Thyroid Function and the Risk of Atherosclerotic Cardiovascular Morbidity and Mortality: The Rotterdam Study

Metabolic Syndrome, Thyroid Dysfunction, and Cardiovascular Risk: The Triptych of Evil

The triad formed by thyroid dysfunction, metabolic syndrome (MetS), and cardiovascular (CV) risk forms a network with many connections that aggravates health outcomes. Thyroid hormones (THs) play an important role in glucose and lipid metabolism and hemodynamic regulation at the molecular level. It is noteworthy that a bidirectional association between THs and MetS and their components likely exists as MetS leads to thyroid dysfunction, whereas thyroid alterations may cause a higher incidence of MetS. Thyroid dysfunction increases insulin resistance, the circulating levels of lipids, in particular LDL-C, VLDL-C, and triglycerides, and induces endothelial dysfunction. Furthermore, THs are important regulators of both white and brown adipose tissue. Moreover, the pathophysiological relationship between MetS and TH dysfunction is made even tighter considering that these conditions are usually associated with inflammatory activation and increased oxidative stress. Therefore, the role of THs takes place starting from the molecular level, then manifesting itself at the clinical level, through an increased risk of CV events in the general population as well as in patients with heart failure or acute myocardial infarction. Thus, MetS is frequently associated with thyroid dysfunction, which supports the need to assess thyroid function in this group, and when clinically indicated, to correct it to maintain euthyroidism. However, there are still several critical points to be further investigated both at the molecular and clinical level, in particular considering the need to treat subclinical dysthyroidism in MetS patients.

The association of aromatic amino acids with coronary artery disease and major adverse cardiovascular events in a Chinese population

This study aimed to evaluate the relationship between aromatic amino acids (AAAs), - phenylalanine (Phe), tyrosine (Tyr) and tryptophan (Trp) - and coronary artery disease (CAD) in a prospective study involving 2970 participants undergoing coronary angiography at Beijing Hospital. Serum levels of Phe, Tyr and Trp were analysed. The cross-sectional data revealed that serum Tyr and Trp levels were significantly and inversely associated with CAD. During a median follow-up period of 44 months, 343 major adverse cardiovascular events (MACEs) and 138 all-cause deaths were recorded. MACE included myocardial infarction, stroke, revascularisation and all-cause mortality. Low serum Trp levels predicted an increased risk of MACE and death. High serum Phe levels were linked to an increased risk of MACE, while low Tyr levels were associated with a higher risk of death. Collectively, our findings underscore a close correlation between AAAs and CAD, as well as their potential predictive value for adverse cardiovascular outcomes.

Prognostic implications of thyroid hormones in acute aortic dissection: mediating roles of renal function and coagulation

Background

Thyroid hormones significantly influence cardiovascular pathophysiology, yet their prognostic role in acute aortic dissection (AAD) remains inadequately explored. This study assesses the prognostic value of thyroid hormone levels in AAD, focusing on the mediating roles of renal function and coagulation.

Methods

We included 964 AAD patients in this retrospective cohort study. Utilizing logistic regression, restricted cubic splines, and causal mediation analysis, we investigated the association between thyroid hormones and in-hospital mortality and major adverse cardiovascular events (MACEs).

Results

In AAD patients overall, an increase of one standard deviation in FT4 levels was associated with a 31.9% increased risk of MACEs (OR 1.319; 95% CI 1.098-1.584) and a 36.1% increase in in-hospital mortality (OR 1.361; 95% CI 1.095-1.690). Conversely, a higher FT3/FT4 ratio was correlated with a 20.2% reduction in risk of MACEs (OR 0.798; 95% CI 0.637-0.999). This correlation was statistically significant predominantly in Type A AAD, while it did not hold statistical significance in Type B AAD. Key renal and coagulation biomarkers, including blood urea nitrogen, creatinine, cystatin C, prothrombin time ratio, prothrombin time, and prothrombin time international normalized ratio, were identified as significant mediators in the interplay between thyroid hormones and MACEs. The FT3/FT4 ratio exerted its prognostic influence primarily through the mediation of renal functions and coagulation, while FT4 levels predominantly impacted outcomes via a partial mediation effect on coagulation.

Conclusion

FT4 levels and the FT3/FT4 ratio are crucial prognostic biomarkers in AAD patients. Renal function and coagulation mediate the association between the thyroid hormones and MACEs.

Potential Risks and Benefits of Desiccated Thyroid Extract for the Treatment of Hypothyroidism: A Systematic Review

Background: Desiccated thyroid extract (DTE) is no longer recommended for the treatment of hypothyroidism but is still in use. This review aimed to summarize the available literature on treatment with DTE in adult patients with hypothyroidism. Methods: The search was conducted up until January 6, 2024, in six electronic databases. Two reviewers independently screened all the search results. The retrieved studies compared DTE treatment with levothyroxine or combination therapy with liothyronine and levothyroxine. The primary outcome was quality of life (QoL), and the secondary outcomes included symptoms, treatment preference, adverse effects, thyroid hormone levels, thyroid autoantibodies, cardiovascular measures, and gene polymorphisms in deiodinase enzymes. Results: In the qualitative synthesis, we included nine nonrandomized studies of interventions (NRSIs), two randomized clinical trials (RCTs), and three case reports. The overall quality of evidence was moderate to very low for the various outcomes. The RCTs found no difference between treatments regarding QoL and symptom score assessments. In the NRSIs, symptom and QoL assessments were in favor of DTE. The included studies indicated that DTE may cause an increase in heart rate, lower body weight, and lower high-density lipoprotein compared with other treatment regimens, but results were conflicting. Conclusions: Most studies of DTE treatment are hampered by an inferior design, and data on long-term effects and side effects are lacking. Two RCTs could not demonstrate any difference in QoL or symptom scores when comparing DTE with other thyroid hormone substitutions. Future trials of DTE in patients with hypothyroidism should be based on adequate study designs, validated measures of QoL, patients with reduced QoL, and the assessment of biomarkers reflecting long-term adverse effects.

Reduced sensitivity to thyroid hormones is associated with lung function in euthyroid individuals

Background

The thyroid gland exhibits a subtle interconnection with the lungs. We further investigated the correlation between thyroid hormone sensitivity and lung function in euthyroid individuals.

Methods

Data on spirometry and mortality for participants aged 19-79 years were extracted from the NHANES database. Obstructive lung function was defined as a forced expiratory volume in 1 s to forced vital capacity ratio (FEV1/FVC) < 0.70, while restrictive lung function was considered when FEV1/FVC ≥0.70 and baseline FVC <80 % predicted. Central and peripheral sensitivities to thyroid hormones were mainly evaluated by Thyroid Feedback Quantile-based Index (TFQI) and Free Triiodothyronine/Free thyroxine (FT3/FT4) ratio. Logistic regression and subgroup analysis were used to examine potential associations between thyroid hormone sensitivity and lung function. The association between TFQI and all-cause mortality risk was also investigated.

Results

A total of 6539 participants were analyzed, 900 with obstructive lung function and 407 with restrictive lung function. The prevalence of impaired lung function, both obstructive and restrictive, increased with higher TFQI levels. Logistic regression analysis showed that increased TFQI and decreased FT3/FT4 levels were independent risk factors for obstructive and restrictive lung function (P < 0.05). After adjusting for the impact of lung function, TFQI (HR = 1.25, 95 % CI 1.00-1.56, P = 0.048) was an independent risk factor for all-cause mortality.

Conclusion

Reduced sensitivity to thyroid hormones has been linked to impaired lung function. TFQI and FT3/FT4 are potential epidemiological tools to quantify the role of central and peripheral thyroid resistance in lung function.

