Risk factors for thyroid cancer: a prospective cohort study

Association of hormonal and reproductive factors with differentiated thyroid cancer risk in women: a pooled prospective cohort analysis

BACKGROUND

The incidence of differentiated thyroid cancer (DTC) is higher in women than in men but whether sex steroid hormones contribute to this difference remains unclear. Studies of reproductive and hormonal factors and thyroid cancer risk have provided inconsistent results.

METHODS

Original data from 1 252 907 women in 16 cohorts in North America, Europe, Australia and Asia were combined to evaluate associations of DTC risk with reproductive and hormonal factors. Multivariable-adjusted Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% CIs.

RESULTS

During follow-up, 2142 women were diagnosed with DTC. Factors associated with higher risk of DTC included younger age at menarche (<10 vs 10-11 years; HR, 1.28; 95% CI, 1.00-1.64), younger (<40; HR, 1.31; 95% CI, 1.05-1.62) and older (≥55; HR, 1.33; 95% CI, 1.05-1.68) ages at menopause (vs 40-44 years), ever use of menopausal hormone therapy (HR, 1.16; 95% CI, 1.02-1.33) and previous hysterectomy (HR, 1.25; 95% CI, 1.13-1.39) or bilateral oophorectomy (HR, 1.14; 95% CI, 1.00-1.29). Factors associated with lower risk included longer-term use (≥5 vs <5 years) of oral contraceptives (HR, 0.86; 95% CI, 0.76-0.96) among those who ever used oral contraception and baseline post-menopausal status (HR, 0.82; 95% CI, 0.70-0.96). No associations were observed for parity, duration of menopausal hormone therapy use or lifetime number of reproductive years or ovulatory cycles.

CONCLUSIONS

Our study provides some evidence linking reproductive and hormonal factors with risk of DTC. Results should be interpreted cautiously considering the modest strength of the associations and potential for exposure misclassification and detection bias. Prospective studies of pre-diagnostic circulating sex steroid hormone measurements and DTC risk may provide additional insight.

Thyroid cancer burden and risk factors in China from 1990-2019: a systematic analysis using the global burden of disease study

Background

Thyroid cancer (TC) is the most common endocrine system malignancy with a rapidly increasing incidence in China. Epidemiological data on TC at the national level are lacking. This study aimed to quantify the TC disease burden in China between 1990 and 2019 and evaluate the current status and trends of the disease burden attributed to a high body mass index (HBMI).

Methods

The 2019 Global Burden of Disease Study dataset was used to explore the TC disease burden. Age-standardized rates of incidence (ASIR), prevalence (ASPR), deaths (ASDR), and disability-adjusted life years (DALYs) were considered and the estimated annual percentage change (EAPC) was calculated as a measure of the average change in age-standardized rates. The trend in TC-related mortality and DALYs attributed to an HBMI, accounting for different age groups and sexes, was examined.

Results

Between 1990 and 2019, the ASDR and DALYs for TC decreased by 0.02/100000 and 1.17/100000, respectively. The ASPR and ASIR increased by 9.88/100000 and 1.04/100000, respectively. The EAPC for ASDR, age-standardized rates of DALYs, ASPR, and ASIR were 0.06 (95% CI: -0.09, 0.21), -0.20 (95% CI: -0.31, -0.10), 3.52 (95% CI: 3.35, 3.68), and 2.73 (95% CI: 2.58, 2.88), respectively. TC-related deaths, DALYs, and their prevalence and incidence in China increased by 118%, 350%, 81%, and 290%, respectively. The disease burden of TC was higher among male than female patients in different age groups, with varying distributions. The disease burden attributed to HBMI gradually increased over the past 30 years according to age-standardized DALYs, particularly in male patients.

Conclusion

The TC burden has increased in China over the past 30 years, and population aging poses a challenge to TC prevention and control. HBMI has become an important factor in the TC disease burden and further research should focus on reducing the disease burden among Chinese male patients with TC.

Cigarette smoking and thyroid cancer risk: A Mendelian randomization study

BACKGROUND

The association between cigarette smoking and thyroid cancer has been reported in prospective cohort studies, but the relationship remains controversial. To investigate this potential correlation further, we employed Mendelian randomization methodology to evaluate the causative impact of smoking on thyroid cancer incidence.

METHODS

From the genome-wide association study and Sequencing Consortium of Alcohol and Nicotine use, we obtained genetic variants associated with smoking initiation and cigarettes per day (1.2 million individuals). We also extracted genetic variants associated with past tobacco smoking from the UK Biobank (424,960 individuals). Thyroid cancer outcomes were selected from the FinnGen GWAS (989 thyroid cancer cases and 217,803 control cases). Sensitivity analyses employing various approaches such as weighted median, MR-Egger, and MR-pleiotropy residual sum and outlier (MR-PRESSO) have been executed, as well as leave-one-out analysis to identify pleiotropy.

RESULTS

Using the IVW approach, we did not find evidence that any of the three smoking phenotypes were related to thyroid cancer (smoking initiation: odds ratio (OR) = 1.56, p = 0.61; cigarettes per day: OR = 0.85, p = 0.51; past tobacco smoking: OR = 0.80, p = 0.78). The heterogeneity (p > 0.05) and pleiotropy (p > 0.05) testing provided confirmatory evidence for the validity of our MR estimates.

CONCLUSIONS

The MR analysis revealed that there may not exist a causative link between smoking exposure and elevated incidence rates of thyroid malignancies.

Molecular Testing Results for Indeterminate Thyroid Nodules and Social Habits

INTRODUCTION

The effects of smoking and alcohol use on the risk of thyroid cancer remain unclear. We sought to investigate the association between these social habits, molecular testing results, and the risk of thyroid cancer.

METHODS

We conducted a retrospective chart review of patients with indeterminate thyroid nodules (Bethesda III and IV) who underwent molecular testing. The frequency of abnormal molecular testing results was compared among patients with varying smoking and alcohol consumption habits.

RESULTS

Of 460 patients, median age was 51.8 y, 78.3% were female, 60.7% were White, and 79.8% presented with Bethesda III nodules. The rate of malignancy was 42.6% overall; 73.4% of molecular testing was performed with Afirma, 20.1% with ThyroSeq, and 5.0% with ThyGeNEXT. For social habits, 72.2% never smoked and 40.9% never drank alcohol. Never/rare drinkers were less likely to have abnormal results compared to routine drinkers when considering all types of molecular testing together (83.2% versus 91.3%, P = 0.046), as were those who underwent ThyroSeq molecular testing (71.8% versus 94.4%, P = 0.045). Multivariable analysis revealed that being a routine drinker (adjusted OR 2.19, 95% CI 1.08-4.88), having a larger lesion (adjusted OR 0.65, 95% CI 0.54-0.77), being tested by ThyroSeq (adjusted OR 0.41, 95% CI 0.22-0.76), and other commercial panels (adjusted OR 0.12, 95% CI 0.02-0.64) were independent predictors of abnormal molecular testing results.

CONCLUSIONS

Our patients' social habits may be associated with the molecular testing results of their indeterminate thyroid nodules but not with their surgical pathology results.

Longitudinal Changes in Smoking Habits in Women and Subsequent Risk of Cancer

INTRODUCTION

This study investigated the association between longitudinal smoking habit changes and cancer risk in a cohort of Korean women.

METHODS

Study population included women aged ≥40 years who underwent 2 biennial cancer screenings (2009-2010 and 2011-2012) and were followed up until 2020. This analysis was conducted in 2021. On the basis of changes in smoking habits, participants were grouped into sustained nonsmokers, sustained quitters, new quitters, relapsers, smoking initiators, and sustained smokers. Outcomes included incident cancer cases, smoking-related cancers, and specific cancer sites.

RESULTS

Of 3,051,946 women, the mean age was 54.8 years, and the median follow-up was 8.9 years. Compared with sustained nonsmokers, other groups had a significantly increased risk of cancer and smoking-related cancers: sustained quitters (adjusted hazard ratio=1.05; 95% CI=1.01, 1.09), new quitters (adjusted hazard ratio=1.12; 95% CI=1.07, 1.17), and sustained smokers (adjusted hazard ratio=1.14; 95% CI=1.09, 1.19). A significantly increased risk of lung, stomach, liver, and pancreas cancers was found in sustained smokers and new quitters. Relapsers/smoking initiators showed a higher risk of liver, lung, and breast cancer than sustained nonsmokers, but the strength of their corresponding adjusted hazard ratio was generally lower than that of sustained smokers. The hazard ratio of cancer risk was 0.92 (95% CI=0.87, 0.97) among sustained quitters and 0.97 (95% CI=0.91, 1.03) among new quitters relative to that among sustained smokers.

