A pooled analysis of case-control studies of thyroid cancer. IV. Benign thyroid diseases

Circulating endogenous sex steroids and risk of differentiated thyroid carcinoma in men and women

Thyroid cancer (TC) is substantially more common in women than in men, pointing to a possible role of sex steroid hormones. We investigated the association between circulating sex steroid hormones, sex hormone binding globulin (SHBG) and the risk of differentiated TC in men and women within the European Prospective Investigation into Cancer and nutrition (EPIC) cohort. During follow-up, we identified 333 first primary incident cases of differentiated TC (152 in pre/peri-menopausal women, 111 in post-menopausal women, and 70 in men) and 706 cancer-free controls. Women taking exogenous hormones at blood donation were excluded. Plasma concentrations of testosterone, androstenedione, dehydroepiandrosterone, estradiol, estrone and progesterone (in pre-menopausal women only) were performed using liquid chromatography/mass spectrometry method. SHBG concentrations were measured by immunoassay. Odds ratios (ORs) were estimated using conditional logistic regression models adjusted for possible confounders. No significant associations were observed in men and postmenopausal women, while a borderline significant increase in differentiated TC risk was observed with increasing testosterone (adjusted OR T3 vs T1: 1.68, 95% CI: 0.96-2.92, ptrend = .06) and androstenedione concentrations in pre/perimenopausal women (adjusted OR T3 vs T1: 1.78, 95% CI: 0.96-3.30, ptrend = .06, respectively). A borderline decrease in risk was observed for the highest progesterone/estradiol ratio (adjusted OR T3 vs T1: 0.54, 95% CI: 0.28-1.05, ptrend = .07). Overall, our results do not support a major role of circulating sex steroids in the etiology of differentiated TC in post-menopausal women and men but may suggest an involvement of altered sex steroid production in pre-menopausal 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.

Thyroid Cancer and Pesticide Use in a Central California Agricultural Area: A Case Control Study

OBJECTIVE

To examine environmental factors that influence risk of thyroid cancer.

METHODS

We performed a case-control study utilizing thyroid cancer cases from the California Cancer Registry (1999-2012) and controls sampled in a population-based manner. Study participants were included if they were diagnosed with thyroid cancer, lived in the study area at their time of diagnosis, and were ≥35 years of age. Controls were recruited from the same area and eligible to participate if they were ≥35 years of age and had been living in California for at least 5 years prior to the interview. We examined residential exposure to 29 agricultural use pesticides, known to cause DNA damage in vitro or are known endocrine disruptors. We employed a validated geographic information system-based system to generate exposure estimates for each participant.

RESULTS

Our sample included 2067 cases and 1003 controls. In single pollutant models and within a 20-year exposure period, 10 out of 29 selected pesticides were associated with thyroid cancer, including several of the most applied pesticides in the United States such as paraquat dichloride [odds ratio (OR): 1.46 (95% CI: 1.23, 1.73)], glyphosate [OR: 1.33 (95% CI: 1.12, 1.58)], and oxyfluorfen [OR: 1.21 (95% CI: 1.02, 1.43)]. Risk of thyroid cancer increased proportionately to the total number of pesticides subjects were exposed to 20 years before diagnosis or interview. In all models, paraquat dichloride was associated with thyroid cancer.

CONCLUSIONS

Our study provides first evidence in support of the hypothesis that residential pesticide exposure from agricultural applications is associated with an increased risk of thyroid cancer.

The association of uric acid with the development of thyroid nodules: a retrospective cohort study

BACKGROUND

Uric acid was found to have a positive correlation with thyroid nodules in the cross-sectional studies recently. We aimed to conduct a retrospective cohort study to investigate whether uric acid is a risk factor for the development of thyroid nodules.

METHODS

We reviewed the data of individuals who attended the medical check-ups in our hospital from 2010 to 2019. A total of 6587 adults without thyroid nodules at baseline were enrolled in this study. Logistic regression with or without restricted cubic spline function was used to investigate the non-linear or linear association between uric acid and thyroid nodules, respectively.

RESULTS

Baseline characteristics showed that subjects mainly consisted of the healthy, young population. After fully adjusting for the potential confounders, such as age, sex, metabolic and inflammatory indicators, hepatic and renal function, a logistic restricted cubic spline regression model suggested that uric acid had a significant association (P = 0.028) with the development of thyroid nodules, but the association was not non-linear (P = 0.516). The results indicate that the association between them is linear, which was demonstrated by a logistic regression model, in which the odds ratio of uric acid per 100 mmol/L was 1.137 (P = 0.004). Age, sex, diastolic blood pressure, fasting blood sugar, and blood monocyte were found to be risk factors for thyroid nodules as well.

CONCLUSION

Uric acid is an independent risk factor for the formation of thyroid nodules. This finding warrants attention to this risk factor in apparently healthy adults.

Risk–benefit assessment of seaweed Allergenicity risk assessment of novel protein

As the world population rapidly grows, there is a clear need for alternative food sources, particularly for the provision of protein. Seaweed is one such alternative source of protein that requires greater investigation. In this context, a working programme within the European Food Risk Assessment (EU‐FORA) Fellowship Programme framework was developed at National Food Institute – Technical University of Denmark. This Programme is an initiative of the EFSA with the aim to build a European risk assessment community. The purpose of this technical report is to describe the activities in which the fellow was involved. As part of the Research Group for Risk–Benefit, the fellow performed a risk–benefit assessment of seaweed Palmaria palmata gaining an in‐depth expertise in all the steps. The health impact of Palmaria palmata consumption was estimated, considering its high nutritional value but also highlighting concerns towards some components. Simultaneous to the work on the risk–benefit, the fellow also worked within the Research Group for Food Allergy, specifically on the allergenicity risk assessment of a plant‐based novel protein (seaweed protein) using different laboratory assays. Seaweed protein digestibility was assessed, and its digestion products were characterised and assessed for immunogenicity. Finally, the fellow collaborated with the Research Group for Microbial Biotechnology and Biorefining in the development of a novel food (alfalfa protein) application dossier to be submitted to EFSA, gaining expertise in the risk assessment of a novel food. In conclusion, the present working programme, together with additional activities and training provided by different institutions, enabled the fellow to gain a broader perspective in food safety, particularly concerning seaweed, novel foods and the safety assessment of novel proteins.

Hashimoto's Thyroiditis and Papillary Cancer Thyroid Coexistence Exerts a Protective Effect: a Single Centre Experience

Papillary thyroid carcinoma (PTC) is the most common malignant tumour of the thyroid and it is often found in association with Hashimoto's thyroiditis (HT). This concomitance is still under debate. The aim of this study is to investigate the influence of Hashimoto's thyroiditis in patients with papillary thyroid carcinoma. Two thousand two hundred eighteen patients underwent thyroidectomy in our department between January 2015 and January 2020. Of these, 435 patients had surgery for papillary thyroid carcinoma and form the basis of our studies. The association between PTC and HT was found in 180 patients (41.4%), mostly represented in the female group (78.9%), with a lower median age than patients with PTC without HT. In comparison to patients with PTC alone, the PTC-HT group had less invasive and smaller tumours, as well as less lymph node involvement. Moreover, tumours of patients with PTC-HT were diagnosed earlier. Our data showed that Hashimoto's thyroiditis may be considered a protective factor when PTC develops. Furthermore, we concluded that patients with PTC and HT had a better prognosis and a lower risk of recurrence than those that did not have HT.

