Correlation between Insulin Resistance and Thyroid Nodule in Type 2 Diabetes Mellitus

A Comprehensive Mendelian Randomization Study Investigating Multiple Exposures and Outcomes: Focusing on Nontoxic Goitre and Type 2 Diabetes Mellitus

OBJECTIVE

Previous research suggests a correlation between nontoxic goitre and type 2 diabetes mellitus (T2DM). However, the causality was vulnerable to confounding variables. Therefore, there is an urgent need for a more rigorous research approach to examine the causal connection between nontoxic goitre and T2DM.

DESIGN

Multiple exposures and outcomes two-sample Mendelian randomization (MR) study was carried out in two stages: nontoxic goitre traits (including nontoxic diffuse goitre, NDG; nontoxic multinodular goitre, NMG; and other/unspecified nontoxic goitre, OUNG) were investigated as exposure while T2DM was investigated as an outcome in the first step, whereas the second step was reversed. The GWAS summary data for nontoxic goitre traits and T2DM were collected from the Finngen database. The summary data for fasting glucose, fasting insulin, and HbA1c were obtained from the open GWAS database established by the MRC Integrated Epidemiology Unit (IEU). The inverse-variance weighted (IVW) approach was used to obtain MR estimates, and various sensitivity analysis was also performed.

RESULTS

NDG had a potential protective causal relationship with T2DM (OR = 0.978; 95% CI: 0.957-0.998; p = 0.034) and fasting glucose (OR = 0.995; 95% CI: 0.990-0.999; p = 0.011), while NMG had a potential protective causal relationship with T2DM (OR = 0.941; 95% CI: 0.902-0.982; p = 0.008) and HbA1c (OR = 0.992; 95% CI: 0.986-0.998; p = 0.015). OUNG was found to decrease the odds of T2DM by 4.4% (OR = 0.966; 95% CI: 0.938-0.995, p = 0.023). T2DM had a potential causal relationship with NDG (OR = 1.239; 95% CI: 1.020-1.504; p = 0.031), and a potential protective effect against NMG (OR = 0.669; 95% CI: 0.566-0.792; p < 0.001) and OUNG (OR = 0.694; 95% CI: 0.545-0.883; p = 0.004). There was no evidence of a positive association between glycemic traits and nontoxic goitre traits (p > 0.05).

CONCLUSIONS

Our findings indicate a potential causal relationship between nontoxic goitre traits and T2DM. Specifically, our study addresses that NMG and T2DM may have a significant causal effect on each other in both directions.

Pituitary-Thyroid Hormones and Related Indices in Euthyroid Type 2 Diabetes: Association With Thyroid Nodules

Aim

Diabetes is an independent risk factor for thyroid nodules (TNs), however, the influencing factors of TNs have not been fully clarified under the condition of diabetes. Previous studies have shown a connection between pituitary-thyroid hormone (TH) functions and TNs in different populations. However, the potential link in euthyroid patients with diabetes is unclear. We aimed to explore the correlates of TNs in euthyroid type 2 diabetes (T2D) patients.

Methods

This cross-sectional study included 1965 euthyroid adults with T2D. Clinical and biochemical data, including TH and relevant covariates were collected. TNs were evaluated using ultrasound. Univariate and multivariate logistic regression analyses were performed to identify factors associated with TNs, with analyses stratified by sex.

Results

The overall prevalence of TNs was 51.9%. The prevalence of TNs was higher in females. Stratified by sex, the results from univariate and further logistic regression analyses showed that free triiodothyronine (FT3) (OR: 1.381; 95% CI: 1.066-1.790) and thyroid-stimulating hormone index (TSHI) (OR: 0.740; 95% CI: 0.584-0.937) were independently correlated with TNs only in females, while no TH-related indicators entered the regression model in males.

Conclusion

The relationship between TH and related indices with TNs exhibited sex differences. Specifically, FT3 and TSHI were independently associated with TNs in females. These findings underscore the importance of evaluating TH and related indices for early monitoring and management of TNs, particularly in euthyroid female T2D patients.

Association between obesity and thyroid nodules in children and adults living in iodine-sufficient areas: analysis of cross-sectional data from Tianjin, China

OBJECTIVE

The main purpose of this study was to analyse the association between obesity and thyroid nodules in children and adults living in iodine-sufficient areas in China.

DESIGN

Analysis of data from two cross-sectional surveys.

SETTING AND PARTICIPANTS

921 children from 2016 to 2021 and 1505 adults from 2018 to 2021 living in iodine-sufficient areas from Tianjin, China were recruited.

OUTCOME MEASURES

Anthropometric measures including height and weight were taken, and body mass index (BMI) and body surface area (BSA) were calculated. Thyroid ultrasonography was performed to assess thyroid nodules. A multifactor logistic regression model and a restricted cubic spline model were used to analyse the association between BMI/BSA and thyroid nodules in children and adults.

RESULTS

Thyroid nodules were detected in 21.72% of children and 40.00% of adults. Compared with children in the low BMI and low BSA groups, children in higher BMI (OR=1.53, 95% CI 1.09 to 2.15) and higher BSA (OR=1.40, 95% CI 1.01 to 1.94) groups had significantly higher risks for thyroid nodules. High BMI and high BSA were also significantly associated with multiple thyroid nodules in children, with ORs and 95% CIs of 1.51 (1.04 to 2.19) and 1.45 (1.01 to 2.08), respectively. The restricted cubic spline model indicated that the risk of thyroid nodules and multiple thyroid nodules in children increased with the increase of BMI-z-score and BSA. In adults, a high BSA (OR=1.34, 95% CI 1.01 to 1.77) was significantly associated with multiple thyroid nodules, but this association was not valid in the restricted cubic spline model.

CONCLUSION

Childhood obesity is associated with the risk of thyroid nodules; however, there is no clear association between adult obesity and thyroid nodules.

Mediating role of triglyceride-glucose index and its derivatives in the relationship between central obesity and Hashimoto thyroiditis in type 2 diabetes

BACKGROUND

Obesity and insulin resistance (IR) may be risk factors for thyroid disease, but there is no clinical-based consensus on this topic. Therefore, this study aims to evaluate the associations between the triglyceride-glucose index (TyG) and its derivatives and Hashimoto thyroiditis (HT) in type 2 diabetes mellitus (T2DM) patients, and explore the relationships between the central obesity indicators and HT risk to provide a reliable basis for the early prevention of HT.