CONCLUSIONS

This study found a significant association between changes in smoking behavior and cancer risk. These findings suggest that smoking cessation is critical for cancer prevention in women.

Mediterranean Diet and Thyroid: An Interesting Alliance

The Mediterranean diet, recognized as being cultural heritage by UNESCO, is mostly plant-based and includes a high consumption of whole-grain, fruit, and vegetables with a moderate consumption of alcohol during meals. Thus, it provides a small amount of saturated fatty acids and a high quantity of antioxidants and fiber. For this reason, it has been considered to have an important role in preventing cardiovascular diseases, chronic kidney diseases, type 2 diabetes mellitus, and cancer, but its relationship with thyroid function and diseases is still under debate. The aim of this review was to search for the possible correlation between the Mediterranean diet and thyroid function, and to critically evaluate the pathophysiological link between selected food intake and thyroid disorders.

Association between Obesity Indexes and Thyroid Cancer Risk in Korean Women: Nested Case-Control Study

Objective: This study aimed to identify the association between various obesity indexes, including waist circumference (WC), waist−hip ratio (WHR), waist−height ratio (WHTR), and BMI, and their combinations with body mass index (BMI) and thyroid cancer risk. Methods: Of the 65,639 participants who completed a follow-up survey of the Health Examinee Study (HEXA), a prospective cohort of the Korean Genome and Epidemiology Study, 412 female incident thyroid cancer cases, and 1648 birth year- and enrollment year-matched female controls were included. Multiple conditional logistic regression was used to estimate the association between obesity indexes and thyroid cancer risk. Results: The risk of developing thyroid cancer was increased by 1.37-fold (95% confidence interval (CI) = 1.03−1.81) higher in the obese BMI group (≥25.0 Kg/m2) compared to that in the normal BMI group (<23.0 Kg/m2). Obesity in terms of WC (≥85.0 cm) and WHTR (≥0.5) was associated with an increased risk of thyroid cancer (OR 1.55, 95% CI = 1.16−2.07; OR 1.37, 95% CI = 1.07−1.75, respectively). However, increased WHR levels did not show any significant association. Women with both obese levels of BMI (≥25.0 Kg/m2) and other obesity indexes (WC ≥ 85.0 cm, WHR ≥ 0.85, or WHTR ≥ 0.5) showed an increased risk of thyroid cancer with OR of 1.63 (95% CI = 1.14−2.31), 1.49 (95% CI = 1.05−2.12), and 1.42 (95% CI = 1.04−1.94), compared to those with normal levels of BMI and each obesity index. Conclusion: These results provide evidence of the contribution of both total and central adiposity across the lifespan of thyroid cancer incidence. Risk factor modifications must be considered to explain the current thyroid cancer epidemic.

Appraising the Effect of Potential Risk Factors on Thyroid Cancer: A Mendelian Randomization Study

CONTEXT

Various risk factors have been associated with the risk of thyroid cancer in observational studies. However, the causality of the risk factors is not clear given the susceptibility of confounding and reverse causation.

OBJECTIVE

A 2-sample Mendelian randomization approach was used to estimate the effect of potential risk factors on thyroid cancer risk.

METHODS

Genetic instruments to proxy 55 risk factors were identified by genome-wide association studies (GWAS). Associations of these genetic variants with thyroid cancer risk were estimated in GWAS of the FinnGen Study (989 cases and 217 803 controls). A Bonferroni-corrected threshold of P = 9.09 × 10-4 was considered significant, and P < 0.05 was considered to be suggestive of an association.

RESULTS

Telomere length was significantly associated with increased thyroid cancer risk after correction for multiple testing (OR 4.68; 95% CI, 2.35-9.31; P = 1.12 × 10-5). Suggestive associations with increased risk were noted for waist-to-hip ratio (OR 1.85; 95% CI, 1.02-3.35; P = 0.042) and diastolic blood pressure (OR 1.60; 95% CI, 1.08-2.38; P = 0.019). Suggestive associations were noted between hemoglobin A1c (HbA1c) (OR 0.20; 95% CI, 0.05-0.82; P = 0.025) and decreased risk of thyroid cancer. Risk of thyroid cancer was not associated with sex hormones and reproduction, developmental and growth, lipids, diet and lifestyle, or inflammatory factors (All P > 0.05).

CONCLUSION

Our study identified several potential targets for primary prevention of thyroid cancer, including central obesity, diastolic blood pressure, HbA1c, and telomere length, which should inform public health policy.

Smoking, Alcohol Consumption, and the Risk of Thyroid Cancer: A Population-Based Korean Cohort Study of 10 Million People

Background: It is unclear if cigarette smoking and alcohol consumption are associated with thyroid cancer risk. Our aim was to explore for any associations between cigarette smoking and alcohol consumption with thyroid cancer, after adjusting for potential confounders. Methods: Using data from the Korean National Health Insurance database, we retrospectively identified individuals aged ≥20 years who participated in the 2009 health screening program and were followed until 2017. We estimated the adjusted hazard ratio (aHR) for the risk of thyroid cancer using a Cox proportional hazard model, adjusted for age, sex, regular exercise, monthly income, body mass index, diabetes mellitus, and dyslipidemia. Results: During a mean follow-up period of 8.33 ± 0.57 years, of 9,699,104 participants, 89,527 (0.9%) were diagnosed with thyroid cancer. Compared with those who never smoked, current smokers had a lower risk of thyroid cancer (aHR: 0.74, 95% confidence interval [CI]: 0.72-0.76), while ex-smokers did not (aHR: 0.98, 95% CI: 0.96-1.01). There was no significant dose-response relationship with regard to daily amount smoked, duration of smoking, or pack-years. A reduced risk of thyroid cancer was observed in subjects who reported the following categories of alcohol intake (compared with none): mild (aHR: 0.92, 95% CI: 0.90-0.93), moderate (aHR: 0.86, 95% CI: 0.84-0.89), and heavy (aHR: 0.86, 95% CI: 0.82-0.89). Inverse associations with thyroid cancer risk were observed regarding the number of drinking episodes per week and the number of drinks per occasion. A submultiplicative effect of smoking and alcohol consumption was observed (p-interaction <0.001). Conclusions: We observed that thyroid cancer risk was inversely associated with smoking and alcohol consumption, with a significant interaction between these variables.

Variations in MAP kinase gladiators and risk of differentiated thyroid carcinoma

Thyroid carcinoma (TC) accounts for ~2.1% of newly diagnosed cancer cases. Mutations in KRAS, HRAS, NRAS and BRAF are primary participants in the development and progression of various types of malignancy, including differentiated TC (DTC). Therefore, the present prospective cohort study aimed to screen patients with DTC for variations in RAS gene family and BRAF gene. Exon 1 and 2 of KRAS, HRAS, NRAS and exon 15 of BRAF gene were screened for hotspot mutations in 72 thyroid tumor and adjacent normal tissue samples using di-deoxy Sanger sequencing. HRAS T81C mutation was found in 21% (15 of 72) of DTC tissue samples, therefore this mutation was investigated in blood samples from patients with DTC and controls as a genetic polymorphism. In addition, HRAS T81C genotypes were determined in 180 patients with DTC and 220 healthy controls by performing restriction fragment length polymorphism. BRAF^V600E mutation was confined to classical variant of papillary thyoid cancer (CPTC; 44.4%) and was significantly associated with multifocality and lymph node (LN) metastasis. No mutation was found in exons 1 and 2 of KRAS and NRAS and exon 2 of HRAS genes, however, mutation was detected in exon 1 of HRAS gene (codon 27) at nucleotide position 81 in 21% (15 of 72) of DTC tumor tissue samples. Furthermore, HRAS T81C single nucleotide polymorphism was significantly associated with the risk of DTC with variant genotypes more frequently detected in cases compared with controls (P≤0.05). Moreover, frequency of variant genotypes (TC+CC) was significantly higher among DTC cases with no history of smoking, males, greater age, multifocality and LN metatasis compared with healthy controls (P<0.05). BRAF^V600E mutation was primarily present in CPTC and associated with an aggressive tumor phenotype but mutations in RAS gene family were not present in patients with DTC. HRAS T81C polymorphism may be involved in the etiopathogenesis of DTC in a Pakistani cohort. Furthermore, testing for the BRAF^V600E mutation may be useful for selecting initial therapy and follow-up monitoring.

