significantly associated with advanced TNM stage (OR 1.55, 95% CI:1.27-1.83).

CONCLUSION

Our results provide strong evidence for the association between higher BMI and ETE, multifocality, and tumor size. Further studies with a larger number of participants are required to elucidate further the association of increased BMI with advanced TNM stage and LN metastasis.

A matrix-assisted laser desorption/ionization imaging mass spectrometric approach to study weight-related changes within thyroid tissue

Obesity is associated with numerous comorbidities along with abnormalities of the endocrine system, more commonly manifesting as dysfunctions of the thyroid gland such as goiter. Changes in weight, especially an increase, could lead to an increase in the incidence of thyroid dysfunction; however, its pathophysiology remains to be elucidated. In the present study, we aimed to interrogate the changes in the protein distribution and abundance between the lean patients and patients with obesity thyroid tissue sections through utilizing this technique. The FFPE-fixed thyroid tissue blocks from the selected cases and controls were identified and targeted for matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) analysis. Patients in the 30 to 75 years age group and undergoing total thyroidectomy for benign thyroid disease were recruited. Patients with thyroid cancers, autoimmune disorders, and other inflammatory conditions were excluded from the study. The selected patients were divided into two groups according to their BMIs: lean (BMI < 25) and obese (BMI > 35). An initial trial set was used as a pilot study for the optimization of the MALDI IMS protocol that was next applied to the selected thyroid tissues. MALDI IMS data from all the samples were aligned and statistical analysis carried out by k-means and linear discriminant analysis (LDA) classification model using principle component analysis (PCA) results were evaluated between the two groups: controls (lean) and cases (obese). Receiver operator characteristic (ROC) curves were alternatively used to calculate the variability of the identified peptides. The discriminating peptides were also independently identified and related to their corresponding proteins by using liquid chromatography and tandem mass spectrometry (LC-MS/MS) analyses. Eight peptides mainly from thyroglobulin were found to be upregulated whereas 10 others were found to be downregulated in the lean compared to the obese group. Through this technique, we will be able to better understand the relationship between the disease entity and obesity.

Obesity and the prevention of thyroid cancer: Impact of body mass index and weight change on developing thyroid cancer - Pooled results of 24 million cohorts

BACKGROUND

Body weight may be a modifiable risk factor predisposing to different cancers. To establish a potential impact of weight change on thyroid cancer risk, we conducted a meta-analysis to evaluate the effect of body mass index (BMI) and weight change over time as a risk of developing thyroid cancer (TC).

METHODS

A systematic search was performed up to February 25, 2020. Pooled relative risk (RR) were estimated using fixed and random models. Heterogeneity between articles was examined using Q-test and I² index. Evaluation of publication bias was conducted with Egger's regression test.

RESULTS

A total of 31 studies including 24,489,477 cohorts were eligible. Pooled analysis revealed that normal and underweight cohorts were associated with a decreased risk of TC (RR = 0.68, 95%CI = 0.65-0.71, p < 0.001) and (RR = 0.92, 95%CI = 0.91-0.93, p < 0.001), respectively. In contrast, overweight and obese cohorts were more likely to develop TC (RR = 1.26, 95%CI = 1.24-1.28, p < 0.001 and RR = 1.50, 95%CI = 1.45-1.55, p < 0.001, respectively). Obesity was associated with higher risk of developing TC among women (RR = 1.29, 95%CI = 1.14-1.46, p < 0.001), but not men (RR = 1.25, 95%CI = 0.97-1.62, p = 0.08). Furthermore, weight gain increased the risk of developing TC (RR = 1.18, 95%CI = 1.14-1.22, p < 0.001), while weight loss decreased the risk (RR = 0.89, 95%CI = 0.85-0.93, p < 0.001). Results showed similar trends of weight change effect in both males and females.

CONCLUSIONS

Obesity is associated with higher risk of developing TC in women. However, maintaining a healthy weight is associated with reduced risk of TC in both women and men. Shifting our practice to include weight control strategies will help lead to cancer prevention.