Thyroid Cancer: Global Burden and Trends

The incidence of thyroid cancer continues to increase, representing the 5th most common cancer type in the USA today (Sherman, Lancet 361(9356):501-11, 2003). The current study sought to analyze the global burden of thyroid cancer utilizing the publicly accessible GLOBOCAN database. An estimated 586,202 cases of thyroid cancer were reported in 2020, making thyroid cancer the 10th most common cancer worldwide. The majority of thyroid cancer cases occurred in countries with a high or very high Human Development Index (HDI), accounting for 91% of new cases. With respect to the World Health Organization (WHO) regions, the Western Pacific had the highest incidence of thyroid cancer accounting for 47.6% of cases despite representing only 25.4% of the world's population. Thyroid cancer incidence and mortality are expected to increase by 29.9% and 67%, respectively, by the year 2040. The African region is projected to experience the highest increase in both incidence (84.3%) and mortality (100.3%) over this time period. The results of our study demonstrate that the incidence and mortality of thyroid cancer vary by the geographic location and socio-economic status. Although the incidence was noted to be the highest in very high HDI countries and the Western Pacific region, mortality was noted to be disproportionately higher in the low HDI countries and African region. This may be due to discrepancies in access to care and/or environmental exposures such as ionizing radiation and iodine deficiency. Further measures are required to improve the outcomes from thyroid cancer regardless of the geographic location or socio-economic status.

Spatial distribution and determinants of thyroid cancer incidence from 1999 to 2013 in Korea

We evaluated the spatial variation in thyroid cancer incidence and its determinants in Korea considering its importance in cancer prevention and control. This study was based on the ecological design with cancer incidence data by administrative district from the National Cancer Center and regional characteristics generated from the Korea Community Health Survey Data. We identified spatial clusters of thyroid cancer incidences based on spatial scan statistics. Determinants of regional variation in thyroid cancer incidence were assessed using the Besag-York-Mollie model with integrated nested Laplace approximations. Spatial clusters for low and high thyroid cancer incidences were detected in the northeastern and southwestern regions, respectively. Regional variations in thyroid cancer incidence can be attributed to the prevalence of recipients of basic livelihood security (coefficient, - 1.59; 95% credible interval [CI], - 2.51 to - 0.67), high household income (coefficient, 0.53; 95% CI, 0.31 to 0.76), heavy smoking (coefficient, - 0.91; 95% CI, - 1.59 to - 0.23), thyroid dysfunction (coefficient, 3.24; 95% CI, 1.47 to 5.00), and thyroid cancer screening (coefficient, 0.38; 95% CI, 0.09 to 0.67). This study presented the spatial variations in thyroid cancer incidence, which can be explained by the prevalence of socioeconomic factors, thyroid cancer screening, thyroid dysfunction, and smoking.

Screening Leads to Overestimated Associations of Thyroid Dysfunction and Thyroiditis with Thyroid Cancer Risk

Simple Summary

The association of thyroid dysfunction and thyroiditis with the risk of thyroid cancer is an important issue in clinical practice, and is controversial due to various confounders, including screening effects. In this large-sample, population-based, nationwide study, we demonstrated that the screening effect likely significantly contributed to the positive associations of thyroid dysfunction and thyroiditis with thyroid cancer. After adjustment for this confounder, thyroid cancer risk was positively associated with hypothyroidism and thyroiditis but negatively associated with hyperthyroidism and Graves’ disease. Multiple subgroup analyses showed consistent results. Given these overestimated associations, we suggest that unnecessary and excessive concerns or screening tests for thyroid cancer could be reduced in patients with thyroid dysfunction or thyroiditis.

Abstract

We aimed to assess the relationships of functional thyroid disease and thyroiditis with subsequent thyroid cancer, which is controversial due to various confounders, and the effect of thyroid disease workup on this association. We used the cohort data from 2002 to 2015 (Study I, n = 28,330) and the entire data from 2002 to 2019 (Study II, n = 883,074) of the Korean National Health Insurance Service database, and performed logistic regression and subgroup analyses with various covariates. In Study I, hypothyroidism, thyroiditis, autoimmune thyroiditis, hyperthyroidism, and Graves’ disease showed positive associations with thyroid cancer. In Study II, after adjustment for covariates including the number of thyroid function tests, the ORs for thyroid cancer were significantly reduced in all thyroid diseases. Hypothyroidism, thyroiditis, and autoimmune thyroiditis were positively associated (adjusted odds ratio, OR (95% confidence interval, CI) 1.28 (1.25–1.32), 1.36 (1.31–1.42), and 1.17 (1.11–1.24), respectively), whereas hyperthyroidism and Graves’ disease were negatively associated with thyroid cancer (adjusted OR (95% CI) 0.80 (0.77–0.83) and 0.69 (0.65–0.74), respectively). Multiple subgroup analyses in both studies showed consistent results. In this large population-based, nationwide study, we confirmed that thyroid disease workup leads to overestimation of associations of thyroid dysfunction and thyroiditis with thyroid cancer risk.

Trends in thyroid function testing, neck ultrasound, thyroid fine needle aspiration, and thyroidectomies in North-eastern Italy

PURPOSE

Evidence of an increased diagnostic pressure on thyroid has emerged over the past decades. This study aimed to provide estimates of a wide spectrum of surveillance indicators for thyroid dysfunctions and diseases in Italy.

METHODS

A population-based study was conducted in North-eastern Italy, including 11.7 million residents (20% of the total Italian population). Prescriptions for TSH testing, neck ultrasound or thyroid fine needle aspiration (FNA), surgical procedures, and drugs for hypo- or hyperthyroidism were extracted from regional health databases. Proportions and rates of selected examinations were calculated from 2010 to 2017, overall and by sex, calendar years, age, and region.

RESULTS

Between 2010 and 2017 in North-eastern Italy, 24.5% of women and 9.8% of men received at least one TSH test yearly. In 2017, 7.1% of women and 1.5% of men were prescribed drugs for thyroid dysfunction, 94.6% of whom for hypothyroidism. Neck ultrasound examinations were performed yearly in 6.9% of women and 4.6% of men, with a nearly two-fold variation between areas. Thyroid FNA and thyroidectomies were three-fold more frequent in women (394 and 85 per 100,000) than in men (128 and 29 per 100,000) with a marked variation between areas. Both procedures decreased consistently after 2013.

CONCLUSIONS

The results of this population-based study describe recent variations over time and between surrounding areas of indicators of 'diagnostic pressure' on thyroid in North-eastern Italy. These results emphasize the need to harmonize practices and to reduce some procedures (e.g., neck ultrasound and total thyroidectomies) in certain areas.

A review of species differences in the control of, and response to, chemical-induced thyroid hormone perturbations leading to thyroid cancer

This review summarises the current state of knowledge regarding the physiology and control of production of thyroid hormones, the effects of chemicals in perturbing their synthesis and release that result in thyroid cancer. It does not consider the potential neurodevelopmental consequences of low thyroid hormones. There are a number of known molecular initiating events (MIEs) that affect thyroid hormone synthesis in mammals and many chemicals are able to activate multiple MIEs simultaneously. AOP analysis of chemical-induced thyroid cancer in rodents has defined the key events that predispose to the development of rodent cancer and many of these will operate in humans under appropriate conditions, if they were exposed to high enough concentrations of the affecting chemicals. There are conditions however that, at the very least, would indicate significant quantitative differences in the sensitivity of humans to these effects, with rodents being considerably more sensitive to thyroid effects by virtue of differences in the biology, transport and control of thyroid hormones in these species as opposed to humans where turnover is appreciably lower and where serum transport of T4/T3 is different to that operating in rodents. There is heated debate around claimed qualitative differences between the rodent and human thyroid physiology, and significant reservations, both scientific and regulatory, still exist in terms of the potential neurodevelopmental consequences of low thyroid hormone levels at critical windows of time. In contrast, the situation for the chemical induction of thyroid cancer, through effects on thyroid hormone production and release, is less ambiguous with both theoretical, and actual data, showing clear dose-related thresholds for the key events predisposing to chemically induced thyroid cancer in rodents. In addition, qualitative differences in transport, and quantitative differences in half life, catabolism and turnover of thyroid hormones, exist that would not operate under normal situations in humans.