Hormonal Replacement Therapy and Risk of Thyroid Cancer in Women: A Meta-Epidemiological Analysis of Prospective Cohort Studies

Objectives

Many experimental studies have reported that female sex hormones involve thyroid cancer development because the incidence rate of thyroid cancer in women (TCW) is 3 times higher than in men. Three previous systematic reviews reporting no association between hormone replacement therapy (HRT) and TCW risk had the same search year of 2014. The aim was to reevaluate the association between HRT use and TCW risk using a meta-epidemiological study of prospective cohort studies.

Methods

The study preferentially used all studies selected by the existing systematic reviews and then secured an additional cohort from the list citing the studies. The selection criterion was defined as the prospective cohort study assessing the association between HRT and TCW risk by adjusted relative risk and its 95% confidence intervals (CI) from multivariate analysis. A random-effects model meta-analysis was applied to estimate summary relative risk (sRR) and its 95% CI. A publication bias was evaluated by Egger’s test; moreover, the statistical significance level was set at 5%.

Results

Nine cohort studies were finally selected. The random-effect model was applied because of heterogeneity (I² = 64.3%). The sRR and its 95% CI from a random-effects model meta-analysis had no statistical significance in the association between HRT and TCW risk (sRR = 1.11; 95% CI, 0.98–1.26). Additionally, Egger’s test revealed no statistical significance (P = 0.91).

Conclusions

HRT is not associated with TCW risk based on the random-effects model meta-analysis of prospective cohort studies published until now.

Thyroid cancer incidence disparities among ethnic Asian American populations, 1990-2014

PURPOSE

Asian/Pacific Islanders (APIs) are at high risk of thyroid cancer, hence we examined thyroid cancer's incidence among disaggregated API subgroups in the United States (U.S.) to identify potential ethnic-specific disparities.

METHODS

Data from 1990 to 2014 in the Surveillance, Epidemiology, and End Results Program (SEER) were used to compare age-adjusted incidence rates (AAIRs) of thyroid cancer for seven API ethnic subgroups to non-Hispanic whites (NHWs) using incidence rate ratios (IRRs) and 95% confidence intervals (CIs). Sex, age, tumor histotype, and year of diagnosis were considered. Trends were evaluated using average annual percent change (AAPC) statistics.

RESULTS

The highest AAIRs (per 100,000 person-years) were among Filipinos (female AAIR=20.49, male AAIR=7.06) and the lowest among Japanese (female AAIR=8.36, male AAIR=3.20). However, Filipinos showed significantly lower incidence of medullary tumors when compared to NHWs (female IRR=0.60, 95% CI 0.40-0.87, male IRR=0.26, 95% CI 0.26-0.51). The largest increasing trends were among Asian Indian/Pakistanis for females (AAPC=5.19, 95% CI 3.81 to 6.58) and Koreans for males (AAPC=4.57, 95% CI 3.14 to 6.03).

CONCLUSIONS

There are clear differences in thyroid cancer incidence and trends when U.S. API ethnic subgroups are examined separately. Disaggregating APIs in research can provide critical information for understanding thyroid cancer risk.

Analysis of the Association between Female Medical History and Thyroid Cancer in Women: A Cross-Sectional Study Using KoGES HEXA Data

The purpose of this study was to evaluate the association between female medical history and thyroid cancer. Methods: Data from the Korean Genome and Epidemiology Study were collected from 2004 to 2016. Among a total of 1303 participants with thyroid cancer and 106,602 control (non-thyroid cancer) participants, the odds ratios (ORs) with 95% confidence intervals (CIs) of hysterectomy, oophorectomy, use of oral contraceptives, and number of children were evaluated. Results: The adjusted OR of hysterectomy for thyroid cancer was 1.73 (95% CI = 1.48-2.01, p < 0.001) in the minimally adjusted model. The adjusted ORs for thyroid cancer were 1.89 (95% CI = 1.06-3.37, p = 0.031), 0.89 (95% CI = 0.83-0.94, p < 0.001), and 0.85 (95% CI = 0.73-0.99, p = 0.040) for bilateral oophorectomy, number of children, and use of oral contraceptives, respectively, in the fully adjusted model. In the subgroup analysis, the adjusted ORs of bilateral oophorectomy were significant in the younger age (OR = 3.62, 95% CI = 1.45-9.03, p = 0.006), while the number of children was significant in the older age (OR = 0.86, 95% CI = 0.80-0.93, p < 0.001). Conclusions: The ORs of hysterectomy and bilateral oophorectomy were significantly higher in the thyroid cancer group in the younger age group. The adjusted ORs of the number of children were significantly low in the older age group.

Effect of Cigarette Smoking on Thyroid Cancer: Meta-Analysis

BACKGROUND

Although smoking is generally carcinogenic, its effect on thyroid cancers is still subject to controversy. The purpose of this study was to summarize the role of smoking in relation to thyroid cancer occurrence.

METHODS

We performed a meta-analysis of 24 eligible studies: 21 case-control studies and three prospective cohort studies. The summary odds ratio (OR) and 95% confidence interval (CI) of all studies were acquired based on random effect model. Further subgroup analyses were conducted according to gender, histological type of thyroid cancer, and smoking status of patients for the case-control studies.

RESULTS

The summary effect size indicated a negative association of smoking for thyroid cancer (OR, 0.798; 95% CI, 0.681 to 0.935). From the subgroup analyses for the case-control studies, reduced risk of thyroid cancer was observed in both men (OR, 0.734; 95% CI, 0.553 to 0.974) and women (OR, 0.792; 95% CI, 0.700 to 0.897). The protective effect of smoking was observed in studies in which thyroid cancer was limited to differentiated thyroid cancers (DTCs) (OR, 0.798; 95% CI, 0.706 to 0.902).

CONCLUSION

Our results suggests that smoking may have a protective effect on thyroid cancer, especially on DTCs. Further studies with larger sample sizes should be conducted in elucidating the dose and time dependent effect of smoking on thyroid cancer with specific focus on the types of thyroid cancers.

Identification of Potential lncRNAs and miRNAs as Diagnostic Biomarkers for Papillary Thyroid Carcinoma Based on Machine Learning

BACKGROUND

Papillary thyroid carcinoma (PTC) accounts for most of the proportion of thyroid cancer (TC). The objective of this study was to identify diagnostic, differentially expressed long noncoding RNAs (lncRNAs) and microRNAs (miRNAs), contributing to understanding the epigenetics mechanism of PTC.

METHODS

The data of lncRNA, miRNA, and mRNA were downloaded from the Cancer Genome Atlas (TCGA) dataset, followed by functional analysis of differentially expressed mRNAs. Optimal diagnostic lncRNA and miRNA biomarkers were identified via random forest. The regulatory network between optimal diagnostic lncRNA and mRNAs and optimal diagnostic miRNA and mRNAs was identified, followed by the construction of ceRNA network of lncRNA-mRNA-miRNA. Expression validation and diagnostic analysis of lncRNAs, miRNAs, and mRNAs were performed. Overexpression of ADD3-AS1 was performed in PTC-UC3 cell lines, and cell proliferation and invasion assay were used for investigating the role of ADD3-AS1 in PTC.

RESULTS

A total of 107 differentially expressed lncRNAs, 81 differentially expressed miRNAs, and 515 differentially expressed mRNAs were identified. 11 lncRNAs and 6 miRNAs were regarded as the optimal diagnostic biomarkers for PTC. The epigenetic modifications via the above diagnostic lncRNAs and miRNAs were identified, including MIR181A2HG-FOXP2-hsa-miR-146b-3p, BLACAT1/ST7-AS1-RPS6KA5-hsa-miR-34a-5p, LBX2-AS1/MIR100HG-CDHR3-hsa-miR-34a-5p, ADD3-AS1-PTPRE-hsa-miR-9-5p, ADD3-AS1-TGFBR1-hsa-miR-214-3p, LINC00506-MMRN1-hsa-miR-4709-3p, and LOC339059-STK32A-hsa-miR-199b-5p. In the functional analysis, MMRN1 and TGFBR1 were involved in cell adhesion and endothelial cell migration, respectively. Overexpression of ADD3-AS1 inhibited cell growth and invasion in PTC cell lines.

CONCLUSION

The identified lncRNAs/miRNAs/mRNA were differentially expressed between normal and cancerous tissues. In addition, identified altered lncRNAs and miRNAs may be potential diagnostic biomarkers for PTC. Additionally, epigenetic modifications via the above lncRNAs and miRNAs may be involved in tumorigenesis of PTC.

Incidence and Risk Factors of Postoperative Bleeding in Patients Undergoing Total Thyroidectomy

Purpose: Our goal was to analyze postoperative bleeding in patients undergoing total thyroidectomy and to explore the possible risk factors.