Metabolic Syndrome and the Risk of Thyroid Cancer: A Nationwide Population-Based Cohort Study

Background: The association of metabolic syndrome and its components with the risk of thyroid cancer is unclear. Thus, we conducted a large-scale, nationwide, population-based, cohort study to investigate this relationship. Methods: We studied 9,890,917 adults without thyroid cancer from the Korean National Health Insurance health checkup database from January 1 to December 31, 2009. Individuals with at least three of the following five components were diagnosed with metabolic syndrome: abdominal obesity, hypertriglyceridemia, low high-density lipoprotein-cholesterol levels, elevated blood pressure, and hyperglycemia. Multivariate Cox proportional hazards models were used to estimate thyroid cancer risk. Results: During the average 7.2 years of follow-up, 77,133 thyroid cancer cases were newly identified. The thyroid cancer risk was higher in the metabolic syndrome group than in the nonmetabolic syndrome group (hazard ratio [HR] 1.15 [95% confidence interval, CI 1.13-1.17]). The association between metabolic syndrome and thyroid cancer risk was significant in the obese group (HR 1.10 [CI 1.07-1.13]) and not in the nonobese group (HR 1.002 [CI 0.98-1.03]). The effect of metabolic syndrome on the risk of thyroid cancer differs according to obesity (p for interaction = 0.017). People with all five components of metabolic syndrome had a 39% higher risk than those without any components (HR 1.39 [CI 1.33-1.44]). The higher risk of thyroid cancer in people with all five components was significant in the obese group (HR 1.29 [CI 1.21-1.38]), but not in the nonobese group (HR 1.06 [CI 0.98-1.14]). There was a significant interaction between the number of metabolic syndrome components and obesity (p for interaction <0.0001). For the combined effect of obesity and metabolic syndrome on the risk of thyroid cancer, obese men with metabolic syndrome had the highest risk of thyroid cancer compared with those without (HR 1.58 [CI 1.52-1.64]), but obese women with metabolic syndrome did not. Conclusions: Metabolic syndrome was associated with an increased risk of thyroid cancer in the Korean general population. Metabolic syndrome had a more significant risk of thyroid cancer in the obese group. Metabolic syndrome and obesity were associated with a higher risk of thyroid cancer in men but not in women.

Serum Adiponectin and Progranulin Level in Patients with Benign Thyroid Nodule or Papillary Thyroid Cancer

BACKGROUND

Obesity is associated with thyroid cancer risk. Adiponectin has insulin-sensitizing and anti-inflammatory effects, while progranulin is associated with inflammation and tumorigenesis. We investigated serum adiponectin and progranulin levels in patients with benign thyroid nodule (benign group) and papillary thyroid cancer (PTC; PTC group). The associations between these levels and the clinicopathological features of PTC were evaluated.

METHODS

We included 157 patients who underwent thyroid surgery (17% of benign and 83% of PTC group). Clinicopathological features including size, lymph node metastasis, extrathyroidal extension (ETE), multifocality, American Thyroid Association risk stratification were evaluated.

RESULTS

The age was 42.0 years, and 69% were female. Serum adiponectin and progranulin levels were 6.3 μg/mL and 101.5 ng/mL in the benign group and 5.4 μg/mL and 106.1 ng/mL in the PTC group, respectively (P=0.6 and P=0.4, respectively). Serum adiponectin levels showed no significant differences according to clinicopathological features of PTC. The proportions of patients with primary tumor size &gt;1 cm were 3%, 5%, 8%, and 8% according to serum progranulin level quartiles, respectively (P=0.03). The proportions of patients with microscopic/gross ETE were 8%/0%, 9%/1%, 11%/1%, and 11%/2% according to serum progranulin level quartiles, respectively. Median serum progranulin level was significantly higher in patients with PTC &gt;1 cm than in patients with papillary thyroid microcarcinoma (P=0.04, 115.3 ng/mL and 104.7 ng/mL, respectively).

CONCLUSION

Serum adiponectin and progranulin levels showed no significant difference between benign and PTC groups. Increased serum progranulin levels were significantly associated with PTC &gt;1 cm and microscopic and gross ETE.

Role of GSTM1 and GSTT1 genotypes in differentiated thyroid cancer and interaction with lifestyle factors: Results from case-control studies in France and New Caledonia

Background

GSTM1 and GSTT1 are involved in detoxification of xenobiotics, products of oxidative stress and in steroid hormones metabolism. We investigated whether GSTM1 and GSTT1 gene deletion was associated with DTC risk and explored interaction with non-genetic risk factors of DTC.

Methods

The study included 661 DTC cases and 736 controls from two case-control studies conducted in France and New Caledonia. Odds ratios (OR) and their confidence interval (CI) for DTC associated with GST genotypes, alcohol drinking, tobacco smoking, body mass index and hormonal factors were calculated using logistic regression models.