METHODS

A total of 1071 T2DM patients aged ≥ 20 years were selected from a tertiary hospital in Tianjin, all of them had normal thyroid function (including free triiodothyronine, free thyroxine, total triiodothyronine, total thyroxine, and thyroid-stimulating hormone). HT was assessed via thyroid-associated antibodies and thyroid colour Doppler ultrasound. TyG and its derivatives were measured via IR. Restricted cubic spline (RCS) models, multivariable logistic regression, and receiver operating characteristic (ROC) curve analysis were used to explore the correlations and predict HT. Mediation analysis explored the mediating role of TyG and its derivatives in the associations between the central obesity indicators and HT.

RESULTS

RCS models revealed that increases in waist circumference (WC), waist-to-height ratio (WHtR), waist-to-hip ratio (WHR), TyG-WC, TyG-WHR, and TyG-WHtR were associated with increased HT risk. Logistic regression revealed that participants in the fourth quartile of TyG-WC, TyG-WHR, and TyG-WHtR had approximately 3.38 times greater HT risk (odds ratio range: 2.807 to 3.375). ROC analysis revealed that WC, WHtR, WHR, TyG-WC, TyG-WHtR and TyG-WHtR could distinguish the presence of HT. In females, the WHR had the highest predictive power, with an area under the ROC curve of 0.651 (95% confidence interval 0.611-0.691, P < 0.001). Mediation analysis revealed that high IR, as assessed by the TyG-body mass index (TyG-BMI), significantly mediated the effects of WC, WHtR, and WHR on the risk of HT. Among them, the TyG-BMI had the highest proportion of mediating effect of WC on HT risk, reaching 74.08%.

CONCLUSION

IR significantly mediates the increased risk of HT associated with central obesity. In clinical practice, WC, WHtR, WHR, TyG-WC, TyG-WHR, and TyG-WHtR serve as sensitive indicators for predicting HT risk in adult T2DM patients.

Unveiling the link between ACR TI-RADS grading and Bethesda score of thyroid nodules in diabetic patients: A comprehensive analysis

This study aimed to explores the factors influencing thyroid nodules (TNs) in individuals with type 2 diabetes mellitus (T2DM) and evaluates the consistency between different American College of Radiology Thyroid Imaging Reporting and Data System (ACR TI-RADS) grades and Bethesda scores. Total of 642 T2DM patients were divided into TN group (245) and control group (397) based on the presence or absence of TNs. TN patients were further categorized into ACR TI-RADS classification (TR) 1 to 4 and TR5 subgroups. Diabetes-related clinical and biochemical parameters were collected, and differences were analyzed using univariate analysis. Logistic regression analysis was utilized to pinpoint independent influencing factors for TN occurrence and different TN classifications. Consequently, age, body mass index (BMI), fasting plasma glucose level (FBGL), low density lipoprotein cholesterol (LDL-C), diabetic progression, and family history of TNs emerged as independent risk factors for TN development in T2DM patients. Additionally, glycosylated hemoglobin (HbA1c), nodule diameter, and family history of TNs were identified as independent risk factors for TR5 TN development in T2DM patients. All TR1 to 2 nodules had a Bethesda score of 2 and all showed benign pathological findings. In 97.10% of cases (67/69), nodules classified as TR3 exhibited a Bethesda score of 2, with all pathological results indicating benign findings, aligning with the Bethesda score. In addition, the concordance between TR4 nodules and Bethesda score was only 78.57% (88/112). In conclusion, TNs and their malignancy in T2DM patients are significantly linked to blood glucose and lipid metabolism indexes. TR3 classification in T2DM patients poses a low malignancy risk, suggesting caution when conducting fine needle aspiration cytology (FNAC) testing.

Predictive value of IGF-1/IGFBP-3 ratio for thyroid nodules in type 2 diabetic mellitus

Aims

To explore the predictive value of the IGF-1/IGFBP-3 ratio for the presence of thyroid nodules in patients with type 2 diabetes mellitus (T2DM).

Methods

This observational study prospectively enrolled patients with T2DM at the Second Hospital of Jilin University between May 2021 and January 2022. Thyroid nodule (TN) status was determined by ultrasonography. Receiver operating characteristic (ROC) curve analysis was performed to assess the predictive value of the serum IGF-1/IGFBP-3 molar ratio for TNs. Multivariable logistic regression analysis was conducted to identify risk factors for thyroid nodules in patients with T2DM.

Results

A total of 122 patients (mean age ± standard deviation: 52.57 ± 11.71 years; 74 males) were enrolled. 37.7% (n=46) of patients did not have TNs, while 62.3% (n=76) had TNs. The duration of diabetes, age, and HDL-C level were significantly higher in the T2DM group with TNs compared to the group without TNs (all P < 0.05). The area under the ROC curve (AUC) for the combination of IGF-1, IGFBP-3, and the serum IGF-1/IGFBP-3 molar ratio in predicting TNs in T2DM patients was 0.619 (P < 0.001). Additionally, multivariable logistic regression analysis revealed that the duration of diabetes, age, fasting plasma glucose (FPG), fasting insulin (FINS), thyroid-stimulating hormone (TSH), IGF-1, and IGFBP-3 levels were independent risk factors for thyroid nodules, while the serum IGF-1/IGFBP-3 molar ratio level was an independent protective factor for thyroid nodules in patients with T2DM (all P < 0.05).

Conclusion

The combination of IGF-1, IGFBP-3, and the serum IGF-1/IGFBP-3 molar ratio may have a better predictive value for TNs in T2DM patients than using any single marker alone. The duration of diabetes, age, FPG, FINS, TSH, IGF-1, IGFBP-3, and the serum IGF-1/IGFBP-3 molar ratio levels were independently associated with thyroid nodules in patients with T2DM.

