Anthropometric factors in differentiated thyroid cancer in French Polynesia: a case–control study

Assessment of Differentiated Thyroid Carcinomas in French Polynesia After Atmospheric Nuclear Tests Performed by France

Importance

Due to the amount of iodine 131 released in nuclear tests and its active uptake by the thyroid, differentiated thyroid carcinoma (DTC) is the most serious health risk for the population living near sites of nuclear tests. Whether low doses to the thyroid from nuclear fallout are associated with increased risk of thyroid cancer remains a controversial issue in medicine and public health, and a misunderstanding of this issue may be associated with overdiagnosis of DTCs.

Design, Setting, and Participants

This case-control study was conducted by extending a case-control study published in 2010 that included DTCs diagnosed between 1984 and 2003 by adding DTCs diagnosed between 2004 and 2016 and improving the dose assessment methodology. Data on 41 atmospheric nuclear tests conducted by France between 1966 and 1974 in French Polynesia (FP) were assessed from original internal radiation-protection reports, which the French military declassified in 2013 and which included measurements in soil, air, water, milk, and food in all FP archipelagos. These original reports led to an upward reassessment of the nuclear fallout from the tests and a doubling of estimates of the mean thyroid radiation dose received by inhabitants from 2 mGy to nearly 5 mGy. Included patients were diagnosed from 1984 to 2016 with DTC at age 55 years or younger and were born in and resided in FP at diagnosis; 395 of 457 eligible cases were included, and up to 2 controls per case nearest by birthdate and matched on sex were identified from the FP birth registry. Data were analyzed from March 2019 through October 2021.

Exposure

The radiation dose to the thyroid gland was estimated using recently declassified original radiation-protection service reports, meteorological reports, self-reported lifestyle information, and group interviews of key informants and female individuals who had children at the time of these tests.

Main Outcomes and Measures

The lifetime risk of DTC based on Biological Effects of Ionizing Radiation (BEIR) VII models was estimated.

Results

A total of 395 DTC cases (336 females [85.1%]; mean [SD] age at end of follow-up, 43.6 [12.9] years) and 555 controls (473 females [85.2%]; mean [SD] age at end of follow-up, 42.3 [12.5] years) were included. No association was found between thyroid radiation dose received before age 15 years and risk of DTC (excess relative risk [ERR] per milligray, 0.04; 95% CI, -0.09 to 0.17; P = .27). When excluding unifocal noninvasive microcarcinomas, the dose response was significant (ERR per milligray, 0.09; 95% CI, -0.03 to 0.02; P = .02), but several incoherencies with the results of the initial study reduce the credibility of this result. The lifetime risk for the entire FP population was 29 cases of DTC (95% CI, 8-97 cases), or 2.3% (95% CI, 0.6%-7.7%) of 1524 sporadic DTC cases in this population.

Conclusions and Relevance

This case-control study found that French nuclear tests were associated with an increase in lifetime risk of PTC in FP residents of 29 cases of PTC. This finding suggests that the number of thyroid cancer cases and the true order of magnitude of health outcomes associated with these nuclear tests were small, which may reassure populations of this Pacific territory.

Accuracy of the 'CUT' Score for Assessing Malignancy in Bethesda 3 and 4 Thyroid Nodules in North American population: a retrospective study

BACKGROUND

The CUT score is a thyroid nodule malignancy risk assessment scoring system intended to guide surgeons in treating Bethesda 3 and 4 thyroid nodules. It is based on clinical (C) and ultrasonographic (U) features and a five-tiered (T) representing cytology.

PURPOSE

Our study aimed to assess the utility of the CUT score in predicting thyroid malignancy in the North American population. The main reason for creating this score is to reduce unnecessary surgeries on these challenging thyroid nodules.

MATERIALS AND METHODS

A retrospective record review study applied the CUT score to 219 Bethesda 3 and 4 thyroid nodules. A total of 203 Bethesda 3 and 16 Bethesda 4 nodules from patients treated between January 2015 and December 2019 at a single institution were assessed. A receiver operating characteristic (ROC) curve analysis was performed to evaluate the CUT diagnostic test. Binary logistic regression analysis was performed. Iteration of analysis was performed after stratification according to body mass index to assess CUT score accuracy in obese and non-obese patients.

RESULTS

Of 219 nodules analyzed, 148 were characterized as benign and 71 as malignant. Prevalence rates of malignancy were 29.6% (n = 60) and 68.8% (n = 11) in Bethesda 3 and 4 nodules, respectively. The mean CU (clinical, ultrasonography) score was 5.35 ± 1.38 in benign nodules versus 4.96 ± 1.5 in malignant nodules (p = 0.08). The area under the curve (AUC =0.433) for the association of CUT scores with nodule malignancy was not significant (p = 0.13). The CUT score was insignificant as a diagnostic test for nodule malignancy in obese (AUC =0.45; p = 0.72) and non-obese patients (AUC =0.39; p = 0.08).

CONCLUSION

The CUT score did not correlate with preoperative malignancy risk estimates in Bethesda 3 thyroid nodules and, therefore, may have limited utility as a predictor of malignancy in these thyroid nodules.

Multiethnic genome-wide association study of differentiated thyroid cancer in the EPITHYR consortium

Incidence of differentiated thyroid carcinoma (DTC) varies considerably between ethnic groups, with particularly high incidence rates in Pacific Islanders. DTC is one of the cancers with the highest familial risk suggesting a major role of genetic risk factors, but only few susceptibility loci were identified so far. In order to assess the contribution of known DTC susceptibility loci and to identify new ones, we conducted a multiethnic genome-wide association study (GWAS) in individuals of European ancestry and of Oceanian ancestry from Pacific Islands. Our study included 1554 cases/1973 controls of European ancestry and 301 cases/348 controls of Oceanian ancestry from seven population-based case-control studies participating to the EPITHYR consortium. All participants were genotyped using the OncoArray-500K Beadchip (Illumina). We confirmed the association with the known DTC susceptibility loci at 2q35, 8p12, 9q22.33 and 14q13.3 in the European ancestry population and suggested two novel signals at 1p31.3 and 16q23.2, which were associated with thyroid-stimulating hormone levels in previous GWAS. We additionally replicated an association with 5p15.33 reported previously in Chinese and European populations. Except at 1p31.3, all associations were in the same direction in the population of Oceanian ancestry. We also observed that the frequencies of risk alleles at 2q35, 5p15.33 and 16q23.2 were significantly higher in Oceanians than in Europeans. However, additional GWAS and epidemiological studies in Oceanian populations are needed to fully understand the highest incidence observed in these populations.

Gene network and biological pathways associated with susceptibility to differentiated thyroid carcinoma

Variants identified in earlier genome-wide association studies (GWAS) on differentiated thyroid carcinoma (DTC) explain about 10% of the overall estimated genetic contribution and could not provide complete insights into biological mechanisms involved in DTC susceptibility. Integrating systems biology information from model organisms, genome-wide expression data from tumor and matched normal tissue and GWAS data could help identifying DTC-associated genes, and pathways or functional networks in which they are involved. We performed data mining of GWAS data of the EPITHYR consortium (1551 cases and 1957 controls) using various pathways and protein-protein interaction (PPI) annotation databases and gene expression data from The Cancer Genome Atlas. We identified eight DTC-associated genes at known loci 2q35 (DIRC3), 8p12 (NRG1), 9q22 (FOXE1, TRMO, HEMGN, ANP32B, NANS) and 14q13 (MBIP). Using the EW_dmGWAS approach we found that gene networks related to glycogenolysis, glycogen metabolism, insulin metabolism and signal transduction pathways associated with muscle contraction were overrepresented with association signals (false discovery rate adjusted p-value < 0.05). Additionally, suggestive association of 21 KEGG and 75 REACTOME pathways with DTC indicate a link between DTC susceptibility and functions related to metabolism of cholesterol, amino sugar and nucleotide sugar metabolism, steroid biosynthesis, and downregulation of ERBB2 signaling pathways. Together, our results provide novel insights into biological mechanisms contributing to DTC risk.