Results

Results are presented for Europeans and Melanesians combined, as no heterogeneity between groups was detected. We found that DTC risk increased with obesity and decrease with alcohol drinking. After stratification by gene deletion status, the OR for obesity was 5.75, (95%CI 2.25–14.7) among individuals with GSTT1 and GSTM1-deleted genotype, and 1.26, (95%CI 0.89–1.77) in carriers of both genes (p-interaction = 0.02). The OR for drinking ≥1 glass/week was 0.33 (95%CI 0.15–0.74) in GSTT1-null individuals while it was 1.01 (95%CI 0.67–1.52) in non-null carriers of the gene (p-interaction = 0.01). No interaction between GST genotypes and other non-genetic risk factors was detected.

Conclusion

GSTM1 and GSTT1 genotypes may modulate the DTC risk associated with BMI and alcohol consumption.

Postthyroidectomy obesity in a Korean population: does the extent of surgery matter?

Purpose

The purpose of this study was to investigate the prevalence of postthyroidectomy obesity, and the relationship between the extent of thyroidectomy and obesity.

Methods

A survey conducted at an outpatient clinic from June to October 2014 and retrospective charts for patients undergoing thyroidectomy at Konkuk University Medical Centers from June 2009 to December 2013 were reviewed. We compared clinical characteristics and pre- and postoperative obesity-related factors in 227 patients who underwent total thyroidectomy or lobectomy.

Results

Patients included 39 males and 188 females with a mean age of 46.0 ± 11.0 years; the mean follow-up period was 23.9 ± 16.7 months, and 90 of the 227 patients showed postthyroidectomy obesity. In effect of operative extent on postoperative obesity, patients who underwent TT (48.2 years) than those who underwent lobectomy (43.4 years). TT group had longer follow-up and the frequency of menopause was higher than in the lobectomy group. No differences in postthyroidectomy obesity, body weight change, or body mass index (BMI), change among 2 groups. The predictors of postthyroidectomy obesity were older age, female, heavy alcohol consumption (P = 0.029), higher preoperative BMI (P < 0.001), larger postoperative weight gain (P = 0.024), and larger BMI change. However, the extent of thyroidectomy did not affect postthyroidectomy obesity. Preoperative BMI (P < 0.001) and heavy alcohol consumption (P = 0.03) were independent factors of postthyroidectomy obesity.

Conclusion

The extent of thyroidectomy does not affect postthyroidectomy obesity. Preoperative BMI and heavy alcohol consumption are risk factors for postthyroidectomy obesity. Studies are needed to suggest preoperative life style modification to prevent postthyroidectomy obesity.

Circulating adipokines and metabolic setting in differentiated thyroid cancer

The associative link relating insulin resistance (IR) and adipokines to the occurrence and phenotype of differentiated thyroid cancer (DTC) is unknown. The aim of this study was to evaluate the relationship between IR and adipokines in DTC patients, as compared with carriers of benign thyroid diseases (BTD) and healthy controls. This observational study enrolled 77 subjects phenotyped as DTC (N = 30), BTD (N = 27) and healthy subjects (N = 20). Each subject underwent preoperative analysis of anthropometric parameters, thyroid function and autoimmunity, insulin resistance (HOMA-IR) and levels of unacylated (UAG) and acylated ghrelin (AG), obestatin, leptin and adiponectin. Multivariate regression models were used to test the predictive role of metabolic correlates on thyroid phenotypes and DTC extension. The three groups showed similar age, gender distribution, smoking habit, BMI and thyroid parameters. Obestatin was significantly higher in DTC group compared to BTD (P < 0.05) and control subjects (P < 0.0001). DTC and BTD groups showed higher levels of UAG (P < 0.01) and AG (P < 0.05). Leptin levels were comparable between groups, whereas adiponectin levels were lower in DTC compared to BTD group (P < 0.0001) and controls (P < 0.01). In parallel, HOMA-IR was higher in DTC than BTD (P < 0.05) and control group (P < 0.01). Stepwise multivariable regression analysis showed that obestatin and UAG were independent predictors of DTC (P = 0.01 for both). In an analysis restricted to the DTC group, obestatin levels were associated with the absence of lymph node metastases (P < 0.05). Our results highlight a potential association between metabolic setting, circulating adipokines and thyroid cancer phenotype.

Metabolic Obesity Phenotypes and Thyroid Cancer Risk: A Cohort Study

BACKGROUND

No cohort studies have evaluated the effect of obesity on the incidence of thyroid cancer according to metabolic health status. Therefore, this study examined the association of body mass index (BMI) and metabolic health status with thyroid cancer risk.

METHODS

A cohort study was performed involving 255,051 metabolically healthy (MH) and metabolically unhealthy (MUH) adults free of thyroid cancer at baseline who were followed for a median of 5.3 years. A parametric proportional hazard model was used to estimate the adjusted hazard ratio (aHR) and confidence interval (CI).