Materials and Methods: Patients undergoing total thyroidectomy were retrospectively enrolled, and the main study outcomes were postoperative bleeding and 30-day mortality. Univariate and multivariate analyses were used to determine the independent risk factors for postoperative bleeding.

Results: A total of 31,706 patients were enrolled for analysis during January 2010 and December 2018 from the Affiliated First Hospital of Zhengzhou University. Benign and malignant disease was reported in 4,521 and 27,185 patients, respectively. Postoperative bleeding occurred in 48 patients with benign disease and in 263 patients with malignant disease. There was one bleeding site in 243 patients. The branch of the superior thyroid artery was the most common arterial bleeding site, occurring in 124 patients, and the anterior jugular vein was the most common venous bleeding site, occurring in 85 patients. Multivariable analysis confirmed that hypertension, diabetes, BMI, and disease pathology were independent factors affecting postoperative bleeding in patients with benign disease and that hypertension, diabetes, BMI, operation time, tumor stage, and tracheotomy were independent factors affecting postoperative bleeding in patients with malignant disease. In patients with postoperative bleeding, there were 5 deaths; in patients without postoperative bleeding, there were 42 deaths, and the difference was significant (p < 0.001).

Conclusions: Compared with malignant disease patients, benign disease patients have a similar postoperative bleeding rate. A previous history of chemotherapy or radiotherapy has no significant effect on postoperative bleeding.

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.

Attributable risk fraction of four lifestyle risk factors of thyroid cancer: a meta-analysis

Background

Lifestyle risk factors such as obesity, overweight, smoking and radiation exposure related to thyroid cancer. This study estimated the amount of excess risk that attributed to risk factors.

Methods

Major electronic databases were searched until February 2016. Epidemiological studies addressing the association between lifestyle risk factors and thyroid cancer were enrolled. The results were expressed as ARF with 95% confidence intervals (CIs) using a random-effects-model.

Results

We identified a total of 13 321 references and included 17 studies. The excess risk of thyroid cancer attributable to radiation exposure was 14% (95% CI: 5%, 23%; eight studies, I2 = 88.7%), to obesity was 13% (95% CI: 5%, 21%; four studies, I2 = 68.7%), to overweight was 10% (95% CI: 2%, 17%; four studies, I2 = 4.1%) and to smoking was -13% (95% CI: -33%, 6%; five studies, I2 = 30.6%). So obesity, overweight and radiation exposure are significantly associated with increased thyroid cancer risk and smoking has a protective effect on thyroid cancer but not significant.

Conclusion

A significant amount of the incidence of thyroid cancer is attributable to lifestyle risk factors. Since these factors are entirely preventable, so it is necessary to reduce factors that are associated with increased thyroid cancer risk and proper education to the community. Thus weight loss and protection against radiation can effectively reduce the incidence rate of thyroid cancer but smoking can have a protective effect.

Reproductive factors and thyroid cancer risk: Meta-analysis

BACKGROUND

Assessed pooled risk on reproductive factors and oral contraceptives (OC) on thyroid cancer (TC) using published studies (1996-2017).

METHODS

Summary odds ratio (OR) for case-control studies (n = 10) and risk ratio (RR) for cohort studies (n = 9) was done.

RESULTS

OR was 1.43 (95% CI: 1.16-1.77) for age at menarche >14 years, 1.49 (95% CI: 1.19-1.86) for parity >2, 1.38 (95% CI: 1.18-1.61) for miscarriage/abortion, and 2.05 (95% CI: 1.39-3.01) for artificial menopause. A protective effect (ORs: 0.85; 95% CI: 0.72-0.99) on TC was observed for prolonged use of OCs. RR was 1.17 (95% CI: 0.90-1.57) for age at menarche >14 years, 1.10 (95% CI: 0.94-1.27) for parity >2, 1.20 (95% CI: 1.03-1.40) for miscarriage/abortion, and 2.16 (95% CI: 1.41-3.31) for artificial menopause and protective effect (RR: 0.78; 95% CI: 0.65-0.92) for prolonged use of OCs.

CONCLUSIONS

This meta-analysis supports an association due to changes in female hormones during menstrual cycle and pregnancy with the risk of TC and explains female preponderance.

Role of phospho-ezrin in differentiating thyroid carcinoma

Comprehensive theory explaining the relationship between estrogen (E2) and ezrin in metastasis of thyroid cancer remains non-elicited. In vitro results revealed that E2 could stimulate the expression and phosphorylation of ezrin in a time and dose dependent manner. Our data clearly showed that E2 enhanced the migration and invasion of cells, which was reversed by the transfection of cells with ezrin specific siRNA. Further, we observed that Phosphoinositide 3-kinase (PI3K) ROCK-2 are among the kinases responsible for E2 induced phosphorylation of ezrin. Clinical validation of ezrin/phospho-ezrin revealed that phospho-ezrin was intensely expressed in follicular thyroid carcinoma (FTC) and follicular variant of papillary thyroid carcinoma (FVPTC), while it was completely absent in follicular adenoma (FA) lesions in which the differentiation of the follicular neoplasms remains subtle. When histology of different carcinomas is correlated with benign FA with respect to phospho-ezrin, we observed that the marker was highly significant (p = 0.0001). 100% sensitivity, specificity and diagnostic accuracy of the above marker in the histological association of FTC, FVPTC with FA, enables us to suggest phospho-ezrin as a diagnostic marker to differentiate the follicular neoplasms. These data are the first to suggest the dynamic regulation of ezrin phosphorylation during metastasis in FTC.

Active and Passive Smoking, BRAFV600E Mutation Status, and the Risk of Papillary Thyroid Cancer: A Large-Scale Case-Control and Case-Only Study

PURPOSE

The association between tobacco smoking and thyroid cancer remains uncertain. We evaluated the associations of active and passive smokingwith the risk of papillary thyroid cancer (PTC), the most common type of thyroid cancer, and with the BRAFV600E mutation, the most common oncogenic mutation in PTC related to poor prognosis.

Materials and Methods

We conducted this study with newly diagnosed PTC patients (n=2,142) and community controls (n=21,420) individually matched to cases for age and sex. Information on active and passive smoking and potential confounders were obtained from structured questionnaires, anthropometric measurements, and medical records. BRAFV600E mutation status was assessed in PTC patients. We evaluated the associations of active and passive smoking with PTC and BRAFV600E mutation risk using conditional and unconditional logistic regression models, respectively.

RESULTS

We did not find associations between exposure indices of active and passive smoking and PTC risk in both men and women, except for the association between current smoking and lower PTC risk. Cumulative smoking ≥ 20 pack-years was associated with lower BRAFV600E mutation risk in male PTC patients (odds ratio [OR], 0.55; 95% confidence interval [CI], 0.30 to 1.00). The CI for the association was wider in female PTC patients (OR, 0.23; 95% CI, 0.02 to 2.62), possibly owing to a smaller sample size in this stratum.

CONCLUSION

We did not find consistent associations between active and passive smoking and PTC risk. Cumulative smoking ≥ 20 pack-years was associated with lower BRAFV600E mutation risk in male PTC patients.

Cigarette smoking and thyroid cancer risk: a cohort study

Background

We evaluated the association between smoking status and thyroid cancer risk and whether this association is mediated by body mass index (BMI) and thyroid-stimulating hormone (TSH).

Methods

We performed a cohort study of 96,855 Korean adults who were followed annually or biennially for a median of 5.9 years.

Results

During 511,052.9 person-years of follow-up, 1,250 participants developed thyroid cancer. In men, we observed a dose-dependent inverse association between current smoking, pack-years, and thyroid cancer. After adjustment for confounders, adjusted hazard ratios (95% confidence intervals) for thyroid cancer comparing current and former smokers to never smokers were 0.58 (0.45–0.75) and 0.93 (0.73–1.18), respectively. After further adjustment for BMI and TSH as potential mediators, this association was slightly attenuated, but remained significant. For women, current smokers tended to have a lower risk of thyroid cancer, but this association did not reach statistical significance.

Conclusions

In this cohort study, current smoking was associated with a decreased risk of incident thyroid cancer in men but not in women and this association was observed even after adjusting for TSH and BMI levels as potential mediators. Further mechanistic studies are needed to elucidate the possible effect of smoking on the pathogenesis of thyroid cancer development.

A Comparison Study: The Risk Factors in the Lifestyles of Thyroid Cancer Patients and Healthy Adults of South Korea

BACKGROUND

In South Korea, there has been a rapid increase in thyroid cancer diagnoses, and the thyroid cancer incidence rate is the highest in the world. This study explored possible risk factors that may influence the development of thyroid cancer by comparing life habits of thyroid cancer patients and healthy adults.

