Associations between deep venous thrombosis and thyroid diseases: a two-sample bidirectional Mendelian randomization study.

BACKGROUND: Some previous observational studies have linked deep venous thrombosis (DVT) to thyroid diseases; however, the findings were contradictory. This study aimed to investigate whether some common thyroid diseases can cause DVT using a two-sample Mendelian randomization (MR) approach. METHODS: This two-sample MR study used single nucleotide polymorphisms (SNPs) identified by the FinnGen genome-wide association studies (GWAS) to be highly associated with some common thyroid diseases, including autoimmune hyperthyroidism (962 cases and 172,976 controls), subacute thyroiditis (418 cases and 187,684 controls), hypothyroidism (26,342 cases and 59,827 controls), and malignant neoplasm of the thyroid gland (989 cases and 217,803 controls. These SNPs were used as instruments. Outcome datasets for the GWAS on DVT (6,767 cases and 330,392 controls) were selected from the UK Biobank data, which was obtained from the Integrative Epidemiology Unit (IEU) open GWAS project. The inverse variance weighted (IVW), MR-Egger and weighted median methods were used to estimate the causal association between DVT and thyroid diseases. The Cochran's Q test was used to quantify the heterogeneity of the instrumental variables (IVs). MR Pleiotropy RESidual Sum and Outlier test (MR-PRESSO) was used to detect horizontal pleiotropy. When the causal relationship was significant, bidirectional MR analysis was performed to determine any reverse causal relationships between exposures and outcomes. RESULTS: This MR study illustrated that autoimmune hyperthyroidism slightly increased the risk of DVT according to the IVW [odds ratio (OR) = 1.0009; p = 0.024] and weighted median methods [OR = 1.001; p = 0.028]. According to Cochran's Q test, there was no evidence of heterogeneity in IVs. Additionally, MR-PRESSO did not detect horizontal pleiotropy (p = 0.972). However, no association was observed between other thyroid diseases and DVT using the IVW, weighted median, and MR-Egger regression methods. CONCLUSIONS: This study revealed that autoimmune hyperthyroidism may cause DVT; however, more evidence and larger sample sizes are required to draw more precise conclusions.

Investigating the causal relationship between thyroid dysfunction diseases and osteoporosis: a two-sample Mendelian randomization analysis.

The prevalence of thyroid dysfunction diseases (TDFDs) and osteoporosis (OP) is high. Previous studies have indicated a potential association between TDFDs and OP, yet the causal direction remains unclear. This study aimed to investigate the potential causal relationship between TDFDs and the risk of developing OP and related fractures. We obtained pooled data from genome-wide association studies (GWASs) conducted on TDFDs and OP in European populations and identified single-nucleotide polymorphisms (SNPs) with genome-wide significance levels associated with exposure to TDFDs as instrumental variables. Inverse variance weighted (IVW) was employed as the primary method for Mendelian randomization (MR) analysis, supplemented by MR‒Egger, weighted median, simple mode and weighted mode methods. Sensitivity analyses were conducted to evaluate the robustness of the findings. The IVW method demonstrated an increased risk of OP in patients with TDFDs, including hyperthyroidism and hypothyroidism (TDFDs: OR = 1.11; 95% CI 1.09, 1.13; hypothyroidism: OR = 1.14; 95% CI 1.10, 1.17; hyperthyroidism: OR = 1.09; 95% CI 1.06, 1.12). These findings were supported by supplementary analysis, which revealed a positive correlation between TDFDs and the risk of OP. Multiple sensitivity analyses confirmed the absence of horizontal pleiotropy in the study, thus indicating the robustness of our results. The causal relationship between TDFDs and increased risk of OP implies the need for early bone mineral density (BMD) screening and proactive prevention and treatment strategies for individuals with TDFDs.

Vitamin D and thyroid function: A mendelian randomization study.

