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

Early-onset and later-onset cancer: trends, risk factors, and prevention in Northern China

The characteristics of early-onset (onset age <50 years) and later-onset (onset age ≽ 50 years) cancers differ significantly. Identifying novel risk factors for both types of cancer is crucial for increasing awareness of cancer prevention and for reducing its burden. This study aimed to analyze the trends in incidence and risk factors for early-onset and late-onset cancers. We conducted a prospective study by drawing data from the Kailuan Study. This study included 6,741 participants with cancer (624 with early-onset cancer and 6,117 with later-onset cancer) and 6,780 matched controls among the 186,249 participants who underwent Kailuan health examinations from 2006 to 2019. The primary outcomes were cancer incidence rates, and associated risk factors for early- and later-onset cancer. Weighted Cox regression was used to calculate hazard ratios and 95% confidence intervals of each exposure factor for early- and later-onset cancer by cancer type. Population-attributable risk proportions were used to estimate the number of cases that could be prevented by eliminating a risk factor from the population. Except for liver cancer, incidence rates for nearly all types of cancer increased during the study period. Smoking, alcohol consumption, lipid metabolism disorders, hypertension, diabetes mellitus, fatty liver, and inflammation were associated with a significantly increased risk of cancer at multiple sites, but risk factors for cancer incidence differed by site. Smoking, alcohol consumption, inflammation, and hypertension were the major contributors to preventable cancer. The incidence of several different types of cancer, including early-onset cancer, is increasing in northeastern China. Differences in risk factors between early-onset and later-onset malignancies may contribute to the divergence in the observed changes in incidence trends between these two specific types of cancer.

Subclinical Hypothyroidism in Patients with Obesity and Metabolic Syndrome: A Narrative Review

The literature on the connection between obesity, metabolic syndrome, and subclinical hypothyroidism is critically analyzed in this narrative review. These conditions are frequently observed among adult populations and various studies and meta-analyses have assessed their association. The prevalence of subclinical hypothyroidism in obese individuals is higher than in non-obese subjects and this trend is more pronounced in unhealthy obesity phenotypes. However, the diagnosis and treatment of subclinical hypothyroidism can be difficult in obese patients. Exaggerated body fat is linked to thyroid hypoechogenicity as evident through ultrasonography and euthyroid obese people have greater TSH, FT3, and FT3/FT4 ratios than non-obese individuals in a euthyroid condition. Moreover, a reduced expression of the TSH receptor and altered function of deiodinases has been found in the adipose tissue of obese patients. Current data do not support the necessity of a pharmacological correction of the isolated hyperthyrotropinemia in euthyroid obese patients because treatment with thyroid hormone does not significantly improve weight loss and the increase in serum TSH can be reversible after hypocaloric diet or bariatric surgery. On the other hand, obesity is linked to elevated leptin levels. Inflammation can raise the risk of Hashimoto thyroiditis, which increases the likelihood that obese patients will experience overt or subclinical hypothyroidism. Both metabolic syndrome and subclinical hypothyroidism are associated with atherosclerosis, liver and kidney disease. Hence, the association of these two illnesses may potentiate the adverse effects noted in each of them. Subclinical hypothyroidism should be identified in patients with obesity and treated with appropriate doses of L-thyroxine according to the lean body mass and body weight. Randomized controlled trials are necessary to verify whether treatment of thyroid deficiency could counteract the expected risks.

Weighty Matters: The Obesity-Thyroid Nodule Connection Unveiling the Impact of Obesity on Thyroid Cancer Risk