Cardiovascular and bone health outcomes in older people with subclinical hypothyroidism treated with levothyroxine: a systematic review and meta-analysis

BACKGROUND

Thyroid dysfunction is common in older people, with females at higher risk. Evidence suggests that thyroid-stimulating hormone (TSH) levels naturally increase with age. However, as uniform serum TSH reference ranges are applied across the adult lifespan, subclinical hypothyroidism (SCH) diagnosis is more likely in older people, with some individuals also being commenced treatment with levothyroxine (LT4). It is unclear whether LT4 treatment in older people with SCH is associated with adverse cardiovascular or bone health outcomes.

METHODS

A systematic review and meta-analysis were performed to synthesise previous studies evaluating cardiovascular and bone health outcomes in older people with SCH, comparing LT4 treatment with no treatment. PubMed, Embase, Cochrane Library, MEDLINE, and Web of Science databases were searched from inception until March 13, 2023, and studies that evaluated cardiovascular and bone health events in people with SCH over 50 years old were selected.

RESULTS

Six articles that recruited 3853 participants were found, ranging from 185 to 1642 participants, with the proportion of females ranging from 45 to 80%. The paucity of data resulted in analysis for those aged over 65 years only. Additionally, a study with 12,212 participants aged 18 years and older was identified; however, only data relevant to patients aged 65 years and older were considered for inclusion in the systematic review. Of these 7 studies, 4 assessed cardiovascular outcomes, 1 assessed bone health outcomes, and 2 assessed both. A meta-analysis of cardiovascular outcomes revealed a pooled hazard ratio of 0.89 (95% CI 0.71-1.12), indicating no significant difference in cardiovascular risk between older individuals with SCH treated with LT4 compared to those without treatment. Due to overlapping sub-studies, meta-analysis for bone health outcomes was not possible.

CONCLUSIONS

This systematic review and meta-analysis found no significant association between LT4 use and cardiovascular and bone health outcomes in SCH participants over 65 years.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42022308006.

Hormonal influences on cerebral aneurysms: unraveling the complex connections

INTRODUCTION

Intracranial aneurysms (IAs) occur in 3-5% of the general population and are characterized by localized structural deterioration of the arterial wall with loss of internal elastic lamina and disruption of the media. The risk of incidence and rupture of aneurysms depends on age, sex, ethnicity, and other different factors, indicating the influence of genetic and environmental factors. When an aneurysm ruptures, there is an estimated 20% mortality rate, along with an added 30-40% morbidity in survivors. The alterations in hormonal levels can influence IAs, while the rupture of an aneurysm can have various impacts on endocrine pathways and affect their outcome.

AREA COVERED

This review explores the reciprocal relationship between endocrinological changes (estrogen, growth hormone, and thyroid hormones) and IAs, as well as the effects of aneurysm ruptures on endocrine fluctuations.

EXPERT OPINION

Based on the data presented in this paper, we recommend further exploration into the influence of hormones on aneurysm formation and rupture. Additionally, we propose conducting endocrine assessments for patients who have experienced a rupture of IAs. Monitoring hormonal changes in patients with IAs could serve as a potential risk factor for rupture, leading to interventions in the approach to managing IAs.

Deciphering thyroid function and CIMT: a Mendelian randomization study of the U-shaped influence mediated by apolipoproteins

Background

Carotid Intima-Media Thickness (CIMT) is a key marker for atherosclerosis, with its modulation being crucial for cardiovascular disease (CVD) risk assessment. While thyroid function's impact on cardiovascular health is recognized, the causal relationship and underlying mechanisms influencing CIMT remain to be elucidated.

Methods

In this study, Mendelian Randomization (MR) was employed to assess the causal relationship between thyroid function and CIMT. Thyroid hormone data were sourced from the Thyroidomics Consortium, while lipid traits and CIMT measurements were obtained from the UK Biobank. The primary analysis method was a two-sample MR using multiplicative random effects inverse variance weighting (IVW-MRE). Additionally, the study explored the influence of thyroid hormones on lipid profiles and assessed their potential mediating role in the thyroid function-CIMT relationship through multivariate MR analysis.

Results

The study revealed that lower levels of Free Thyroxine (FT4) within the normal range are significantly associated with increased CIMT. This association was not observed with free triiodothyronine (FT3), thyroid-stimulating hormone (TSH), or TPOAb. Additionally, mediation analysis suggested that apolipoprotein A-I and B are involved in the relationship between thyroid function and CIMT. The findings indicate a potential U-shaped curve relationship between FT4 levels and CIMT, with thyroid hormone supplementation in hypothyroid patients showing benefits in reducing CIMT.

Conclusion

This research establishes a causal link between thyroid function and CIMT using MR methods, underscoring the importance of monitoring thyroid function for early cardiovascular risk assessment. The results advocate for the consideration of thyroid hormone supplementation in hypothyroid patients as a strategy to mitigate the risk of carotid atherosclerosis. These insights pave the way for more targeted approaches in managing patients with thyroid dysfunction to prevent cardiovascular complications.

Systematic review and meta-analysis of levothyroxine effect on blood pressure in patients with subclinical hypothyroidism

This study aims to evaluate the effect of levothyroxine therapy on blood pressure (BP) in patients with subclinical hypothyroidism (SCH). Were searched Six databases, and randomized controlled trials (RCT) and prospective cohort studies evaluating the effect of levothyroxine therapy on BP in patients with SCH were included. 37 articles (9 RCTs and 28 prospective cohorts) were included in this meta-analysis. Pooled analysis of RCT studies was insignificant; however, pooled analysis of 28 prospective cohort studies showed a significant difference before and after the therapy, reducing both systolic blood pressure (SBP) and diastolic blood pressure (DBP) (MD=-4.02 [-6.45, -4.58] and MD=-2.13 [-3.69, -0.56], both P-values<0.05). Levothyroxine therapy can play a role in lowering BP in patients with SCH. However, this effect is more observed in Caucasians, SCH patients with higher initial TSH followed by more remarkable TSH change to normal levels, and SCH patients with hypertension.

Multi-trait analysis characterizes the genetics of thyroid function and identifies causal associations with clinical implications

To date only a fraction of the genetic footprint of thyroid function has been clarified. We report a genome-wide association study meta-analysis of thyroid function in up to 271,040 individuals of European ancestry, including reference range thyrotropin (TSH), free thyroxine (FT4), free and total triiodothyronine (T3), proxies for metabolism (T3/FT4 ratio) as well as dichotomized high and low TSH levels. We revealed 259 independent significant associations for TSH (61% novel), 85 for FT4 (67% novel), and 62 novel signals for the T3 related traits. The loci explained 14.1%, 6.0%, 9.5% and 1.1% of the total variation in TSH, FT4, total T3 and free T3 concentrations, respectively. Genetic correlations indicate that TSH associated loci reflect the thyroid function determined by free T3, whereas the FT4 associations represent the thyroid hormone metabolism. Polygenic risk score and Mendelian randomization analyses showed the effects of genetically determined variation in thyroid function on various clinical outcomes, including cardiovascular risk factors and diseases, autoimmune diseases, and cancer. In conclusion, our results improve the understanding of thyroid hormone physiology and highlight the pleiotropic effects of thyroid function on various diseases.