Genetic Mutations and Variants in the Susceptibility of Familial Non-Medullary Thyroid Cancer

Thyroid cancer is the most frequent endocrine malignancy with the majority of cases derived from thyroid follicular cells and caused by sporadic mutations. However, when at least two or more first degree relatives present thyroid cancer, it is classified as familial non-medullary thyroid cancer (FNMTC) that may comprise 3-9% of all thyroid cancer. In this context, 5% of FNMTC are related to hereditary syndromes such as Cowden and Werner Syndromes, displaying specific genetic predisposition factors. On the other hand, the other 95% of cases are classified as non-syndromic FNMTC. Over the last 20 years, several candidate genes emerged in different studies of families worldwide. Nevertheless, the identification of a prevalent polymorphism or germinative mutation has not progressed in FNMTC. In this work, an overview of genetic alteration related to syndromic and non-syndromic FNMTC is presented.

BRAFV600E, hypothyroidism, and human relaxin in thyroid carcinogenesis

PURPOSE

BRAF^V600E, a major driver of thyroid cancer, evaluated in the context of thyroid hormones and human relaxin.

METHODS

Immunohistochemical expressions of BRAF^V600E, TSH, TSH receptor (TSHR), T4, T3 receptor (T3R), RLNH2, and its receptor, RXFP1, were evaluated in thyroid tumors from a retrospective U.S. population of 481 cancer cases diagnosed in 1983-2004.

RESULTS

BRAF^V600E was expressed in 52% of all thyroid tumors; expression of other markers ranged from 25% for T4 to 98% for RLNH2. Tumors predominantly exhibited hypothyroid-like conditions characterized by elevated TSH and TSHR and reduced T4. BRAF^V600E prevalence was significantly higher in tumors expressing TSH, TSHR, T3R, and RXFP1 and lower in tumors expressing T4. The proportion of BRAF^V600E mutation in classic papillary tumors significantly increased from 56 to 72% over the 21-year period of diagnoses, while expression of RXFP1, TSH, TSHR, and T3R decreased in non-tumor. Racial/ethnic differences were observed in thyroid hormone marker expression. Non-tumor expression of TSH, TSHR, and T3R were each associated with shorter overall survival, but did not remain significant after adjustment for demographic and clinical factors.

CONCLUSIONS

Our study provides the first evidence of the potential interaction of BRAF^V600E mutation, relaxin, and thyroid hormones in thyroid carcinogenesis. Moreover, our results suggest that hypothyroidism, influenced by RLNH2 activity, may underlie the development of the majority of thyroid cancers and mediate the role of BRAF^V600E in thyroid carcinogenesis. BRAF^V600E mutation is increasing in papillary thyroid cancers and may be contributing to the rising incidence of this malignancy.

Changes in the Demographic and Clinicopathological Characteristics of Thyroid Cancer: A Population-Based Investigation in Algeria, 1993-2013

Over the last three decades, the incidence of thyroid cancer has increased worldwide. The reasons for this increase remain controversial. In Algeria, however, to date, information on thyroid cancer has been limited to a hospital-based case series. We analyzed data from a population-based cohort study in Oran District, Algeria, to describe demographic and clinicopathological characteristics of patients diagnosed with thyroid cancer between 1993 and 2013. Medical records and pathology reports of thyroid cancer patients who had surgery were reviewed. Changes in demographic and clinicopathological features over the 21-year period are described. During the study period, thyroid cancer was diagnosed in 1248 women (86.5%, mean age 43.7 ± 15.2 years) and 195 men (23.4%, mean age 48.1 ± 15.9 years). Most cases (83.1% for women and 69.8% for men) sought a diagnosis following a self-neck check. The most common histologic types were papillary (58.3%), follicular (29.7%), anaplastic (4.1%), and medullary (0.8%) carcinomas. The incidence of papillary carcinomas significantly increased (p < 0.001) while the incidence of other histologic types significantly decreased over time. Tumor size overall significantly decreased (p < 0.001) while the frequency of small (≤20 mm) and larger (>20 mm) carcinomas significantly increased (p < 0.05). The frequency of thyroid cancers with capsular effractions and angioinvasions also decreased over time. Thyroid cancer incidence in Algeria has increased substantially in line with international trends with changes in clinical practice being a possible contributing factor. However, the increasing papillary-to-follicular cancer ratio may be due to changes in iodine nutrition status in Algeria. Further research, including exploration of biological and molecular features of thyroid cancer, will enable a better understanding of risk factors and etiopathogenetic mechanisms.

A rapidly increasing trend of thyroid cancer incidence in selected East Asian countries: Joinpoint regression and age-period-cohort analyses

BACKGROUND

This study described the incidence and mortality trends and analyzed age-period-cohort effects on incidences in China, Japan, and Korea.

METHODS

Data were extracted from the Cancer Incidence in Five Continents series and the World Health Organization Cancer Mortality Database, and the age-standardized incidence and mortality rates by Segi's world population were calculated. Joinpoint regression analysis was used to evaluate the time trend of age-standardized incidence and mortality rates and the age-period-cohort model with intrinsic estimator was applied for estimating the effects of age, period, and cohort on thyroid cancer (TC) incidence in individuals between 20 and 84 years of age.

RESULTS

An increasing trend in TC incidence rates was observed among males from China (10.3%), Japan (4.7%), and Korea (20.8%) and among females from China (9.4%), Japan (3.5%), and Korea (20.5%). TC incidence rates in females were much higher than those in males. A downward trend of TC mortality rates was observed, especially in both sexes of Japan and Chinese females. The slope of the age effect curve peaked at an earlier age in females than males in Japan and Korea. A strong period effect and remarkedly increasing rate ratios were observed in all regions and for both sexes. The cohort effect had a declining tendency on TC incidence in males and females in these areas.

CONCLUSIONS

The rapidly upward incidence trend and strong period effect suggest that overdiagnosis caused by higher diagnostic intensity might be an explanation for the upward trend, and some environmental risk factor exposures are also not excluded. In addition, the discrepant trends of TC incidence and mortality reveal the need to identify the few high-risk patients who needed further treatment from those patients who may not need treatment.

Does Obesity Cause Thyroid Cancer? A Mendelian Randomization Study

BACKGROUND

The incidence of thyroid cancer is rising, and relatively little is known about modifiable risk factors for the condition. Observational studies have suggested a link between adiposity and thyroid cancer; however, these are subject to confounding and reverse causality. Here, we used data from the UK Biobank and Mendelian randomization approaches to investigate whether adiposity causes benign nodular thyroid disease and differentiated thyroid cancer.

METHODS

We analyzed data from 379 708 unrelated participants of European ancestry in the UK Biobank and identified 1812 participants with benign nodular thyroid disease and 425 with differentiated thyroid carcinoma. We tested observational associations with measures of adiposity and type 2 diabetes mellitus. One and 2-sample Mendelian randomization approaches were used to investigate causal relationships.

RESULTS

Observationally, there were positive associations between higher body mass index (odds ratio [OR], 1.15; 95% confidence interval [CI], 1.08-1.22), higher waist-hip ratio (OR, 1.16; 95% CI, 1.09-1.23), and benign nodular thyroid disease, but not thyroid cancer. Mendelian randomization did not support a causal link for obesity with benign nodular thyroid disease or thyroid cancer, although it did provide some evidence that individuals in the highest quartile for genetic liability of type 2 diabetes had higher odds of thyroid cancer than those in the lowest quartile (OR, 1.45; CI, 1.11-1.90).

CONCLUSIONS

Contrary to the findings of observational studies, our results do not confirm a causal role for obesity in benign nodular thyroid disease or thyroid cancer. They do, however, suggest a link between type 2 diabetes and thyroid cancer.