Background and Objectives: The effect of obesity on the development/progression of thyroid nodules with uncertain cytology is unknown. Therefore, our objective was to assess the role of body mass index (BMI) in predicting malignancy in patients with atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) nodules. Materials and Methods: We retrospectively analyzed 113 patients with available BMI data and final histopathology of benign or differentiated thyroid cancer. Patients were classified into four groups based on BMI: <18.5 (underweight), 18.5-24.9 (normal weight), 25-29.9 (overweight), and ≥30 (obesity) kg/m2. The association between risk of malignancy and BMI was examined for all data and subgroups based on nodule size, sex, and age. Results: Overall, 44.2% were obese, 36.3% were ≥45 years, and 75.4% were women. Final pathological results showed malignant nodules in 52 patients (46%) and benign nodules in 61 patients (54%) (mean age: 41 ± 11.6 vs. 39.9 ± 11.7 years; p = 0.62). Men had more malignant nodules than benign nodules (32.7% vs. 16.4%, p < 0.05). Overall, no significant correlation was identified between the risk of thyroid cancer and BMI, and the risk of malignancy was not significantly different between obese men and women (p = 0.4). However, in individuals with BMI < 30 kg/m2 (non-obese group), malignant nodules were more frequent in men than in women (71% vs. 41%, p = 0.04). No significant difference was observed in mean nodule size between the benign and malignant groups. Furthermore, BMI was not related to increased risk of malignancy in multiple logistic regression models using all data, even after controlling for confounding variables (odds ratio, 0.99, 95% confidence interval: 0.93-1.06, p = 0.87) or when stratifying by sex. Conclusions: Our study showed no correlation between obesity and thyroid cancer in patients with AUS/FLUS. Moreover, men had more malignant nodules than benign nodules. Further well-designed prospective studies are required to confirm our findings.

Thyroid Nodules and Obesity

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

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

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

Point of Care Measurement of Body Mass Index and Thyroid Nodule Malignancy Risk Assessment

BACKGROUND

Large scale epidemiology studies have suggested obesity may increase the risk of thyroid cancer, though no prospective analyses using real-world measurement of BMI at a time proximate to initial thyroid nodule evaluation have been performed.

METHODS

We performed a prospective, cohort analysis over 3 years of consecutive patients presenting for thyroid nodule evaluation. We measured BMI proximate to the time of initial evaluation and correlated this with the final diagnosis of benign or malignant disease. We further correlated patient BMI with aggressivity of thyroid cancer, if detected.

RESULTS

Among 1,259 consecutive patients with clinically relevant nodules, 199(15%) were malignant. BMI averaged 28.6 kg/m² (SD: 6.35, range:16.46-59.26). There was no correlation between the measurement of BMI and risk of thyroid cancer (p=0.58) as mean BMI was 28.9 kg/m² and 28.6 kg/m² in cancerous and benign cohorts, respectively. Similarly, BMI did not predict aggressive thyroid cancer (p=0.15). While overall nodule size was associated with increased BMI (p<0.01), these data require further validation as obesity may hinder nodule detection until large.

CONCLUSION

In contrast to findings published from large scale association studies drawn from national databases, these prospective data of consecutive patients presenting for nodule evaluation detect no association of obesity (as measured by BMI) with thyroid cancer. Real time measurement of BMI at the time of thyroid nodule evaluation does not contribute to cancer risk assessment.

Charting the Unknown Association of COVID-19 with Thyroid Cancer, Focusing on Differentiated Thyroid Cancer: A Call for Caution

BACKGROUND

Conceived of as the "silver lining" of the dark cloud of the coronavirus disease 2019 (COVID-19) pandemic, lessons taught by this catastrophe should be leveraged by medical authorities and policy makers to optimize health care globally. A major lesson is that resilient health systems should absorb sudden shocks incited by overwhelming health emergencies without compromising the continuum of care of chronic diseases, especially of cancer.

METHODS

The present review dissects the association between COVID-19 and thyroid cancer (TC), especially with differentiated TC (DTC), focusing on available data, knowledge gaps, current challenges, and future perspectives.

RESULTS

Obesity has been incriminated in terms of both COVID-19 severity and a rising incidence of TC, especially of DTC. The current conceptualization of the pathophysiological landscape of COVID-19-(D)TC association implicates an interplay between obesity, inflammation, immunity, and oxidative stress. Whether COVID-19 could aggravate the health burden posed by (D)TC or vice versa has yet to be clarified. Improved understanding and harnessing of the pathophysiological landscape of the COVID-19-(D)TC association will empower a mechanism-guided, safe, evidence-based, and risk-stratified management of (D)TC in the COVID-19 era and beyond.