RESULTS

During 1,402,426.3 person-years of follow-up, 2927 incident thyroid cancers were identified. Among men, the multivariable aHR for thyroid cancer comparing obesity, defined as a BMI ≥25 kg/m², with a BMI of 18.5-22.9 kg/m² was 1.47 [CI 1.12-1.93] in MH individuals, whereas the corresponding HR in MUH individuals was 1.26 [CI 1.03-1.53]. Among women, the corresponding HR in MH individuals was 1.05 [CI 0.80-1.36], whereas the corresponding HR in MUH individuals was 1.43 [CI 1.22-1.69]. Increasing quartiles of waist circumference were positively associated with risk of thyroid cancer in MUH men and women (p for trend <0.005) but not in MH individuals.

CONCLUSIONS

In both MH and MUH men, obesity was associated with an increased risk of incident thyroid cancer, indicating excessive adiposity per se as an independent risk factor for thyroid cancer. Conversely, women with MUH obesity but not MH obesity were found to have an increased risk of thyroid cancer, indicating that obesity with accompanying metabolic abnormalities may affect thyroid cancer risk in women.

Evolving Understanding of the Epidemiology of Thyroid Cancer

The incidence of thyroid cancer worldwide has increased significantly over the past 3 decades, due predominantly to an increase in papillary thyroid cancer. Although most of these cancers are small and localized, population-based studies have documented a significant increase in thyroid cancers of all sizes and stages, in addition to incidence-based mortality for papillary thyroid cancer. This suggests that the increasing incidence of thyroid cancer is due in large part to increasing surveillance and overdiagnosis, but that there also appears to be a true increase in new cases of thyroid cancer.

Weight change is significantly associated with risk of thyroid cancer: A nationwide population-based cohort study

Obesity is a risk factor for many cancers including breast, esophageal, colon, and thyroid cancer. We aimed to evaluate the association of thyroid cancer with body mass index (BMI), waist circumference (WC), and weight change. This nationwide population-based cohort study included 11,323,006 adults who joined the national health screening program. Weight change was defined as the difference between the weight of the subjects measured during the study period and the weight at the time of four years ago. For evaluating the association between the weight change and the risk of thyroid cancer, subjects without weight change for four years were defined as the reference group. Mean age was 50.1 ± 13.7 years and 44% were female. In total, 50,464 subjects (0.4%) had newly-diagnosed thyroid cancer. After multivariable analyses, the incidence of thyroid cancer increased significantly in subjects with larger WC as well as higher BMI (P < 0.001 and P < 0.001, respectively). In subjects who were lean and became obese, the incidence of thyroid cancers increased significantly (hazard ratio [HR] 1.15 [1.11-1.19]). In subjects who were obese and became lean, the incidence of thyroid cancers decreased significantly (HR 0.89 [0.86-0.93]). These results demonstrated that higher BMI and larger WC were significantly associated with an increased risk of thyroid cancer. Weight gain in lean subjects was associated with an increased risk of thyroid cancer, and weight reduction in subjects with obesity was associated with a decreased risk of thyroid cancer.

The impact of BMI on clinical progress, response to treatment, and disease course in patients with differentiated thyroid cancer

Introduction

Obesity is a serious health problem worldwide, particularly in developed countries. It is a risk factor for many diseases, including thyroid cancer. The relationship between obesity and prognostic factors of thyroid cancer is unclear.

Aims

We sought to ascertain the relationship between body mass index (BMI) and clinicopathological features increasing the risk of poor clinical course, treatment response, and clinical outcome in patients with differentiated thyroid cancer (DTC).

Subjects & methods

The study included 1181 patients with DTC (88% women and 12% men) treated at a single center from 2000 to 2016. BMI before surgery and aggressive clinicopathological features, according to the American Thyroid Initial Risk stratification system, were analyzed. The relationship between BMI and initial risk, treatment response, and final status of the disease was evaluated, incorporating the revised 2015 American Thyroid Association guidelines and the 8^th edition of the American Joint Committee on Cancer/Tumor-Node-Metastasis (AJCC/TNM) staging system. Patients were stratified according to the World Health Organization classification of BMI. Statistical analysis was performed using univariate and multivariate logistic regression analysis.

Results

Median follow-up was 7.7 years (1–16 years). There were no significant associations between BMI and extrathyroidal extension (microscopic and gross), cervical lymph node metastasis, or distant metastasis in univariate and multivariate analyses. BMI did not affect initial risk, treatment response or disease outcome. Obesity was more prevalent in men (p = 0.035) and in patients ≥55 years old (p = 0.001). There was no statistically significant relationship between BMI and more advanced TNM stage in patients ≤55 years old (stage I vs. stage II) (p = 0.266) or in patients >55 years old (stage I–II vs. III–IV) (p = 0.877).