OBJECTIVE

The aims of this study were to identify lifestyle and habit differences in thyroid cancer patients and healthy adults and to investigate risk factors that influence the development of thyroid cancer.

METHODS

The study was designed as a retrospective comparison survey study of thyroid cancer patient group and healthy adult group. One hundred two thyroid cancer patients in a university hospital and 115 healthy adults were recruited for this study. Data were analyzed using descriptive statistics, χ test/t test, and logistic regression with SPSS program.

RESULTS

Previous smoking history, lower physical activity level, higher stress, and unhealthy eating habits (consumption of instant food products) were shown to be risk factors in the development of thyroid cancer.

CONCLUSION

Based on the results of this study comparing thyroid cancer patients and healthy adults, it is recommended to encourage an increase in physical activity, minimize both direct and indirect exposure to smoking, develop healthy eating habits of consuming more vegetables, and effectively manage stress levels.

IMPLICATIONS FOR PRACTICE

Lifestyle preferences and habits may influence the development of thyroid cancer. It is imperative to identify and modify the risk factors in order to prevent thyroid cancer development.

Programmed death-ligand 1 expression by digital image analysis advances thyroid cancer diagnosis among encapsulated follicular lesions

Recognition of noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP) that distinguishes them from invasive malignant encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC) can prevent overtreatment of NIFTP patients. We and others have previously reported that programmed death-ligand 1 (PD-L1) is a useful biomarker in thyroid tumors; however, all reports to date have relied on manual scoring that is time consuming as well as subject to individual bias. Consequently, we developed a digital image analysis (DIA) protocol for cytoplasmic and membranous stain quantitation (ThyApp) and evaluated three tumor sampling methods [Systemic Uniform Random Sampling, hotspot nucleus, and hotspot nucleus/3,3'-Diaminobenzidine (DAB)]. A patient cohort of 153 cases consisting of 48 NIFTP, 44 EFVPTC, 26 benign nodules and 35 encapsulated follicular lesions/neoplasms with lymphocytic thyroiditis (LT) was studied. ThyApp quantitation of PD-L1 expression revealed a significant difference between invasive EFVPTC and NIFTP; but none between NIFTP and benign nodules. ThyApp integrated with hotspot nucleus tumor sampling method demonstrated to be most clinically relevant, consumed least processing time, and eliminated interobserver variance. In conclusion, the fully automatic DIA algorithm developed using a histomorphological approach objectively quantitated PD-L1 expression in encapsulated thyroid neoplasms and outperformed manual scoring in reproducibility and higher efficiency.

Interaction between alcohol consumption and methylenetetrahydrofolate reductase polymorphisms in thyroid cancer risk: National Cancer Center cohort in Korea

The effect of alcohol intake on thyroid cancer is unestablished, and its interaction effects with genetic susceptibility are unclear. In this case-control study, the relationship among alcohol intake, the methylenetetrahydrofolate reductase (MTHFR) gene, and thyroid cancer risk has been evaluated. In total, 642 cases and 642 controls of Korean origin were included, and the genetic variants C677T and A1298C of the MTHFR gene were analysed. The interactions between alcohol-consumption behaviour and genetic variants were analysed with a likelihood ratio test, wherein a multiplicative interaction term was added to a logistic regression model. There was an independent association between the C677T polymorphism and thyroid cancer risk but not for drinking history. For C677T C/C homozygotes, individuals with a history of alcohol consumption showed a protective OR (95% CI) of 0.42 (0.15–1.13) when never drinkers were used as the reference. However, this protective association was not observed among individuals with a T+ allele with an OR (95% CI) of 1.27 (0.89–1.82), showing different directions for the association between genotypes with a significant interaction (P_interaction = 0.009). Based on the genetic characteristics of individuals included, an interaction between alcohol intake and MTHFR C677T may modify the risk of thyroid cancer.

A meta-analysis of alcohol consumption and thyroid cancer risk

Background

It is still inconclusive whether alcohol consumption affects the risk of thyroid cancer. We conducted a meta-analysis of available epidemiological data to address this issue.

Results

Compared with nondrinkers, the pooled relative risks (RRs) and corresponding 95% confidential intervals (CIs) of thyroid cancer were 0.80 (95% CI 0.71-0.90) for any drinkers, 0.81 (95% CI 0.70-0.93) for light and 0.71 (95% CI 0.63-0.79) for moderate drinkers. The dose–response analysis suggested that there is no evidence of a dose-risk relationship between alcohol intaking and thyroid cancer risk (P = 0.112).

Methods

Eligible studies were identified by searching PubMed and EMbase databases. A total of 24 studies, included 9,990 cases with thyroid cancer, were included in this meta-analysis. We defined light alcohol intake as ≤ one drink/day and moderate as >one drink/day. The summary risk estimates were calculated by the random effects model. A dose-response analysis was also conducted for modeling the dose-risk relation.

Conclusion

This meta-analysis confirmed an inverse association between alcohol consumption and thyroid cancer risk. Further studies are needed to better understand the potential mechanisms underlying this association.

Risk factors for well-differentiated thyroid cancer in men

Aims and background

Thyroid cancers are relatively rare tumors that appear more frequently in women than in men. Accordingly, most studies focus on studying risk factors for thyroid cancer in women and consequently on various hormonal or reproductive factors that are specific for women. The aim of our study was to examine risk factors for developing well-differentiated thyroid cancer in men. Heretofore, we did not encounter in the literature a study that was solely focused on studying risk factors for well-differentiated thyroid cancer in men.

Methods

A case-control study was performed from 2005 to 2010. The case group included 204 consecutive well-differentiated thyroid cancers in male patients (180 papillary and 24 follicular including Hürthle cell). The control group comprised the same number of cases. Patients were individually matched by gender, age and place of residence. Statistical analysis included conditional univariate and multivariate logistic regression Methods.

Results

According to univariate logistic regression, well-differentiated thyroid cancer in men was significantly related to smoking status, duration of smoking, number of cigarettes smoked per day, history of goiter or thyroid nodules, history of non-thyroid cancer, diabetes mellitus, radiotherapy of the head and neck, and history of malignant tumors. According to multivariate logistic regression, it was independently related to smoking status (OR = 0.36; 95% CI, 0.19–0.69), history of goiter or thyroid nodules (OR = 9.19; 95% CI, 1.25–64.58), and a history of malignant tumors (OR = 2.11; 95% CI, 1.19–7.33).

Conclusions

Risk factors for well-differentiated thyroid cancer in men were goiter or thyroid nodules and family history of malignant tumors. Cigarette smoking was negatively associated with the disease.

Type 2 diabetes mellitus is more prevalent among patients with thyroid carcinoma and influences overall survival: a propensity score matching analysis

The relationship between Type 2 Diabetes Mellitus(T2DM) and cancer risk has been investigated for more than a decade. Many types of cancer were confirmed to be related with T2DM. The aim of this study is to identify the relationship between T2DM and the prevalence and long-term survivals of Thyroid Carcinoma(TC) using propensity score matching. In present study, 1658 thyroid nodule patients who were diagnosis in Beijing Shijitan hospital were divided into two groups: the TC group (N = 455, 27.4%), and the benign thyroid nodule(BTN) group (N = 1203, 73.6%). Propensity scores analyses were used to compare the overall survival (OS) and recurrence-free survival (RFS) between patients with or without T2DM. After propensity scores analyses, the prevalance of T2DM was significantly increased in the TC group compared with BTN group. Of the 455 TC patients, with T2DM in thyroid carcinoma was associated with increasing 1-, 3-, 5-year OS rates from 98.8, 76.5, and 70.9% to 99.7, 92.2, and 82.7%, respectively (P=0.017). While the 1-, 3-, and 5-year RFS rates in the group with T2DM were 92.3, 69.5, and 58.3%, which were significantly lower than those in the group without T2DM (97.6, 82.7, and 72.4%, P=0.009). After propensity scores analyses, with T2DM was significantly associated with increased risks of OS and RFS in the entire TC cohort.