CONCLUSION

A multidisciplinary patient-centered decision-making will ensure high-quality (D)TC care for patients, with or without COVID-19.

Morbid Obesity and Thyroid Cancer Rate. A Review of Literature

In the past three decades, several recent studies have analyzed the alarming increase of obesity worldwide, and it has been well established that the risk of many types of malignancies is increased in obese individuals; in the same period, thyroid cancer has become the fastest growing cancer of all malignancies. We investigated the current literature to underline the presence of a connection between excess body weight or Body Mass Index (BMI) and risk of thyroid cancer. Previous studies stated that the contraposition between adipocytes and adipose-resident immune cells enhances immune cell production of multiple pro-inflammatory factors with subsequent induction of hyperlipidemia and vascular injury; these factors are all associated with oxidative stress and cancer development and/or progression. Moreover, recent studies made clear the mitogenic and tumorigenic action of insulin, carried out through the stimulation of mitogen-activated protein kinase (MAPK) and phosphoinositide-3 kinase/AKT (PI3K/AKT) pathways, which is correlated to the hyperinsulinemia and hyperglycemia found in obese population. Our findings suggest that obesity and excess body weight are related to an increased risk of thyroid cancer and that the mechanisms that combine overweight with this cancer should be searched for in the adipokine pathways and chronic inflammation onset.

Influence of body mass index on the clinicopathological features of 13,995 papillary thyroid tumors

PURPOSE

This retrospective study aimed to assess the association between obesity, gender, and specific clinicopathological features in patients with papillary thyroid cancer (PTC) and whether diagnostic ultrasonography (US) is adversely affected by obesity in these patients.

MATERIALS AND METHODS

This study retrospectively analyzed 13,995 adult patients with PTC from a single medical center in China. Data stratification was performed to assess the association of obesity with US features and aggressive clinicopathological features in different models according to the World Health Organization Body Mass Index (WHO-BMI) and Chinese BMI classification (CN-BMI). The odds ratio (OR) of malignant US features and aggressive clinicopathological features was calculated from binary logistic regression models.

RESULTS

The BMI, obesity ratio, malignant US features, and aggressive pathological characteristics of males were significantly higher than those of females. After adjusting for confounding factors, the association of obesity with malignant US features and aggressive pathological characteristics was found to be sex-dependent. Next, obesity (WHO-BMI) was found to have an "interfering effect" on the US assessment of PTC (OR = 0.754, 95% CI 0.609-0.932, P = 0.009) in women. Among both sexes, obesity (WHO-BMI) increased the risk of tumor size (OR_male = 1.539 and OR_female = 1.521) and multifocality (OR_male = 1.659 and OR_female = 1.449). However, obesity did not increase the risk of capsular invasion or tumor staging in males. The above results are consistent with the CN-BMI. In addition, age was found to have an "interfering effect" on the US evaluation of malignant nodules in both sexes.

CONCLUSION

The results of our study confirm that higher BMI is significantly associated with aggressive clinicopathological features of PTC. Gender differences were present with obesity ratios and aggressive clinicopathological features being significantly higher in men.

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.

Thyroid Nodules in Severely Obese Patients: Frequency and Risk of Malignancy on Ultrasonography