Is Thyroid Dysfunction Associated with Unruptured Intracranial Aneurysms? A Population-Based, Nested Case-Control Study from Korea

Background: Few risk factors for the development of intracranial aneurysms (IAs) are known. We investigated the potential role of thyroid diseases in IA development using nationwide real-world data. Methods: A nested case-control study within the National Health Insurance Service-National Sample Cohort data from 2002 to 2019 was performed. A total of 5335 patients with unruptured IA were matched by age and sex with 80,025 controls at a ratio of 1:15. We estimated the odds ratios (ORs) and corresponding confidence intervals [CIs] between thyroid diseases and unruptured IA using a multivariable conditional logistic regression model. Results: Tobacco smoking, use of antihypertensive medication, and hypothyroidism were significantly associated with an elevated risk for unruptured IA in univariate analysis. In multivariable analysis, a history of hypothyroidism was associated with unruptured IA (adjusted OR: 1.46 [CI: 1.26-1.69]). Among patients with hypothyroidism, long-term use of thyroid hormone for >5 years was associated with a reduced risk for unruptured IA (adjusted OR: 0.69 [CI: 0.48-0.99]). A history of hyperthyroidism was associated with a reduced risk for unruptured IAs (adjusted OR: 0.71 [CI: 0.54-0.93]). In secondary analyses of the data according to sex, the respective observed associations between hypothyroidism and hyperthyroidism and the risk of IAs were found to be statistically significant in females but not in males. Conclusions: Hypothyroidism is associated with an increased risk of unruptured IAs, whereas hyperthyroidism is associated with a reduced risk. Overall, the findings suggest that thyroid hormones may play a protective role in the development of unruptured IAs. Further studies are needed to clarify potential direct causality and the biologic mechanisms relating thyroid dysfunction and unruptured IA.

Association of serum thyroid hormone and coronary artery calcification in patients who underwent invasive coronary angiography: an observational study

BACKGROUND

Thyroid hormones (TH) are known to have a range of effects on the cardiovascular system. However, there is still controversy regarding the relationship between thyroid function and coronary artery calcification (CAC). The purpose of this paper is to investigate the relationship between TH and CAC, especially severe CAC, in patients who underwent invasive coronary angiography (ICA). This may provide further insights into the potential role of TH in the development and progression of cardiovascular disease.

METHOD

This observational study included 4221 patients who underwent ICA after completing CTA in a single center. We collected demographic, clinical, and laboratory data from electronic medical records and measured CAC scores via non-contrast cardiac CT.

RESULT

The study found that there is a negative correlation between the CAC score and FT3 level, even after adjusting for potential confounding factors, but there was no correlation between the CAC score and FT4 or TSH. When categorized into quartiles, the highest quartile of FT3 was associated with a decrease (β = -104.37, 95%CI: -172.54, -36.21) in calcification score compared to the lowest quartile. This correlation was more significant in the subgroup of individuals with diabetes or hypertension.

CONCLUSION

The study found a negative correlation between FT3 and CAC in patients who underwent ICA. The correlation was consistent with other studies and may suggest that low levels of FT3 are associated with severe CAC. The study may provide new evidence for future research on CAC and potential therapeutic approaches.

Exploring the Association between Thyroid Function and Frailty: Insights from Representative Korean Data

BACKGRUOUND

This study investigates the association between thyroid function and frailty in the old patients using representative data.

METHODS

The study was conducted using data from the Korea National Health and Nutrition Examination Survey conducted from 2013 to 2015. The study population included 2,416 participants aged 50 years and older with available thyroid function test data. Frailty assessment was performed using the Fried frailty phenotype. The prevalence of frailty was analyzed across different thyroid diseases and thyroid function parameters.

RESULTS

The significant association between thyroid dysfunction and frailty was observed in overt hyperthyroidism and subclinical hyperthyroidism. After adjusting for various factors, the association between thyroid dysfunction and frailty remained significant. On the other hand, overt hypothyroidism did not show a significant association with frailty in the adjusted analysis. For individuals with overt hyperthyroidism and subclinical hyperthyroidism, higher levels of free thyroxine (FT4) were significantly associated with an increased risk of frailty (aOR >999; 95% CI, >999 to 999). Among individuals with overt hypothyroidism, lower level of FT4 levels and high thyrotropin (TSH) levels showed a significant association with frailty risk (FT4: aOR, <0.01; TSH: aOR, 999). In participants with subclinical hypothyroidism, there were no significant associations between parameters for thyroid and frailty risk.

CONCLUSION

These findings suggest that thyroid dysfunction, particularly overt hyperthyroidism and subclinical hyperthyroidism, may be associated with an increased risk of frailty in the old patients.

Association Between Thyroid Parameters and Subclinical Atherosclerosis in Hospitalised Euthyroid Patients with Type 2 Diabetes Mellitus

Purpose

To explore the association between thyroid parameters and subclinical atherosclerosis (AS) in hospitalised euthyroid patients with type 2 diabetes mellitus (T2DM).

Patients and Methods

A retrospective analysis was conducted involving 1245 inpatients with T2DM. Free triiodothyronine (FT3), free thyroxine (FT4), and thyroid stimulating hormone (TSH) levels were measured, and carotid artery ultrasonography was performed. Thyroid hormone (TH) sensitivity was evaluated using thyroid feedback quantile-based index (TFQI), TSH index (TSHI), thyrotropin thyroxine resistance index (TT4RI), and free triiodothyronine/free thyroxine ratio (FT3/FT4).

Results

In inpatients with T2DM having normal thyroid function, the incidence of subclinical AS declined with increasing levels of FT3, FT4, and FT3/FT4 (P trend < 0.05). Logistic regression analysis revealed that FT4 (OR, 0.914; 95% CI, 0.845-0.989), FT3 (OR, 0.374; 95% CI, 0.277-0.504), and FT3/FT4 (OR, 0.036; 95% CI, 0.013-0.061) were independently associated with subclinical AS (P < 0.05). However, TSH, TFQI, TSHI, and TT4RI levels were not associated with subclinical AS (P > 0.05). FT3/FT4 demonstrated superior predictive accuracy for subclinical AS than that of FT3 or FT4 alone (P < 0.001), with a cutoff point of 0.25.

Conclusion

In euthyroid inpatients with T2DM, subclinical AS exhibited negative correlation with FT3, FT4, and FT3/FT4 levels, independent of other risk factors for AS. Additionally, FT3/FT4 ratio had a good predictive value for subclinical AS.

The optimal healthy ranges of thyroid function defined by the risk of cardiovascular disease and mortality: systematic review and individual participant data meta-analysis

BACKGROUND

Reference intervals of thyroid-stimulating hormone (TSH) and free thyroxine (FT4) are statistically defined by the 2·5-97·5th percentiles, without accounting for potential risk of clinical outcomes. We aimed to define the optimal healthy ranges of TSH and FT4 based on the risk of cardiovascular disease and mortality.

METHODS

This systematic review and individual participant data (IPD) meta-analysis identified eligible prospective cohorts through the Thyroid Studies Collaboration, supplemented with a systematic search via Embase, MEDLINE (Ovid), Web of science, the Cochrane Central Register of Controlled Trials, and Google Scholar from Jan 1, 2011, to Feb 12, 2017 with an updated search to Oct 13, 2022 (cohorts found in the second search were not included in the IPD). We included cohorts that collected TSH or FT4, and cardiovascular outcomes or mortality for adults (aged ≥18 years). We excluded cohorts that included solely pregnant women, individuals with overt thyroid diseases, and individuals with cardiovascular disease. We contacted the study investigators of eligible cohorts to provide IPD on demographics, TSH, FT4, thyroid peroxidase antibodies, history of cardiovascular disease and risk factors, medication use, cardiovascular disease events, cardiovascular disease mortality, and all-cause mortality. The primary outcome was a composite outcome including cardiovascular disease events (coronary heart disease, stroke, and heart failure) and all-cause mortality. Secondary outcomes were the separate assessment of cardiovascular disease events, all-cause mortality, and cardiovascular disease mortality. We performed one-step (cohort-stratified Cox models) and two-step (random-effects models) meta-analyses adjusting for age, sex, smoking, systolic blood pressure, diabetes, and total cholesterol. The study was registered with PROSPERO, CRD42017057576.