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.

Fine-mapping of two differentiated thyroid carcinoma susceptibility loci at 2q35 and 8p12 in Europeans, Melanesians and Polynesians

Differentiated thyroid carcinoma (DTC) incidence is characterized by wide ethnic and geographic variations, with high incidence rates observed in Oceanian populations. Genome-wide association studies (GWAS) identified mainly four DTC susceptibility loci at 9q22.33, 14q13.3, 2q35 and 8p12. Here we performed fine-mapping of the 2q35 and 8p12 loci in the population of the EPITHYR consortium that includes Europeans, Melanesians and Polynesians to identify likely causal variants for DTC risk. We conducted a colocalization analysis using eQTLs data to determine the SNPs with the highest probability of causality. At 2q35, we highlighted rs16857609 located in DIRC3. This SNP has a high probability of causality in the three populations, and a significant association in Europeans (OR = 1.4, p = 1.9 x 10-10). It is also associated with expression of DIRC3 and of the nearby gene IGFBP5 in thyroid tumour cells. At 8p12, we identified rs7844425 which was significantly associated with DTC in Europeans (OR = 1.32, p = 7.6 x 10-8) and rs2439304, which was highlighted by the colocalization analysis but only moderately associated with DTC in our dataset (OR = 1.2, p = 0.001). These SNPs are linked to the expression of NRG1 in thyroid tissue. Hence, our study identified novel variants at 2q35 and 8p12 to be prioritized for further functional studies.

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.

Nutritional status and follicular-derived thyroid cancer: An update

The incidence of differentiated thyroid cancer has been increasing in the last decades all over the world. Such a steady growth cannot be entirely attributable to more intensive thyroid nodule screening and more sensitive diagnostic procedures. Several environmental factors have changed with sufficient rapidity in the same time frame and may represent credible candidates for this increase. They include modified iodine intake, lifestyle-associated risk factors, exposure to various toxic compounds, pollutants and xenobiotics, nutritional deficiencies, eating habits and comorbidities. Foremost, nutritional patterns have gained high interest as possible promoters and modifiable risk factors for thyroid cancer in recent years. The aim of this narrative review is to focus on the relationship between thyroid cancer and nutritional factors, dietary habits and obesity. Low iodine intake has been associated to increased risk of thyroid cancer, favoring the development of more aggressive histotypes. Moreover, correction of iodine deficiency can shift thyroid cancer subtypes toward less aggressive forms, without affecting the overall risk for cancer. Actually, evidence regarding the association between selenium and vitamin D deficiency and thyroid cancer is very limited, despite their well-known anti-cancer potentials, and the clinical usefulness of their supplementation is still uncertain in this setting. Albeit the relationship between single foods and thyroid cancer is difficult to examine, fish and iodine-rich foods, vegetables, and fruits might exert protective effects on thyroid cancer risk. Conversely, no clear association has been found for other foods to date. Lastly, a clear association between obesity and the risk of thyroid cancer, with more aggressive behavior, seems to emerge from most studies, likely involving variations in thyroid function and chronic inflammation mediated by cytokines, insulin, leptin and adiponectins. Although no definite association between dietary factors and thyroid cancer has been firmly established so far, some nutritional patterns, together with excessive weight, seem to play a relevant role in thyroid cancer carcinogenesis as well as in its severity and aggressiveness. These effects may play an additive role to the well-established one exerted by environmental carcinogens, such as pollutants and radiation exposure.

Thyroid Cancer after Exposure to Radioiodine in Childhood and Adolescence: 131I-Related Risk and the Role of Selected Host and Environmental Factors

In this study, we expanded on a previously published population-based case-control study on subjects exposed to iodine-131 (131I) from Chernobyl fallout at age ≤18 years using improved individual 131I absorbed thyroid doses. We further studied the impact of iodine deficiency and other selected host risk factors on 131I-related thyroid cancer risk after childhood exposure. We included 298 thyroid cancer cases and 1934 matched controls from the most contaminated regions of Belarus and the Russian Federation. We performed statistical analysis using conditional logistic regression models. We found a statistically significant linear quadratic dose-effect association between thyroid cancer and 131I thyroid dose in the range up to 5 grays (Gy). Self-reported personal history of benign nodules, any thyroid disease except thyroid cancer, family history of thyroid cancer, increased body mass index, and deficient stable iodine status at the time of the accident were statistically significant risk factors (p < 0.05 for each factor) for thyroid cancer after adjustment for thyroid 131I dose effect. Subjects who received stable iodine supplementation in the years after the accident had a significantly lower 131I-related risk of thyroid cancer. Our findings are important for thyroid cancer prevention, and for further improvement of medical surveillance in the affected populations.

Healthcare expenditures among community-dwelling adults with thyroid cancer in the United States: A propensity score matched analysis

Objective

This study assessed the excess healthcare expenditures and factors associated with it among community-dwelling adults with thyroid cancer compared to non-cancer controls in the United States.

Method

A retrospective, cross-sectional, matched case-control study design was used by pooling multiple years of Medical Expenditure Panel Survey (MEPS) data (2002–2012). The eligible study sample comprised of adults (age ≥18 years), who were alive during the calendar year and reported positive healthcare expenditure. The case group consisted of adults with thyroid cancer only while the control group consisted of adults who did not have any form of cancer. Total and subtypes of mean annual healthcare expenditures comprised the main study outcome. We also calculated the total and subtypes of out-of-pocket (OOP) expenditures as well as OOP as a percentage of household income. Ordinary Least Square (OLS) regressions on log-transformed expenditures were conducted to elucidate the influence of different factors on healthcare expenditures among adults with thyroid cancer.

Results

The yearly average total healthcare expenditures among adults with thyroid cancer was significantly higher compared to propensity score matched controls ($9,585 vs. $5,830, p < 0.001). Similar observations were found in terms of inpatient, and outpatient expenditures. Functional status as well as comorbid conditions were significantly associated with excess expenditures. The yearly average total OOP expenditure for adults with thyroid cancer was significantly higher compared to matched controls ($1,425 vs. $974, p < 0.001), with major differences observed in inpatient OOP ($178 vs. $24, p = 0.003), outpatient OOP ($435vs. $256, p < 0.001), and prescription OOP ($554 vs. $423, p < 0.001) expenditures. There was a significant (p < 0.001) difference between the average OOP as a percentage of household income between adults with thyroid cancer (Mean: 7.54%, S.E: 1.52%) and matched controls (Mean: 5.80%, S.E: 0.47%).

Conclusions

Our findings suggest that holistic care approach could be helpful to significantly reduce the economic burden in this population. Viable strategies such as limits on OOP costs are required to minimize this high OOP burden among cancer survivors and their families.