Background: We aimed to compare the thyroid ultrasonographic findings of severely obese versus nonobese individuals, and the frequency, characteristics, and risk of malignancy in detected nodules.Design: Case-control study including 67 adults with severe obesity (body mass index [BMI] ≥ 35 kg/m²) and 67 nonobese controls (BMI < 30 kg/m²). The participants underwent ultrasound evaluation of the thyroid and cervical subcutaneous tissue. The risk of malignancy in detected nodules was determined using the American Thyroid Association (ATA) 2015 and the Thyroid Imaging Reporting and Data System (TI-RADS) classifications. Fine-needle aspiration biopsy (FNAB) was performed in nodules for which the procedure was recommended according to the ATA-2015 or TI-RADS criteria, and the cytological evaluation followed the Bethesda classification.Results: The mean BMI values in the case and control groups were 47.0 ± 6.1 kg/m² and 22.8 ± 2.7 kg/m², respectively. There were no differences between groups regarding sex, age, total T3, and antiperoxidase (antiTPO) antibody positivity. When compared with controls, severely obese individuals showed a greater frequency of parenchymal hypoechogenicity (p = 0.042), cervical subcutaneous tissue thickness (p < 0.001), overall frequency of thyroid nodules (p = 0.038), and frequency of multiple nodules (p = 0.013). No significant differences were observed in terms of risk of nodular malignancy according to both the ATA-2015 and TI-RADS classifications in severely obese compared with nonobese individuals.Conclusions: Severely obese individuals (versus nonobese controls) presented increased parenchymal hypoechogenicity and frequency of thyroid nodules on ultrasonographic evaluation. However, no significant differences were observed in terms of risk of nodular malignancy between both groups according to the ATA-2015 and TI-RADS criteria. Thus, ultrasonographic thyroid screening of severely obese individuals is not justified.

Association of obesity with the clinicopathological features of thyroid cancer in a large, operative population: A retrospective case-control study

We aimed to investigate the association between excess body mass index (BMI) and papillary thyroid cancer (PTC) in an operative population, and the impact of higher BMI on clinicopathological aggressiveness of PTC.Charts of 10,844 consecutive patients with thyroid nodules undergoing partial or total thyroidectomy between 1993 and 2015 were reviewed. Patients diagnosed with PTC were stratified in 4 groups: BMI < 18.5 (underweight), 18.5 ≤ BMI < 24 (normal-weight), 24 ≤ BMI < 28 (overweight) and BMI ≥ 28(obese). The impacts of high BMI on prevalence and clinicopathological parameters of PTC were retrospectively analyzed in both univariate and multivariate binary logistic regression analysis.For every 5-unit increase in body mass, the odds of risk-adjusted malignance increased by 36.6%. The individuals who were obese and overweight were associated with high risk of thyroid cancer [odds ratio (OR)= 1.982, P < .001; OR= 1.377, P < .001; respectively] compared to normal weight patients, and this positive association was found in both genders. Obesity was independent predictors for tumors larger than 1 cm (OR = 1.562, P < .001) and multifocality (OR = 1.616, P < .001). However, there was no difference in cervical lymph node (LN) metastasis among BMI groups. Crude analysis showed BMI was associated with advanced tumor-node-metastasis (TNM) stage (relative risk, approximately 1.23 per 5 BMI units, P < .001), but this association disappeared after adjusting for confounding factors.Obesity was significantly associated with the risk of PTC in a large, operative population. Higher BMI was significantly associated with larger tumor size and multifocal tumor.

Lack of association between obesity and aggressiveness of differentiated thyroid cancer

PURPOSE

Aim of this study was to evaluate the association between body mass index (BMI) and aggressive features of differentiated thyroid cancer (DTC) in a prospective cohort.

METHODS

Patients with DTC were prospectively enrolled at a tertiary referral center and grouped according to their BMI. Aggressive clinic-pathological features were analyzed following the American Thyroid Association Initial Risk Stratification System score.

RESULTS

The cohort was composed of 432 patients: 5 (1.2%) were underweight, 187 (43.3%) normal weight, 154 (35.6%) overweight, 68 (15.7%) grade 1 obese, 11 (2.5%) grade 2 obese and 7 (1.6%) grade 3 obese. No single feature of advanced thyroid cancer was more frequent in obese patients than in others. No significant correlation was found between BMI, primary tumor size (Spearman's ρ - 0.02; p = 0.71) and ATA Initial Risk Stratification System score (ρ 0.03; p = 0.49), after adjustment for age. According to the multivariate logistic regression analysis, male gender and pre-surgical diagnosis of cancer were significant predictors of cancer with high or intermediate-high recurrence risk according to the ATA system (OR 2.06 and 2.51, respectively), while older age at diagnosis was a protective factor (OR 0.98), and BMI was not a predictor. BMI was a predictor of microscopic extrathyroidal extension only (OR 1.06).