BACKGROUND: Numerous organs, including the thyroid gland, depend on vitamin D to function normally. Insufficient levels of serum 25-hydroxyvitamin D [25(OH)D] are seen as a potential factor contributing to the emergence of several thyroid disorders, however, the causal relationship remains unclear. Here we use a Mendelian randomization (MR) approach to investigate the causal effect of serum 25(OH)D concentration on the indicators of thyroid function. METHODS: We conducted a two-sample MR analysis utilizing summary data from the most extensive genome-wide association studies (GWAS) of serum 25(OH)D concentration (n = 443,734 and 417,580), thyroid-stimulating hormone (TSH, n = 271,040), free thyroxine (fT4, n = 119,120), free triiodothyronine (fT3, n = 59,061), total triiodothyronine (TT3, n = 15,829), as well as thyroid peroxidase antibody levels and positivity (TPOAb, n = 12,353 and n = 18,297), low TSH (n = 153,241), high TSH (n = 141,549), autoimmune hypothyroidism (n = 287,247) and autoimmune hyperthyroidism (n = 257,552). The primary analysis was conducted using the multiplicative random-effects inverse variance weighted (IVW) method. The weighted mode, weighted median, MR-Egger, MR-PRESSO, and Causal Analysis Using Summary Effect estimates (CAUSE) were used in the sensitivity analysis. RESULTS: The IVW, as well as MR Egger and CAUSE analysis, showed a suggestive causal effect of 25(OH)D concentration on high TSH. Each 1 SD increase in serum 25(OH)D concentration was associated with a 12% decrease in the risk of high TSH (p = 0.02). Additionally, in the MR Egger and CAUSE analysis, we found a suggestive causal effect of 25(OH)D concentration on autoimmune hypothyroidism. Specifically, each 1 SD increase in serum 25(OH)D concentration was associated with a 16.34% decrease in the risk of autoimmune hypothyroidism (p = 0.02). CONCLUSIONS: Our results support a suggestive causal effect which was negative in direction across all methods used, meaning that higher genetically predicted vitamin D concentration possibly lowers the odds of having high TSH or autoimmune hypothyroidism. Other thyroid parameters were not causally influenced by vitamin D serum concentration.

The causal relationship between major depression disorder and thyroid diseases: A Mendelian randomization study and mediation analysis.

BACKGROUND: Studies have been conducted on the relationship between depression and thyroid diseases and function, its causal relationship remains unclear. METHODS: Using summary statistics of genome-wide association studies of European and East Asian ancestry, we conducted 2-sample bidirectional Mendelian randomization to estimate the association between MDD and thyroid function (European: normal range TSH, T4, T3, fT4, TPOAb levels and TPOAb-positives; East Asian: T4) and thyroid diseases (hypothyroidism, hyperthyroidism, and Hashimoto's thyroiditis), and used Mediation analysis to evaluate potential mediators (alcohol intake, antidepressant) of the association and calculate the mediated proportions. RESULTS: It was observed a significant causal association between MDD on hypothyroidism (P = 8.94 × 10-5), hyperthyroidism (P = 8.68 × 10-3), and hashimoto's thyroiditis (P = 3.97 × 10-5) among European ancestry, which was mediated by Alcohol intake (alcohol intake versus 10 years previously for hypothyroidism (P = 0.026), hashimoto's thyroiditis (P = 0.042), and alcohol intake frequency for hypothyroidism (P = 0.015)) and antidepressant (for hypothyroidism (P = 0.008), hashimoto's thyroiditis (P = 0.010)), but not among East Asian ancestry (PMDD-hypothyroidism = 0.016, but ß direction was different; PMDD-hyperthyroidism = 0.438; PMDD-hashimoto's thyroiditis = 0.496). There was no evidence for bidirectional causal association between thyroid function mentioned above and MDD among both ancestry (all P > 0.05). CONCLUSION: We importantly observed a significant causal association between MDD on risk of hypothyroidism, hyperthyroidism, and hashimoto's thyroiditis among European ancestry, and Alcohol intake and antidepressant as mediators for prevention of hypothyroidism, hashimoto's thyroiditis attributable to MDD.

Hyperthyroidism-driven bone loss depends on BMP receptor Bmpr1a expression in osteoblasts.

Hyperthyroidism is a well-known trigger of high bone turnover that can lead to the development of secondary osteoporosis. Previously, we have shown that blocking bone morphogenetic protein (BMP) signaling systemically with BMPR1A-Fc can prevent bone loss in hyperthyroid mice. To distinguish between bone cell type-specific effects, conditional knockout mice lacking Bmpr1a in either osteoclast precursors (LysM-Cre) or osteoprogenitors (Osx-Cre) were rendered hyperthyroid and their bone microarchitecture, strength and turnover were analyzed. While hyperthyroidism in osteoclast precursor-specific Bmpr1a knockout mice accelerated bone resorption leading to bone loss just as in wildtype mice, osteoprogenitor-specific Bmpr1a deletion prevented an increase of bone resorption and thus osteoporosis with hyperthyroidism. In vitro, wildtype but not Bmpr1a-deficient osteoblasts responded to thyroid hormone (TH) treatment with increased differentiation and activity. Furthermore, we found an elevated Rankl/Opg ratio with TH excess in osteoblasts and bone tissue from wildtype mice, but not in Bmpr1a knockouts. In line, expression of osteoclast marker genes increased when osteoclasts were treated with supernatants from TH-stimulated wildtype osteoblasts, in contrast to Bmpr1a-deficient cells. In conclusion, we identified the osteoblastic BMP receptor BMPR1A as a main driver of osteoporosis in hyperthyroid mice promoting TH-induced osteoblast activity and potentially its coupling to high osteoclastic resorption.