Conclusions

Obesity is not associated with more aggressive clinicopathological features of thyroid cancer. Obesity is not a risk factor for progression to more advanced stages of disease, nor is it a prognostic factor for poorer treatment response and clinical outcome.

Association of Obesity and Thyroid Cancer at a Tertiary Care Hospital in Pakistan

Objective

Thyroid cancer (TC) is one of the most common endocrine malignancies with a rapidly increasing worldwide presence. In Pakistan, it is more prevalent in females than males and has an incidence rate of 2.1%. Obesity and excess body mass index (BMI) has been linked to several cancers and is thought to be a risk factor for TC. We aim to investigate the incidence of TC in our population and understand it’s correlation with obesity.

Subjects

The study was a retrospective case series conducted in the years 2000 to 2014, at the Aga Khan University Hospital (AKUH), Karachi, Pakistan where 156 patients who had been diagnosed and treated for TC were analyzed. Clinicopathological data was collected from medical records of these patients and weight and height were measured, pre-surgery, post-surgery, and at follow up. The BMI was correlated with patient variables for any significant associations.

Results

The patient set comprised of 38.5% males and 61.5% females with a mean age of 47.77 (SD ± 14.35). The BMI was significantly associated with age as 72.8% of participants were obese and >45 years old as compared to 27.2% who were under 45 years and obese (p-value <0.001). Upon comparison of the pre-surgery, post-surgery, and current mean BMI, Bonferroni pairwise comparisons showed no significant difference (p>0.999).

Conclusion 

The majority of-of TC patients among the Pakistani population were obese and female. Age was significantly associated with the risk of having a higher BMI. Moreover, differences in BMI pre and post-surgery could not be statistically proven.

Galectins and Carcinogenesis: Their Role in Head and Neck Carcinomas and Thyroid Carcinomas

Head and neck cancers are among the most frequently occurring cancers worldwide. Of the molecular drivers described for these tumors, galectins play an important role via their interaction with several intracellular pathways. In this review, we will detail and discuss this role with specific reference to galectins-1, -3, and -7 in angiogenesis, cell proliferation, and invasion as well as in cell transformation and cancer progression. Furthermore, we will evaluate the prognostic value of galectin expression in head and neck cancers including those with oral cavity, salivary gland, and nasopharyngeal pathologies. In addition, we will discuss the involvement of these galectins in thyroid cancers where their altered expression is proposed as a new diagnostic biomarker.

Role of microRNAs in endocrine cancer metastasis

The deregulation of transcription and processing of microRNAs (miRNAs), as well as their function, has been involved in the pathogenesis of several human diseases, including cancer. Despite advances in therapeutic approaches, cancer still represents one of the major health problems worldwide. Cancer metastasis is an aggravating factor in tumor progression, related to increased treatment complexity and a worse prognosis. After more than one decade of extensive studies of miRNAs, the fundamental role of these molecules in cancer progression and metastasis is beginning to be elucidated. Recent evidences have demonstrated a significant role of miRNAs on the metastatic cascade, acting either as pro-metastatic or anti-metastatic. They are involved in distinct steps of metastasis including epithelial-to-mesenchymal transition, migration/invasion, anoikis survival, and distant organ colonization. Studies on the roles of miRNAs in cancer have focused mainly on two fronts: the establishment of a miRNA signature for different tumors, which may aid in early diagnosis using these miRNAs as markers, and functional studies of specific miRNAs, determining their targets, function and regulation. Functional miRNA studies on endocrine cancers are still scarce and represent an important area of research, since some tumors, although not frequent, present a high mortality rate. Among the endocrine tumors, thyroid cancer is the most common and best studied. Several miRNAs show lowered expression in endocrine cancers (i.e. miR-200s, miR-126, miR-7, miR-29a, miR-30a, miR-137, miR-206, miR-101, miR-613, miR-539, miR-205, miR-9, miR-195), while others are commonly overexpressed (i.e. miR-21, miR-183, miR-31, miR-let7b, miR-584, miR-146b, miR-221, miR-222, miR-25, miR-595). Additionally, some miRNAs were found in serum exosomes (miR-151, miR-145, miR-31), potentially serving as diagnostic tools. In this review, we summarize studies concerning the discovery and functions of miRNAs and their regulatory roles in endocrine cancer metastasis, which may contribute for the finding of novel therapeutic targets. The review focus on miRNAs with at least some identified targets, with established functions and, if possible, upstream regulation.

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.