Body fatness at a young age and risks of eight types of cancer: systematic review and meta-analysis of observational studies

The associations between body fatness at a young age (childhood, adolescence and young adulthood; age ≤ 30 years) and diffuse large B-cell lymphoma (DLBCL), oesophageal adenocarcinoma, gastric cardia cancer, hepatocellular carcinoma, multiple myeloma, pancreatic cancer, renal cell cancer and thyroid cancer remain inconclusive. We performed a comprehensive systematic literature review and meta-analysis of observational studies to clarify the associations between body fatness at a young age and the risks of these cancers. PubMed and Web of Science databases were searched for relevant observational studies. Fifty-six articles yielded data on 27,559 cancer cases, including 3,170 DLBCL, 1,491 oesophageal adenocarcinoma, 1,103 gastric cardia cancer, 1,067 hepatocellular carcinoma, 3,090 multiple myeloma, 7,220 pancreatic cancer, 6,212 renal cell cancer and 4,206 thyroid cancer cases. Each 5 kg m^-2 increase in body mass index at a young age was positively associated with DLBCL (relative risk [RR] 1.21, 95% confidence interval [CI] 1.09, 1.35), oesophageal adenocarcinoma (RR 1.88, 95% CI 1.37, 2.57), gastric cardia cancer (RR 1.59, 95% CI 1.15, 2.21), hepatocellular carcinoma (RR 1.31, 95% CI 1.13, 1.51), multiple myeloma (RR 1.23, 95% CI 1.15, 1.30), pancreatic cancer (RR 1.17, 95% CI 1.11, 1.24), renal cell cancer (RR 1.22, 95% CI 1.16, 1.28) and thyroid cancer (RR 1.12, 95% CI 1.07, 1.17). In summary, higher body fatness at a young age increases the risks of developing various types of cancer later in life. Prevention of overweight and obesity in children, adolescents and young adults should therefore be emphasized to reverse the obesity epidemic and thereby avoid further increases in the burden of cancer attributed to excess body fatness.

The association between thyroid cancer and insulin resistance, metabolic syndrome and its components: A systematic review and meta-analysis

BACKGROUND

Thyroid cancer is rapidly increasing in incidence worldwide in the past several decades, same as the incidence of metabolic syndrome. We performed a system review and meta-analysis of the association between metabolic syndrome, its components and insulin resistance and thyroid cancer incidence.

METHODS

We searched several computer-assisted databases PUBMED, EMBASE and ISI Web of Science to identify studies published before 31st January 2018. Every study must report either risk estimates of thyroid cancer incidence with 95% confidence interval (CI) or related data can speculate. Two investigators independently identified eligible studies and extracted data. Evaluating the summaries of relative risk estimates use both fixed and random effects methods.

RESULTS

We found 42 articles met the inclusion criteria of this review. There is an increased risk for thyroid cancer for patients with insulin resistance (relative risk [RR] = 1.59, 95%confidence interval [CI] = 1.12-2.27, P = 0.01), dysglycemia (RR = 1.40, 95%CI = 1.15-1.70,P < 0.001), high BMI (RR = 1.35,95%CI = 1.23-1.48,P < 0.001) and hypertension(RR = 1.34,95%CI = 1.22-1.47, p < 0.001). However, patients with dyslipidemia, both total cholesterol (RR = 1.09, 95%CI = 0.98-1.21, P = 0.13) and triglyceride (RR = 1.01, 95%CI = 0.91-1.12, P = 0.82) was not associated with thyroid cancer.

CONCLUSIONS

Our meta-analysis showed Insulin Resistance, dysglycemia, high BMI and hypertension significantly increased the thyroid cancer risk. These results may help identify people with high risk of thyroid cancer and change to healthy life style.

The risk of thyroid cancer and obesity: A nationwide population-based study using the Korea National Health Insurance Corporation cohort database

INTRODUCTION

In recent years, the incidence of thyroid cancer and obesity has increased rapidly worldwide. Many studies have been conducted on the relationship between thyroid cancer and obesity; however, the potential mechanisms are not well understood, and few studies have been performed in Asia. This study aimed to identify the relationship between the risk of thyroid cancer and obesity in the Korean population based on a large cohort of data.

METHOD

We analyzed clinical data from a total of 351,402 individuals (males: 181,709, females: 169,693) aged over 20 years who received medical examinations arranged by the national insurance program from 2003 to 2008. Newly diagnosed thyroid cancer was identified using insurance claims data. The median follow-up duration was 7.01 years.

RESULTS

The mean body mass index (BMI) of the subjects was 23.6 ± 3.2 kg/m² (males, 24 ± 3; females, 23.1 ± 3.3). A total of 3308 individuals (0.94%) developed thyroid cancer during the study period. The risk of thyroid cancer was higher with increasing BMI in both men and women. Hazard ratios (95% confidence interval) for obese (25-29.9 kg/m²) and extremely obese (≥30 kg/m²) groups were 1.23 (1.13-1.34) and 1.26 (1.02-1.50), respectively, compared to the normal group (18.5-22.9 kg/m2). In particular, the association between the risk of thyroid cancer and BMI was more remarkable in the male group than female group.

CONCLUSION

Our findings show that higher BMI is positively associated with the risk of thyroid cancer. Furthermore, this study supports the positive association between obesity and the increased incidence of thyroid cancer.

Pretreatment BMI Is Associated with Aggressive Clinicopathological Features of Papillary Thyroid Carcinoma: A Multicenter Study

OBJECTIVES

The aim of the present study was to analyze the association between pretreatment body mass index (BMI) and the aggressiveness of papillary thyroid carcinoma (PTC) along with its clinical outcomes in a Chinese population with BMI classification for Asians.

METHODS

A retrospective, observational study was conducted on patients from two teaching hospitals in China. 1622 classical PTC patients were categorized into four groups according to BMI.

RESULTS

We found that increased BMI was associated with extrathyroidal extension, multifocality, the presence of lymph node (LN) metastasis, and advancing TNM stage in PTC patients. Furthermore, compared to patients with normal weight, those in the overweight and obese group exhibited a significantly increased risk of extrathyroidal extension, multifocality, cervical LN metastasis, and advanced TNM stage. 40 and 37 patients experienced persistent and recurrent disease, respectively. No differences regarding persistent disease or recurrence were observed among the BMI groups.

CONCLUSION

A higher pretreatment BMI has been strongly associated with aggressive features of PTC according to the BMI classification for Asians. Obesity was not found to be associated with a greater risk of recurrence.

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.

Obesity Does Not Modify the Risk of Differentiated Thyroid Cancer in a Cytological Series of Thyroid Nodules

BACKGROUND

A possible impact of obesity on the risk of thyroid cancer has been postulated in some studies, but it remains controversial.

OBJECTIVE

To investigate the association between obesity and differentiated thyroid carcinoma in a population of unselected patients subjected to fine-needle aspiration cytology (FNAC) for thyroid nodules.

METHODS

We retrospectively evaluated the results of FNAC of thyroid nodules in 4,849 patients (3,809 females and 1,040 males; mean age 55.9 ± 14.1 years). Patients were stratified according to their body mass index (BMI). There were 1,876 (38.7%) normal-weight patients (BMI 18-24.9), 1,758 (36.2%) overweight (BMI 25-29.9), 662 (13.7%) grade 1 obese (BMI 30-34.9), 310 (6.4%) grade 2 obese (BMI 35-39.9) and 243 (5.0%) grade 3 obese (BMI >40).

RESULTS

The prevalence of suspicious or malignant nodules (Thy4/Thy5) did not differ across the 5 BMI groups, i.e. it was 6.8% in normal-weight patients, 6.3% in overweight patients, 6.3% in grade 1 obese patients, 4.0% in grade 2 obese patients and 4.2% in grade 3 obese patients (p = 0.29). The prevalence of Thy4/Thy5 nodules did not differ when males and females were evaluated separately (p = 0.22 and p = 0.12, respectively). A significant, lower rate of Thy4/5 cytology was observed in female patients with grade 2-3 obesity (odds ratio 0.51; 95% confidence interval 0.284-0.920; p = 0.009).