Causal relationship between thyroid dysfunction and gastric cancer: a two-sample Mendelian randomization study.

Backgroud: Gastric cancer is one of the most common cancers worldwide, and its development is associated with a variety of factors. Previous observational studies have reported that thyroid dysfunction is associated with the development of gastric cancer. However, the exact relationship between the two is currently unclear. We used a two-sample Mendelian randomization (MR) study to reveal the causal relationship between thyroid dysfunction and gastric cancer for future clinical work. Materials and methods: This study is based on a two-sample Mendelian randomization design, and all data are from public GWAS databases. We selected hyperthyroidism, hypothyroidism, free thyroxine (FT4), and thyroid-stimulating hormone (TSH) as exposures, with gastric cancer as the outcome. We used three statistical methods, namely Inverse-variance weighted (IVW), MR-Egger, and weighted median, to assess the causal relationship between thyroid dysfunction and gastric cancer. The Cochran's Q test was used to assess the heterogeneity among SNPs in the IVW analysis results, and MR-PRESSO was employed to identify and remove IVs with heterogeneity from the analysis results. MR-Egger is a weighted linear regression model, and the magnitude of its intercept can be used to assess the horizontal pleiotropy among IVs. Finally, the data were visualized through the leave-one-out sensitivity test to evaluate the influence of individual SNPs on the overall causal effect. Funnel plots were used to assess the symmetry of the selected SNPs, forest plots were used to evaluate the confidence and heterogeneity of the incidental estimates, and scatter plots were used to assess the exposure-outcome relationship. All results were expressed as odds ratios (OR) and 95% confidence intervals (95% CI). P<0.05 represents statistical significance. Results: According to IVW analysis, there was a causal relationship between hypothyroidism and gastric cancer, and hypothyroidism could reduce the risk of gastric cancer (OR=0.936 (95% CI:0.893-0.980), P=0.006).This means that having hypothyroidism is a protective factor against stomach cancer. This finding suggests that hypothyroidism may be associated with a reduced risk of gastric cancer.Meanwhile, there was no causal relationship between hyperthyroidism, FT4, and TSH and gastric cancer. Conclusions: In this study, we found a causal relationship between hypothyroidism and gastric cancer with the help of a two-sample Mendelian randomisation study, and hypothyroidism may be associated with a reduced risk of gastric cancer, however, the exact mechanism is still unclear. This finding provides a new idea for the study of the etiology and pathogenesis of gastric cancer, and our results need to be further confirmed by more basic experiments in the future.

The association between three prevalent autoimmune disorders and the likelihood of developing prostate cancer: a Mendelian randomization study.

Numerous studies establish a significant correlation between autoimmune disorders (AIDs) and prostate cancer (PCa). Our Mendelian randomization (MR) analysis investigates the potential connection between rheumatoid arthritis (RA) and PCa, aiming to confirm causal links between systemic lupus erythematosus (SLE), hyperthyroidism, and PCa. Summary statistics from genome-wide association studies provided data on PCa and three AIDs. MR analysis, using IVW as the main approach, assessed causal relationships, validated by sensitivity analysis. IVW revealed a correlation between genetically anticipated RA and PCa, notably in Europeans (OR = 1.03; 95% CI 1.01-1.04, p = 2*10-5). Evidence supported a lower PCa risk in individuals with SLE (OR = 0.94; 95% CI 0.91-0.97, p = 2*10-4) and hyperthyroidism (OR = 0.02; 95% CI 0.001-0.2, p = 2*10-3). Weighted mode and median confirmed these findings. No pleiotropic effects were observed, and MR heterogeneity tests indicated dataset homogeneity. Our study establishes a causal link between RA, SLE, hyperthyroidism, and PCa.

Causal relationship between thyroid dysfunction and ovarian cancer: a two-sample Mendelian randomization study.