FINDINGS

We identified 3935 studies, of which 53 cohorts fulfilled the inclusion criteria and 26 cohorts agreed to participate. We included IPD on 134 346 participants with a median age of 59 years (range 18-106) at baseline. There was a J-shaped association of FT4 with the composite outcome and secondary outcomes, with the 20th (median 13·5 pmol/L [IQR 11·2-13·9]) to 40th percentiles (median 14·8 pmol/L [12·3-15·0]) conveying the lowest risk. Compared with the 20-40th percentiles, the age-adjusted and sex-adjusted hazard ratio (HR) for FT4 in the 80-100th percentiles was 1·20 (95% CI 1·11-1·31) for the composite outcome, 1·34 (1·20-1·49) for all-cause mortality, 1·57 (1·31-1·89) for cardiovascular disease mortality, and 1·22 (1·11-1·33) for cardiovascular disease events. In individuals aged 70 years and older, the 10-year absolute risk of composite outcome increased over 5% for women with FT4 greater than the 85th percentile (median 17·6 pmol/L [IQR 15·0-18·3]), and men with FT4 greater than the 75th percentile (16·7 pmol/L [14·0-17·4]). Non-linear associations were identified for TSH, with the 60th (median 1·90 mIU/L [IQR 1·68-2·25]) to 80th percentiles (2·90 mIU/L [2·41-3·32]) associated with the lowest risk of cardiovascular disease and mortality. Compared with the 60-80th percentiles, the age-adjusted and sex-adjusted HR of TSH in the 0-20th percentiles was 1·07 (95% CI 1·02-1·12) for the composite outcome, 1·09 (1·05-1·14) for all-cause mortality, and 1·07 (0·99-1·16) for cardiovascular disease mortality.

INTERPRETATION

There was a J-shaped association of FT4 with cardiovascular disease and mortality. Low concentrations of TSH were associated with a higher risk of all-cause mortality and cardiovascular disease mortality. The 20-40th percentiles of FT4 and the 60-80th percentiles of TSH could represent the optimal healthy ranges of thyroid function based on the risk of cardiovascular disease and mortality, with more than 5% increase of 10-year composite risk identified for FT4 greater than the 85th percentile in women and men older than 70 years. We propose a feasible approach to establish the optimal healthy ranges of thyroid function, allowing for better identification of individuals with a higher risk of thyroid-related outcomes.

FUNDING

None.

Thyroid Function in Causal Relation to MRI Markers of Cerebral Small Vessel Disease: A Mendelian Randomization Analysis

CONTEXT

Observational studies have provided insufficient information on the association between thyroid function and the risk of cerebral small vessel disease (CSVD); moreover, the causality of this link is still unclear.

OBJECTIVE

This study aims to investigate whether genetically predicted variation within thyroid function is causally associated with the risk of CSVD using 2-sample Mendelian randomization (MR) analysis.

METHODS

In this 2-sample MR study with genome-wide association variants, we estimated the causal effects of genetically predicted thyrotropin (thyroid-stimulating hormone, TSH; n = 54 288), free thyroxine (FT4; n = 49 269), hypothyroidism (n = 51 823), and hyperthyroidism (n = 51 823) on 3 neuroimaging markers of CSVD, including white matter hyperintensity (WMH; n = 42 310), mean diffusivity (MD; n = 17 467), and fractional anisotropy (FA, n = 17 663). The primary analysis was conducted by the inverse variance-weighted MR method, followed by sensitivity analyses using MR-PRESSO, MR-Egger, weighted median, and weighted mode methods.

RESULTS

Genetically increased TSH was associated with increased MD (β = .311, 95% CI 0.0763, 0.548, P = .01). Genetically increased FT4 was associated with increased FA (β = .540, 95% CI 0.222, 0.858, P < .001). Sensitivity analyses using different MR methods showed similar directions but lower precision. No significant associations of hypothyroidism or hyperthyroidism with WMH, MD, or FA were found (all P > .05).

CONCLUSION

This study indicated that genetically predicted increased TSH was associated with increased MD, as well as increased FT4 with increased FA, implying the causal effect of thyroid dysfunction on white matter microstructural injury. There were no significant causal relationships of hypothyroidism or hyperthyroidism with CSVD. Further investigations should verify these findings and clarify the underlying pathophysiological mechanisms.

Lower free triiodothyronine levels are associated with higher all-cause and cardiovascular mortality in people with diabetes-NHANES 2007-2012

OBJECTIVE

Thyroid hormone plays a key role in maintaining cardiovascular system homeostasis. However, there is limited evidence regarding the correlation between normal range thyroid hormone levels and all-cause mortality or cardiovascular mortality among individuals with diabetes.

METHOD

This retrospective study analyzed data from 1,208 individuals with diabetes who participated in the National Health and Nutrition Survey (NHANES) conducted in the United States between 2007 and 2012. Weighted Kaplan-Meier (KM) analysis and Cox proportional hazards models were used to explore the association between thyroid hormone indices and mortality.

RESULTS

The Weighted Kaplan-Meier (KM) analysis revealed statistically significant differences in survival probabilities across free triiodothyronine (FT3), free thyroxine (FT4), FT3/FT4 ratio and thyroid-stimulating hormone (TSH) groups (p < 0.05 or < 0.001). In the multivariate adjusted Cox proportional hazards models, higher levels of FT3 were founded to be associated with decreased all-cause mortality (HR (95% CI), 0.715 (0.567, 0.900)), cardio-cerebrovascular mortality (0.576 (0.408, 0.814)) and cardiovascular mortality (0.629 (0.438, 0.904)). Notably, this correlation was more significant among individuals over the age of 60, as indicated by the results of the nonlinear regression analysis.

CONCLUSION

FT3 is an independent predictor of all-cause death, cardio-cerebrovascular and cardiovascular death in euthyroid subjects with diabetes.

Thyroid-stimulating hormone within the normal reference range has a U-shaped association with the severity of coronary artery disease in nondiabetic patients but is diluted in diabetic patients

Too high or too low thyroid-stimulating hormone (TSH) has been associated with the progress and prognosis of coronary artery disease (CAD). However, whether TSH within its normal reference range plays a role in the severity of CAD remains unclear. In this observational study, we explored the potential relationship of hypersensitive TSH (hs-TSH) with the severity of CAD in euthyroid patients with or without diabetes mellitus. A total of 7357 CAD patients with euthyroidism were enrolled in this study. Of those, 1997 had diabetes mellitus. The severity of CAD was evaluated through the presence of myocardial infarction (MI) and the severity of coronary lesions, which was calculated using the Gensini score (GS). Logistic regression models treating hs-TSH as a categorical variable and restricted cubic spline analyses treating it as a continuous variable were used to evaluate the associations of hs-TSH with the severity of CAD. The propensity score matching method was used to further validate the differences between diabetic and nondiabetic patients. CAD patients with diabetes mellitus had lower levels of hs-TSH (1.6 (0.97-2.53) vs 1.67 (1.00-2.64)) in serum compared with CAD patients without diabetes mellitus. Meanwhile, hs-TSH was independently related to the severity of CAD. In CAD patients with vs without diabetes mellitus, the U-shaped relationship between hs-TSH and MI was more prominent in patients without diabetes mellitus, and the significant U-shaped association between higher GS and hs-TSH remained only in nondiabetes. Therefore, hs-TSH within the normal reference range has a U-shaped association with the severity of CAD in nondiabetic patients, which is markedly diluted in diabetic patients.

Chemotherapy, hypothyroidism and oral dysbiosis as a novel risk factor of cardiovascular pathology development

Cardiovascular disease (CVD) remains the leading cause of morbidity and mortality in the population, as well as the economic burden of the health care system. Currently, CVDs account for more than 17.6 million deaths a year and are projected to exceed 23.6 million by 2030. Unstable atheroma, and its rupture, underlies the pathology of most cardiovascular complications, particularly acute coronary syndrome, mortality from which, compared with other CV events, remains the leading one. Despite numerous efforts by WHO, national health systems, and medical authorities, the incidence and mortality from cardiovascular events remain critically high. Thus, the search for new risk factors for the development of CV pathology looks very relevant. Our working group decided to amalgamate our research data, which reflects the study of modern risk factors from the Armenian, Russian, Georgian, and Iranian medical schools. In particular, the aspects of cardiotoxic effects of chemotherapy, hypothyroidism, and oral dysbiosis are discussed.