Review of Factors Related to the Thyroid Cancer Epidemic

Thyroid cancer is the most common endocrine cancer, of which the incidence has dramatically increased worldwide in the past few decades. The reasons for the observed rapid increase still are not fully understood, but evidence suggests that overdiagnosis, with the advancement in detection methods and screening policies, is not the sole driver of the substantial increase of the incidence. However, the effect of environmental/lifestyle factors remains speculative other than that of radiation exposure at a young age. This review tries to give a balanced view of debated factors leading to the thyroid cancer epidemic, to offer some alternatives in understanding the controversies, and to suggest potential directions in the search of modifiable risk factors to help reduce thyroid cancer.

Insulin Resistance: Any Role in the Changing Epidemiology of Thyroid Cancer?

In the past few decades, the incidence of thyroid cancer (TC), namely of its papillary hystotype (PTC), has shown a steady increase worldwide, which has been attributed at least in part to the increasing diagnosis of early stage tumors. However, some evidence suggests that environmental and lifestyle factors can also play a role. Among the potential risk factors involved in the changing epidemiology of TC, particular attention has been drawn to insulin-resistance and related metabolic disorders, such as obesity, type 2 diabetes, and metabolic syndrome, which have been also rapidly increasing worldwide due to widespread dietary and lifestyle changes. In accordance with this possibility, various epidemiological studies have indeed gathered substantial evidence that insulin resistance-related metabolic disorders might be associated with an increased TC risk either through hyperinsulinemia or by affecting other TC risk factors including iodine deficiency, elevated thyroid stimulating hormone, estrogen-dependent signaling, chronic autoimmune thyroiditis, and others. This review summarizes the current literature evaluating the relationship between metabolic disorders characterized by insulin resistance and the risk for TC as well as the possible underlying mechanisms. The potential implications of such association in TC prevention and therapy are discussed.

The changing incidence of thyroid cancer

During the past few decades, the incidence of thyroid cancer has increased substantially in many countries, including the USA. The rise in incidence seems to be attributable both to the growing use of diagnostic imaging and fine-needle aspiration biopsy, which has led to enhanced detection and diagnosis of subclinical thyroid cancers, and environmental factors. The latest American Thyroid Association (ATA) practice guidelines for the management of adult patients with thyroid nodules and differentiated thyroid cancer differ substantially from the previous ATA guidelines published in 2009. Specifically, the problems of overdiagnosis and overtreatment of a disease that is typically indolent, where treatment-related morbidity might not be justified by a survival benefit, now seem to be acknowledged. As few modifiable risk factors for thyroid cancer have been established, the specific environmental factors that have contributed to the rising incidence of thyroid cancer remain speculative. However, the findings of several large, well-designed epidemiological studies have provided new information about exposures (such as obesity) that might influence the development of thyroid cancer. In this Review, we describe the changing incidence of thyroid cancer, suggest potential explanations for these trends, emphasize the implications for patients and highlight ongoing and potential strategies to combat this growing clinical and public health issue.

Body mass index and incidence of thyroid cancer in Korea: the Korean Cancer Prevention Study-II

PURPOSE

The prevalence of thyroid cancer and obesity has increased worldwide. However, their association has remained controversial and few studies have been performed in Asia. Our study evaluated the correlation between the incidence of thyroid cancer and body mass index (BMI) in Korea.

METHODS

This is a multi-centered, prospective cohort study from the Korean Cancer Prevention Study-II. A total of 141,157 individuals between 1994 and 2012, including 1546 newly developed thyroid cancer patients, were enrolled. Subjects were divided into four groups on the BMI. Person-years, incidence rate, and hazard ratios (HRs) were calculated using the Cox proportional hazard model.

RESULTS

The increasing trends of HRs of thyroid cancer in men and women younger than 50 years of age were observed as BMI increased (P trend <0.001 in both groups). However, in women older than 50 years of age, there was no association between thyroid cancer incidence and BMI.

CONCLUSIONS

Our findings suggest that positive association between thyroid cancer incidence and high BMI in men and women under 50 years old. Based on these results, we suggest that obese men and women under 50 years old are better to be considered for the higher possibility of thyroid cancer development, and more efforts are needed to control weight gain.