PURPOSE: Observational studies and clinical validation have suggested a link between thyroid dysfunction and an elevated ovarian cancer (OC) risk. However, whether this association indicates a cause-and-effect relationship remains uncertain. We aimed to investigate the plausible causal impact of thyroid dysfunction on OC through a Mendelian randomization (MR) study. METHODS: Genome-wide association study (GWAS) data for thyrotropin (TSH), free thyroxine (FT4), hypothyroidism, and hyperthyroidism were obtained as exposures and those for OC (N = 199,741) were selected as outcomes. Inverse variance-weighted method was used as the main estimation method. A series of sensitivity analyses, including Cochran's Q test, MR-Egger intercept analysis, forest plot scatter plot, and leave-one-out test, was conducted to assess the robustness of the estimates. RESULTS: Genetic prediction of hyperthyroidism was associated with a potential increase in OC risk (odds ratio = 1.094, 95% confidence interval: 1.029-1.164, p = 0.004). However, no evidence of causal effects of hypothyroidism, TSH, and FT4 on OC or reverse causality was detected. Sensitivity analyses demonstrated consistent and reliable results, with no significant estimates of heterogeneity or pleiotropy. CONCLUSIONS: This study employed MR to establish a correlation between hyperthyroidism and OC risk. By genetically predicting OC risk in patients with hyperthyroidism, our research suggests new insights for early prevention and intervention of OC.

A Novel TSHR Gene Mutation in a Family with Non-autoimmune Hyperthyroidism.

Background: Familial non-autoimmune hyperthyroidism is a rare disorder characterized by the absence of thyroid autoimmunity, particularly TSH receptor antibody [TRAb]. Objective: The aim of this study was to describe a novel TSHR mutation identified in a family of two siblings and their father. Methods: Two siblings presented for endocrine assessment at ages 7 and 14 years with mild T3 toxicosis, and the father presented at 30 years of age with non-autoimmune thyrotoxicosis. Both siblings were treated with oral antithyroid therapy to achieve reasonable symptom control and thyroid function normalization. The father was treated with oral antithyroid therapy, radioactive iodine, thyroidectomy, and thyroid replacement therapy. Peripheral blood DNA was extracted from both affected siblings and father. Mutation analysis of TSHR was carried out by PCR and Sanger sequencing of both strands of the extracted DNA. Results: Both siblings and their father were heterozygous for the missense TSHR variant c.1855G>C, p.[Asp619His], in exon 10. Conclusions: This novel TSHR variant is associated with T3 toxicosis during childhood. Therefore, early identification and treatment may improve patient outcomes.

The genetic association between hyperthyroidism and heart failure: a Mendelian randomization study.

Background and aims: Hyperthyroidism is an endocrine disease with multiple etiologies and manifestations. Heart failure (HF) is a common, costly, and deadly medical condition in clinical practice. Numerous studies have suggested that abnormal thyroid function can induce or aggravate the development of heart disease. However, no study has demonstrated a causal relationship between hyperthyroidism and heart failure. Therefore, the purpose of this study was to explore the causal link between hyperthyroidism and HF. Methods: Summary data for genetically predicted hyperthyroidism were obtained from a genetic association study. The data examined for genetically determined all-cause heart failure came from 218,208 individuals from the FinnGen Consortium. Two-sample Mendelian randomization (MR) analysis was used to estimate the causal link between hyperthyroidism and heart failure. Statistical analyses were conducted using the inverse variance-weighted, weighted median, simple median, weighted mode, MR-PRESSO (number of distribution = 5000), MR-Egger, and leave-one-out. Results: The results of the inverse-variance weighted analysis indicated a causal association between hyperthyroidism and an increased risk of all-cause heart failure (IVW: ß=0.048, OR=1.049, 95%CI: [1.013 to 1.087], P=0.007). Similarly, the weighted median approach demonstrated a positive correlation between hyperthyroidism and all-cause heart failure (OR=1.049, [95% CI, 1.001-1.100]; P=0.044). Additionally, no horizontal pleiotropy or heterogeneity was observed. The leave-one-out analysis revealed that the majority of the SNP-driven associations were not influenced by a single genetic marker. Conclusion: Our study observed a causal relationship between hyperthyroidism and all-cause heart failure. Hyperthyroidism may associate with heart failure genetically.

Thyroid function and polycystic ovary syndrome: a Mendelian randomization study.