Fluctuations in Thyroid Hormone Levels During Initial Treatment for Differentiated Thyroid Carcinoma are Associated with Changes in Hemostasis: A Prospective Cohort Study

Background: During treatment for differentiated thyroid carcinoma (DTC), patients go from euthyroidism to severe hypothyroidism to subclinical hyperthyroidism induced by thyroid hormone suppression therapy (THST). Severe hypothyroidism may induce a tendency toward bleeding, whereas hyperthyroidism is thrombogenic. Therefore, treatment for DTC may increase the risk of bleeding during thyroid hormone withdrawal, and thrombosis during THST. This study aims to provide prospective analysis of changes in the hemostatic system from euthyroidism to hypothyroidism, and during THST, in patients treated for DTC. Methods: This is a secondary study in a larger Dutch prospective cohort. Consecutive samples were obtained from 20 patients (18 female [90%]; median age 48 [interquartile range 35.8-56.5] years) throughout their treatment for DTC during euthyroidism (n = 5), severe hypothyroidism (n = 20), and THST (n = 20). We measured selected hemostatic proteins and C-reactive protein (CRP), performed functional tests of hemostasis (a thrombin generation test and a plasma-based clot lysis test), and assessed markers of in vivo activation of hemostasis (thrombin-antithrombin complexes, plasmin-antiplasmin [PAP] complexes, and D-dimer levels). Results: During hypothyroidism, the majority of measured parameters did not change. During THST, plasma levels of nearly all measured hemostatic proteins were higher than during hypothyroidism. Additionally, CRP significantly increased from 1.3 (0.5-3.3) to 3.2 (1.3-5.1) mg/L during THST (p < 0.01). Ex vivo thrombin generation increased from 626.0 (477.0-836.3) to 876.0 (699.0-1052.0) nM × min (p = 0.02), and ex vivo clot lysis time increased from 60.6 (55.6-67.4) to 76.0 (69.7-95.0) minutes during THST (p < 0.01). PAP levels reduced from 266.5 (211.8-312.0) to 192.0 (161.0-230.0) μg/L during THST (p < 0.01); other markers of in vivo activation of coagulation remained unaffected. Conclusions: During THST-induced hyperthyroidism, a shift toward a more hypercoagulable and hypofibrinolytic state occurred. However, in vivo activation of hemostasis did not increase. The rise in CRP levels suggests the presence of a low-grade inflammation in patients during THST. Both a hypercoagulable and hypofibrinolytic state and a low-grade inflammation are associated with an increased risk of cardiovascular diseases (CVD). Therefore, the subtle changes found during THST could potentially play a role in the pathogenesis of CVD as observed in DTC patients. Clinical Trial Registration: This study is part of a larger clinical trial registered at the Netherlands Trial Register (NTR ID 7228).

A Novel Inflammatory Marker for the Diagnosis of Hashimoto's Thyroiditis: Platelet-Count-to-Lymphocyte-Count Ratio

BACKGROUND

Hashimoto's thyroiditis (HT) is a chronic autoimmune thyroiditis that causes systemic inflammation in the body, leading to hypothyroidism and an enlargement of the thyroid gland.

OBJECTIVES

This study aims to reveal whether there is a relationship between Hashimoto's thyroiditis and the platelet-count-to-lymphocyte-count ratio (PLR), which is used as a new inflammatory marker.

METHODS

In this retrospective study, we compared the PLR of the euthyroid HT group and the hypothyroid-thyrotoxic HT group to the controls. We also evaluated the values of thyroid-stimulating hormone (TSH), free T4 (fT4), C-reactive protein (CRP), aspartate transaminase (AST), alanine transaminase (ALT), white blood cell count, lymphocyte count, hemoglobin, hematocrit, and platelet count in each group.

RESULTS

The PLR of the subjects with Hashimoto's thyroiditis was found to be significantly different from the control group (p < 0.001), with the rankings as follows: hypothyroid-thyrotoxic HT 177% (72-417) > euthyroid HT 137% (69-272) > control group 103% (44-243). In addition to the increased PLR values, an increase in CRP values was also observed, revealing a strong positive correlation between the PLR and CRP in the HT patients.

CONCLUSION

In this study, we found out that the PLR was higher in the hypothyroid-thyrotoxic HT and euthyroid HT patients than in a healthy control group.

Thyroid hormone levels paradox in acute ischemic stroke

Objective

Accumulating evidence has suggested that thyroid hormone levels affect the prognosis of acute ischemic stroke (AIS), but the results have been inconsistent.

Methods

Basic data, neural scale scores, thyroid hormone levels, and other laboratory examination data of AIS patients were collected. The patients were divided into excellent and poor prognosis group at discharge and 90 days after discharge. Logistic regression models were applied to evaluate the relationship between thyroid hormone levels and prognosis. A subgroup analysis was performed based on stroke severity.

Results

A number of 441 AIS patients were included in this study. Those in the poor prognosis group were older, with higher blood sugar levels, higher free thyroxine (FT4) levels, and severe stroke (all p < 0.05) at baseline. Free thyroxine (FT4) showed a predictive value (all p < 0.05) for prognosis in the model adjusted for age, gender, systolic pressure, and glucose level. However, after adjustment for types and severity of stroke, FT4 showed insignificant associations. In the severe subgroup at discharge, the change in FT4 was statistically significant (p = 0.015), odds ratio (95% confidence interval) = 1.394 (1.068-1.820) but not in the other subgroups.

Conclusions

High-normal FT4 serum levels in patients with severe stroke receiving conservative medical treatment at admission may indicate a worse short-term prognosis.

There is urgent need to treat atherosclerotic cardiovascular disease risk earlier, more intensively, and with greater precision: A review of current practice and recommendations for improved effectiveness

Atherosclerotic cardiovascular disease (ASCVD) is epidemic throughout the world and is etiologic for such acute cardiovascular events as myocardial infarction, ischemic stroke, unstable angina, and death. ASCVD also impacts risk for dementia, chronic kidney disease peripheral arterial disease and mobility, impaired sexual response, and a host of other visceral impairments that adversely impact the quality and rate of progression of aging. The relationship between low-density lipoprotein cholesterol (LDL-C) and risk for ASCVD is one of the most highly established and investigated issues in the entirety of modern medicine. Elevated LDL-C is a necessary condition for atherogenesis induction. Basic scientific investigation, prospective longitudinal cohorts, and randomized clinical trials have all validated this association. Yet despite the enormous number of clinical trials which support the need for reducing the burden of atherogenic lipoprotein in blood, the percentage of high and very high-risk patients who achieve risk stratified LDL-C target reductions is low and has remained low for the last thirty years. Atherosclerosis is a preventable disease. As clinicians, the time has come for us to take primordial and primary prevention more serously. Despite a plethora of therapeutic approaches, the large majority of patients at risk for ASCVD are poorly or inadequately treated, leaving them vulnerable to disease progression, acute cardiovascular events, and poor aging due to loss of function in multiple visceral organs. Herein we discuss the need to greatly intensify efforts to reduce risk, decrease disease burden, and provide more comprehensive and earlier risk assessment to optimally prevent ASCVD and its complications. Evidence is presented to support that treatment should aim for far lower goals in cholesterol management, should take into account many more factors than commonly employed today and should begin significantly earlier in life.