CONCLUSIONS

The results of this study, in a retrospective series of patients with thyroid nodules, do not confirm previous findings reporting an association between obesity and differentiated thyroid carcinoma. Thus, obese patients with nodular thyroid disease should be managed the same as normal-weight patients.

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.

Relationship of anthropometric measurements to thyroid nodules in a Chinese population

OBJECTIVE

Previous studies have found that overweight and obesity are related to numerous diseases, including thyroid cancer and thyroid volume. This study evaluates the relationship between body size and the presence of thyroid nodules in a Chinese population.

METHODS

A total of 6793 adults and 2410 children who underwent thyroid ultrasonography were recruited in this cross-sectional study in Hangzhou, Zhejiang Province, China, from March to October, 2010. Sociodemographic characteristics and potential risk factors of thyroid nodules were collected by questionnaire. Height and weight were measured using standard protocols. Associations of height, weight, body mass index (BMI) and body surface area (BSA) with the presence of thyroid nodules were evaluated using multiple logistic regression models.

RESULTS

After adjustment for potential risk factors, an increased risk of thyroid nodule incidence was associated with height (OR 1.15, 95% CI 1.02 to 1.30), weight (OR 1.40, 95% CI 1.24 to 1.58), BMI (OR 1.26, 95% CI 1.11 to 1.42) and BSA (OR 1.43, 95% CI 1.27 to 1.62) in all adults, but most obviously in women. In children, similar associations were observed between risk of thyroid nodule incidence and weight, BMI and BSA, but not height. BSA was the measurement most significantly associated with thyroid nodules in both adults and children.

CONCLUSIONS

This study identified that the presence of thyroid nodules was positively associated with weight, height, BMI and BSA in both women and girls. It suggests that tall, obese individuals have increased susceptibility to thyroid nodules.

TRIAL REGISTRATION NUMBER

NCT01838629.

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.

The influence of body mass index on the diagnostic performance of pre-operative staging ultrasound in papillary thyroid carcinoma

OBJECTIVE

The aim of this study was to investigate the diagnostic performance of pre-operative staging ultrasound (US) according to body mass index (BMI) in patients with papillary thyroid carcinoma (PTC) PATIENTS AND METHODS: This retrospective study included 625 patients with PTC who underwent pre-operative staging US and surgical excision at a referral centre between December 2012 and April 2013. Four experienced radiologists prospectively evaluated the extent of primary tumours, multifocality and the presence of lymph node metastasis. Patients were grouped according to BMI (normal <25; overweight 25 ≤ and <30; obese ≥30, or nonobese <30; obese ≥30 kg/m(2) ). Diagnostic performances of pre-operative staging US (sensitivity, specificity, positive predictive value, negative predictive value and accuracy) were compared according to BMI based on pathologic findings of surgical specimens.

RESULTS

Pre-operative staging US in the obese group (BMI ≥30 kg/m(2) ) showed a significantly lower negative predictive value and accuracy in the detection of central lymph node metastasis (P = 0·010 and P = 0·025, respectively) than in the nonobese (BMI <30 kg/m(2) ) group. However, there were no significant differences in the diagnostic performance of pre-operative staging US for extrathyroidal extension, bilateral multifocality and lateral lymph node metastasis in analyses using the two (nonobese vs obese) and three BMI (normal vs overweight vs obese) groups, respectively.

CONCLUSION

Obesity (BMI ≥30 kg/m(2) ) may affect the pre-operative US staging of central lymph node metastasis in patients with PTC.

Higher body mass index and larger waist circumference may be predictors of thyroid carcinoma in patients with Hürthle-cell lesion/neoplasm fine-needle aspiration diagnosis

OBJECTIVE

High body mass index (BMI) has been found to be associated with raised thyroid cancer risk, particularly in women. We examined the associations for BMI and waist circumference (WC) with thyroid cancer risk among women with Hürthle-cell lesion/neoplasm (HLN) on fine-needle aspiration biopsy (FNAB) with the hypothesis that BMI and WC could guide the management of these challenging indeterminate lesions.

METHODS

This cross-sectional study included 224 women with HLN who underwent thyroidectomy. In all patients, TSH and thyroid auto-antibodies were evaluated, and thyroid nodule features were recorded. Patients were grouped according to BMI (<30 or ≥30 kg/m(2)) and WC (<88 or ≥88 cm). Relationships of thyroid cancer with BMI and WC were assessed using logistic regression analysis.

RESULTS

Mean weight, BMI (31·26 ± 5·1 vs 26·47 ± 5·9, P < 0·001), WC (98·23 ± 7·6 vs 86·18 ± 11, P = 0·001), and proportion of patients with high BMI (≥30 kg/m(2)) (65·9 vs 33·8%, P < 0·001) or large WC (≥88 cm) (84·1 vs 47·9%, P < 0·001) were significantly higher in malignant group compared to benign group. In regression analysis, BMI and WC significantly associated with existence of malignancy. Malignancy risk was 3·819-fold higher (95% CI: 2·068-7·054) in BMI≥30 kg/m(2) group compared to BMI<30 kg/m(2), which was independent of TSH and age. Large WC was also associated with increased risk (OR = 5·593, 95% CI: 2·736-11·434). Baseline tumour characteristics were similar according to BMI and WC groups.

CONCLUSIONS

A great BMI and large WC were associated with higher thyroid cancer risk in patients with FNAB diagnosis of HLN. Further studies are needed to use BMI or WC in the management of patients with HLN.

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.

Adolescent and mid-life diet and subsequent risk of thyroid cancer in the NIH-AARP diet and health study

Although thyroid cancer is suspected to have a nutritional etiology, prospective studies examining the relationship between diet and thyroid cancer are lacking. During 1996-1997, NIH-AARP Diet and Health Study participants, ages 51-72 years, completed a 37-item food frequency questionnaire about diet at ages 12-13 years (adolescence) and 10 years before baseline (mid-life). Over a median 10 years of follow-up, 325 individuals (143 men and 182 women) were diagnosed with thyroid cancer. Multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated for intakes of foods and food groups comparing the highest to the lowest quartiles. Adolescent intakes of chicken/turkey (HR = 1.59, 95% CI: 0.97-2.60; ptrend  < 0.01) and sweet baked goods (HR = 1.59, 95% CI: 1.09-2.34; ptrend  = 0.04) were positively associated with thyroid cancer risk, while intake of butter/margarine was inversely associated with risk (HR = 0.64, 95% CI: 0.44-0.91; ptrend  < 0.02). Similar to adolescent diet, mid-life intake of sweet baked goods was nonsignificantly associated with an increased risk of thyroid cancer (HR = 1.39, 95% CI: 0.96-2.00; ptrend  = 0.11), but intake of butter/margarine was inversely associated with risk (HR = 0.66, 95% CI: 0.46-0.95; ptrend  = 0.03). Among men, higher adolescent consumption of canned tuna was positively associated with risk of thyroid cancer (HR = 1.69, 95% CI: 1.01-2.83; ptrend  = 0.03), and greater mid-life intake of broccoli was associated with a twofold increased risk (HR = 2.13, 95% CI: 1.13-3.99; ptrend  < 0.01). This large prospective study suggests that several components of the adolescent and mid-life diet, including iodine-rich foods and goitrogens, may influence thyroid cancer risk.