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.

Does relatively low iodine intake contribute to thyroid cancer? An ecological comparison of epidemiology

Research on the relationship between iodine intake and thyroid cancer (TC) risk is limited, and the findings are inconclusive. The objective of this study was to provide emerging evidence for the association between iodine intake and TC risk in a Chinese population.An ecological study of epidemiology is used to compare the iodine intake among populations with different TC incidence in Zhoushan, China. Incidence rates of TC were investigated and compared among four counties of the Zhoushan Islands from 2014 to 2018. Iodized salt consumption rate and the level of urinary iodine concentration (UIC) were analyzed for pupils and pregnant women from four counties.During 2014 to 2018, a total of 2495 new cases of TC were diagnosed in Zhoushan Islands. The mean crude incidence rate of TC was 51.29 per 100,000 inhabitants, and the standardized (world population) incidence rate (SIR) was 31.34 per 100,000 population. Incidence rates (SIR and crude incidence rates) were significantly higher in women than in men (χ test, P < .05). Both male and female, the incidence of TC in Daishan County is higher than the other three counties of Zhoushan. Iodized salt consumption rate and median UIC in pupils and pregnant women in Daishan County was significantly lower than the other three counties (χ test and Kruskal-Wallis test, all P < .05). The population with high TC incidence has a lower iodized salt consumption and a lower level of UIC compare with the relative low TC incidence populations.The low consumption of iodized salt with mild iodine deficiency may contribute to explain the exceptionally high incidence of TC in Daishan County. Further subtle designed studies are needed to provide additional insights into the epidemiology and etiology of TC and help identify the safe limit of iodine intake for prevention.

Association of benign thyroid diseases with thyroid cancer risk: a meta-analysis of prospective observational studies

PURPOSE

Evidence showed that benign thyroid disease was one of the risk factors for thyroid cancer. However, the results of some studies were inconsistent and were previously meta-analyses of case-control studies. Therefore, we performed a meta-analysis of prospective studies to investigate the relationship between benign thyroid diseases and thyroid cancer risk.

METHODS

All eligible studies were identified via systematic searches of multiple literature databases. The combined RR (relative risk)/HR (hazard ratio) or SIR (standardized incidence ratio) with 95% confidence interval was calculated. Heterogeneity was assessed with the I² test. Publication bias and subgroup analyses were also performed.

RESULTS

Twelve studies were eligible for inclusion in the meta-analysis. The pooled RR/HR of thyroid carcinoma in benign thyroid diseases was 4.39 (95% CI 3.22-5.55). The pooled SIR of thyroid carcinoma in benign thyroid diseases was 5.98 (95% CI 4.09-7.86). Subgroup analysis was performed using the type of benign thyroid diseases. Effect value was RR/HR: hyperthyroidism (RR/HR = 3.89, 95% CI = 1.69-6.08), hypothyroidism (RR/HR = 2.72, 95% CI = 1.04-4.41), and goiter (RR/HR = 22.18, 95% CI = 12.09-32.28). Effect value was SIR: hyperthyroidism (RR/HR = 5.96, 95% CI = 1.88-10.03), goiter (RR/HR = 7.65, 95% CI = 6.94-8.37), and thyroiditis (RR/HR = 3.25, 95% CI = 1.62-4.89).

CONCLUSIONS

Our study has shown that benign thyroid diseases might be associated with increased risk of thyroid cancer, especially in hyperthyroidism, hypothyroidism, and goiter. However, further investigation is needed to better understand the underlying biological mechanisms.

Human relevance of follicular thyroid tumors in rodents caused by non-genotoxic substances

Chronic stimulation of the thyroid gland of rodents by TSH leads to thyroid follicular hyperplasia and subsequently to thyroid follicular adenomas and carcinomas. However, the interpretations of rodent thyroid tumors are contradictory. The U.S. Food and Drug Administration (FDA) concluded that findings with drugs that lead to increased levels of thyroid-stimulating hormone (TSH) in rats are not relevant to humans, whereas the U.S. Environmental Protection Agency (US EPA) concluded that chemicals that produce rodent thyroid tumors may pose a carcinogenic hazard for humans although the thyroid of rodents appears to be more sensitive to a carcinogenic stimulus than that of humans. Meanwhile, based on the CLP Criteria of the European Chemicals Agency (ECHA), rodent thyroid tumors caused by the induction of uridine-diphosphate-glucuronosyl transferases (UDGT) were assessed as not relevant to humans. To clarify these discrepant positions, the function and regulation of the thyroid gland are described and the types of thyroid tumors and the causes of their development in humans and animals are examined. Based on these data and the evidence that so far, except radiation, no chemical is known to increase the incidence of thyroid tumors in humans, it is concluded that rodent thyroid tumors resulting from continuous stimulation of the thyroid gland by increased TSH levels are not relevant to humans. Consequently, compounds that induce such tumors do not warrant classification as carcinogenic.

Benign Thyroid Diseases and Risk of Thyroid Cancer: A Nationwide Cohort Study

CONTEXT

Thyroid nodules, adenomas, and goiter have consistently been associated with thyroid cancer risk. Few studies have assessed whether thyroid dysfunction and thyroid autoimmunity influence this risk.

OBJECTIVE

To examine thyroid cancer risk after diagnoses of a wide range of benign thyroid conditions.

DESIGN

Hospital and cancer registry linkage cohort study for the years 1978 to 2013.

SETTING

Nationwide (Denmark).

PARTICIPANTS

Patients diagnosed with hyperthyroidism (n = 85,169), hypothyroidism (n = 63,143), thyroiditis (n = 12,532), nontoxic nodular goiter (n = 65,782), simple goiter (n = 11,582), other/unspecified goiter (n = 21,953), or adenoma (n = 6,481) among 8,258,807 residents of Denmark during the study period.

MAIN OUTCOME MEASURES

We computed standardized incidence ratios (SIRs) for differentiated thyroid cancer, excluding the first 12 months of follow-up after benign thyroid disease diagnosis.

RESULTS

SIRs were significantly elevated for all benign thyroid diseases apart from hypothyroidism. SIRs were higher for men than women and in the earlier follow-up periods. Elevated SIRs were observed for localized and regional/distant thyroid cancer. After excluding the first 10 years of follow-up, hyperthyroidism [n = 27 thyroid cancer cases; SIR = 2.00; 95% confidence interval (CI): 1.32 to 2.92], nontoxic nodular goiter (n = 83; SIR = 4.91; 95% CI: 3.91 to 6.09), simple goiter (n = 8; SIR = 4.33; 95% CI: 1.87 to 8.53), other/unspecified goiter (n = 20; SIR = 3.94; 95% CI: 2.40 to 6.08), and adenoma (n = 9; SIR = 6.02; 95% CI: 2.76 to 11.5) remained positively associated with thyroid cancer risk.

CONCLUSIONS

We found an unexpected increased risk of differentiated thyroid cancer, including regional/distant disease, following diagnosis of hyperthyroidism and thyroiditis that could not be solely attributed to increased medical surveillance. Hypothyroidism was less clearly associated with thyroid cancer risk.

The impact of overdiagnosis on thyroid cancer epidemic in Italy,1998-2012

AIMS

In Italy, incidence rates of thyroid cancer (TC) are among the highest worldwide with substantial intracountry heterogeneity. The aim of the study was to examine time trends of TC incidence in Italy and to estimate the proportion of TC cases potentially attributable to overdiagnosis.

METHODS

Data on TC cases reported to Italian cancer registries during 1998-2012 aged <85 years were included. Age-standardised incidence rates (ASR) were computed by sex, period, and histology. TC overdiagnosis was estimated by sex, period, age, and Italian region.