Genome-wide association study of hyperthyroidism based on electronic medical record from Taiwan

Excess thyroid hormones have complex metabolic effects, particularly hyperthyroidism, and are associated with various cardiovascular risk factors. Previous candidate gene studies have indicated that genetic variants may contribute to this variable response. Electronic medical record (EMR) biobanks containing clinical and genomic data on large numbers of individuals have great potential to inform the disease comorbidity development. In this study, we combined electronic medical record (EMR) -derived phenotypes and genotype information to conduct a genome-wide analysis of hyperthyroidism in a 35,009-patient cohort in Taiwan. Diagnostic codes were used to identify 2,767 patients with hyperthyroidism. Our genome-wide association study (GWAS) identified 44 novel genomic risk markers in 10 loci on chromosomes 2, 6, and 14 (P < 5 × 10–14), including CTLA4, HCP5, HLA-B, POU5F1, CCHCR1, HLA-DRA, HLA-DRB9, TSHR, RPL17P3, and CEP128. We further conducted a comorbidity analysis of our results, and the data revealed a strong correlation between hyperthyroidism patients with thyroid storm and stroke. In this study, we demonstrated application of the PheWAS using large EMR biobanks to inform the comorbidity development in hyperthyroidism patients. Our data suggest significant common genetic risk factors in patients with hyperthyroidism. Additionally, our results show that sex, body mass index (BMI), and thyroid storm are associated with an increased risk of stroke in subjects with hyperthyroidism.

The Effects of Common Genetic Variation in 96 Genes Involved in Thyroid Hormone Regulation on TSH and FT4 Concentrations

OBJECTIVE

While most of the variation in thyroid function is determined by genetic factors, single nucleotide polymorphisms (SNPs) identified via genome-wide association analyses have only explained ~5% to 9% of this variance so far. Most SNPs were in or nearby genes with no known role in thyroid hormone (TH) regulation. Therefore, we performed a large-scale candidate gene study investigating the effect of common genetic variation in established TH regulating genes on serum thyrotropin [thyroid-stimulating hormone (TSH)] and thyroxine (FT4) concentrations.

METHODS

SNPs in or within 10 kb of 96 TH regulating genes were included (30 031 TSH SNPs, and 29 962 FT4 SNPs). Associations were studied in 54 288 individuals from the ThyroidOmics Consortium. Linkage disequilibrium-based clumping was used to identify independently associated SNPs. SNP-based explained variances were calculated using SumHer software.

RESULTS

We identified 23 novel TSH-associated SNPs in predominantly hypothalamic-pituitary-thyroid axis genes and 25 novel FT4-associated SNPs in mainly peripheral metabolism and transport genes. Genome-wide SNP variation explained ~21% (SD 1.7) of the total variation in both TSH and FT4 concentrations, whereas SNPs in the 96 TH regulating genes explained 1.9% to 2.6% (SD 0.4).

CONCLUSION

Here we report the largest candidate gene analysis on thyroid function, resulting in a substantial increase in the number of genetic variants determining TSH and FT4 concentrations. Interestingly, these candidate gene SNPs explain only a minor part of the variation in TSH and FT4 concentrations, which substantiates the need for large genetic studies including common and rare variants to unravel novel, yet unknown, pathways in TH regulation.

Thyroid Status and Brain Circulation: The Rotterdam Study

CONTEXT

Whether thyroid dysfunction is related to altered brain circulation in the general population remains unknown.

OBJECTIVE

We determined the association of thyroid hormones with different markers of brain circulation within community-dwelling elderly people.

METHODS

This was a population-based study of 3 subcohorts of the Rotterdam Study, starting in 1989, 2000, and 2006. A total of 5142 participants (mean age, 63.8 years; 55.4% women), underwent venipuncture to measure serum thyroid-stimulating hormone (TSH) and free thyroxine (FT4). Between 2005 and 2015, all participants underwent phase-contrast brain magnetic resonance imaging to assess global brain perfusion (mL of blood flow/100 mL of brain/minute). Arteriolar retinal calibers were assessed using digitized images of stereoscopic fundus color transparencies in 3105 participants as markers of microcirculation. We investigated associations of TSH, FT4 with brain circulation measures using (non)linear regression models.

RESULTS

FT4 (in pmol/L) levels had an inverse U-shaped association with global brain perfusion, such that high and low levels of FT4 were associated with lower global brain perfusion than middle levels of FT4. The difference in global brain perfusion between high FT4 levels (25 pmol/L) and middle FT4 levels (FT4 = 15 pmol/L; P nonlinearity = .002) was up to -2.44 mL (95% CI -4.31; -0.56). Higher and lower levels of FT4, compared with middle FT4 levels, were associated with arteriolar retinal vessels (mean difference up to -2.46 µm, 95% CI -4.98; 0.05 for lower FT4).

CONCLUSION

These results suggest that thyroid dysfunction could lead to brain diseases such as stroke or dementia through suboptimal brain circulation that is potentially modifiable.

Free thyroxine, brain frailty and clock drawing test performance in patients with acute minor stroke or transient ischaemic attack

OBJECTIVE

Thyroid dysfunction is associated with an elevated risk of cognitive decline, but the mechanism underlying this relationship is elusive. In this study, we investigate the relationships between free thyroxine (FT4), brain frailty and clock drawing test (CDT) performance in patients with acute minor stroke or transient ischaemic attack (TIA).

DESIGN, PATIENTS AND MEASUREMENTS

A total of 204 consecutive patients admitted to our hospital within 72 h after the onset of acute minor stroke or TIA were prospectively enroled and categorized in terms of quartiles of FT4 between March 2018 and August 2019. Brain frailty on magnetic resonance imaging was rated according to previously published criteria. Cognitive performance was assessed with the CDT.

RESULTS

Generalized linear analysis revealed that FT4 was independently associated with higher brain frailty score after adjusting potential confounders (β, 0.03; 95% confidence interval [CI], 0.00-0.06; p = 0.0205), which is consistent with the result of FT4 (quartile) as a categorical variable (β, 0.34; 95% CI, 0.01-0.68; p = 0.0059; p_trend  = 0.0807). A nonlinear relationship was detected between FT4 and brain frailty score, which had an inflection point of 1.19. FT4 was also associated with poor CDT performance (odds ratio, 1.15; 95% CI, 1.04-1.26; p = 0.0051). And mediation analysis found that brain frailty partially mediated the positive relationship between FT4 and poor CDT performance (indirect effect = 0.0024; 95% CI, 0.0003-0.01, p = 0.04).

CONCLUSIONS

Our findings suggested that a higher FT4 level was associated with a higher brain frailty score and poorer CDT performance, and brain frailty might play an important effect on the association between FT4 and cognitive decline.

Assessment of causal direction between thyroid function and cardiometabolic health: a Mendelian randomization study

BACKGROUND

Growing evidence have demonstrated that thyroid hormones have been involved in the processes of cardiovascular metabolism. However, the causal relationship of thyroid function and cardiometabolic health remains partly unknown.

METHODS

The Mendelian randomization (MR) was used to test genetic, potentially causal relationships between instrumental variables and cardiometabolic traits. Genetic variants of free thyroxine (FT4) and thyrotropin (TSH) levels within the reference range were used as instrumental variables. Data for genetic associations with cardiometabolic diseases were acquired from the genome-wide association studies of the FinnGen, CARDIoGRAM and CARDIoGRAMplusC4D, CHARGE, and MEGASTROKE. This study was conducted using summary statistic data from large, previously described cohorts. Association between thyroid function and essential hypertension (EHTN), secondary hypertension (SHTN), hyperlipidemia (HPL), type 2 diabetes mellitus (T2DM), ischemic heart disease (IHD), myocardial infarction (MI), heart failure (HF), pulmonary heart disease (PHD), stroke, and non-rheumatic valve disease (NRVD) were examined.

RESULTS

Genetically predicted FT4 levels were associated with SHTN (odds ratio = 0.48; 95% CI = 0.04−0.82,P = 0.027), HPL (odds ratio = 0.67; 95% CI = 0.18−0.88,P = 0.023), T2DM (odds ratio = 0.80; 95% CI = 0.42−0.86,P = 0.005), IHD (odds ratio = 0.85; 95% CI = 0.49−0.98,P = 0.039), NRVD (odds ratio = 0.75; 95% CI = 0.27−0.97,P = 0.039). Additionally, genetically predicted TSH levels were associated with HF (odds ratio = 0.82; 95% CI = 0.68−0.99,P = 0.042), PHD (odds ratio = 0.75; 95% CI = 0.32−0.82,P = 0.006), stroke (odds ratio = 0.95; 95% CI = 0.81−0.97,P = 0.007). However, genetically predicted thyroid function traits were not associated with EHTN and MI.