The determinants of leptin, angiopoietin like 8, and thyroid hormones levels in Saudi females with type 2 diabetes mellitus: A retrospective study

This study aimed to assess the prevalence of thyroid dysfunction, as measured by hormone levels, in Saudi women with type 2 diabetes mellitus (T2DM). The study will also assess thyroid hormones and leptin, angiopoietin like 8 (ANGPTL8), obesity, and cardiovascular diseases (CVD) in T2D patients. A total of 250 women aged 40 to 60 years with T2DM were retrospectively studied between 2021 and 2022. This research examined medical records for T2DM patients. In this investigation, no T2DM patients had thyroid autoantibodies in their medical records. These patients were chosen for their FT4 and TSH values. All participants were Saudi females with T2DM, aged 54.5 years. Of the 250 participants, 32% had hypothyroidism, 14.8% had hyperthyroidism, and 40.8% (102) had no thyroid disease. Hypothyroidism (7.8 ± 0.67 mmol/L) exhibited greater fasting blood glucose (FBG) levels than hyperthyroidism (7.1 ± 0.64 mmol/L) (P < .05). Hypothyroid and hyperthyroid females had significant differences in high density lipoprotein-cholestrol (HDL-C), triglycerides, triglyceride glucose (TyG) index, body mass index (BMI), waist circumstance (WC), high-sensitivity C-reactive protein (hs-CRP), leptin, ANGPTL8, insulin resistance (IR), and insulin levels (P < .05). Pearson's correlation test showed that T2DM patients' HDL-C levels were favorably but negatively correlated with leptin and ANGPTL8 levels. In hypothyroidism, thyroid stimulation hormone (TSH) is favorably linked with glycated hemoglobin (HbA1c), triglyscride (TG), TyG index, BMI, WC, leptin, ANGPTL8, hs-CRP, and IR. T2DM is linked to thyroid malfunction, notably hypothyroidism, which correlates positively with TSH. TSH variations due to increasing leptin, ANGPTL8, and TyG index may enhance the risk of insulin resistance diseases, such as obesity and CVD, in Saudi females with T2DM.

Cardiovascular and metabolic comorbidities in patients with thyroid nodules: the impact of incidental diagnosis

PURPOSE

The prevalence of thyroid nodules (TN) in the general population has increased as screening procedures are implemented and an association with metabolic and cardiovascular disorders has been reported. The aim of this study was to investigate the reason leading to the diagnosis of TN and to compare the clinical characteristics of patients diagnosed incidentally with those of patients diagnosed for thyroid-related reasons.

METHODS

We designed a retrospective cross-sectional study including consecutive patients with TN from two high-volume hospital-based centers for thyroid diseases (Pavia and Messina) in Italy. Data regarding reason leading to TN diagnosis, age, sex, BMI, presence of cardio-metabolic comorbidities were collected.

RESULTS

Among the 623 enrolled subjects, the US diagnosis of TN was prompted by thyroid-related reasons in 421 (67.6%, TD group) and incidental in 202 (32.4%, ID group) with a similar distribution in the two centers (p = 0.960). The ID group patients were more frequently males (38.6% vs 22.1%, p < 0.001) and significantly older (58.9 ± 13.7 vs 50.6 ± 15.5 years, p < 0.001) than the TD group ones, and had a higher rate of cardiovascular comorbidities (73.8% vs 47.5%, p < 0.001), despite having a similar BMI (27.9 ± 5.2 vs 27.8 ± 13.5, p = 0.893).

CONCLUSIONS

Stratification of patients with TN according to the diagnostic procedure leading to diagnosis allows a better epidemiological characterization of this inhomogeneous and large population.

Effects of Metformin Therapy on Thyroid Volume and Functions in Patients with Newly Diagnosed Type 2 Diabetes Mellitus: A Single-center Prospective Study

OBJECTIVE

Patients with impaired glucose metabolism have increased thyroid volume and a higher prevalence of nodules. Yet, some studies show that there is an improvement in these thyroid parameters after diabetes treatment. Our observational study aimed to reveal the effect of treatment on thyroid function, thyroid volume, and the presence of nodules in newly diagnosed type 2 diabetes mellitus (T2DM) patients who were started on metformin treatment.

METHODS

Euthyroid and subclinically hypothyroid patients with a serum TSH level of <10 mU/L, who were newly diagnosed with T2DM and started on metformin as an antidiabetic treatment and not used any thyroid medication previously, were included in our study. Patients' characteristics were recorded. Baseline and 6th-month serum thyroid function tests were scheduled. Baseline and 6th-month thyroid gland characteristics were examined by thyroid ultrasonography.

RESULTS

A total of 101 (37 males, 64 females) newly diagnosed T2DM patients with euthyroid (n=95) or subclinical hypothyroidism (n=6) were included in the study. The mean age of the patients was 53.02 ± 11.9 years, and the mean BMI was 29.60 ± 3.9 kg/m2. Fifty-two (52%) patients were classified as obese. Body weight, BMI, serum TSH, ALT, Anti-TPO levels, and thyroid volume decreased significantly in the 6th-month compared to baseline values (p = 0.000; p = 0.000; p = 0.011; p = 0.022; p = 0.000, respectively). Serum anti-Tg, fT4, fT3 levels, and thyroid nodule count did not change significantly. A high agreement was found between the baseline and 6thmonth nodule counts (gamma= 0.886; p < 0.001) and the presence of multi-nodularity in the thyroid (gamma= 0.941; p < 0.001), but no significant change was observed. Anti-TPO levels showed a significant decrease in both with and without obesity groups at the end of 6 months (p = 0.003, p = 0.009, respectively). Serum TSH level decreased significantly only in non-obese subjects (p = 0.004), and thyroid volume decreased significantly only in obese subjects (p = 0.000).

CONCLUSION

Our results suggest that metformin treatment significantly reduces body weight, BMI, thyroid volume, and serum TSH, ALT, and Anti-TPO levels in patients with newly diagnosed T2DM. Moreover, serum TSH levels showed a significant decrease in non-obese subjects, while thyroid volume showed a significant decrease in obese subjects.

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

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

Survey of iodized salt coverage in areas with different water iodine concentrations and the iodine status of local women

PURPOSE

There were only two definitions of iodine-deficient (water iodine concentration < 10 μg/L) and iodine-excess areas (water iodine concentration > 100 μg/L) in China before 2020. Areas with water iodine concentration between 10 and 100 μg/L implement the same policy as iodine-deficient areas to provide iodized salt. The definition of iodine-adequate areas was formulated in 2020 for the first time. The paper aims to investigate the coverage rate of iodized salt (CR) in different areas defined according to the latest national standards, evaluate the iodine status of local women, and provide a basis for the revision and improvement of relevant policies.