Annual Average Changes in Adult Obesity as a Risk Factor for Papillary Thyroid Cancer: A Large-Scale Case-Control Study

We evaluated the association between weight change in middle-aged adults and papillary thyroid cancer (PTC) based on a large-scale case-control study. Our study included data from 1551 PTC patients (19.3% men and 80.7% women) who underwent thyroidectomy at the 3 general hospitals in Korea and 15,510 individually matched control subjects. The subjects' weight history, epidemiologic information, and tumor characteristics confirmed after thyroidectomy were analyzed. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were determined for the annual average changes in weight and obesity indicators (body mass index (BMI), body surface area, and body fat percentage (BF%) in subjects since the age of 35 years. Subjects with a total weight gain ≥10 kg after age 35 years were more likely to have PTC (men, OR, 5.39, 95% CI, 3.88-7.49; women, OR, 3.36, 95% CI, 2.87-3.93) compared with subjects with a stable weight (loss or gain <5 kg). A marked increase in BMI since age 35 years (annual average change of BMI ≥0.3 kg/m/yr) was related to an elevated PTC risk, and the association was more pronounced for large-sized PTC risks (<1 cm, OR, 2.34, 95% CI, 1.92-2.85; ≥1 cm, OR, 4.00, 95% CI, 2.91-5.49, P heterogeneity = 0.005) compared with low PTC risks. Weight gain and annual increases in obesity indicators in middle-aged adults may increase the risk of developing PTC.

Anthropometric Factors and Thyroid Cancer Risk by Histological Subtype: Pooled Analysis of 22 Prospective Studies

BACKGROUND

Greater height and body mass index (BMI) have been associated with an increased risk of thyroid cancer, particularly papillary carcinoma, the most common and least aggressive subtype. Few studies have evaluated these associations in relation to other, more aggressive histologic types or thyroid cancer-specific mortality.

METHODS

This large pooled analysis of 22 prospective studies (833,176 men and 1,260,871 women) investigated thyroid cancer incidence associated with greater height, BMI at baseline and young adulthood, and adulthood BMI gain (difference between young-adult and baseline BMI), overall and separately by sex and histological subtype using multivariable Cox proportional hazards regression models. Associations with thyroid cancer mortality were investigated in a subset of cohorts (578,922 men and 774,373 women) that contributed cause of death information.

RESULTS

During follow-up, 2996 incident thyroid cancers and 104 thyroid cancer deaths were identified. All anthropometric factors were positively associated with thyroid cancer incidence: hazard ratios (HR) [confidence intervals (CIs)] for height (per 5 cm) = 1.07 [1.04-1.10], BMI (per 5 kg/m2) = 1.06 [1.02-1.10], waist circumference (per 5 cm) = 1.03 [1.01-1.05], young-adult BMI (per 5 kg/m2) = 1.13 [1.02-1.25], and adulthood BMI gain (per 5 kg/m2) = 1.07 [1.00-1.15]. Associations for baseline BMI and waist circumference were attenuated after mutual adjustment. Baseline BMI was more strongly associated with risk in men compared with women (p = 0.04). Positive associations were observed for papillary, follicular, and anaplastic, but not medullary, thyroid carcinomas. Similar, but stronger, associations were observed for thyroid cancer mortality.

CONCLUSION

The results suggest that greater height and excess adiposity throughout adulthood are associated with higher incidence of most major types of thyroid cancer, including the least common but most aggressive form, anaplastic carcinoma, and higher thyroid cancer mortality. Potential underlying biological mechanisms should be explored in future studies.

Follicular cell-derived thyroid cancer

Follicular cell-derived thyroid cancers are derived from the follicular cells in the thyroid gland, which secrete the iodine-containing thyroid hormones. Follicular cell-derived thyroid cancers can be classified into papillary thyroid cancer (80-85%), follicular thyroid cancer (10-15%), poorly differentiated thyroid cancer (<2%) and undifferentiated (anaplastic) thyroid cancer (<2%), and these have an excellent prognosis with the exception of undifferentiated thyroid cancer. The advent and expansion of advanced diagnostic techniques has driven and continues to drive the epidemic of occult papillary thyroid cancer, owing to overdiagnosis of clinically irrelevant nodules. This transformation of the thyroid cancer landscape at molecular and clinical levels calls for the modification of management strategies towards personalized medicine based on individual risk assessment to deliver the most effective but least aggressive treatment. In thyroid cancer surgery, for instance, injuries to structures outside the thyroid gland, such as the recurrent laryngeal nerve in 2-5% of surgeries or the parathyroid glands in 5-10% of surgeries, negatively affect quality of life more than loss of the expendable thyroid gland. Furthermore, the risks associated with radioiodine ablation may outweigh the risks of persistent or recurrent disease and disease-specific mortality. Improvement in the health-related quality of life of survivors of follicular cell-derived thyroid cancer, which is decreased despite the generally favourable outcome, hinges on early tumour detection and minimization of treatment-related sequelae. Future opportunities include more widespread adoption of molecular and clinical risk stratification and identification of actionable targets for individualized therapies.