Common variants at 9q22.33, 14q13.3, and ATM loci, and risk of differentiated thyroid cancer in the French Polynesian population

BACKGROUND

French Polynesia has one of the highest incidence rates of thyroid cancer worldwide. Relationships with the atmospheric nuclear weapons tests and other environmental, biological, or behavioral factors have already been reported, but genetic susceptibility has yet to be investigated. We assessed the contribution of polymorphisms at the 9q22.33 and 14q13.3 loci identified by GWAS, and within the DNA repair gene ATM, to the risk of differentiated thyroid cancer (DTC) in 177 cases and 275 matched controls from the native population.

PRINCIPAL FINDINGS

For the GWAS SNP rs965513 near FOXE1, an association was found between genotypes G/A and A/A, and risk of DTC. A multiplicative effect of allele A was even noted. An excess risk was also observed in individuals carrying two long alleles of the poly-alanine tract expansion in FOXE1, while no association was observed with rs1867277 falling in the promoter region of the gene. In contrast, the GWAS SNP rs944289 (NKX2-1) did not show any significant association. Although the missense substitution D1853N (rs1801516) in ATM was rare in the population, carriers of the minor allele (A) also showed an excess risk. The relationships between these five polymorphisms and the risk of DTC were not contingent on the body surface area, body mass index, ethnicity or dietary iodine intake. However, an interaction was evidenced between the thyroid radiation dose and rs944289.

SIGNIFICANCE

A clear link could not be established between the high incidence in French Polynesia and the studied polymorphisms, involved in susceptibility to DTC in other populations. Important variation in allele frequencies was observed in the Polynesian population as compared to the European populations. For FOXE1 rs965513, the direction of association and the effect size was similar to that observed in other populations, whereas for ATM rs1801516, the minor allele was associated to an increased risk in the Polynesian population and with a decreased risk in the European population.

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.

Higher body mass index may be a predictor of extrathyroidal extension in patients with papillary thyroid microcarcinoma

Recently, higher body mass index (BMI) has been associated with aggressive pathologic features of papillary thyroid carcinoma. The aim of this study was to clarify the relationship between BMI and aggressive pathologic features of papillary thyroid microcarcinoma (PTMC) and to evaluate whether the BMI can be a prognostic factor of PTMC. This retrospective study included 612 PTMC patients who underwent surgical excision at a referral center between April 2006 and December 2007. Patients were grouped according to BMI (<25 or ≥25 kg/m2). Multivariable logistic regression analysis was performed to determine independent predictors of aggressive pathologic features (advanced stage, extrathyroidal extension, and lymph node metastasis), with adjustment for age, gender, tumor size, multifocality, thyroid stimulating hormone (TSH) level, and BMI (value/group). PTMC patients with a BMI≥25 kg/m2 showed significantly higher prevalences of extrathyroidal extension, advanced pathologic TNM stage, and male gender, compared to those of patients with a BMI<25 kg/m2. Lymph node metastasis and mean TSH level were not significantly different between the two BMI subgroups. In multivariable analysis, the BMI≥25 kg/m2 group was positively associated with the presence of extrathyroidal extension (adjusted odds ratio 1.49, P=0.05). Higher BMI was associated with extrathyroidal extension in PTMC patients. This study suggests that the BMI could be considered as a prognostic factor for predicting the presence of extrathyroidal extension and it may help decide the appropriate surgical extent for PTMC patients.

Obesity and risk of thyroid cancer: evidence from a meta-analysis of 21 observational studies

BACKGROUND

Several studies have evaluated the association between obesity and thyroid cancer risk. However, the results remain uncertain. In this study, we conducted a meta-analysis to assess the association between obesity and thyroid cancer risk.

MATERIAL/METHODS

Published literature from PubMed, EMBASE, Springer Link, Ovid, Chinese Wanfang Data Knowledge Service Platform, Chinese National Knowledge Infrastructure (CNKI), and Chinese Biology Medicine (CBM) were retrieved before 10 August 2014. We included all studies that reported adjusted risk ratios (RRs), hazard ratios (HRs) or odds ratios (ORs), and 95% confidence intervals (CIs) of thyroid cancer risk.

RESULTS

Thirty-two studies (n=12 620 676) were included in this meta-analysis. Obesity was associated with a significantly increased risk of thyroid cancer (adjusted RR=1.33; 95% CI, 1.24-1.42; I2=25%). In the subgroup analysis by study type, increased risk of thyroid cancer was found in cohort studies and case-control studies. In subgroup analysis by sex, both obese men and women were at significantly greater risk of thyroid cancer than non-obese subjects. When stratified by ethnicity, significantly elevated risk was observed in Caucasians and in Asians. In the age subgroup analysis, both young and old populations showed increased thyroid cancer risk. Subgroup analysis on smoking status showed that increased thyroid cancer risks were found in smokers and in non-smokers. In the histology subgroup analyses, increased risks of papillary thyroid cancer, follicular thyroid cancer, and anaplastic thyroid cancer were observed. However, obesity was associated with decreased risk of medullary thyroid cancer.

CONCLUSIONS

Our results indicate that obesity is associated with an increased thyroid cancer risk, except medullary thyroid cancer.

Menstrual and reproductive factors in the risk of differentiated thyroid carcinoma in young women in France: a population-based case-control study

The incidence of thyroid cancer has increased in eastern Europe since the Chernobyl nuclear power plant accident. Although the radioactive fallout was much less severe and the thyroid radiation dose was much lower in France, a case-control study was initiated in eastern France. The present study included 633 young women who were diagnosed with differentiated thyroid cancer before 35 years of age between 2002 and 2006 and matched with 677 controls. Face-to-face interviews were conducted from 2005 to 2010. Odds ratios were calculated using conditional logistic regressions and were reported in the total group and by histopathological type of cancer ("only papillary" and "excluding microcarcinomas"). The risk of thyroid cancer was higher in women who had a higher number of pregnancies, used a lactation suppressant, or had early menarche. Conversely, breastfeeding, oral contraceptive use, and late age at first pregnancy were associated with a lower risk of thyroid cancer. No association was observed between thyroid cancer and having irregular menstrual cycle, undergoing treatment for menstrual cycle regularity shortly after menarche, having a cessation of menstruation, use of another contraceptive, history of miscarriage or abortion for the first pregnancy, or having had gestational diabetes. This study confirms the role of hormonal and reproductive factors in thyroid cancer, and our results support the fact that exposure to estrogens increases thyroid cancer risk.

Insights into genetic and epigenetic determinants with impact on vitamin d signaling and cancer association studies: the case of thyroid cancer

Vitamin D is a key regulator of calcium metabolism and has been implicated as a cancer preventive agent. However, clinical studies have revealed conflicting results on its cancer preventive properties, attributed in part to multiple metabolic and regulatory factors susceptible to affect individual responses to exogenous vitamin D. Vitamin D is obtained from dietary sources and sun exposure, which depends on numerous parameters such as skin type, latitude, and lifestyle factors. Focusing on thyroid cancer (TC), we document that genetic and epigenetic determinants can greatly impact individual response to vitamin D and may outweigh the classical clinical correlative studies that focus on sun exposure/dietary intake factors. In particular, genetic determinants innate to host intrinsic metabolic pathways such as highly polymorphic cytochromes P450s responsible for the metabolic activation of vitamin D are expressed in many organs, including the thyroid gland and can impact vitamin D interaction with its nuclear receptor (VDR) in thyroid tissue. Moreover, downstream regulatory pathways in vitamin D signaling as well as VDR are also subject to wide genetic variability among human populations as shown by genome-wide studies. These genetic variations in multiple components of vitamin D pathways are critical determinants for the revaluation of the potential preventive and anticancer properties of vitamin D in TC.