METHODS

A total of 1948 women aged 18-60 were recruited from the iodine extra-high areas (IEHA), iodine-excess areas (IEA), iodine-adequate areas (IAA), inland iodine-deficient areas (IIDA), and coastal iodine-deficient areas (CIDA). Information on daily diet was collected with the Food Frequency Questionnaire. Drinking water, salt, food, and urine samples were collected and tested in our laboratory. Based on the recommended daily iodine intake, we assessed whether the subjects' daily iodine intake levels were adequate.

RESULTS

The CR and the median urinary iodine concentrations (UICs) were 4.02% and 98.03 μg/L in CIDA, 89.74% and 144.93 μg/L in IIDA, 26.55% and 178.60 μg/L in IAA, 8.78% and 446.5 μg/L in IEA, 3.95% and 605.4 μg/L in IEHA, respectively. The differences among these five areas were statistically significant (P < 0.0001). The daily dietary iodine intakes were mainly from drinking water in IAA (63.92%), IEA (92.29%), and IEHA (92.93%), and were mainly from iodized salt in IIDA (59.22%) and food in CIDA (86.6%).

CONCLUSION

Women in IAA and IIDA were in an adequate iodine state. Women in IEA and IEHA were in an iodine-excess state, and it is necessary to carry out water improvements projects. Women in CIDA were in a slight iodine-deficient state, and health education on scientific iodine fortification should be strengthened to increase iodine intake.

Relationship between complications of type 2 diabetes and thyroid nodules

OBJECTIVE

Recent evidence suggests that diabetes is a risk factor for thyroid nodules. However, the relationship between complications of type 2 diabetes and the risk of thyroid nodules remains unclear. This present study aims to investigate the association between thyroid nodules and complications of type 2 diabetes.

METHODS

This retrospective study collected 4696 adult inpatients with type 2 diabetes between January 2021 and December 2021. The complications examined in this paper included diabetic nephropathy, peripheral neuropathy, eye disorder, and peripheral vascular disease.

RESULTS

A total of 4696 patients with type 2 diabetes participated in the study, of whom 19.6% had thyroid nodules. Among all the complications, eye disorder had the highest incidence of thyroid nodules (incidence rate, 29.4%; 95% CI, 26.23%-32.51%). The prevalence of thyroid nodules was lower among patients without complications (incidence rate, 14.1%; 95% CI, 12.48% -15.67%) compared to patients who had complications (incidence rate, 23.1%; 95% CI, 21.59%-24.68%) (p < 0.001). Logistic regression revealed that peripheral neuropathy (adjusted OR, 1.6; 95% CI, 1.4-1.9), eye disorder (adjusted OR, 1.8; 95% CI, 1.5-2.2), and peripheral vascular disease (adjusted OR, 1.8; 95% CI, 1.6-2.1) were all significantly associated with an increased risk of thyroid nodules. However, no significant correlation was found between diabetic nephropathy and the risk of thyroid nodules.

CONCLUSION

One of the key findings of this study is that type 2 diabetes without complications is negatively correlated with the risk of thyroid nodules, while several complications are associated with a significantly increased risk of thyroid nodules.

Short night-time sleep duration is associated with thyroid nodules: A community-based survey from Guangzhou, China

BACKGROUND

Sleep plays a critical role in maintaining human health. This study aimed to explore the association between sleep status and thyroid nodules.

METHODS

A total of 2414 individuals aged 18 or older with euthyroidism were enrolled in this community-based survey. Sleep status was self-reported. Thyroid ultrasonography was performed to measure nodules. Multiple logistic analyses were applied to adjust for confounding factors.

RESULTS

The percentages of thyroid nodules among individuals who slept <5 hours, 5-8 hours, and >8 hours per night were 57.79% (115/199), 44.19% (833/1885) and 42.73% (141/330), respectively (p = 0.001). Individuals who slept <5 hours per night had a significantly higher percentage of thyroid nodules than those who slept 5-8 hours per night (57.79% vs. 44.19%, p = 0.001) or >8 hours per night (57.79% vs. 42.73%, P < 0.001). However, no similar result was shown between individuals who slept >8 hours and 5-8 hours per night (42.73% vs. 44.19%, p = 0.621). Multiple logistic analysis showed that a sleep duration of <5 hours per night was significantly associated with thyroid nodules (odds ratio (OR) 1.643, 95% confidence interval (CI) 1.084-2.490, p = 0.019) when compared to a sleep duration of >8 hours per night. However, a sleep duration of <5 hours per night was not associated with thyroid nodules compared to a sleep duration of 5-8 hours (OR 1.294, 95% CI 0.918-1.824, p = 0.141). Similarly, no significant differences were seen among sleep duration per day, time of falling asleep, habit of daytime napping or thyroid nodules in multiple logistic analyses (all p > 0.05).

CONCLUSIONS

Short nighttime sleep duration was associated with thyroid nodules in our community-based population. Screening for thyroid nodules among these individuals is recommended.

The effects of pathophysiological changes in Type-2 diabetic patients on thyroid dysfunction and nodular goiter development in Turkey

Objective: The prevalence of thyroid dysfunction is higher in patients with diabetes, and its diagnosis could cause better diabetes management. The purpose of the present study is to examine the impact of pathophysiological changes in patients with Type-2 diabetes on the frequency of thyroid dysfunction, thyroid autoimmunity, thyroid nodule, and thyroid cancer in Turkey. Methods: The study was conducted on a total of 3.276 patients with Type-2 diabetes who underwent thyroid tests and thyroid ultrasonography (US). The demographic characteristics, biochemical and hormonal values, thyroid US reports, and histopathology reports were collected from the patient's electronic records. Results: Thyroid autoimmunity positive TPOab 15.9% (n = 524) and/or positive TGab 9.9% (n = 327), the rate of positivity of both antibodies (TPOab + TGab) in the same patient, and total thyroid autoimmunity was found to be 32.57% (n=1067) in Type-2 diabetic patients. Thyroid dysfunction was detected in 18.3% (n = 602) of these patients. The distribution of thyroid dysfunction was 9.09% (n = 298) subclinical hypothyroidism, 4.1% (n = 135) clinical hypothyroidism, 3.1% (n = 102) subclinical hyperthyroidism, 2.0% (n = 67) clinical hyperthyroidism. Also, 67.9% (n = 2225) thyroid nodules, and 5% (n = 164) thyroid cancer were detected. Conclusion: Thyroid dysfunction was found to have increased in patients with Type-2 diabetes at significant levels.