Adiposity and risk of thyroid cancer: a systematic review and meta-analysis

Thyroid cancer incidence has increased rapidly over time, as has obesity prevalence. A link between the two appears plausible, but the relation of adiposity to thyroid cancer remains incompletely understood. We performed a meta-analysis of adiposity measures and thyroid cancer using studies identified through October 2014. Twenty-one articles yielded data on 12,199 thyroid cancer cases. We found a statistically significant 25% greater risk of thyroid cancer in overweight individuals and a 55% greater thyroid cancer risk in obese individuals as compared with their normal-weight peers. Each 5-unit increase in body mass index (BMI), 5 kg increase in weight, 5 cm increase in waist or hip circumference and 0.1-unit increase in waist-to-hip ratio were associated with 30%, 5%, 5% and 14% greater risks of thyroid cancer, respectively. When evaluated by histologic type, obesity was significantly positively related to papillary, follicular and anaplastic thyroid cancers, whereas it revealed an inverse association with medullary thyroid cancer. Both general and abdominal adiposity are positively associated with thyroid cancer. However, relations with BMI vary importantly by tumour histologic type.

Anthropometric Risk Factors for Differentiated Thyroid Cancer in Young Men and Women From Eastern France: A Case-Control Study

The incidence of thyroid cancer has risen over the past decade, along with a rise in obesity. We studied the role of anthropometric risk factors for differentiated thyroid cancer at the time of diagnosis and at age 20 years in a case-control study conducted in eastern France between 2005 and 2010. The study included 761 adults diagnosed with differentiated thyroid cancer before 35 years of age between 2002 and 2006. They were matched with 825 controls from the general population. Odds ratios were calculated using conditional logistic regression models and were reported for all participants, those with papillary cancer only, and women only. The risk of thyroid cancer was higher for participants with a high body surface area (BSA), great height, or excess weight and for women with a high body fat percentage. Conversely, no significant association was found between body mass index and the risk of thyroid cancer. In the present study, we provide further evidence of the role of BSA and excess weight in the risk of thyroid cancer. These epidemiologic observations should be confirmed by further exploration of the biological mechanisms responsible for the associations of obesity and BSA with thyroid cancer.

Thyroid volume and its relation to anthropometric measures in a healthy cuban population

OBJECTIVES

The aim of this study was to describe the thyroid volume in healthy adults by ultrasound and to correlate this volume with some anthropometric measures and other differentiated thyroid cancer risk factors.

STUDY DESIGN

Thyroid volume and anthropometric measures were recorded in a sample of 100 healthy adults, including 21 men and 79 women aged 18-50 years, living in a non-iodine-deficient area of Havana city.

RESULTS

The average thyroid volume was 6.6 ± 0.26 ml; it was higher in men (7.3 ml) than in women (6.4 ml; p = 0.15). In the univariate analysis, thyroid volume was correlated with all anthropometric measures, but in the multivariate analysis, body surface area was found to be the only significant anthropometric parameter. Thyroid volume was also higher in current or former smokers and in persons with blood group AB or B.

CONCLUSION

Specific reference values of thyroid volume as a function of body surface area could be used for evaluating thyroid volume in clinical practice. The relation between body surface area and thyroid volume is coherent with what is known about the relation of thyroid volume to thyroid cancer risk, but the same is not true about the relation between thyroid volume and smoking habit.

Thyroglobulin test at 3 weeks after surgery in well-differentiated thyroid cancer and its predictive value: the role of endocrine–metabolic status

Aim & methods: The present pilot study included 50 differentiated thyroid cancer (DTC) patients (mean age: 45.8 ± 1.8 years, range: 18–73 years) who were followed after surgery for in average 30.0 ± 2.6 months. All patients were subdivided into two groups as having either <2 ng/ml or ≥2 ng/ml blood thyroglobulin level 3 weeks after the operation (3-WTT). Results: Subsequent tumor progression was revealed more often in patients with higher thyroglobulinemia (≥2 ng/ml) in both low- and high-risk DTC groups. Patients with high-risk DTC and 3-week thyroglobulin levels ≥2 ng/ml were more likely to have a higher pre-surgical thyrotropin (TSH) levels. On the contrary, patients with low-risk DTC and 3-week thyroglobulin level ≥2 ng/ml demonstrated tendency to higher preoperative serum insulin levels and higher BMI. Conclusion: These differential findings could suggest that, whereas maximal suppression of TSH is reasonable in high-risk DTC patients, in low-risk DTC patients, for whom this is not justified, a moderate TSH suppression supplemented by multivalent drugs, such as antidiabetic biguanide metformin, could be advised.