Parity and Risk of Thyroid Cancer: a Population-Based Study in Lithuania

An association between parity and thyroid cancer risk has been investigated in a number of independent studies but yielded contradictory findings. The aim of this study was to explore the association between parity and thyroid cancer risk. The population-based cohort study in Lithuanian was conducted. The study dataset based on the linkages between all records from the 2001 population census, all cancer incidence records from the Lithuanian Cancer Registry, and all death and emigration records from Statistics Lithuania for the period between 6 April 2001 and 31 December 2009. Cox's proportional hazards regression models were used to estimate the hazard ratios (HRs) for parity, age at first birth, number of children, place of residence, education, and age at census. The cohort of 868,105 women was followed for 8.6 years, and 1775 thyroid cancer cases were diagnosed during the study period. The significantly higher thyroid cancer risk was observed among parous women (HR = 1.45, 95% CI: 1.20, 1.75) and in women with 1, 2, and 3 children, after adjusting for the possible confounding effects of relevant demographic variables. The findings of this study are consistent with the hypothesis that parity might be associated with the risk of thyroid cancer in women.

Female Reproductive Factors and Differentiated Thyroid Cancer

Differentiated thyroid cancer (DTC) is markedly more common in women than men, the highest female-to-male ratio being recorded during the reproductive period. This evidence has led to the suggestion that female hormonal and reproductive factors may account for the observed DTC gender disparity. This review focuses on current evidence on the risk of DTC in conjunction with major female reproductive factors, including the impact of pregnancy on DTC occurrence and progression/recurrence. Overall, studies exploring the link between the risk of DTC and menstrual and menopausal factors, oral contraceptives and/or hormone replacement therapy, showed these associations, if any, to be generally weak. Nonetheless, there is some evidence that higher levels of exposure to estrogens during reproductive years may confer an increased risk of DTC. As far as pregnancy is concerned, it is unclear whether a potential association between parity and risk of DTC actually exists, and whether it is enhanced in the short-term following delivery. A possible role for pregnancy-related factors in DTC progression has been recently suggested by some reports, the results of which are consistent with a worse outcome in the short-term of women diagnosed with DTC during gestation compared to non-pregnant control patients. Also, some progression of disease has been described in women with structural evidence of disease prior to pregnancy. However, there seems to be no impact from pregnancy in DTC-related death or overall survival. Several in vitro and animal studies have evaluated the influence of estrogens (E) and estrogen receptors (ERs) on thyroid cell proliferation. Presently available data are indicative of a role of E and ERs in thyroid cancer growth, although considerable discrepancies in respect to ER expression patterns in thyroid cancer tissues actually exist. Further studies providing more direct evidence on the possible role of E and of placental hormones and growth factors on thyroid growth may expand our knowledge on the mechanisms beyond the gender disparity of proliferative thyroid diseases.

Alcohol Intake and Risk of Thyroid Cancer: A Meta-Analysis of Observational Studies

Purpose

The purpose of this study was to assess whether alcohol intake is associated with the risk of thyroid cancer by a meta-analysis of observational studies.

Materials and Methods

We searched PubMed and EMBASE in June of 2015 to locate eligible studies. We included observational studies such as cross-sectional studies, case-control studies, and cohort studies reporting odd ratios (ORs) or relative risk (RRs) with 95% confidence intervals (CIs).

Results

We included 33 observational studies with two cross-sectional studies, 20 case-controls studies, and 11 cohort studies, which involved a total of 7,725 thyroid cancer patients and 3,113,679 participants without thyroid cancer in the final analysis. In the fixed-effect model meta-analysis of all 33 studies, we found that alcohol intake was consistently associated with a decreased risk of thyroid cancer (OR or RR, 0.74; 95% CI, 0.67 to 0.83; I²=38.6%). In the subgroup meta-analysis by type of study, alcohol intake also decreased the risk of thyroid cancer in both case-control studies (OR, 0.77; 95% CI, 0.65 to 0.92; I²=29.5%; n=20) and cohort studies (RR, 0.70; 95% CI, 0.60 to 0.82; I²=0%; n=11). Moreover, subgroup meta-analyses by type of thyroid cancer, gender, amount of alcohol consumed, and methodological quality of study showed that alcohol intake was significantly associated with a decreased risk of thyroid cancer.

Conclusion

The current meta-analysis of observational studies found that, unlike most of other types of cancer, alcohol intake decreased the risk of thyroid cancer.

The Trend of Age-Group Effect on Prognosis in Differentiated Thyroid Cancer

Age has been included in various prognostic scoring systems for differentiated thyroid cancer (DTC). The aim of this study is to re-examine the relationship between age and prognosis by using Surveillance, Epidemiology, and End Results (SEER) population-based database. We identified 51,061 DTC patients between 2004 and 2012. Patients were separated into 10-year age groups. Cancer cause-specific survival (CSS) and overall survival (OS) data were obtained. Kaplan-Meier and multivariable Cox models were built to analyze the outcomes and risk factors. Increasing age gradient with a 10-year interval was associated with the trend of higher proportions for male gender, grade III/IV and summary stage of distant metastases. Both CSS and OS continued to worsen with increasing age, being poorest in in the oldest age group (≥71); multivariate analysis confirmed that CSS continued to fall with each age decade, significantly starting at 60 years (HR = 7.5, 95% 1.0–54.1, p = 0.047) compared to the young group (≤20). Similarly, multivariate analysis suggested that OS continued worsening with increasing age, but starting at 40 years (HR = 3.7, 95% 1.4–10.1, p = 0.009) compared to the young group. The current study suggests that an age exceeding 60 years itself represents an unfavorable prognostic factor and high risk for cancer-specific death in DTC.

Parity and thyroid cancer risk: a meta-analysis of epidemiological studies

Although observational studies have assessed the relationship between parity and thyroid cancer risk, the findings are inconsistent. To quantitatively assess the association, we conducted a systematic review and meta-analysis. PubMed and Embase were searched up to January 2015. Prospective or case-control studies that evaluated the association between parity and thyroid cancer risk were included. We used the fixed-effects model to pool risk estimates. After literature search, 10 prospective studies, 12 case-control studies and 1 pooled analysis of 14 case-control studies including 8860 patients were identified. The studies had fair methodological quality. Pooled analysis suggested that there was a significant association between parity and risk of thyroid cancer (RR for parous versus nulliparous: 1.09, 95% CI 1.03-1.15; I2=33.4%). The positive association persisted in almost all strata of subgroup analyses based on study design, location, study quality, type of controls, and confounder adjustment, although in some strata statistical significance was not detected. By evaluating the number of parity, we identified that both parity number of 2 versus nulliparous and parity number of 3 versus nulliparous demonstrated significant positive associations (RR=1.11, 95% CI 1.01-1.22; I2=31.1% and RR=1.16, 95% CI 1.01-1.33; I2=19.6% respectively). The dose-response analysis suggested neither a non-linear nor linear relationship between the number of parity and thyroid cancer risk. In conclusion, this meta-analysis suggests a potential association between parity and risk of thyroid cancer in females. However, the lack of detection of a dose-response relationship suggests that further studies are needed to better understand the relationship.

Baseline and lifetime alcohol consumption and risk of differentiated thyroid carcinoma in the EPIC study

BACKGROUND

Results from several cohort and case-control studies suggest a protective association between current alcohol intake and risk of thyroid carcinoma, but the epidemiological evidence is not completely consistent and several questions remain unanswered.

METHODS

The association between alcohol consumption at recruitment and over the lifetime and risk of differentiated thyroid carcinoma was examined in the European Prospective Investigation into Cancer and Nutrition. Among 477 263 eligible participants (70% women), 556 (90% women) were diagnosed with differentiated thyroid carcinoma over a mean follow-up of 11 years. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using multivariable Cox proportional hazards models.

RESULTS

Compared with participants consuming 0.1-4.9 g of alcohol per day at recruitment, participants consuming 15 or more grams (approximately 1-1.5 drinks) had a 23% lower risk of differentiated thyroid carcinoma (HR=0.77; 95% CI=0.60-0.98). These findings did not differ greatly when analyses were conducted for lifetime alcohol consumption, although the risk estimates were attenuated and not statistically significant anymore. Similar results were observed by type of alcoholic beverage, by differentiated thyroid carcinoma histology or according to age, sex, smoking status, body mass index and diabetes.

CONCLUSIONS

Our study provides some support to the hypothesis that moderate alcohol consumption may be associated with a lower risk of papillary and follicular thyroid carcinomas.