RESULTS

In Italy between 1998-2002 and 2008-2012, TC ASR increased of 74% in women (from 16.2 to 28.2/100,000) and of 90% in men (from 5.3 to 10.1/100,000). ASR increases were nearly exclusively due to papillary TC (+91% in women, +120% in men). In both sexes, more than three-fold differences emerged between regions with highest and lowest ASR. Among TC cases diagnosed in 1998-2012 in Italy, we estimated that overdiagnosis accounted for 75% of cases in women and 63% in men and increased over the study period leading to overdiagnosis of 79% in women and 67% in men in 2008-2012. Notably, overdiagnosis was over 80% among women aged <55 years, and substantial variations were documented across Italian regions, in both genders.

CONCLUSION(S)

Incidence rates of TC are steadily increasing in Italy and largely due to overdiagnosis. These findings call for an update of thyroid gland examination practices in the asymptomatic general population, at national and regional levels.

Adipokines and inflammation markers and risk of differentiated thyroid carcinoma: The EPIC study

Other than the influence of ionizing radiation and benign thyroid disease, little is known about the risk factors for differentiated thyroid cancer (TC) which is an increasing common cancer worldwide. Consistent evidence shows that body mass is positively associated with TC risk. As excess weight is a state of chronic inflammation, we investigated the relationship between concentrations of leptin, adiponectin, C-reactive protein, interleukin (IL)-6, IL-10 and tumor necrosis factor (TNF)-α and the risk of TC. A case-control study was nested within the European Prospective Investigation into Cancer and Nutrition (EPIC) study and included 475 first primary incident TC cases (399 women and 76 men) and 1,016 matched cancer-free cohort participants. Biomarkers were measured in serum samples using validated and highly sensitive commercially available immunoassays. Odds ratios (ORs) of TC by levels of each biomarker were estimated using conditional logistic regression models, adjusting for BMI and alcohol consumption. Adiponectin was inversely associated with TC risk among women (ORT3vs.T1  = 0.69, 95% CI: 0.49-0.98, Ptrend  = 0.04) but not among men (ORT3vs.T1  = 1.36, 95% CI: 0.67-2.76, Ptrend  = 0.37). Increasing levels of IL-10 were positively associated with TC risk in both genders and significantly so in women (ORT3vs.T1  = 1.59, 95% CI: 1.13-2.25, Ptrend  = 0.01) but not in men (ORT3vs.T1  = 1.78, 95% CI: 0.80-3.98, Ptrend  = 0.17). Leptin, CRP, IL-6 and TNF-α were not associated with TC risk in either gender. These results indicate a positive association of TC risk with IL-10 and a negative association with adiponectin that is probably restricted to women. Inflammation may play a role in TC in combination with or independently of excess weight.

Occupational pesticide exposure and subclinical hypothyroidism among male pesticide applicators

OBJECTIVES

Animal studies suggest that exposure to pesticides may alter thyroid function; however, few epidemiologic studies have examined this association. We evaluated the relationship between individual pesticides and thyroid function in 679 men enrolled in a substudy of the Agricultural Health Study, a cohort of licensed pesticide applicators.

METHODS

Self-reported lifetime pesticide use was obtained at cohort enrolment (1993-1997). Intensity-weighted lifetime days were computed for 33 pesticides, which adjusts cumulative days of pesticide use for factors that modify exposure (eg, use of personal protective equipment). Thyroid-stimulating hormone (TSH), thyroxine (T4), triiodothyronine (T3) and antithyroid peroxidase (anti-TPO) autoantibodies were measured in serum collected in 2010-2013. We used multivariate logistic regression to estimate ORs and 95% CIs for subclinical hypothyroidism (TSH >4.5 mIU/L) compared with normal TSH (0.4-<4.5 mIU/L) and for anti-TPO positivity. We also examined pesticide associations with TSH, T4 and T3 in multivariate linear regression models.

RESULTS

Higher exposure to the insecticide aldrin (third and fourth quartiles of intensity-weighted days vs no exposure) was positively associated with subclinical hypothyroidism (ORQ3=4.15, 95% CI 1.56 to 11.01, ORQ4=4.76, 95% CI 1.53 to 14.82, ptrend <0.01), higher TSH (ptrend=0.01) and lower T4 (ptrend=0.04). Higher exposure to the herbicide pendimethalin was associated with subclinical hypothyroidism (fourth quartile vs no exposure: ORQ4=2.78, 95% CI 1.30 to 5.95, ptrend=0.02), higher TSH (ptrend=0.04) and anti-TPO positivity (ptrend=0.01). The fumigant methyl bromide was inversely associated with TSH (ptrend=0.02) and positively associated with T4 (ptrend=0.01).

CONCLUSIONS

Our results suggest that long-term exposure to aldrin, pendimethalin and methyl bromide may alter thyroid function among male pesticide applicators.

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.

Association between chronic exposure to different water iodine and thyroid cancer: A retrospective study from 1995 to 2014

The controversy that iodine intake may increase the risk of thyroid cancer has heightened over the past twenty years. In this retrospective study, we mainly analyzed the association between water iodine and thyroid cancer and discussed the possible cause of the increase in thyroid cancer. This study was supported by three hospitals in areas with different water iodine concentration. 5574 patients with thyroid disease were recruited, of which 1429 patients had been diagnosed with thyroid cancer. These samples collectively were used to analyze the relationship of incidence and prevalence associated with water iodine. In addition, the ratio of maximum tumor diameter was analyzed. By analyzing the proportion of patients with thyroid cancer in thyroid diseases, we found a decrease in the proportion of thyroid cancer with increasing water iodine (P<0.0001). In addition, there was no significant correlation between the median water iodine and the prevalence of thyroid cancer, including papillary thyroid cancer (P>0.05). Meanwhile, the 5years' cumulative incidence of thyroid cancer increased with years (P<0.01). Comparing Cao county and Shan county, which are areas with high water iodine, to adequate iodine area such as in Mudan district, an increasing incidence is observed in 2010-2014 in Mudan district. Again, we observed a significant increase in the proportion of thyroid cancer with tumor size <1cm (P<0.01). Therefore, we concluded that cause(s) of increase in thyroid cancer may be ascribed to the sensitive diagnostic techniques and the improvement of living condition, but not water iodine.

Risk of Thyroid Cancer Among Solid Organ Transplant Recipients

Solid organ transplant recipients have an elevated incidence of thyroid cancer. We evaluated a wide range of potential risk factors in a cohort of 229 300 U.S. solid organ transplant recipients linked with 15 stage/regional cancer registries (1987-2012). Incidence rate ratios (IRRs) were adjusted for age, sex, race/ethnicity, transplanted organ, year of transplantation, and time since transplantation. Hazard ratios (HRs) for death and/or graft failure were adjusted for age, sex, race/ethnicity, transplanted organ, and year of transplantation. After transplantation, 356 thyroid cancers were diagnosed. Thyroid cancer incidence was 2.50-fold higher in transplant recipients than the general population (95% confidence interval [CI] 2.25-2.77). Among recipients of different organs, kidney recipients had the highest incidence of thyroid cancer (IRR = 1.26, 95% CI 1.03-1.53). Elevated thyroid cancer incidence was associated with cholestatic liver disease/cirrhosis as an indication for liver transplantation (IRR = 1.69, 95% CI 1.09-2.63), hypertensive nephrosclerosis as an indication for kidney transplantation (IRR = 1.41, 95% CI 1.03-1.94), and longer prior dialysis among kidney recipients (5+ vs. <1 year, IRR = 1.92, 95% CI 1.32-2.80; p-trend <0.01). Posttransplantation diagnosis of thyroid cancer was associated with modestly increased risk of death (HR = 1.33, 95% CI 1.02-1.73). Overall, our results suggest that end-stage organ disease and longer duration of dialysis may contribute to higher thyroid cancer incidence in transplant recipients.