CONCLUSIONS

Our study suggests FT4 and TSH are associated with cardiometabolic diseases, underscoring the importance of the pituitary-thyroid-cardiac axis in cardiometabolic health susceptibility.

Association of Thyroid Dysfunction With Cognitive Function: An Individual Participant Data Analysis

IMPORTANCE

In clinical guidelines, overt and subclinical thyroid dysfunction are mentioned as causal and treatable factors for cognitive decline. However, the scientific literature on these associations shows inconsistent findings.

OBJECTIVE

To assess cross-sectional and longitudinal associations of baseline thyroid dysfunction with cognitive function and dementia.

DESIGN, SETTING, AND PARTICIPANTS

This multicohort individual participant data analysis assessed 114 267 person-years (median, 1.7-11.3 years) of follow-up for cognitive function and 525 222 person-years (median, 3.8-15.3 years) for dementia between 1989 and 2017. Analyses on cognitive function included 21 cohorts comprising 38 144 participants. Analyses on dementia included eight cohorts with a total of 2033 cases with dementia and 44 573 controls. Data analysis was performed from December 2016 to January 2021.

EXPOSURES

Thyroid function was classified as overt hyperthyroidism, subclinical hyperthyroidism, euthyroidism, subclinical hypothyroidism, and overt hypothyroidism based on uniform thyrotropin cutoff values and study-specific free thyroxine values.

MAIN OUTCOMES AND MEASURES

The primary outcome was global cognitive function, mostly measured using the Mini-Mental State Examination. Executive function, memory, and dementia were secondary outcomes. Analyses were first performed at study level using multivariable linear regression and multivariable Cox regression, respectively. The studies were combined with restricted maximum likelihood meta-analysis. To overcome the use of different scales, results were transformed to standardized mean differences. For incident dementia, hazard ratios were calculated.

RESULTS

Among 74 565 total participants, 66 567 (89.3%) participants had normal thyroid function, 577 (0.8%) had overt hyperthyroidism, 2557 (3.4%) had subclinical hyperthyroidism, 4167 (5.6%) had subclinical hypothyroidism, and 697 (0.9%) had overt hypothyroidism. The study-specific median age at baseline varied from 57 to 93 years; 42 847 (57.5%) participants were women. Thyroid dysfunction was not associated with global cognitive function; the largest differences were observed between overt hypothyroidism and euthyroidism-cross-sectionally (-0.06 standardized mean difference in score; 95% CI, -0.20 to 0.08; P = .40) and longitudinally (0.11 standardized mean difference higher decline per year; 95% CI, -0.01 to 0.23; P = .09). No consistent associations were observed between thyroid dysfunction and executive function, memory, or risk of dementia.

CONCLUSIONS AND RELEVANCE

In this individual participant data analysis of more than 74 000 adults, subclinical hypothyroidism and hyperthyroidism were not associated with cognitive function, cognitive decline, or incident dementia. No rigorous conclusions can be drawn regarding the role of overt thyroid dysfunction in risk of dementia. These findings do not support the practice of screening for subclinical thyroid dysfunction in the context of cognitive decline in older adults as recommended in current guidelines.

Relationship between Blood Trihalomethane Concentrations and Serum Thyroid Function Measures in U.S. Adults

Toxicological studies show that exposure to disinfection byproducts, including trihalomethanes (THMs), negatively affects thyroid function; however, few epidemiological studies have explored this link. This study included 2233 adults (ages ≥20 years) from the 2007-2008 National Health and Nutrition Examination Survey (NHANES) who were measured for blood THM concentrations [chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), or bromoform (TBM)] and serum thyroid function biomarkers [thyroid-stimulating hormone, free thyroxine (FT4), total thyroxine (TT4), free triiodothyronine (FT3), total triiodothyronine (TT3), thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb)]. Multivariable linear regression models showed positive associations between blood TCM, BDCM, and total THMs (the sum of all four THMs) concentrations and serum FT4, whereas inverse associations were found between blood DBCM and total brominated THM (Br-THM; the sum of BDCM, DBCM, and TBM) concentrations and serum TT3 (all p < 0.05). Besides, positive associations were observed between blood TCM concentrations and FT4/FT3 ratio, between BDCM, DBCM, and Br-THM concentrations and TT4/TT3 ratio, and between DBCM and Br-THM concentrations and FT3/TT3 ratio (all p < 0.05). Blood THM concentrations were unrelated to the serum levels of thyroid autoantibodies TgAb or TPOAb. In summary, exposure to THMs was associated with altered serum biomarkers of thyroid function but not with thyroid autoimmunity among U.S. adults.

Treatment Modality and Risk of Heart Failure in Patients With Long-Standing Graves' Disease: A Nationwide Population-Based Cohort Study

Background

Optimal treatment for persistent Graves' disease following 12-18 months of treatment with anti-thyroid drugs (ATDs) is unclear. Given the increased risk of cardiovascular morbidity and mortality with hyperthyroidism, assessing the risk of cardiovascular events associated with different treatment modalities after the conventional ATD course would be valuable in determining the appropriate next-line therapy.

Methods

This retrospective cohort study included data from the Korean National Health Insurance database of 16,882 patients with newly diagnosed hyperthyroidism who received primary ATD treatment for 24 months. Patients were categorized based on the treatment they received after receiving ATD for 24 months: continued ATD for at least 12 more months (ATD group), radioiodine ablation (RIA) with remission (RIA group 1), and RIA without remission (RIA group 2). The incidence and risk of heart failure (HF), the leading cause of cardiovascular mortality in hyperthyroidism, were compared between patients and age-and sex-matched controls.

Results

There were 16,516 (97.8%) patients in the ATD group, 230 (1.4%) in RIA group 1, and 136 (0.8%) in RIA group 2. Compared to that of controls, a significant difference in the cumulative incidence of HF was observed according to second-line treatment modality after adjusting for covariates; the risk was highest in patients in RIA group 2, with a hazard ratio (HR) of 2.54 (95% confidence interval (CI) 1.60-4.03), followed by those in the ATD group, with an HR of 1.23 (95% CI 1.20-1.36). Patients in RIA group 1 were not at an increased risk of HF compared to their matched controls (HR 0.77; 95% CI 0.38-1.54). When patients in the ATD group were further classified by the duration of ATD treatment at one-year intervals, the risk of HF was higher in patients with longer ATD use (p for linear trend < 0.001).

Conclusions

In patients with long-standing hyperthyroidism treated with conventional duration of ATD therapy, the risk of HF was attenuated by RIA with remission of hyperthyroidism and increased as ATD was required for longer duration. To reduce the risk of HF, resolution of hyperthyroidism with RIA should be considered in patients with long-standing Graves' disease.

Thyroid Hormone Therapy and Incident Stroke

CONTEXT

Stroke is a leading cause of death and disability and there is a need to identify modifiable risk factors.

OBJECTIVE

We aimed to determine the relationship between thyroid hormone treatment intensity and incidence of atrial fibrillation and stroke.

METHODS

We conducted a retrospective cohort study using data from the Veterans Health Administration between 2004 and 2017, with a median follow-up of 59 months. The study population comprised 733 208 thyroid hormone users aged ≥18 years with at least 2 thyroid stimulating hormone (TSH) measurements between thyroid hormone initiation and incident event (atrial fibrillation or stroke) or study conclusion (406 030 thyroid hormone users with at least 2 free thyroxine [T4] measurements).