Selenium and Selenoproteins at the Intersection of Type 2 Diabetes and Thyroid Pathophysiology

Type 2 diabetes (T2D) is considered one of the largest global public-health concerns, affecting approximately more than 400 million individuals worldwide. The pathogenesis of T2D is very complex and, among the modifiable risk factors, selenium (Se) has recently emerged as a determinant of T2D pathogenesis and progression. Selenium is considered an essential element with antioxidant properties, and is incorporated into the selenoproteins involved in the antioxidant response. Furthermore, deiodinases, the enzymes responsible for homeostasis and for controlling the activity of thyroid hormones (THs), contain Se. Given the crucial action of oxidative stress in the onset of insulin resistance (IR) and T2D, and the close connection between THs and glucose metabolism, Se may be involved in these fundamental relationships; it may cover a dual role, both as a protective factor and as a risk factor of T2D, depending on its basal plasma concentration and the individual’s diet intake. In this review we discuss the current evidence (from experimental, observational and randomized clinical studies) on how Se is associated with the occurrence of T2D and its influence on the relationship between thyroid pathophysiology, IR and T2D.

Gender-Specific Associations Between Metabolic Disorders and Thyroid Nodules: A Cross-Sectional Population-Based Study from China

Background: Metabolic disorders (MDs) and the metabolic syndrome (MetS) may be associated with thyroid diseases. The aim of this study was to investigate the relationship between MDs and various types of thyroid nodules (TNs), according to gender. Methods: We analyzed cross-sectional data from the Thyroid Disorders, Iodine Status, and Diabetes Epidemiological (TIDE) survey in China. A total of 56,729 subjects ≥18 years of age were included. Thyroid gland morphology was assessed by thyroid standardized ultrasonography. A multivariate logistic regression model was used to explore the odds ratio (OR) and confidence intervals [CIs] for any associations between MDs and TNs. Subgroup analyses were conducted according to gender and TN type (solitary, S-TN; multiple, M-TNs). Results: The prevalence of TNs was increased in several MDs, and was higher in women than men regardless of whether they suffered from MDs (22.0%, CI [21.6-22.5%] vs. 15.7%, CI [15.3-16.7%], p < 0.001). TNs were associated with the presence of MDs (OR = 1.189, CI [1.107-1.278], p < 0.001), hypercholesterolemia (OR = 1.235, CI [1.177-1.296], p < 0.001), high low-density lipoprotein cholesterol (LDL-C; OR = 1.249, CI [1.186-1.316], p < 0.001), and hyperuricemia (OR = 1.206, CI [1.126-1.293], p < 0.001). MDs and MetS were, respectively, significantly associated with TNs, S-TNs, and M-TNs in men, while MDs were significantly associated with the three TN profiles in women. With respect to dyslipidemia, hypercholesterolemia and high LDL-C had the strongest association with TNs, whereas hypertriglyceridemia had no effect. Conclusions: TNs (especially M-TNs) may be associated with MDs and their various components, and there appear to be some gender-specific associations.

Metformin in Differentiated Thyroid Cancer: Molecular Pathways and Its Clinical Implications

Metformin is a synthetic biguanide that improves insulin sensitivity and reduces hepatic gluconeogenesis. Aside being the first-line therapy for Type 2 Diabetes (T2D), many pleiotropic effects have been discovered in recent years, such as its capacity to reduce cancer risk and tumorigenesis. Although widely studied, the effect of metformin on thyroid cancer remains controversial. Potential mechanisms for its growth inhibitory effects have been elucidated in various preclinical studies that involved pathways related to adenosine mono-phosphate-activated protein kinase (AMPK), mammalian target of rapamycin (mTOR), mitochondrial glycerophosphate dehydrogenase (mGPDH), and the nuclear factor κB (NF-κB). Hyperinsulinemia increases cell glucose uptake and oxidative stress, and promotes thyroid cell growth, leading to hyperproliferation, carcinogenesis, and the development of malignant tumors. Furthermore, it has also been related to thyroid nodules size in nodular disease, as well as tumoral size in patients with thyroid cancer. Several clinical studies concluded that metformin might have an important role as an adjuvant therapy to reduce the growth of benign and malignant thyroid neoplasms. This suggests that metformin might be useful for patients with differentiated or poorly differentiated thyroid cancer and metabolic diseases such as insulin resistance or diabetes.

Impaired Glucose Metabolism, Anti-Diabetes Medications, and Risk of Thyroid Cancer

Simple Summary

An epidemiologic link exists between obesity, insulin resistance, diabetes, and some cancers, such as breast cancer and colon cancer. The prevalence of obesity and diabetes is increasing, and additional epidemiologic data suggest that there may be a link between obesity and risk of thyroid abnormalities. Factors that may link obesity and diabetes with thyroid proliferative disorders include elevated circulating levels of insulin, increased body fat, high blood sugars, and exogenous insulin use. However, mechanisms underlying associations of obesity, diabetes, and thyroid proliferative disorders are not yet fully understood. The present manuscript reviews and summarizes current evidence of mechanisms and epidemiologic associations of obesity, insulin resistance, and use of anti-diabetes medications with benign and malignant proliferative disorders of the thyroid.

Abstract

The prevalence of obesity is progressively increasing along with the potential high risk for insulin resistance and development of type 2 diabetes mellitus. Obesity is associated with increased risk of many malignancies, and hyperinsulinemia has been proposed to be a link between obesity and cancer development. The incidence of thyroid cancer is also increasing, making this cancer the most common endocrine malignancy. There is some evidence of associations between obesity, insulin resistance and/or diabetes with thyroid proliferative disorders, including thyroid cancer. However, the etiology of such an association has not been fully elucidated. The goal of the present work is to review the current knowledge on crosstalk between thyroid and glucose metabolic pathways and the effects of obesity, insulin resistance, diabetes, and anti-hyperglycemic medications on the risk of thyroid cancer development.