Reproductive Factors but Not Hormonal Factors Associated with Thyroid Cancer Risk: A Systematic Review and Meta-Analysis

Many studies have investigated the association between hormonal and reproductive factors and thyroid cancer risk but provided contradictory and inconclusive findings. This review was aimed at precisely estimating this association by pooling all available epidemiological studies. 25 independent studies were retrieved after a comprehensive literature search in databases of PubMed and Embase. Overall, common hormonal factors including oral contraceptive and hormone replacement therapy did not alter the risk of thyroid cancer. Older age at menopause was associated with weakly increased risk of thyroid cancer in overall analysis (RR = 1.24, 95% CI 1.00–1.53, P = 0.049); however, longer duration of breast feeding was related to moderately reduced risk of thyroid cancer, suggested by pooled analysis in all cohort studies (RR = 0.7, 95% CI 0.51–0.95, P = 0.021). The pooled RR in hospital-based case-control studies implicated that parous women were more susceptible to thyroid cancer than nulliparous women (RR = 2.30, 95% CI 1.31–4.04, P = 0.004). The present meta-analysis suggests that older age at menopause and parity are risk factors for thyroid cancer, while longer duration of breast feeding plays a protective role against this cancer. Nevertheless, more relevant epidemiological studies are warranted to investigate roles of hormonal and reproductive factors in thyroid carcinogenesis.

Linear reduction in thyroid cancer risk by oral contraceptive use: a dose-response meta-analysis of prospective cohort studies

STUDY QUESTION

Is there an association between oral contraceptive (OC) use and thyroid cancer risk in females?

SUMMARY ANSWER

OC use is inversely associated with the risk of thyroid cancer in females.

WHAT IS KNOWN ALREADY

OC use may be relevant to the risk of thyroid cancer as suggested by some epidemiological studies. However, the findings are inconsistent regarding the effect direction and size.

STUDY DESIGN, SIZE, DURATION

This systematic review and meta-analysis included a total of 1906 patients from about 1.3 million individuals who had participated in 9 prospective cohort studies. The follow-up length ranged 7.5-15.9 years.

PARTICIPANTS/MATERIALS, SETTING, METHODS

PubMed (MEDLINE) was searched through to January 2015 for eligible studies. References of relevant review articles were also manually screened. Prospective cohort studies that evaluated the association between OC use and thyroid cancer risk were included. Study characteristics including patients' characteristics, length of the follow-up and risk estimates were extracted. The quality of the studies was also assessed.

MAIN RESULTS AND THE ROLE OF CHANCE

The included studies were of high methodological quality according to the Newcastle-Ottawa Quality Assessment Scale. After pooling risk estimates from all the studies, there was a significant inverse association between the longest versus shortest duration of OC use and the risk of thyroid cancer [relative risk (RR) = 0.84, 95% confidence interval (CI) 0.73-0.97], with no considerable heterogeneity (I(2) = 26.1%). There was no significant publication bias. The significant association persisted in the subgroup of high-quality studies (RR = 0.84, 95% CI 0.72-0.97). By dose-response analysis, there was a linear relationship (P = 0.0001) between the duration of OC use and thyroid cancer risk. The summary RR for an increment of 1 year of OC use was 0.96 (95% CI 0.94-0.98), with no significant heterogeneity.

LIMITATIONS, REASONS FOR CAUTION

Individual patient data were unavailable for a more accurate estimation.

WIDER IMPLICATIONS OF THE FINDINGS

These results indicate that OC use may decrease the risk of thyroid cancer in females. This may have implications for women's decisions regarding the use of OC.

STUDY FUNDING/COMPETING INTERESTS

No funding was involved for this study. No conflicts of interest are declared.

Menstrual and reproductive history and use of exogenous sex hormones and risk of thyroid cancer among women: a meta-analysis of prospective studies

PURPOSE

Thyroid cancer has a higher incidence in women than in men, and it has been hypothesized that hormonal factors may explain such disparity. We performed a meta-analysis of observational prospective studies to investigate the association between menstrual and reproductive variables and exogenous hormone use and the risk of thyroid cancer among women.

METHODS

We calculated summary relative risks and 95% confidence intervals (95% CI) using random effect models.

RESULTS

Overall, 5,434 thyroid cancer cases from twenty-four papers were included. Increasing age at first pregnancy/birth (SRR 1.56, 95% CI 1.01-2.42) and hysterectomy (SRR 1.43, 95% CI 1.15-1.78) were associated with thyroid cancer risk. Women that were in menopause at enrolment had a reduced thyroid cancer risk (SRR 0.79, 95% CI 0.62-1.01). No other menstrual, reproductive, and hormonal variable was associated with thyroid cancer risk.

CONCLUSIONS

Menstrual and reproductive factors may play a role in the etiology of thyroid cancer, possibly through the mediation of estrogen receptors.

Reproductive and menstrual factors and risk of differentiated thyroid carcinoma: the EPIC study

Differentiated thyroid carcinoma (TC) is threefold more common in women than in men and, therefore, a role of female hormones in the etiology of differentiated TC has been suggested. We assessed these hypotheses in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Among 345,157 women (mean age 51) followed for an average of 11 years, 508 differentiated TC cases were identified. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards regression models. No significant associations were observed between differentiated TC risk and number of pregnancies, breast feeding, menopausal status, and age at menarche and at menopause. Significant associations were found with history of infertility problems (HR 1.70; 95% CI 1.12-2.60), a recent pregnancy (HR for ≤ 5 vs. >5 years before recruitment 3.87; 95% CI 1.43-10.46), menopause type (HR for surgical vs. natural menopause: 2.16; 95% CI 1.41-3.31), oral contraceptive (OC) use at recruitment (HR: 0.48; 95% CI 0.25-0.92) and duration of OC use (HR for ≥ 9 vs. ≤ 1 year: 0.66; 95% CI: 0.50-0.89). An increased risk was also found with hormone replacement therapy use at recruitment (HR = 1.30, 95% CI 1.02-1.67), but this was not significant after adjustment for type of menopause (HR = 1.22, 95% CI 0.95-1.57). Overall, our findings do not support a strong role of reproductive and menstrual factors, and female hormone use in the etiology of differentiated TC. The few observed associations may be real or accounted for by increased surveillance in women who had infertility problems, recent pregnancies or underwent surgical menopause.

Modifiable risk factors and thyroid cancer

OBJECTIVE

To evaluate the association between modifiable patient risk factors including tobacco use, alcohol consumption, body mass index (BMI), and thyroid cancer.

STUDY DESIGN

Retrospective study with chart review.

SETTING

Midwest university hospital.

SUBJECTS AND METHODS

Retrospective study comparing Midwest patients with thyroid cancer from our Thyroid Tumor and Cancer Registry with Midwest controls without a personal history of cancer. Descriptive statistics were created from patient questionnaires and chart reviews. Odds ratios (ORs) were reported for significant associations.

RESULTS

There were 467 patients with cancer and 255 controls. The thyroid cancer group included 404 papillary, 47 follicular, 13 medullary, and 3 anaplastic cancers. When comparing all patients with cancer with controls, smoking more than 100 lifetime cigarettes was associated with a reduced cancer risk (OR, 0.68; 95% confidence interval [CI], 0.50-0.94). Secondhand smoke exposure did not show a statistically significant relationship to thyroid cancer. Compared with never drinking, current drinking was associated with a reduced cancer risk (OR, 0.46; 95% CI, 0.29-0.73) as was consuming 1 to 2 drinks daily compared to drinking <1 drink daily (OR, 0.58; 95% CI, 0.34-0.89). There was no difference between median BMI at age 20 years, lifetime maximum BMI, or current BMI between patients with cancer and controls.

CONCLUSION

Our data showed no positive correlation between tobacco use, alcohol consumption, or obesity and thyroid cancer risk. Our data suggest that tobacco use and mild alcohol consumption may be associated with a slightly reduced risk of thyroid cancer. There was no association between BMI and thyroid cancer in our study population.

Biomarkers of thyroid function and autoimmunity for predicting high-risk groups of thyroid cancer: a nested case-control study

Background

A remarkable increase in the number of thyroid cancer cases has been reported in recent years; however, the markers to predict high-risk groups have not been fully established.

Methods

We conducted a case–control study (257 cases and 257 controls) that was nested in the Cancer Screenee Cohort Study between August 2002 and December 2010; the mean follow-up time for this study was 3.1 ± 2.2 years. The levels of total triiodothyronine (TT3), free thyroxine (FT4), thyroid-stimulating hormone (TSH), thyroglobulin (Tg), anti-thyroperoxidase antibody (TPOAb), and anti-thyroglobulin antibody (TgAb) were measured using samples with pre-diagnostic status. Logistic regression models were used to examine the association between thyroid function/autoimmunity and thyroid cancer risk.