Background: Multiple evidence suggests that thyroid function is associated with polycystic ovary syndrome (PCOS), but whether thyroid function is causally related to PCOS is unclear. To investigate whether the association reflect causality, a Mendelian randomization (MR) analysis was conducted. Methods: Single nucleotide polymorphisms (SNPs) involved in this study were acquired from The ThyroidOmics Consortium and the IEU Open Genome-wide association study (GWAS) database, respectively. In forward MR analysis, we included normal free thyroxine (FT4, n=49,269), normal thyroid-stimulating hormone (TSH, n=54,288), hypothyroidism (n=53,423) and hyperthyroidism (n=51,823) as exposure. The outcome was defined as PCOS in a sample size of 16,380,318 individuals. The exposure in the reverse MR analyses was chosen as PCOS, while the outcome consisted of the four phenotypes of thyroid function. The inverse-variance weighted (IVW) method was performed as the major analysis, supplemented by sensitivity analyses. Results: The occurrence of PCOS was associated with increased risk of hyperthyroidism (IVW, OR=1.08, 95%CI=1.02-1.13, P=0.004). No evidence suggested that other phenotypes of thyroid function were related to PCOS. Conclusions: Our findings demonstrate a cause-and-effect connection between PCOS and hyperthyroidism. The study established foundation for further investigation for interaction between thyroid function and PCOS.

Protective effect of higher free thyroxine levels within the reference range on biliary tract cancer risk: a multivariable mendelian randomization and mediation analysis.

Background: Hepatobiliary cancer (HBC), including hepatocellular carcinoma (HCC) and biliary tract cancer (BTC), is currently one of the malignant tumors that mainly cause human death. Many HBCs are diagnosed in the late stage, which increases the disease burden, indicating that effective prevention strategies and identification of risk factors are urgent. Many studies have reported the role of thyroid hormones on HBC. Our research aims to assess the causal effects and investigate the mediation effects between thyroid function and HBC. Methods: Utilizing the Mendelian randomization (MR) approach, the study employs single nucleotide polymorphisms (SNPs) as instrumental variables (IVs) to explore causal links between thyroid function [free thyroxine (FT4), thyroid stimulating hormone (TSH), hyperthyroidism and hypothyroidism] and HBC. Data were sourced from the ThyroidOmic consortium and FinnGen consortium. The analysis included univariable and multivariable MR analysis, followed by mediation analysis. Results: The study found a significant causal association between high FT4 levels and the reduced risk of BTC, but not HCC. However, TSH, hyperthyroidism and hypothyroidism had no causal associations with the risk of HBC. Notably, we also demonstrated that only higher FT4 levels with the reference range (FT4-RR) could reduce the risk of BTC because this protective effect no longer existed under the conditions of hyperthyroidism or hypothyroidism. Finally, we found that the protective effect of FT4-RR on BTC was mediated partially by decreasing the risk of metabolic syndrome (MetS) and reducing the waist circumference (WC). Conclusion: The findings suggest that higher FT4-RR may have a protective effect against BTC, which is partially mediated by decreased risk of MetS and a reduction in WC. This study highlights the potential role of FT4 in the pathogenesis of BTC and underscores that MetS and WC may play mediation effects as two mediators in this process.

CXCL9 mediating the effect of thyroid disorders on oral and oropharyngeal cancer risk: A mediation Mendelian randomization study.

INTRODUCTION: The established association between thyroid disorders (TD) and its two main subtypes-hyperthyroidism and hypothyroidism-and the incidence of oral and oropharyngeal cancer (OCPC) has been substantiated. However, the direct causal relationship and potential intermediary mechanisms linking these conditions have not been clearly defined in prior studies. MATERIAL & METHODS: This study employed univariate Mendelian randomization (MR) analysis to explore those relationship. Instrumental variables from genome-wide association study (GWAS) datasets for TD (n = 218,792), hyperthyroidism (n = 460,499), hypothyroidism (n = 213,990), and OCPC (n = 12,619), along with 41 intermediary inflammatory cytokines (n = 8293), were analyzed. Inverse variance weighting (IVW) method assessed the causal relationships, while summary MR analysis with pQTL datasets from decode and 91 inflammatory cytokines explored the cytokines' roles as biomarkers and therapeutic targets for OCPC. Multivariable MR (MVMR) analysis quantified the mediation effect of these cytokines in the TD-OCPC relationship. RESULTS: UVMR analysis provided strong evidence for a causal relationship between TD (OR = 1.376, 95 % CI = 1.142-1.656, p = 0.001), hyperthyroidism (OR = 1.319, 95 % CI=1.129-1.541, p = 0.001), hypothyroidism (OR = 1.224, 95 % CI = 1.071-1.400, p = 0.003), and the risk of OCPC. CXCL9 was identified as a significant intermediary in mediating the risk of OCPC from TD and its two subtypes (OR = 1.218, 95 % CI = 1.016-1.461, P = 0.033), suggesting its potential as a predictive biomarker for OCPC. MVMR analysis further revealed that CXCL9 mediated 7.94 %, 14.4 %, and 18 % of the effects of TD, hyperthyroidism, and hypothyroidism on OCPC risk, respectively. DISCUSSION: This study not only elucidated the potential causal relationships between TD including its two subtypes and OCPC risk, but also highlighted CXCL9 as a pivotal mediator in this association.