The Correlation between Microalbuminuria and Thyroid Nodules in Type 2 Diabetic Mellitus

OBJECTIVE

To investigate the correlation between thyroid nodules and microalbuminuria in type 2 diabetic mellitus.

METHODS

A total of 270 patients with type 2 diabetes at Tongzhou Branch of Dongzhimen Hospital were enrolled in this retrospective study. Data were collected from the inpatient electronic files between January 2018 and January 2020. The laboratory indexes of the two groups (thyroid nodule group with 172 cases and control group including 98 cases without thyroid nodules) were statistically analyzed by binomial logistic regression analysis and Spearman correlation analysis.

RESULTS

The proportion of microalbuminuria (MAU) in the thyroid nodule group was larger than that in the control group. Age, serum TT4, and FT4 in the thyroid nodule group were significantly higher compared with the control group. The binary logistic regression analysis indicated that age, sex, FT4, and MAU were the risk factors for thyroid nodule in T2DM patients. Spearman correlation analysis showed that the thyroid nodule was significantly positively correlated with MAU, age, FT4, and TT4.

CONCLUSIONS

MAU might be an independent risk factor for thyroid nodule in type 2 diabetic mellitus.

The Relationship Between Type 2 Diabetes Mellitus and Related Thyroid Diseases

Diabetes and thyroid diseases are caused by endocrine dysfunction and both have been demonstrated to mutually impact each other. Variation in thyroid hormone levels, even within the normal range, can trigger the onset of type 2 diabetes mellitus (T2DM), particularly in people with prediabetes. However, the available evidence is contradictory.

The purpose of this review is to understand the pathological relationship between thyroid-related disorders and T2DM.

T2DM in thyroid dysfunction is thought to be caused by altered gene expression of a group of genes, as well as physiological abnormalities that result in decreased glucose uptake increased, splanchnic glucose absorption, disposal in muscles, increased hepatic glucose output. Additionally, both hyperthyroidism and hypothyroidism can cause insulin resistance. Insulin resistance can develop in subclinical hypothyroidism as a result of a reduced rate of insulin-stimulated glucose transfer caused by a translocation of the glucose transporter type 2 (GLUT 2) gene. On the other hand, novel missense variations in (Thr92Ala) can cause insulin resistance. Furthermore insulin resistance and hyperinsulinemia resulting from diabetes can cause culminate in goitrous transformation of the thyroid gland.

Thyroid-related diseases and T2DM are closely linked. Type 2 diabetes can be exacerbated by thyroid disorders, and diabetes can worsen thyroid dysfunction. Insulin resistance has been found to play a crucial role in both T2DM and thyroid dysfunction. Therefore, failure to recognize inadequate thyroid hormone levels in diabetes and insulin resistance in both conditions can lead to poor management of patients.

Association between thyroid dysfunction and type 2 diabetes: a meta-analysis of prospective observational studies

BACKGROUND

Diabetes mellitus and thyroid disease are two areas of broad interest in the field of endocrinology and metabolism. Variation of thyroid hormone concentration, even within the normal range, may portend the onset of type 2 diabetes mellitus (T2DM), especially among those with prediabetes. However, current evidence is mixed.

METHODS

Prospective studies which assessed diabetes incidence were identified using a database search of MEDLINE and Embase through May 1, 2021. The Sidik-Jonkman random-effects model and cubic spline model were used to evaluate the associations and dose-response relationships between thyroid function/hormone levels and risk of T2DM and cardiovascular disease (CVD) risk among T2DM patients.

RESULTS

A total of 12 prospective studies were included. We found that high baseline TSH levels were related to a 17% higher risk of T2DM (RR 1.17, 95% CI 1.01, 1.36; I²=78%, P<0.01), compared with normal TSH levels. Low FT3 (RR 1.40, 95% CI 1.09, 1.80; I²=59%, P=0.03) and low FT4 (RR 1.33, 95% CI 1.04, 1.71; I²=62%, P=0.02) levels were significantly associated with risk of T2DM. The cubic spline model indicated a J-shaped relationship with TSH, but inverted-J-shaped relationships with FT3 and FT4. CVD events and all-cause deaths were prospectively evaluated in four studies, but were not associated with abnormal thyroid function.

CONCLUSIONS

Our meta-analysis determined that abnormal thyroid hormone level is associated with an increased risk of T2DM, showing a J-shaped relationship with TSH and inverted-J-shaped relationships with FT3 and FT4.

TRIAL REGISTRATION

Registered number in PROSPERO: CRD42021225695 .

Video mediastinoscopy-assisted superior mediastinal dissection in the treatment of thyroid carcinoma with mediastinal lymphadenopathy: preliminary results

Background

Mediastinal lymph node metastases (MLNM) are not rare in thyroid cancer, but their treatment has not been extensively studied. This study aimed to explore the preliminary application of video mediastinoscopy-assisted superior mediastinal dissection in the diagnosis and treatment of thyroid carcinoma with mediastinal lymphadenopathy.

Materials and methods

We retrospectively reviewed the clinical pathologic data and short-term outcomes of thyroid cancer patients with suspicious MLNM treated with video mediastinoscopy-assisted mediastinal dissection at our institution from 2017 to 2020.

Results

Nineteen patients were included: 14 with medullary thyroid carcinoma and five with papillary thyroid carcinoma. Superior mediastinal nodes were positive in nine (64.3%) patients with medullary thyroid carcinoma and in four (80.0%) patients with papillary carcinoma. No fatal bleeding occurred. There were three cases of temporary recurrent laryngeal nerve (RLN) palsy postoperatively, one of which was bilateral. Four patients had temporary hypocalcemia requiring supplementation, one had a chyle fistula, and one developed wound infection after the procedure. Postoperative serum molecular markers decreased in all patients. One patient died of cancer while the other 18 patients remained disease-free, with a median follow-up of 33 months.