Obesity and thyroid cancer

Many studies have provided observational data on the association of obesity and thyroid cancers, but only few of them propose mechanisms that would permit a better understanding of the causal molecular mechanisms of this association. Considering that there is an increasing incidence of both obesity and thyroid cancers, we need to summarize and link recent studies in order to characterize and understand the contribution of obesity-related factors that might affect thyroid cancer development and progression. Adipose tissue is involved in many vital processes, including insulin sensitivity, angiogenesis, regulation of energy balance, activation of the complement system, and responses such as inflammation. Although these processes have their own molecular pathways, they involve the same molecules through which obesity and adipose tissue might exert their roles in carcinogenesis, not only affecting MAPK and PI3K or even insulin pathways, but also recruiting local inflammatory responses that could result in disease formation and progression. This review describes five important issues that might explain the link between excessive weight and thyroid cancer: thyroid hormones, insulin resistance, adipokines, inflammation, and sexual hormones.

Obesity and the risk of papillary thyroid cancer: a pooled analysis of three case-control studies

BACKGROUND

There is a correlation between temporal trends of obesity prevalence and papillary thyroid cancer (PTC) incidence in the United States. Obesity is a well-recognized risk factor for many cancers, but there are few studies on the association between obesity and PTC risk. We investigated the association between anthropometric measurements and PTC risk using pooled individual data from three case-control populations.

METHODS

Height and weight information were obtained from three independent case-control studies, including 1917 patients with PTC (1360 women and 557 men) and 2127 cancer-free controls from the United States, Italy, and Germany. Body mass index (BMI), body fat percentage, and body surface area (BSA) were calculated. An unconditional logistic regression model was used to calculate odds ratios (ORs) and confidence intervals (CIs) with respect to risk of PTC, adjusted by age, sex, race/ethnicity, and study site.

RESULTS

In the pooled population, for both men and women, an increased risk of PTC was found to be associated with greater weight, BMI, body fat percentage, and BSA, whereas a reduced risk of PTC was associated with greater height, in the pooled population for both men and women. Compared with normal-weight subjects (BMI 18.5-24.9 kg/m2), the ORs for overweight (BMI 25-29.9 kg/m2) and obese (BMI≥30 kg/m2) subjects were 1.72 [CI 1.48-2.00] and 4.17 [CI 3.41-5.10] respectively. Compared with the lowest quartile of body fat percentage, the ORs for the highest quartile were 3.83 [CI 2.85-5.15] in women and 4.05 [CI 2.67-6.15] in men.

CONCLUSION

Anthropometric factors, especially BMI and body fat percentage, were significantly associated with increased risk of PTC. Future studies of anthropometric factors and PTC that incorporate intermediate factors, including adiposity and hormone biomarkers, are essential to help clarify potential mechanisms of the relationship.

The incidence of papillary thyroid carcinoma and outcomes in operative patients according to their body mass indices

BACKGROUND

The connection between high body mass index (BMI), risk of papillary thyroid carcinoma (PTC), and the aggressiveness of PTC is still debated. We aimed to establish the relationship between excess BMI and the risk of PTC in an operative population, and the impact of obesity on histopathologic aggressiveness of PTC and on the outcome of patients.

METHODS

All consecutive patients who underwent thyroid operation from June 2002 to December 2009 were reviewed in this retrospective study. BMI groupings were based on standardized categories: normal-weight, overweight, and obesity. We performed a total thyroidectomy with lymph node dissection in patients with preoperative or operative diagnosis of PTC. Radioiodine ablation was performed in every N1 patient, in case of tumor size greater than 10 mm, and if there was extrathyroidal invasion. During a median follow-up of 6.2 years, patients who were retreated by operation or (131)I were considered to have a persistent (<18 months of the initial operative treatment) or recurrent (≥ 18 months) disease.

RESULTS

Of 6,684 patients who had a thyroid gland resection, we identified 1,216 (18.2%) patients with PTC. Patients who were overweight or obese were not at greater risk of PTC than normal-weight subjects. Indications for operation or radioiodine therapy were similar in the three BMI groups. During follow-up, 86 patients (7.1%) experienced persistent (4.5%) or recurrent (2.5%) disease. When excluding micro-PTCs (≤ 10 mm), we found an association between recurrent or residual locoregional thyroid cancer and BMI: 18.7% in obese patients versus 8.5% if BMI <25 kg/m(2) and 9.8% if 25 ≥ BMI < 30 kg/m(2) (P = .03). This difference was clearly marked for persistence. When adjusted for other cofounder factors, we observed that BMI was an independent factor associated with the risk of postoperative locoregional event (odds ratio 3.8, 95% confidence interval 1.6-8.8), with sex, age, lymph node metastasis, and tumor bilaterality.

CONCLUSION

In macro-PTC, obese patients had an increased risk of developing a locoregional event during the follow-up, specifically a persistence of the disease. According to these results, overweight and obese patients with macro-PTC should be monitored more carefully for early detection of cancer persistence.

Obesity and thyroid cancer: a clinical update

BACKGROUND

In the last decade, significant contributions have been made to our knowledge on the connection between the thyroid and adipose tissue. Modern society is faced with climbing rates of obesity and metabolic syndrome, and there is accumulating evidence of an association between obesity and increased cancer risk. The aim of this review is to summarize clinical data on the association between thyroid cancer (TC) and obesity and briefly to present plausible hypotheses explaining this interplay.

SUMMARY

We performed a search on the PubMed database for studies published in English from 1980 to March 2013 using the terms "thyroid cancer," "obesity," and "body mass index." Although there is inconsistency among the clinical studies, it seems that overweight and obesity are related to a modestly increased TC risk. Various factors, such as sex, ethnicity, and body changes during certain life periods, for example adolescence, may influence the association between obesity and TC risk. There are preliminary data linking obesity with a less favorable clinicopathologic profile of TC. However, validation with larger multicenter studies is needed. The precise underlying mechanisms have not yet been elucidated, but the insulin-IGF axis and adipokines, such as leptin and adiponectin, might be implicated in the link between excess weight and TC.

CONCLUSIONS

Given the rising prevalence of TC and the development of obesity as an epidemic, it is important to clarify its connection with TC as well as the mediating pathways. However, unless this association is confirmed and causation proven, screening for TC in overweight and obese subjects-a rapidly increasing body of the general population-does not seem justified.

Childhood height and body mass index were associated with risk of adult thyroid cancer in a large cohort study

Taller stature and obesity in adulthood have been consistently associated with an increased risk of thyroid cancer, but few studies have investigated the role of childhood body size. Using data from a large prospective cohort, we examined associations for height and body mass index (BMI) at ages 7 to 13 years with risk of thyroid cancer in later life. The study population included 321,085 children from the Copenhagen School Health Records Register, born between 1930 and 1989 in Copenhagen, Denmark, with measurements of height and weight from 7 to 13 years of age. These data were linked with the Danish Cancer Registry to identify incident thyroid cancer cases (1968-2010). Hazard ratios (HR) and 95% confidence intervals (CI) were calculated for age- and sex-specific height and BMI SD scores (SDS) using proportional hazards models stratified by birth cohort and sex. During follow-up (median = 38.6 years), 171 women and 64 men were diagnosed with thyroid cancer. Both height and BMI were positively associated with thyroid cancer risk, and these associations were similar by age at measurement. Using age 10 as an example, HRs per 1 unit increase in SDS for height (~6-7 cm) and BMI (~1.5-2 kg/m(2)) were 1.22 (95% CI, 1.07-1.40) and 1.15 (95% CI, 1.00-1.34), respectively. These results, together with the relatively young ages at which thyroid cancers are diagnosed compared with other malignancies, suggest a potential link between early-life factors related to growth and body weight and thyroid carcinogenesis.