Association of Iodine and Iron with Thyroid Function

Iodine and iron are essential elements for healthy thyroid function. However, little is known about the association of iron and iodine with thyroid function in the general US population. We investigated iron and iodine status in relation to concentrations of thyroid hormones. We included 7672 participants aged 20 and older from three surveys (2007-2008, 2009-2010, and 2011-2012) of the National Health and Nutrition Examination Survey. Serum thyroid measures (including free and total T3 and T4, and TSH), serum iron concentration, and urinary iodine concentrations were measured. Multivariate linear regression models were conducted with serum thyroid measures as dependent variables and combinations of serum iron concentration and urinary iodine concentration as predictors with covariate adjustment. Logistic regression models were performed with TSH levels (low, normal, and high) and combinations of serum iron concentration and urinary iodine concentration. Overall, 10.9% of the study population had low iron; 32.2 and 18.8% had low or high iodine levels, respectively. Compared with normal levels of iron and iodine, normal iron and high iodine were associated with reduced free T3 and increased risk of abnormal high TSH. Combined low iron and low iodine was associated with reduced free T3 and increased TSH. In addition, high iodine was associated with increased risk of abnormal high TSH in females but not in males. Thyroid function may be disrupted by low levels of iron or abnormal iodine, and relationships are complex and sex-specific. Large prospective studies are needed to understand the mechanisms by which iron interacts with iodine on thyroid function.

"Nodule in Nodule" on Thyroid Ultrasonography: Possibility of Follicular Carcinoma Transformed from Benign Thyroid Tumor

BACKGROUND

It is generally considered impossible to differentiate follicular carcinomas from follicular adenomas by means of ultrasonography or cytology before surgery. Therefore, follicular carcinoma is histopathologically diagnosed by verifying capsular and/or vascular invasion after surgery. However, ultrasonography may play an important role in diagnosing follicular carcinoma preoperatively in a small number of cases.

CASE DESCRIPTION

Four cases of follicular carcinoma or follicular neoplasm that transformed from a benign thyroid tumor and demonstrated a "nodule in nodule" appearance on ultrasonography are presented in this report. Characteristic ultrasound features of such patients are: (1) a "nodule in nodule" appearance, (2) a well-defined boundary line between the nodules, and (3) separate distribution of blood signals within each nodule.

CONCLUSION

A small number of patients with follicular carcinomas or follicular neoplasms may present with a "nodule in nodule" appearance on ultrasonography. It was suggested a long time ago that follicular carcinomas may develop from benign thyroid tumors. The fact that follicular carcinomas appear within benign tumors may be evidence of thyroid tumorigenesis.

Prospective Study of Ultraviolet Radiation Exposure and Thyroid Cancer Risk in the United States

Background: Thyroid cancer incidence has tripled in the past three decades, yet relatively few risk factors have been identified. Some studies have suggested that ultraviolet radiation (UVR) may affect thyroid cancer risk.Methods: We conducted a prospective analysis of 44,039 participants in the United States Radiologic Technologists Study (153 thyroid cancer cases) from all 50 states. We examined the association between risk of thyroid cancer and exposure to UVR, estimated by ambient UVR, time outdoors, and a combined variable. Participants reported location of residence and time outdoors during five age periods starting in childhood. Ambient UVR was estimated by linking satellite-based UVR measurements to geocoded residences. We assessed the association of UVR by age and average lifetime UVR with thyroid cancer risk using Cox proportional hazards models, starting at the time of the baseline questionnaire (2003-2005) through 2012-2013.Results: Combined UVR from the latest age period (age 40+) was associated with a decreased risk of thyroid cancer (HR for 4th vs. 1st quartile = 0.56; 95% CI, 0.31-1.02, P_trend = 0.04). This was limited to participants with benign thyroid disease and to those with darker complexions, although we found no evidence of effect modification. Thyroid cancer risk was unrelated to all metrics of UVR in earlier age periods and for average lifetime exposure.Conclusions: Recent UVR exposure was associated with a decreased risk of thyroid cancer. This association appeared to be modified by benign thyroid disease and skin complexion.Impact: UVR exposure may be associated with a decreased risk of thyroid cancer. Cancer Epidemiol Biomarkers Prev; 26(5); 684-91. ©2016 AACR.

Thyroid cancer burden in Central and South America

RATIONALE AND OBJECTIVE

Incidence of thyroid cancer (TC) is rapidly increasing worldwide, but little is known about the TC burden in Central and South America (CSA). We describe the geographic patterns and trends of TC by sex in CSA.

METHODS

We obtained regional- and national-level incidence data from 48 population-based cancer registries in 13 countries and nationwide cancer deaths from the WHO mortality database for 18 countries. We estimated world population age-standardized incidence rates (ASRs) and age-standardized mortality rates (ASMRs) per 100,000 person-years. We calculated ASRs by histological subtype. We estimated the annual percentage change (EAPC) to describe time trends.

RESULTS

Between CSA countries, TC incidence and mortality rates varied from 8-fold to 12-fold and from 2-fold to 5-fold, respectively. In 2003-2007, the highest TC ASRs in females and males were in Ecuador (16.0 and 3.5, respectively), Brazil (14.4 and 3.4), Costa Rica (12.6 and 2.1) and Colombia (10.7 and 2.5). The highest ASMRs were in Ecuador, Colombia, Mexico, Peru and Panama (0.68-0.91 in females and 0.41-0.48 in males). Papillary TC was the most commonly diagnosed histological subtype, following the same incidence pattern as overall TC. In Argentinean, Brazilian, Chilean and Costa Rican females TC incidence increased by 2.2-17.9% annually, and papillary TC increased by 9.1-15.0% annually, while mortality remained stable between 1997 and 2008. In males, trends in TC were stable.

CONCLUSION

TC occurred more frequently in females than in males. The overall high incidence and low mortality of TC suggest identification of subclinical disease due to improved detection methods.

Energy and macronutrient intake and risk of differentiated thyroid carcinoma in the European Prospective Investigation into Cancer and Nutrition study

Incidence rates of differentiated thyroid carcinoma (TC) have increased in many countries. Adiposity and dietary risk factors may play a role, but little is known on the influence of energy intake and macronutrient composition. The aim of this study was to investigate the associations between TC and the intake of energy, macronutrients, glycemic index (GI) and glycemic load in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. The study included 477,274 middle-age participants (70.2% women) from ten European countries. Dietary data were collected using country-specific validated dietary questionnaires. Total carbohydrates, proteins, fats, saturated, monounsaturated and polyunsaturated fats (PUFA), starch, sugar, and fiber were computed as g/1,000 kcal. Multivariable Cox regression was used to calculate multivariable adjusted hazard ratios (HR) and 95% confidence interval (CI) by intake quartile (Q). After a mean follow-up time of 11 years, differentiated TC was diagnosed in 556 participants (90% women). Overall, we found significant associations only with total energy (HRQ4 vs .Q1 , 1.29; 95% CI, 1.00-1.68) and PUFA intakes (HRQ4 vs .Q1 , 0.74; 95% CI, 0.57-0.95). However, the associations with starch and sugar intake and GI were significantly heterogeneous across body mass index (BMI) groups, i.e., positive associations with starch and GI were found in participants with a BMI ≥ 25 and with sugar intake in those with BMI < 25. Moreover, inverse associations with starch and GI were observed in subjects with BMI < 25. In conclusion, our results suggest that high total energy and low PUFA intakes may increase the risk of differentiated TC. Positive associations with starch intake and GI in participants with BMI ≥ 25 suggest that those persons may have a greater insulin response to high starch intake and GI than lean people.

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.