Results

When the markers were categorized by the tertile distributions of the control group, the highest tertile of FT4 (OR = 1.73, 95% CI = 1.11 - 2.69) and the middle tertile of TSH (OR = 1.77, 95% CI = 1.14 - 2.74) were associated with an increased risk of thyroid cancer by multivariate analyses. In addition, an elevated risk for thyroid cancer was found in subjects with TPOAb levels above 30 IU/mL (OR = 8.47, 95% CI = 5.39 - 13.33 for 30–60 IU/mL and OR = 4.48, 95% CI = 2.59 - 7.76 for ≥60 IU/mL). Stratified analyses indicated that some of these associations differed by sex, BMI, smoking status, and the duration of follow-up.

Conclusions

This study demonstrated that the levels of biomarkers of thyroid function/autoimmunity, particularly the presence of TPOAb, might be used as diagnostic markers for predicting thyroid cancer risk. Our findings suggest that careful monitoring of thyroid biomarkers may be helpful for identifying Korean populations at high-risk for thyroid cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-873) contains supplementary material, which is available to authorized users.

Dietary factors and the risk of thyroid cancer: a review

In the past few decades, the incidence of thyroid cancer has rapidly increased worldwide. Thyroid cancer incidence is relatively high in regions where the population's daily iodine intake is insufficient. While low dietary iodine has been considered as a risk factor for thyroid cancer development, previous studies found controversial results across different food types. Among different ethnic groups, dietary factors are influenced by various dietary patterns, eating habits, life-styles, nutrition, and other environmental factors. This review reports the association between dietary factors and thyroid cancer risk among ethnic groups living in different geologic regions. Iodine-rich food such as fish and shellfish may provide a protective role in populations with insufficient daily iodine intake. The consumption of goitrogenic food, such as cruciferous vegetables, showed a positive association with risk. While considered to be a risk factor for other cancers, alcohol intake showed a protective role against thyroid cancer. High consumption of meat such as chicken, pork, and poultry showed a positive association with the risk, but dairy products showed no significant association. Regular use of multivitamins and dietary nitrate and nitrite also showed a positive association with thyroid cancer risk. However, the study results are inconsistent and investigations into the mechanism for how dietary factors change thyroid hormone levels and influence thyroid function are required.

Thyroid cancer risk and smoking status: a meta-analysis

PURPOSE

Previous researchers have reported an inverse association between cigarette smoking and thyroid cancer risk. To summarize the role of smoking in relation to thyroid cancer occurrence, we conducted a meta-analysis.

METHODS

We performed a meta-analysis of 31 eligible studies to summarize the data describing the association between thyroid cancer occurrence and smoking. The case-control studies consisted of 6,260 thyroid cancer cases and 32,935 controls. Cohort studies contained 2,715 thyroid cancer patients that participated from recruitment to follow-up. Q-statistic and I (2) statistic were calculated to examine heterogeneity. Summary relative risks (RRs) and 95 % confidence intervals (95 % CIs) were calculated using a random effects model. Potential sources of heterogeneity were investigated via subgroup and sensitivity analyses, and publication biases were estimated.

RESULTS

Thyroid cancer risk was reduced in persons who had ever-smoked (RR = 0.79; 95 % CI 0.70-0.88) compared with never-smokers. However, strong evidence of heterogeneity was found among the investigated studies; therefore, subgroup analyses were conducted according to study type, smoking status, study location, source of controls, sex, and histological type of thyroid cancer. When the data were stratified by smoking status, an inverse association was observed only among current smokers (RR = 0.74; 95 % CI 0.64-0.86), not former smokers (RR = 1.01; 95 % CI 0.92-1.10). An inverse association was observed only in case-control studies (RR = 0.75; 95 % CI 0.66-0.85).

CONCLUSIONS

This meta-analysis of geographically diverse epidemiological data suggests that smoking, particularly current smoking, may influence susceptibility to thyroid cancer. Further well-designed studies with larger sample sizes should be conducted.

Incidence of thyroid cancer in England by ethnic group, 2001-2007

BACKGROUND

Thyroid cancer incidence is increasing worldwide, but with large variations in incidence that may reflect either diagnostic bias or true ethnic differences. We sought to determine the effect of ethnicity on the incidence of thyroid cancer in England, a multiethnic population with a single health-care system.

METHODS

We analysed 11,263 thyroid cancer registrations with ethnicity obtained by linkage to the Hospital Episodes Statistics database. Incidence rate ratios (RRs) adjusted for age, sex and income were calculated for the six main non-White ethnic groups in England compared with Whites and to each other.

RESULTS

Thyroid cancer incidence was higher in all ethnic groups, except Indians, compared with Whites: in Pakistanis (RR 1.79, 99% floating confidence interval (FCI) 1.47-2.19); Bangladeshis (RR 1.99, 99% FCI 1.46-2.71); Black Africans (RR 1.69, 99% FCI 1.34-2.13); Black Caribbeans (RR 1.56, 99% FCI 1.25-1.93); and Chinese (RR 2.14, 99% FCI 1.63-2.80).

CONCLUSION

The risk of thyroid cancer in England varies significantly by ethnicity. The elevated incidence in most ethnic minorities is unlikely to be due to diagnostic bias and warrants further investigation.

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.

Impact of alcohol use on thyroid function

Alcohol is one of the commonest illicit psychoactive substances consumed globally and is the world's third largest risk factor for disease and disability. It has been reported to have multiple effects on the hypothalamo-pituitary-thyroid axis and the functioning of the thyroid gland. It has been reported to cause direct suppression of thyroid function by cellular toxicity, and indirect suppression by blunting thyrotropin-releasing hormone response. It causes a decrease of peripheral thyroid hormones during chronic use and in withdrawal. Alcohol use may also confer some protective effect against thyroid nodularity, goiter, and thyroid cancer. This article presents a review of the clinically relevant effects of alcohol on the functioning of the thyroid gland and also discusses the effect of medication used in treatment of alcohol dependence on thyroid function.

Increased incidence of thyroid cancer in Latina, Italy: a possible role of detection of subclinical disease

OBJECTIVE

To describe the thyroid cancer incidence trends and geographical patterns in the Latina Province of Lazio, Italy using the population-based cancer registry.

METHODS

We extracted from the Latina cancer registry all cases of thyroid cancer from 1997 to 2006. Cases were classified according to morphological type and diameter. Data for diagnostic procedures for Latina Province residents from 2001 to 2006 were extracted from the regional outpatient procedures information system.

RESULTS

A total of 982 cases were diagnosed, for a standardized incidence of 8.3 and of 27.9 per 100,000 in males (n, 220) and in females (n, 762), respectively. The annual percent change (APC) was +16.7% (95% CI +7.2, +27.2) and +10.5% (95% CI +6.5, +14.6) in males and females, respectively. The increase was mostly due to papillary (n, 759) and small (≤20 mm) cancers (n, 617), with no difference by age (<45 years; n, 431). The APC of neck ultrasound performed was +8.7% (95% CI +0.1, +18.1) and +9.0% (95% CI +1.1, +17.4) and that of biopsy/cytology was +17.0% (95% CI +13.0, +21.3) and +16.6% (95% CI +6.2, +28.1) in men and women, respectively. The geographic pattern of biopsy/cytology was similar to that of cancer incidence but not to that of neck ultrasound.

CONCLUSIONS

In Latina, the increase in thyroid cancer incidence was more rapid than in the rest of Italy, particularly for types with a good prognosis. While tumor size and histotype suggest an increase in detection instead of an increase in disease occurrence, data on diagnostic procedure reimbursements cannot provide an explanation.

Menstrual and reproductive factors, exogenous hormone use, and risk of thyroid carcinoma in postmenopausal women

PURPOSE

To investigate the association of reproductive factors and hormone therapy, including type of hormone therapy, with risk of thyroid cancer in postmenopausal women.

METHODS

We assessed these associations with risk of incident thyroid cancer in a cohort of 145,007 postmenopausal women enrolled in the Women's Health Initiative. Over 12.7 years of follow-up, 296 cases of thyroid cancer were identified, including 243 with papillary thyroid cancer. Cox proportional hazards models were used to estimate hazard ratios and 95 % confidence intervals for exposures of interest.

RESULTS

In both age-adjusted and multivariable-adjusted analyses, menstrual and reproductive factors including age at menarche, age at menopause, age at first birth, age at last live birth, parity, duration of breastfeeding, miscarriages, stillbirths, hysterectomy, bilateral oophorectomy, and use of oral contraceptives were not associated with risk of all thyroid cancer or papillary thyroid cancer. In addition, ever use of menopausal hormone therapy, current or former use, duration of use, and type were not associated with risk.

CONCLUSION

We found little support for associations of reproductive or hormonal factors with risk of developing thyroid cancer. Importantly, our study showed no association of type of hormone therapy used with thyroid cancer risk.