Obesity and thyroid cancer: epidemiologic associations and underlying mechanisms

The incidence of thyroid cancer has been rising over the past few decades along with a parallel increase in obesity. Observational studies have provided evidence for a potential association between the two. By contrast, clinical data for a link between type 2 diabetes mellitus, a condition strongly associated with obesity, and thyroid cancer are limited and largely not supportive of such an association. Obesity leads to hypoadiponectinemia, a pro-inflammatory state, and insulin resistance, which, in turn, leads to high circulating insulin and insulin-like growth factor-1 levels, thereby possibly increasing the risk for thyroid cancer. Thus, insulin resistance possibly plays a pivotal role in underlying the observed association between obesity and thyroid cancer, potentially leading to the development and/or progression of thyroid cancer, through its interconnections with other factors including insulin-like growth factor-1, adipocytokines/cytokines and thyroid-stimulating hormone. In this review, epidemiological and clinical evidence and potential mechanisms underlying the proposed association between obesity and thyroid cancer risk are reviewed. If the association between obesity and thyroid cancer demonstrated in observational studies proves to be causal, targeting obesity (and/or downstream mediators of risk) could be of importance in the prevention and management of thyroid cancer.

Overweight, obesity and thyroid cancer risk: a meta-analysis of cohort studies

OBJECTIVE

This meta-analysis examined the relationship between excess body weight or body mass index (BMI) and risk of thyroid cancer.

METHODS

PubMed(®), MEDLINE(®), EMBASE™ and Academic Search™ Premier databases were searched to identify cohort studies examining the effect of being overweight or obese on the risk of thyroid cancer.

RESULTS

The inclusion criteria were met by seven cohort studies (total number of thyroid cancer cases, 5154). The pooled relative risk (RR) of thyroid cancer was 1.13 (95% confidence interval [CI] 1.04, 1.22) for overweight. Obesity was also linked with increased thyroid cancer risk in males and females, the strength of the association increasing with increasing BMI. The combined RR of thyroid cancer was 1.18 (95% CI 1.11, 1.25) for excess body weight (overweight and obesity combined). Being overweight was associated with a significant increase in thyroid cancer risk among non-Asians, but not among Asians. Overweight, obesity and excess body weight were all associated with papillary thyroid carcinoma risk.

CONCLUSIONS

The association between overweight/obesity/excess body weight and thyroid cancer risk was confirmed.

Obesity and excess protein and carbohydrate consumption are risk factors for thyroid cancer

Conflicting data concerning the association between obesity and differentiated thyroid cancer (DTC) may be attributed to the lack of records showing dietary intake and inadequate evaluation of nutrient composition. We evaluated 115 DTC patients carefully paired with 103 healthy control individuals by using a structured questionnaire, including a 24-h recordatory during 3 days, to investigate calorie intake and macronutrient (proteins, carbohydrates, and lipids) composition of the diet. We observed that excess weight (body mass index > 25 kg/m(2)) increased individual susceptibility to DTC [odds ratio (OR) = 3.787; 95% confidence interval (CI) = 1.115-6.814; P < 0.0001). This augmented risk was evident in women (OR = 1.925; 95% CI = 1.110-3.338; P = 0.0259) but not in men (P = 0.3498). Excess calorie intake was more frequent in patients with DTC than in controls (OR = 5.890; 95% CI = 3.124-11.103; P < 0.0001), and both excess protein (OR = 4.601; 95% CI = 1.634-12.954; P = 0.0039) and carbohydrate (OR = 4.905; 95% CI = 2.593-9.278; P < 0.0001) consumption were associated with an increased risk of DTC, contrarily to lipid/fiber intake and physical activity (P = 0.894 and 0.5932, respectively). In conclusion, our data indicate that overweight and risk of DTC are associated with higher protein and carbohydrate consumption than the rates recommended by the World Health Organization. The nutritional orientation should be part of preventive strategy targets designed to combat the increasing incidence of both obesity and DTC.

Associations between body mass index and clinico-pathological characteristics of papillary thyroid cancer

OBJECTIVE

Epidemiological studies have demonstrated that excess weight increases the risk of thyroid cancer. However, the associations between excess weight and prognostic factors for thyroid cancer are uncertain. We evaluated the relationships between body mass index (BMI) and clinico-pathological features and outcomes of papillary thyroid cancer (PTC).

PATIENTS AND METHODS

Retrospective analysis of 2057 patients with PTC was performed. Patients were grouped according to BMI (underweight, normal weight, overweight and obesity)-based World Health Organization standardized categories. Logistic regression models were used to assess the relationships between BMI and clinico-pathological features of PTC. A Cox proportional hazards model was used to examine the association between BMI and disease recurrence.

RESULTS

A 5-kg/m(2) increase in BMI was associated with PTC tumours larger than 1 cm [odds ratio (OR) 1.31, P < 0.001], with microscopic extrathyroidal invasion (OR 1.23, P = 0.006), and with advanced tumour-node-metastasis (TNM) stage (OR, 1.30, P = 0.003), which is independent of confounding variables such as gender, age, serum TSH, total cholesterol and fasting glucose level. The multivariate-adjusted OR [95% confidence intervals (CI)] in the overweight (25.0-29.9 kg/m(2)) and obese (BMI ≥ 30) groups for tumours larger than 1 cm were 1.41 (1.10-1.81) and 2.17 (1.23-3.82), respectively, compared to the normal weight group (BMI 18.5-24.9). The multivariate-adjusted OR (95% CI) for microscopic extrathyroidal extension in the obesity group was 1.88 (1.06-3.32), and the OR for advanced TNM stage in the overweight group was 1.35 (1.02-1.79) compared to the normal weight group. During follow-up (median, 84 month; range, 1-185), 43 patients (2.1%) experienced recurrence. There were no significant differences in recurrence of PTCs among BMI groups.

CONCLUSIONS

Higher BMI was strongly associated with larger tumour size, extrathyroidal invasion and advanced TNM stage of PTCs. However, there was no difference in recurrence rate among BMI groups. This study suggests that excess weight is associated with aggressive features of PTCs. Further studies with long-term follow-up are needed to confirm this finding.

Neck circumference correlates with tumor size and lateral lymph node metastasis in men with small papillary thyroid carcinoma

BACKGROUND/AIMS

Obesity is correlated with numerous diseases, including thyroid cancer, but the clinical significance of obesity with regard to the clinical characteristics of thyroid cancer remains unclear. Neck circumference is an index of upper-body adipose tissue distribution.

METHODS

In total, 401 patients with papillary thyroid carcinoma (PTC) measuring ≤ 2 cm were included. Neck circumference was measured horizontally at the level just below the thyroid cartilage on preoperative neck computed tomographic images.

RESULTS

Neck circumference correlated significantly with tumor size in men (p = 0.001) but not in women (p = 0.930). Body mass index (BMI) did not significantly correlate with tumor size in either sex. Neck circumference was significantly larger in men with lateral lymph node (LN) metastasis than in those without (p = 0.004). Neck circumference and BMI did not differ significantly in women according to other factors such as tumor size, multifocality, extrathyroid extension, and LN metastasis. Tumor size and the prevalence of lateral LN metastasis in men tended to increase in the middle/large neck circumference subgroup compared with those in the low neck circumference subgroup. Multivariate logistic regression analysis revealed that neck circumference (p = 0.009) was a predictor for the presence of lateral LN metastasis in men. BMI was not a predictive factor for lateral LN involvement in either sex.