Indicators of microbial-rich environments and the development of papillary thyroid cancer in the California Teachers Study

BACKGROUND

Little epidemiologic research has focused on the role of immune function in papillary thyroid cancer risk despite scattered observations suggesting it may be important (e.g., hygiene hypothesis). Here we investigate papillary thyroid cancer risk associated with self-reported living environments across the lifespan reflecting immunologically relevant exposures to microbial-rich environments.

METHODS

Among 61,803 eligible participants in the California Teachers Study cohort, 100 were diagnosed with invasive papillary thyroid cancer between 2005 and 2012. Multivariate Cox proportional hazards regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

Living in a rural area during early childhood was associated with significantly reduced risk of developing papillary thyroid cancer as an adult (HR=0.51, 95% CI: 0.28-0.94). Specifically, reduced risks were observed for living within a half mile of hoofed animals (HR=0.47, 95% CI: 0.26-0.84), as was having an indoor dog or cat (HR=0.51, 95% CI: 0.32-0.80). Neither sharing a bedroom or living in a rented home as a child nor attending daycare or kindergarten was associated with reduced risk.

CONCLUSIONS

Early childhood exposures to hoofed animals or indoor furry pets were associated with reduced risk of subsequently developing papillary thyroid cancer.

IMPACT

Our findings point to immunologically relevant, early-life exposures to microbial-rich environments as potentially important in reducing thyroid cancer risk, consistent with the hygiene hypothesis and suggesting that certain, possibly animal-derived, microbial exposures may be important to immune calibration or priming.

Organophosphate insecticide use and cancer incidence among spouses of pesticide applicators in the Agricultural Health Study

OBJECTIVES

Organophosphates (OPs) are among the most commonly used insecticides. OPs have been linked to cancer risk in some epidemiological studies, which have been largely conducted in predominantly male populations. We evaluated personal use of specific OPs and cancer incidence among female spouses of pesticide applicators in the prospective Agricultural Health Study cohort.

METHODS

At enrolment (1993-1997), spouses provided information about ever use of specific pesticides, including 10 OPs, demographic information, reproductive health history and other potential confounders. We used Poisson regression to estimate relative risks (RRs) and 95% CIs for all cancers diagnosed through 2010 for North Carolina and through 2011 for Iowa.

RESULTS

Among 30,003 women, 25.9% reported OP use, and 718 OP-exposed women were diagnosed with cancer during the follow-up period. Any OP use was associated with an elevated risk of breast cancer (RR=1.20, 95% CI 1.01 to 1.43). Malathion, the most commonly reported OP, was associated with increased risk of thyroid cancer (RR=2.04, 95% CI 1.14 to 3.63) and decreased risk of non-Hodgkin lymphoma (RR=0.64, 95% CI 0.41 to 0.99). Diazinon use was associated with ovarian cancer (RR=1.87, 95% CI 1.02 to 3.43).

CONCLUSIONS

We observed increased risk with OP use for several hormonally-related cancers, including breast, thyroid and ovary, suggesting potential for hormonally-mediated effects. This study represents the first comprehensive analysis of OP use and cancer risk among women, and thus demonstrates a need for further evaluation.

Iodine intake as a risk factor for thyroid cancer: a comprehensive review of animal and human studies

Thyroid cancer (TC) is the most common endocrine malignancy and in most countries, incidence rates are increasing. Although differences in population iodine intake are a determinant of benign thyroid disorders, the role of iodine intake in TC remains uncertain. We review the evidence linking iodine intake and TC from animal studies, ecological studies of iodine intake and differentiated and undifferentiated TC, iodine intake and mortality from TC and occult TC at autopsy, as well as the case–control and cohort studies of TC and intake of seafood and milk products. We perform a new meta-analysis of pooled measures of effect from case–control studies of total iodine intake and TC. Finally, we examine the post-Chernobyl studies linking iodine status and risk of TC after radiation exposure. The available evidence suggests iodine deficiency is a risk factor for TC, particularly for follicular TC and possibly, for anaplastic TC. This conclusion is based on: a) consistent data showing an increase in TC (mainly follicular) in iodine deficient animals; b) a plausible mechanism (chronic TSH stimulation induced by iodine deficiency); c) consistent data from before and after studies of iodine prophylaxis showing a decrease in follicular TC and anaplastic TC; d) the indirect association between changes in iodine intake and TC mortality in the decade from 2000 to 2010; e) the autopsy studies of occult TC showing higher microcarcinoma rates with lower iodine intakes; and f) the case control studies suggesting lower risk of TC with higher total iodine intakes.

Iodine deficiency and thyroid disorders

Iodine deficiency early in life impairs cognition and growth, but iodine status is also a key determinant of thyroid disorders in adults. Severe iodine deficiency causes goitre and hypothyroidism because, despite an increase in thyroid activity to maximise iodine uptake and recycling in this setting, iodine concentrations are still too low to enable production of thyroid hormone. In mild-to-moderate iodine deficiency, increased thyroid activity can compensate for low iodine intake and maintain euthyroidism in most individuals, but at a price: chronic thyroid stimulation results in an increase in the prevalence of toxic nodular goitre and hyperthyroidism in populations. This high prevalence of nodular autonomy usually results in a further increase in the prevalence of hyperthyroidism if iodine intake is subsequently increased by salt iodisation. However, this increase is transient because iodine sufficiency normalises thyroid activity which, in the long term, reduces nodular autonomy. Increased iodine intake in an iodine-deficient population is associated with a small increase in the prevalence of subclinical hypothyroidism and thyroid autoimmunity; whether these increases are also transient is unclear. Variations in population iodine intake do not affect risk for Graves' disease or thyroid cancer, but correction of iodine deficiency might shift thyroid cancer subtypes toward less malignant forms. Thus, optimisation of population iodine intake is an important component of preventive health care to reduce the prevalence of thyroid disorders.

Thyroid cancer mortality and incidence: a global overview

In most areas of the world, thyroid cancer incidence has been appreciably increasing over the last few decades, whereas mortality has steadily declined. We updated global trends in thyroid cancer mortality and incidence using official mortality data from the World Health Organization (1970-2012) and incidence data from the Cancer Incidence in Five Continents (1960-2007). Male mortality declined in all the major countries considered, with annual percent changes around -2/-3% over the last decades. Only in the United States mortality declined up to the mid 1980s and increased thereafter. Similarly, in women mortality declined in most countries considered, with APCs around -2/-5% over the last decades, with the exception of the UK, the United States and Australia, where mortality has been declining up to the late 1980s/late 1990s to level off (or increase) thereafter. In 2008-2012, most countries had mortality rates (age-standardized, world population) between 0.20 and 0.40/100,000 men and 0.20 and 0.60/100,000 women, the highest rates being in Latvia, Hungary, the Republic of Moldova and Israel (over 0.40/100,000) for men and in Ecuador, Colombia and Israel (over 0.60/100,000) for women. In most countries, a steady increase in the incidence of thyroid cancer (mainly papillary carcinomas) was observed in both sexes. The declines in thyroid cancer mortality reflect both variations in risk factor exposure and changes in the diagnosis and treatment of the disease, while the increases in the incidence are likely due to the increase in the detection of this neoplasm over the last few decades.

Thyroid-stimulating hormone, thyroglobulin, and thyroid hormones and risk of differentiated thyroid carcinoma: the EPIC study

BACKGROUND

Increased levels of thyroglobulin (Tg) and thyroid-stimulating hormone (TSH) are associated with differentiated thyroid carcinoma (TC) risk, but strong epidemiological evidence is lacking.

METHODS

Three hundred fifty-seven incident TC case patients (n = 300 women and 57 men; mean age at blood collection = 51.5 years) were identified in the EPIC cohort study and matched with 2 (women) or 3 (men) control subjects using incidence density sampling. Matching included study center, sex, age, date, time, and fasting status at blood collection. Levels of total and free (f) thyroxine (T4) and triiodo-thyronine (T3), TSH, Tg, and anti-Tg antibodies (TgAb) were measured by commercially available immunoassays. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed using conditional logistic regression. All statistical tests were two-sided.