Hypothyroidism is a causal determinant of age-related cataract risk in European population: a Mendelian randomization study.

Objective: To determine whether there is a causal relationship between thyroid dysfunction and the risk of age-related cataract (ARC) in the European population. Design: A two-sample Mendelian randomization (MR) study. Methods: Hypothyroidism, hyperthyroidism, free thyroxine (fT4), and thyrotropin (TSH) were selected as exposures. The single nucleotide polymorphisms (SNP) of hypothyroidism and hyperthyroidism were obtained from the genome-wide association studies (GWAS) of the IEU database, including 337,159 subjects. Data for fT4 and TSH (72,167 subjects) were extracted from the ThyroidOmics Consortium. ARC was used as the outcome. The SNPs associated with ARC were selected from a GWAS of 216,362 individuals in the FinnGen database. The main method used was the inverse variance-weighted method, together with four complementary methods. Sensitivity analyses were performed using Cochran's Q test, MR-PRESSO, MR-Egger regression and leave-one-out test. MR pleiotropy was used to test for pleiotropy. MR Steiger test was used to test for the directionality. Results: Two-sample MR analysis revealed a positive association between genetically predicted hypothyroidism and risk of ARC (OR = 2.501, 95% CI: 1.325-4.720; P = 0.004). Hyperthyroidism, circulating fT4 and TSH levels did not have a significant causal effect on ARC (P > 0.05). The results were robust and reliable, and no horizontal pleiotropy was found after sensitivity analyses. In the MR Steiger test, we found no reverse causal effects of hypothyroidism on the ARC (P <0.001). Conclusions: Our study provides strong evidence that hypothyroidism is a causal determinant of ARC risk.

Causal relationship between hypothyroidism and temporomandibular disorders: evidence from complementary genetic methods.

BACKGROUND: The role of thyroid health in temporomandibular disorders (TMDs) has been emphasized in observational studies. However, whether the causation exists is unclear, and controversy remains about which specific disorder, such as hypothyroidism or hyperthyroidism, is destructive in TMDs. This study aims to investigate the overall and specific causal effects of various thyroid conditions on TMDs. METHODS: Mendelian randomization (MR) studies were performed using genetic instruments for thyrotropin (TSH, N = 119,715), free thyroxine (fT4, N = 49,269), hypothyroidism (N = 410,141), hyperthyroidism (N = 460,499), and TMDs (N = 211,023). We assessed the overall effect of each thyroid factor via inverse-variance weighted (IVW), weighted median, and MR-Egger methods, and performed extensive sensitivity analyses. Additionally, multivariable MR was conducted to evaluate the direct or indirect effects of hypothyroidism on TMDs whilst accounting for TSH, fT4 and hyperthyroidism, and vice versa. RESULTS: Univariable MR analyses revealed a causal effect of hypothyroidism on an increased risk of TMDs (IVW OR: 1.12, 95% CI: 1.05-1.20, p = 0.001). No significant association between genetically predicted hyperthyroidism, TSH, or fT4 and TMDs. In the multivariable MR analyses, the effects of hypothyroidism on TMDs occurrence remained significant even after adjSusting for TSH, fT4 and hyperthyroidism (multivariable IVW OR: 1.10, 95% CI: 1.03-1.17, p = 0.006). No pleiotropy and heterogeneity were detected in the analyses (p > 0.05). CONCLUSIONS: Hypothyroidism might causally increase the risk of TMDs through a direct pathway, highlighting the critical role of managing thyroid health in the prevention of TMDs. Clinicians should give heightened attention to patients with hypothyroidism when seeking medical advice for temporomandibular discomfort. However, caution is warranted due to the potential confounders, pleiotropy, and selection bias in the MR study.