CONCLUSIONS

Neck circumference, an indicator of central or visceral obesity but not BMI, may be associated with some prognostic factors in men with small PTC.

The insulin and igf-I pathway in endocrine glands carcinogenesis

Endocrine cancers are a heterogeneous group of diseases that may arise from endocrine cells in any gland of the endocrine system. These malignancies may show an aggressive behavior and resistance to the common anticancer therapies. The etiopathogenesis of these tumors remains mostly unknown. The normal embryological development and differentiation of several endocrine glands are regulated by specific pituitary tropins, which, in adult life, control the function and trophism of the endocrine gland. Pituitary tropins act in concert with peptide growth factors, including the insulin-like growth factors (IGFs), which are considered key regulators of cell growth, proliferation, and apoptosis. While pituitary TSH is regarded as tumor-promoting factor for metastatic thyroid cancer, the role of other pituitary hormones in endocrine cancers is uncertain. However, multiple molecular abnormalities of the IGF system frequently occur in endocrine cancers and may have a role in tumorigenesis as well as in tumor progression and resistance to therapies. Herein, we will review studies indicating a role of IGF system dysregulation in endocrine cancers and will discuss the possible implications of these findings for tumor prevention and treatment, with a major focus on cancers from the thyroid, adrenal, and ovary, which are the most extensively studied.

Dietary iodine and thyroid cancer risk in French Polynesia: a case-control study

BACKGROUND

French Polynesia has one of the world's highest thyroid cancer incidence rates. Iodine is suspected to play a role in this high incidence. The objective of this study was to assess whether low dietary iodine is related to a higher risk of thyroid cancer in the French Polynesian population.

METHODS

A case-control study was performed among native residents of French Polynesia. It included 229 cases of differentiated thyroid cancer diagnosed between 1979 and 2004 (203 women, 26 men) matched with 371 population controls (324 women, 47 men) on the date of birth. The current study is focused on dietary iodine intake and fish consumption (food rich in iodine) and analyzed by conditional logistic regression.

RESULTS

Daily dietary iodine intake was insufficient (<150 μg/day) in 60% of both cases and controls. A decreased risk of thyroid cancer was observed with a higher consumption of fish (p(trend)=0.008) and shellfish (p(trend)=0.002), and also with a higher dietary iodine intake (p(trend)=0.03). There was no significant interaction between the effects of the thyroid radiation dose and the dietary iodine intake (p=0.2).

CONCLUSION

French Polynesia is a mild iodine deficiency area in which a higher consumption of food from the sea and a higher dietary iodine intake are significantly associated with a decreased risk of thyroid cancer. The quantification of this reduction requires specific investigation of iodine intake in traditional Polynesian food.

Body fat distribution, weight change during adulthood, and thyroid cancer risk in the NIH-AARP Diet and Health Study

Body mass index (BMI) has been positively associated with thyroid cancer risk in several studies, but the underlying mechanisms remain unclear. We examined the associations for waist and hip circumference and weight change during adulthood with thyroid cancer risk among 125,347 men and 72,363 women in the NIH-AARP Diet and Health Study who completed a second mailed questionnaire in 1996-1997. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated separately by sex and adjusted for race/ethnicity, education and smoking status. During follow-up (median = 10.1 years), 106 men and 105 women were diagnosed with a first primary thyroid cancer, as identified through linkage to state cancer registries. Having a large waist circumference (above the clinical cutpoint for normal: > 102 cm in men and > 88 cm in women) was associated with increased risk in both men (HR = 1.79, 95% CI: 1.21-2.63) and women (HR = 1.54, 95% CI: 1.05-2.26). Having both a large waist and BMI in the obese range (≥ 30 kg/m2) approximately doubled the risk of thyroid cancer (HR in men = 2.13, 95% CI: 1.18-3.85; HR in women = 1.91, 95% CI: 1.31-3.25) compared to having a normal waist circumference/normal BMI (18.5-24.9 kg/m2). We also observed positive association for weight gain between ages 18-35 in men (gained ≥ 10.0 kg vs. lost/gained < 5 kg, HR = 1.49, 95% CI: 0.93-2.39, p-trend = 0.03), but the association was less pronounced in women. No clear association for weight gain in later life was observed. These results support a potential role for hormonal and metabolic parameters common to central adiposity in thyroid carcinogenesis.

Physical activity, diabetes, and thyroid cancer risk: a pooled analysis of five prospective studies

PURPOSE: Although many studies have linked obesity with increased risk of thyroid cancer, few have investigated the role of obesity-related lifestyle characteristics and medical conditions in the etiology of this disease. We examined the associations of self-reported physical activity and diabetes history with thyroid cancer risk in a large pooled analysis of prospective cohort studies. METHODS: Data from five prospective studies in the U.S. (n = 362,342 men, 312,149 women) were coded using standardized exposure, covariate, and outcome definitions. Hazard ratios (HR) and 95% confidence intervals (CI) for thyroid cancer were estimated using age as the time metric and adjusting for sex, education, race, marital status, cigarette smoking, body mass index, alcohol intake, and cohort. Effect modification by other risk factors (e.g., age, sex, and body mass index) and differences by cancer subtype (e.g., papillary, follicular) were also examined. RESULTS: Over follow-up (median = 10.5 years), 308 men and 510 women were diagnosed with a first primary thyroid cancer. Overall, subjects reporting the greatest amount of physical activity had an increased risk of the disease (HR = 1.18, 95% CI:1.00-1.39); however, this association was restricted to participants who were overweight/obese (≥25 kg/m(2); HR = 1.34, 95% CI:1.09-1.64) as opposed to normal-weight (<25 kg/m(2); HR = 0.92, 95% CI:0.69-1.22; P-interaction = 0.03). We found no overall association between self-reported history of diabetes and thyroid cancer risk (HR = 1.08, 95% CI:0.83-1.40). CONCLUSION: Neither physical inactivity nor diabetes history was associated with increased risk of thyroid cancer. While it may have been a chance finding, the possible increased risk associated with greater physical activity warrants further investigation.

BMI, diet and female reproductive factors as risks for thyroid cancer: a systematic review

Background

Thyroid cancer incidence rates have been increasing worldwide but the reason behind this is unclear. Both the increasing use of diagnostic technologies allowing the detection of thyroid cancer and a true increase in thyroid cancer incidence have been proposed. This review assesses the role of body mass index (BMI), diet, and reproductive factors on the thyroid cancer trend.

Methods

Epidemiologic studies of the selected risk factors up to June 2010 were reviewed and critically assessed.

Results

Among the thirty-seven studies reviewed and despite variation in the risk estimates, most papers supported a small but positive association for BMI (risk estimate range: 1.1–2.3 in males and 1.0–7.4 in females.). Among specific dietary components, there was no consistent association of thyroid cancer risk with iodine intake through fortification (risk estimate range: 0.49–1.6) or fish consumption (risk estimate range 0.6–2.2), nor with diets high in cruciferous vegetables (risk estimate range 0.6–1.9). A small number of studies showed a consistent protective effect of diets high in non-cruciferous vegetable (risk estimate range: 0.71–0.92). Among reproductive factors (pregnancy, parity, number of live births, use of prescription hormones, menstrual cycle regularity, and menopausal status), none were consistently associated with higher thyroid cancer risk.

Conclusions

BMI had the strongest link to thyroid cancer risk among those examined. Detailed examinations of population-level risk factors can help identify and support prevention efforts to reduce the burden of thyroid cancer.