CONCLUSIONS

Obesity was not associated with aggressive features in this prospective, European cohort of patients with DTC.

THYROID NODULE LOCATION ON ULTRASONOGRAPHY AS A PREDICTOR OF MALIGNANCY

OBJECTIVE

The diagnostic capacity of ultrasonography (US) for differentiating between malignant and benign thyroid nodules is crucial in preventing unnecessary invasive procedures. This is the first study to evaluate whether thyroid nodule location on US has predictive value for malignancy.

METHODS

We retrospectively reviewed data from 219 patients with thyroid nodules who underwent fine-needle aspiration biopsy in 1 year. Patients' demographics as well as nodule's laterality, polarity, morphology, and multinodularity were analyzed. All malignant lesions were confirmed by surgical pathology.

RESULTS

The majority of the patients were female (86.2%). Nodules were evenly distributed between the right lobe (46.3%) and left lobe (49.5%). Eight nodules (4.2%) were located in the isthmus. Most nodules (79.3%) were located in the lower pole, while 9.6% were located in the upper pole and 6.9% in the middle pole. Seventy-five patients (39.9%) had multiple nodules. Fourteen nodules were malignant, representing a prevalence of 7.4%. A significantly higher frequency of malignancy was observed in upper pole (22.2%) compared to lower pole (4.7%) and middle pole (15.4%). A multiple logistic regression model confirmed such association after adjusting for age, body mass index, multinodularity, and laterality. The odds of malignancy in the upper pole were 4 times higher than other locations (odds ratio, 4.6; P = .03).

CONCLUSION

Our study is the first showing that thyroid nodules located in the upper pole can be considered as having higher risk for malignancy. It may enhance the predictive value of malignancy if it is included in thyroid nodule ultrasound classification guidelines.

ABBREVIATIONS

AACE = American Association of Clinical Endocrinologists; ATA = American Thyroid Association; BMI = body mass index; FNA = fine-needle aspiration; TMS = total malignancy score; TTW = taller than wide; US = ultrasonography.

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

Introduction

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

Aims

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

Subjects & methods

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

Results

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

Conclusions

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

The obesity paradox in cancer: clinical insights and perspectives

A series of evidence demonstrated that obesity represents an established risk factor for an increase in the incidence of multiple cancer types and for poor cancer survival. Nevertheless, recent studies suggested that, in a series of cancers, patients with a normal body mass index (BMI) have worse outcomes than obese patients. This phenomenon, named 'obesity paradox' or 'reverse epidemiology' in cancer, is not well understood and presents controversial aspects. Therefore, this review aims to explore the available studies concerning the relationship between obesity and cancer incidence or survival and to highlight the hypothetical explanations and the methodological framework. In this regard, we underline the limits of BMI as a potential marker of adiposity and the relevance to assessing body composition, beyond the body size. Further studies are needed to define the impact of obesity in cancer patients, to tailor weight management after cancer diagnosis and to hopefully improve overall clinical outcome.

Mitochondrial DNA haplogroup K as a contributor to protection against thyroid cancer in a population from southeast Europe

We aimed to analyze the contribution of mitochondrial DNA (mtDNA) haplogroups of the mtDNA control region to thyroid cancer risk in a population from southeastern Europe consisting of 235 thyroid tumor patients, including 114 patients with thyroid follicular adenoma, 121 patients with papillary thyroid carcinoma, and 419 healthy controls. Binary logistic regression with adjustment for age and gender revealed that mtDNA haplogroup K was significantly associated with a protective role for thyroid cancer in the combined tumor group versus controls. These results indicate a potential role for mtDNA haplogroups as important candidate susceptibility markers for the patients with thyroid nodules.