Conclusion

Video mediastinoscopy-assisted superior mediastinal dissection can be performed relatively safely in patients with suspicious MLNM. This diagnostic and therapeutic approach may help control locoregional recurrences.

MiR-7-5p inhibits thyroid cell proliferation by targeting the EGFR/MAPK and IRS2/PI3K signaling pathways

The aberrant expression of miRNAs is often correlated to tumor development. MiR-7-5p is a recently discovered downregulated miRNA in thyroid papillary carcinoma (PTC). The goal of this project was to characterize its functional role in thyroid tumorigenesis and to identify the targeted modulated pathways. MiR-7-5p overexpression following transfection in TPC1 and HT-ori3 cells decreased proliferation of the two thyroid cell lines. Analysis of global transcriptome modifications showed that miR-7-5p inhibits thyroid cell proliferation by modulating the MAPK and PI3K signaling pathways which are both necessary for normal thyroid proliferation and play central roles in PTC tumorigenesis. Several effectors of these pathways are indeed targets of miR-7-5p, among which EGFR and IRS2, two upstream activators. We confirmed the upregulation of IRS2 and EGFR in human PTC and showed the existence of a negative correlation between the decreased expression of miR-7-5p and the increased expression of IRS2 or EGFR. Our results thus support a tumor-suppressor activity of miR-7-5p. The decreased expression of miR-7-5p during PTC tumorigenesis might give the cells a proliferative advantage and delivery of miR-7-5p may represent an innovative approach for therapy.

The Relationship and Gender Disparity Between Thyroid Nodules and Metabolic Syndrome Components Based on a Recent Nationwide Cross-Sectional Study and Meta-Analysis

BACKGROUND

Metabolic syndrome (MetS) has a potential connection with thyroid disease, but its relationship with thyroid nodules (TNs) is still controversial. This study aims to clarify the relationship between MetS and TNs, and this relationship in the subgroup of gender.

METHODS

The recent nationwide cross-sectional study called Thyroid Disorders, Iodine Status, and Diabetes Epidemiological survey provided the newest data on the relationship between MetS and TNs from China and included 56,729 subjects. We also researched related literature in PubMed, EMBASE, Cochrane Library, and MEDLINE until Oct 30, 2020, in order to perform a meta-analysis. The relevant articles were examined, and the eligible studies were included to assess the association between MetS and TNs.

RESULTS

The meta-analysis included 15 studies (involving 468,845 subjects). Of these, 14 studies were from the databases, and one study was this cross-sectional data. The meta-analysis showed that TNs were associated with a higher prevalence of MetS (OR=1.87, 95% CI: 1.44-2.45) and the components of MetS, including central obesity (OR=1.41, 95% CI: 1.15-1.72), hypertriglyceridemia (OR=1.13, 95% CI: 1.10-1.15), low high-density lipoprotein cholesterolemia (OR=1.11, 95% CI: 1.02-1.20), abnormal blood pressure (OR=1.68, 95% CI: 1.62-1.75), and hyperglycemia (OR=1.59, 95% CI: 1.46-1.74). Central obesity displayed gender differences, being a risk factor in males (OR=1.38, 95% CI: 1.02-1.86) but not in females (OR=1.47, 95% CI: 0.97-2.23).

CONCLUSION

TNs were indeed associated with a higher prevalence of MetS. In addition, its component diseases, such as central obesity, hypertriglyceridemia, abnormal blood pressure, and hyperglycemia, were also associated with TNs. Females with MetS or its components had a higher risk of suffering from TNs than males.

Insulin resistance and pancreatic β cell dysfunction are associated with thyroid hormone functions: A cross-sectional hospital-based study in Turkey

BACKGROUND AND AIMS

The prevalence of thyroid disease in diabetic patients is significantly higher than the general population. This indicates a possible interaction between thyroid functions and insulin sensitivity. This study aimed to investigate the relationship between insulin resistance (IR), pancreatic β cell function, and thyroid function tests.

METHODS

This cross-sectional study was conducted with adults who applied to Eskişehir Osmangazi University Hospital for general control. Fasting insulin, glucose, TSH, fT3, and fT4 levels in the serum of 1340 adult (18-60 aged) patients without any chronic diseases were examined retrospectively. The fT3/fT4 ratio, Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), and HOMA-β values were calculated. The correlation between HOMA-IR and HOMA-β values with thyroid function tests and differences between hormone levels of patients with and without IR were evaluated.

RESULTS

There was a positive correlation between HOMA-IR and TSH, negative with fT4. Also, a positive correlation between HOMA-β and fT3, negative correlation with fT4 were observed. In the IR group, fT3 levels were found significantly higher and fT4 levels were significantly lower. TSH levels were higher in the IR group but not statistically significant. The fT3/fT4 ratio was found significantly higher in the IR group and was correlated positively with both HOMA-IR and HOMA-β.

CONCLUSION

Our results revealed that thyroid dysfunction prevalence is quite high in adults who have not yet been diagnosed with diabetes but have insulin resistance and the onset of pancreatic β cell dysfunction.

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.

Review of Factors Contributing to Nodular Goiter and Thyroid Carcinoma

There is an increased incidence of thyroid nodules and cancer. In this article, the reasons for this increase are evaluated and discussed. The factors causing increases in the incidence of nodules are the same as those causing increases in thyroid cancer. There are publications from all over the world regarding the rising incidence of thyroid cancer; it is especially associated with papillary cancer. The literature was reviewed and evaluated with regard to this significant phenomenon. Thyroid-stimulating hormone (TSH) is the main mitotic factor. Any agent that elevates TSH will stimulate nodule formation. Therefore, the incidence of thyroid nodules is high in endemic goiter regions due to iodine deficiency. This paper has described many of the factors causing this higher incidence. Of note, metabolic syndrome and insulin resistance are important factors associated with the increased incidence of nodular goiter and papillary thyroid cancer today. However, these data must be confirmed by other studies in the future.

The Prevalence of Single and Multiple Thyroid Nodules and Its Association with Metabolic Diseases in Chinese: A Cross-Sectional Study

PURPOSE

The present study aims to investigate the prevalence of single and multiple thyroid nodules and its association with metabolic diseases in subjects who participated in the heath examination in China.