Can inactivation mutation in the thyroid stimulating hormone receptor gene and hyperthyroidism coexist?: A case report.

INTRODUCTION: We found the G132R heterozygous mutation of thyroid stimulating hormone receptor (TSHR) gene in a patient with recurrent hypokalemia. Because the patient had a medical history of hyperthyroidism, the mutation was suspected to be related to hyperthyroidism at first. Subsequently, the expression and function studies in vitro were conducted. METHODS: Wide-type TSHR and mutant TSHR (mutTSHR) were constructed in the phage vector and pEGFP-C1 vector. After transfection, the samples were collected for detection of mRNA level, protein expression, cell activity and cAMP content. RESULTS: Compared with the wild-type TSHR, the mRNA level of the mutTSHR was not significantly different. But the protein expression, cell activity and cAMP content of the mutTSHR were significantly lower. So this indicated that the G132R mutation is a loss-of-function mutation. CONCLUSION: We identified the G132R monoallelic heterozygous mutation of TSHR gene in a patient with hyperthyroidism. Based on disease history of the patient, we speculated that the heterozygous mutation did not cause thyroid dysplasia or hypothyroidism for her. Our study enriched experiment content in vitro studies and clinical phenotype about the G132R mutation in TSHR gene.

Periodontitis and thyroid function: A bidirectional Mendelian randomization study.

BACKGROUND AND OBJECTIVE: Previous studies suggest interaction between periodontitis and thyroid function, while the causality has not yet been established. We applied the Mendelian randomization (MR) method to assess bidirectional causal association between periodontitis and thyroid-related traits, including free thyroxine (FT4), thyroid stimulating hormone (TSH), hypothyroidism, hyperthyroidism and autoimmune thyroid disease (AITD). METHODS: Genetic instruments were extracted from large-scale genome-wide association studies on normal-range FT4 (N = 49 269) and TSH (N = 54 288) levels, TSH in full range (N = 119 715); hypothyroidism (discovery/replication cohorts: N = 53 423/334 316), hyperthyroidism (discovery/replication cohorts: N = 51 823/257 552), AITD (N = 755 406) and periodontitis (N = 45 563). Here, the inverse variance weighted (IVW) method was applied as the primary analysis, and robustness of results were assessed by several pleiotropic-robust methods. Results were adjusted for Bonferroni correction thresholds with significant p < .004 (0.05/13) and suggestive p between .004 and .05. RESULTS: The IVW analysis revealed a suggestively causal linkage between genetic predisposition to periodontitis and the increased risk of hypothyroidism (discovery cohort: odds ratio [OR] = 1.24, 95% confidence interval [CI] = 1.05-1.46, p = .012; replication cohort: OR = 1.06, 95% CI = 1.01-1.11, p = .011). No evidence was found for supporting the impact of periodontitis on hyperthyroidism and AITD risks (associated p ≥ .209), as well as thyroid-related traits on periodontitis risk (associated p ≥ .105). These findings were robust and consistent through sensitivity analysis with other MR models. CONCLUSION: This bidirectional MR reveals periodontitis should not be attributed to variations in thyroid function but it has potential causal effect on hypothyroidism risk, which provides a better understanding of the relationship between periodontitis and thyroid function, and potential evidence for the clinical intervention of hypothyroidism. Further investigations are warranted to elucidate the nature and underlying mechanisms of this finding.

Diagnosis of Resistance to Thyroid Hormone due to a Rare Mutation in the Thyroid Hormone Receptor Beta Gene in a Patient Previously Presumed to Have Graves' Disease.

Clinicians may confuse an impaired sensitivity to thyroid hormone with hyperthyroidism and offer an inappropriate treatment. We report a diagnosis of resistance to thyroid hormone (RTH) caused by a rare mutation in the thyroid hormone receptor beta gene in a patient previously presumed to have Graves' disease. We have found only one published case of a novel point mutation, c.749T>C (p.Ile250Thr variant) associated with 50% reduction in thyroid hormone receptor binding affinity for triiodothyronine in the I250T mutant; it was found in this patient. A 66-year-old male veteran, with a history of non-ischemic cardiomyopathy and arrhythmias, was referred by a cardiologist with concerns for a possible thyrotropin (TSH) adenoma on account of elevated TSH and free thyroxine (FT4) levels. Pituitary imaging was negative. He was previously treated with radioiodine for presumptive Graves' disease in the civilian sector. Examination revealed a goiter with no nodules. Repeat TSH and FT4 levels were elevated and also free triiodothyronine (FT3) and reverse triiodothyronine. These findings and other test results were consistent with RTH, which was confirmed by genetic testing. Mutation analysis showed the patient to be heterozygous for the p.Ile250Thr variant. He later developed hypothyroidism. Resistance to thyroid hormone can be misdiagnosed as hyperthyroidism with consequent inappropriate treatment. Treatment is not needed in most RTH-beta patients. Thyroid ablation should generally be avoided. Clinicians must be cautious whenever they encounter concurrent elevation of TSH, FT4, and FT3. This RTH-beta patient has a rare I250T mutant of the thyroid hormone receptor beta gene, the second reported case in the literature.