RESULTS

TC risk was positively associated with Tg (OR for the highest vs lowest quartile = 9.15; 95% CI = 5.28 to 15.90; P < .001) and negatively associated with TSH level (OR = 0.56; 95% CI = 0.38 to 0.81; P = .001). Odds ratios were not modified by adjustment for weight and height and were consistent across sexes, age groups, and countries. The association with Tg was stronger in follicular than papillary TC. The odds ratio for TgAb-positivity was 1.50 (95% CI = 1.05 to 2.15; P = .03). Among case patients, TSH level was stable over time, whereas Tg level was higher in proximity to TC diagnosis. Areas under the receiver operating characteristic curve were 57% and 74% for TSH and Tg level, respectively.

CONCLUSIONS

High Tg levels precede by up to 8 years the detection of TC, pointing to a long sojourn time of the disease. Low TSH levels may predispose to TC onset. Neither marker has sufficient accuracy to be a screening test.

Insulin-like growth factor-i and risk of differentiated thyroid carcinoma in the European prospective investigation into cancer and nutrition

BACKGROUND

Little is known about the causes of thyroid cancer, but insulin-like growth factor-I (IGF-I) might play an important role in its development due to its mitogenic and antiapoptotic properties.

METHODS

This study prospectively investigated the association between serum IGF-I concentrations and risk of differentiated thyroid carcinoma in a case-control study nested within the European Prospective Investigation into Cancer and Nutrition. The 345 incident cases of differentiated thyroid carcinoma were individually matched to 735 controls by study center, sex and age, date, time, and fasting status at blood collection, follow-up duration, and for women menopausal status, use of exogenous hormones, and phase of menstrual cycle at blood collection. Serum IGF-I concentrations were measured by immunoassay, and risk of differentiated thyroid cancer in relation to IGF-I concentration was estimated using conditional logistic regression.

RESULTS

There was a positive association between IGF-I concentrations and risk of differentiated thyroid carcinoma: the OR for a doubling in IGF-I concentration was 1.48 (95% confidence interval, 1.06-2.08; Ptrend = 0.02). The positive association with IGF-I was stable over time between blood collection and cancer diagnosis.

CONCLUSION

These findings suggest that IGF-I concentrations may be positively associated with risk of differentiated thyroid carcinoma.

IMPACT

This study provides the first prospective evidence of a potential association between circulating IGF-I concentrations and risk of differentiated thyroid carcinoma and may prompt the further investigations needed to confirm the association.

The geographical pattern of thyroid cancer mortality between 1980 and 2009 in Italy

BACKGROUND

Mortality for thyroid cancer (TC) is low and has been decreasing worldwide; yet few population studies based on mortality have been conducted. Several nonradiation risk factors have been associated with TC, including residence in goiter-endemic areas (as an indicator of iodine deficiency). We used mortality data to perform a spatial-temporal analysis regarding TC in Italy and investigated the association between mortality and socioeconomic status and geographical features (residing in a mountainous area is a proxy for iodine deficiency).

METHODS

We analyzed data from Italy's National Mortality Database (1980-2009). To evaluate temporal trends in mortality the age-standardized death rate (ASR) was used; to identify geographic areas with excess deaths due to TC standardized mortality rates (SMR) were calculated. We also calculated the rate ratios (RR) of the ASR and the 95% CI by sex. We performed a cluster analysis to identify municipalities with major departures from expected mortality, both in the entire study period and in two separate periods to evaluate the spatial-temporal variability. Finally, we evaluated the association between mortality and index of deprivation and altitude.

RESULTS

There were 16,473 deaths due to TC (10,690 females, 5783 males). The mean ASR was unsurprisingly low (0.58/100.000). There was a trend of decrease in mortality throughout Italy (-42% for 2007-2009 vs. 1980-1984), more pronounced among women. The decrease was greater in the north. Four geographic clusters were identified when considering the entire study period, two in the north and two in the south; however, the clusters in northern Italy refer to the earlier period (1980-1994) and those in southern Italy to the later period (1995-2009). Mortality was associated with residing in a mountainous area. A slight association with high socioeconomic status was found.

CONCLUSIONS

This study reveals space-time differences in TC mortality in Italy. It shows an association between mortality and residing in mountainous areas, which is a proxy of iodine deficiency. The observed temporal north-south shift cannot be explained by socioeconomic differences, whereas the efficient prophylaxis program implemented in the 1980s in some areas of northern Italy can help to explain the disappearance of the clusters in those areas in the period 1995-2009.

Synchronous and antecedent nonthyroidal malignancies in patients with papillary thyroid carcinoma

BACKGROUND

There is a known association between the development of papillary thyroid cancer (PTC) after a primary nonthyroidal cancer (NTC). However, the prevalence of synchronous or antecedent NTCs in patients with PTC is undetermined, as are the clinicopathologic characteristics of PTC in these patients.

STUDY DESIGN

A review was performed of our prospectively maintained PTC database between January 1995 and December 2010. Information collected included patient and tumor characteristics, medical history, PTC presentation, and treatment modality.

RESULTS

Four hundred and thirty-three adult patients underwent thyroid resection and had PTC on final pathology. Sixty-seven cases of synchronous or antecedent NTCs were observed in 60 patients (13.9%). The most commonly associated antecedent NTCs were breast (n = 11), prostate (n = 8), and melanoma (n = 5), whereas renal cell carcinoma (n = 3) and melanoma (n = 3) were the synchronous NTCs most observed. Compared with patients without an NTC, those with an NTC were older (56.4 ± 15.5 years vs 44.9 ± 14.2 years; p < 0.0001), had experienced radiation exposure (35.0% vs 3.5%; p < 0.001), and more commonly presented with a thyroid mass incidentally on imaging (41.7% vs 9.1%; p ≤ 0.001). Papillary thyroid cancer tumor characteristics were similar between groups, except that NTC patients presented at a more advanced stage. However, when analyzed independently, primary tumor size, and nodal and distant metastases were comparable.

CONCLUSIONS

The prevalence of synchronous or antecedent NTCs in patients surgically treated for PTC is 13.9%. These patients present with PTC tumor characteristics similar to those without additional NTCs, and should therefore be managed equivalently. In addition, surgeons should be aware of the frequency of synchronous PTC with these types of tumors and consider evaluation of the neck at the time of NTC diagnosis.

Are risk factors common to thyroid cancer and nodule? A forty years observational time-trend study

A progressive increase in the incidence of thyroid cancer (TC) has been reported over the last few decades. This either reflects the increased number of newly discovered and accurately selected thyroid nodules with more sensitive technologies and a relative more potent carcinogenic effect of pathogenetic factors in malignant, but not benign nodules. This observational time-trend study addresses this issue by analysing the proportion of TC within 8411 consecutive thyroid nodule (TN) patients evaluated in Pisa by the same pathology Department and individual clinician over a four-decade period. From 1972 to 1979 surgery was used to detect TC among the TN patients: 1140 TN patients were operated on and 35 cancers were detected (3.1% of all the TN patients). Subsequently, needle aspiration techniques were used to select TN for surgery. From 1980 to 1992, 5403 TN patients were examined, 483 were selected for surgery, and 150 cancers were found (2.8% of all the TN patients). From 1993 to 2010, 1568 TN patients were examined, 143 were selected for surgery, and 46 cancers were found (2.9% of all the TN patients). Therefore, in the University Hospital of Pisa, and independent of preoperative TN selection protocols, these proportions of TN eventually found to harbor TC remained statistically unchanged over 40 years (p = 0.810). This finding suggests that pathogenic risk factors and more sensitive diagnostic technologies did not differentially affect the incidence of TN and TC.