METHODS

This is a cross-sectional study. The participants who attend the physical examination at the Health Management Center of Southwest Hospital, Army Military Medical University, between January 2014 and December 2018, were included. Thyroid nodules were diagnosed by thyroid ultrasound. Multivariable logistic regression was used to investigate the association between metabolic diseases and nodular thyroid disease.

RESULTS

A total of 9,146 subjects were included in this study; of them, 2,961 were diagnosed with thyroid nodules, with a prevalence of 32.4%. The prevalence in women was significantly higher than that in men (45.2% vs 26.0%; χ ²  = 339.56, P < 0.001), and the prevalence was gradually increased with age (Z = 20.05, P < 0.001), and the prevalence was gradually increased with age (.

CONCLUSIONS

The prevalence of thyroid nodules was relatively high. Age, female gender, and diabetes are positively associated with nodular thyroid disease. High LDL cholesterolemia is more likely to be associated with multiple thyroid sarcoidosis.

Thyroid Dysfunction and Type 2 Diabetes Mellitus: Screening Strategies and Implications for Management

Diabetes mellitus (DM) and thyroid dysfunction (TD) often tend to coexist in patients. Both hypothyroidism and hyperthyroidism are more common in type 2 diabetes mellitus (T2DM) patients than in their nondiabetic counterparts. Current guidelines are neither clear nor specific about the frequency of thyroid function monitoring in T2DM patients. Circulating thyroid hormones affect several different organs and cells, have a major impact on glucose, lipid, and protein metabolism, and can worsen glycaemic control in T2DM. Hyperthyroidism and thyrotoxicosis can worsen subclinical DM and cause hyperglycaemia in T2DM patients, increasing the risk of diabetic complications. T2DM reduces thyroid-stimulating hormone levels and impairs the conversion of thyroxine (T4) to triiodothyronine (T3) in the peripheral tissues. Poorly managed T2DM can lead to insulin resistance and hyperinsulinaemia, which causes thyroid tissue proliferation and increases nodule formation and goitre size. In addition, while metformin can be beneficial in both T2DM and TD patients, other antidiabetics such as sulfonylureas, pioglitazone, and thiazolidinediones can negatively impact TD. Antithyroid drugs such as methimazole can impair glycaemic control in T2DM patients. Thyrovigilance in T2DM patients and diabetovigilance in TD patients may therefore be necessary to facilitate individualized care and management.Funding: Abbott India Ltd.

The role of an anti-diabetic drug metformin in the treatment of endocrine tumors

Incidence of endocrine cancers is rising every year. Over the last decade, evidence has accumulated that demonstrates the anti-cancer effects of an anti-diabetic drug, metformin, in endocrine malignancies. We performed a literature review utilizing the PubMed, Medline and clinicaltrials.gov databases using the keyword 'metformin' plus the following terms: 'thyroid cancer', 'thyroid nodules', 'parathyroid', 'hyperparathyroidism', 'adrenal adenoma', 'Cushing syndrome', 'hyperaldosteronism', 'adrenocortical cancer', 'neuroendocrine tumor (NET)', 'pancreatic NET (pNET)', 'carcinoid', 'pituitary adenoma', 'pituitary neuroendocrine tumor (PitNET)', 'prolactinoma', 'pheochromocytoma/paraganglioma'. We found 37 studies describing the preclinical and clinical role of metformin in endocrine tumors. The available epidemiological data show an association between exposure of metformin and lower incidence of thyroid cancer and pNETs in diabetic patients. Metformin treatment has been associated with better response to cancer therapy in thyroid cancer and pNETs. Preclinical evidence suggests that the primary direct mechanisms of metformin action include inhibition of mitochondrial oxidative phosphorylation via inhibition of both mitochondrial complex I and mitochondrial glycerophosphate dehydrogenase, leading to metabolic stress. Decreased ATP production leads to an activation of a cellular energy sensor, AMPK, and subsequent downregulation of mTOR signaling pathway, which is associated with decreased cellular proliferation. We also describe several AMPK-independent mechanisms of metformin action, as well as the indirect mechanisms targeting insulin resistance. Overall, repositioning of metformin has emerged as a promising strategy for adjuvant therapy of endocrine tumors. The mechanisms of synergy between metformin and other anti-cancer agents need to be elucidated further to guide well-designed prospective trials on combination therapies in endocrine malignancies.

Efficacy of Metformin for Benign Thyroid Nodules in Subjects With Insulin Resistance: A Systematic Review and Meta-Analysis

Background: To evaluate the effect of metformin therapy on decreasing benign thyroid nodule volume in subjects with insulin resistance (IR). Method: Randomized controlled trials (RCTs) and self-controlled trials for the meta-analysis published, before January 31, 2018 were selected from the PubMed, Cochrane Library, Embase, Web of Science, Chinese Biomedical Literature Database, National Knowledge Infrastructure, WANFANG and VIP Database. Pooled standard mean difference with 95% confidence interval was estimated by fixed- or random-effects model depending on heterogeneity. The risk of bias using the Cochrane Collaboration's tool was used to assess the quality of the RCTs contained. The quality of self-controlled studies was evaluated using the Methodological index for non-randomized studies (MINORS) method. Results: 7 studies (3 RCTs and 4 prospective self-controlled studies) with 240 patients were considered to be appropriate for the meta-analysis. The results of the meta-analysis indicated that the volume of thyroid nodule decreased significantly after metformin therapy (SMD -0.62, 95% CI -0.98 ~ -0.27). 6 studies reported the changes of the level of TSH. TSH levels decreased significantly after metformin therapy (SMD -0.27, 95% CI -0.47 ~ -0.07). The pooled data indicated an increase in FT3 level, and an unchanged FT4 level after metformin therapy (FT3, SMD 0.25, 95% CI 0.05 ~ 0.45; FT4, SMD -0.07, 95% CI -0.27 ~ 0.13). HOMA-IR levels decreased significantly after metformin therapy based on the pooled results of 3 RCTs and 3 prospective self-controlled studies (SMD -1.08, 95% CI -1.69 ~ -0.47). Conclusion: The meta-analysis demonstrated that metformin was safe and useful in shrinking benign thyroid nodules volume, improving thyroid function and IR. A large number of high-quality prospective studies still need to be carried out.