No causal relationship between thyroid function and Parkinson's disease: A bidirectional Mendelian randomization study.

BACKGROUND: Parkinson's disease (PD) is the second most prevalent degenerative disease globally. While observational studies have demonstrated a correlation between thyroid function and PD, the causal relationship between these two factors remains uncertain. METHODS: A bidirectional Mendelian randomization (MR) analysis was performed to explore the causal relationship between thyroid function (free thyroxine [FT4], thyroid-stimulating hormone [TSH], hyperthyroidism, and hypothyroidism) and PD. GWAS summary-level statistics of thyroid function and PD were obtained from publicly available GWAS databases. The inverse variance weighted method was the main MR approach to assess causal associations. In addition, two additional MR methods (MR-Egger regression and weighted median) were performed to supplement the IVW. Furthermore, various sensitivity tests were performed to verify the reliability of the MR findings: (i) Heterogeneity was examined by Cochrane's Q test. (ii) Horizontal pleiotropy was assessed by the MR-Egger intercept test and MR-PRESSO global test. (iii) The robustness of MR results was estimated using the leave-one-out method. RESULTS: Various MR results showed that FT4, TSH, hyperthyroidism, and hypothyroidism did not causally affect PD (P > 0.05). Likewise, PD did not causally affect FT4, TSH, hyperthyroidism, and hypothyroidism (P > 0.05). Cochrane's Q test indicated that MR analysis was not affected by significant heterogeneity (P > 0.05). MR-Egger intercept test and MR-PRESSO global test indicated that MR analysis was not affected by a remarkable horizontal pleiotropy (P > 0.05). The leave-one-out method demonstrated the stability of MR results. CONCLUSION: MR analysis did not support a causal relationship between thyroid function and PD.

Causal relationship between rheumatoid arthritis and hypothyroidism or hyperthyroidism: a bidirectional two-sample univariable and multivariable Mendelian randomization study.

Objective: The causal relationship between Rheumatoid arthritis (RA) and hypothyroidism/hyperthyroidism remains controversial due to the limitations of conventional observational research, such as confounding variables and reverse causality. We aimed to examine the potential causal relationship between RA and hypothyroidism/hyperthyroidism using Mendelian randomization (MR). Method: We conducted a bidirectional two-sample univariable analysis to investigate the potential causal relationship between hypothyroidism/hyperthyroidism and RA. Furthermore, we performed a multivariate analysis to account for the impact of body mass index (BMI), smoking quantity, and alcohol intake frequency. Results: The univariable analysis indicated that RA has a causative influence on hypothyroidism (odds ratio [OR]=1.07, 95% confidence interval [CI]=1.01-1.14, P=0.02) and hyperthyroidism (OR=1.32, 95% CI=1.15-1.52, P<0.001). When hypothyroidism/hyperthyroidism was considered as an exposure variable, we only observed a causal relationship between hypothyroidism (OR=1.21, 95% CI=1.05-1.40, P=0.01) and RA, whereas no such connection was found between hyperthyroidism (OR=0.91, 95% CI=0.83-1.01, P=0.07) and RA. In the multivariate MR analyses, after separately and jointly adjusting for the effects of daily smoking quantity, alcohol intake frequency, and BMI, the causal impact of RA on hypothyroidism/hyperthyroidism and hypothyroidism on RA remained robust. However, there is no evidence to suggest a causal effect of hyperthyroidism on the risk of RA (P >0.05). Conclusion: Univariate and multivariate MR analyses have validated the causal association between RA and hypothyroidism/hyperthyroidism. Hypothyroidism confirmed a causal relationship with RA when employed as an exposure variable, whereas no such relationship was found between hyperthyroidism and RA.