RESULTS

Overall, 71 333/643 687 (11.08%) participants developed incident atrial fibrillation and 41 931/663 809 (6.32%) stroke. In multivariable analyses controlling for pertinent factors such as age, sex, and prior history of atrial fibrillation, higher incidence of stroke was associated with low TSH or high free T4 levels (ie, exogenous hyperthyroidism; eg, TSH <0.1 mIU/L; OR 1.33; 95% CI, 1.24-1.43; free T4>1.9 ng/dL, OR 1.17, 95% CI 1.06-1.30) and high TSH or low free T4 levels (ie, exogenous hypothyroidism; eg, TSH >5.5 mIU/L; OR 1.29; 95% CI, 1.26-1.33; free T4 <0.7 ng/dL; OR 1.29; 95% CI, 1.22-1.35) compared with euthyroidism (TSH >0.5-5.5 mIU/L and free T4 0.7-1.9 ng/dL). Risk of developing atrial fibrillation and stroke was cumulative over time for both patients with exogenous hyperthyroidism and hypothyroidism.

CONCLUSION

Both exogenous hyper- and hypothyroidism were associated with increased risk of stroke, highlighting the importance of patient medication safety.

Molecular Biomarkers Associated with Early-Onset Symptomatic Intracranial Atherosclerosis

Purpose

Previous studies have shown a rising incidence of early-onset symptomatic intracranial atherosclerosis (sICAS), which has brought a severe economic burden to social development. This study aimed to evaluate the molecular biomarkers associated with early-onset sICAS and to seek possible intervention strategies for early prevention.

Patients and Methods

We consecutively recruited patients with sICAS and divided them into two groups based on age: early-onset sICAS group as age ≤60 years old and late-onset sICAS group as age >60 years old. We collected and compared the demographic data and laboratory results of each group. A bivariate logistic regression model was applied to evaluate the independent molecular biomarkers of early-onset sICAS.

Results

A total of 1007 subjects with sICAS were enrolled in this study, comprising 519 patients in the early-onset sICAS group and 488 patients in the late-onset sICAS group. Bivariate logistic regression analysis demonstrated an increased level of white blood cell, platelet, albumin globulin ratio, free triiodothyronine, and a decreased level of total bile acid, urea nitrogen, high-density lipoprotein, homocysteine, and fibrinogen in the early-onset sICAS group when compared to the late-onset group.

Conclusion

Our study showed the relevance between early sICAS and circulating levels of different molecular biomarkers. Detection of these related molecular biomarkers may provide a simple way for early sICAS preventions in the future.

Variation in Normal Range Thyroid Function Affects Serum Cholesterol Levels, Blood Pressure, and Type 2 Diabetes Risk: A Mendelian Randomization Study

Background: Observational studies have demonstrated that variation in normal range thyroid function is associated with major cardiovascular risk factors, including dyslipidemia, hypertension, type 2 diabetes (T2D), and obesity. As observational studies are prone to residual confounding, reverse causality, and selection bias, we used a Mendelian randomization (MR) approach to investigate whether these associations are causal or not. Methods: Two-sample MR analysis using data from the largest available genome-wide association studies on normal range thyrotropin (TSH) and free thyroxine (fT4) levels, serum lipid levels, blood pressure measurements, T2D, and obesity traits (body mass index [BMI] and waist/hip ratio). Results: A one standard deviation (SD) increase in genetically predicted TSH levels was associated with a 0.037 SD increase in total cholesterol levels (p = 3.0 × 10-4). After excluding pleiotropic instruments, we also observed significant associations between TSH levels and low-density lipoprotein levels (β = 0.026 SD, p = 1.9 × 10-3), pulse pressure (β = -0.477 mmHg, p = 7.5 × 10-10), and T2D risk (odds ratio = 0.95, p = 2.5 × 10-3). While we found no evidence of causal associations between TSH or fT4 levels and obesity traits, we found that a one SD increase in genetically predicted BMI was associated with a 0.075 SD decrease in fT4 levels (p = 3.6 × 10-4). Conclusions: Variation in normal range thyroid function affects serum cholesterol levels, blood pressure, and T2D risk.

Epigenome-Wide Association Study of Thyroid Function Traits Identifies Novel Associations of fT3 With KLF9 and DOT1L

CONTEXT

Circulating concentrations of free triiodothyronine (fT3), free thyroxine (fT4), and thyrotropin (TSH) are partly heritable traits. Recent studies have advanced knowledge of their genetic architecture. Epigenetic modifications, such as DNA methylation (DNAm), may be important in pituitary-thyroid axis regulation and action, but data are limited.

OBJECTIVE

To identify novel associations between fT3, fT4, and TSH and differentially methylated positions (DMPs) in the genome in subjects from 2 Australian cohorts.

METHOD

We performed an epigenome-wide association study (EWAS) of thyroid function parameters and DNAm using participants from: Brisbane Systems Genetics Study (median age 14.2 years, n = 563) and the Raine Study (median age 17.0 years, n = 863). Plasma fT3, fT4, and TSH were measured by immunoassay. DNAm levels in blood were assessed using Illumina HumanMethylation450 BeadChip arrays. Analyses employed generalized linear mixed models to test association between DNAm and thyroid function parameters. Data from the 2 cohorts were meta-analyzed.

RESULTS

We identified 2 DMPs with epigenome-wide significant (P < 2.4E-7) associations with TSH and 6 with fT3, including cg00049440 in KLF9 (P = 2.88E-10) and cg04173586 in DOT1L (P = 2.09E-16), both genes known to be induced by fT3. All DMPs had a positive association between DNAm and TSH and a negative association between DNAm and fT3. There were no DMPs significantly associated with fT4. We identified 23 differentially methylated regions associated with fT3, fT4, or TSH.

CONCLUSIONS

This study has demonstrated associations between blood-based DNAm and both fT3 and TSH. This may provide insight into mechanisms underlying thyroid hormone action and/or pituitary-thyroid axis function.

Thyroid Hormones within the Normal Range and Cardiac Function in the General Population: The EPIPorto Study

BACKGROUND

Hypothyroidism and hyperthyroidism are associated with marked changes in cardiac structure and function. However, the association of thyroid function within the normal range with cardiac structure and function in the general population remains uncertain.

METHODS

Eight hundred thirty-five subjects aged ≥45 years from the EPIPorto cohort (evaluation between 2006 and 2008) were cross-sectionally analyzed. We excluded participants with TSH, free T4 (FT4), or free T3 (FT3) outside of the reference range or with self-reported cardiovascular or thyroid disease. Cardiac structure and function were evaluated by echocardiography. We used linear regression models unadjusted and adjusted for sex and age (model 1), and sex, age, BMI, diabetes, hypertension, and smoking (model 2). Nonlinear associations were assessed using restricted cubic splines.

RESULTS

The mean age was 61.5 years (SD 10.5); 61.1% of the patients were women. In the adjusted model 2, heart rate was positively associated with FT3; diastolic blood pressure was positively associated with TSH; LV end-diastolic and end-systolic volumes were inversely associated with TSH, and ejection fraction was nonlinearly associated with FT3, with higher ejection fractions near the limits of the reference range. Left ventricle (LV) posterior wall thickness was nonlinearly associated with FT4 in the adjusted model 1, with a greater thickness near the limits of the reference range. Regarding diastolic function, no significant associations were observed in adjusted models.

CONCLUSIONS

Thyroid function within the reference range was associated with heart rate, blood pressure, cardiac structure, and function. Increasing thyroid function (lower TSH, higher FT4, or higher FT3) was associated with a higher heart rate, a lower diastolic blood pressure, and larger LV volumes. LV wall thickness and ejection fraction had a U-shaped association with thyroid hormones.

Predictive Value of Free Triiodothyronine to Free Thyroxine Ratio in Euthyroid Patients With Myocardial Infarction With Nonobstructive Coronary Arteries

BACKGROUND

Thyroid function is closely involved in cardiovascular diseases. The free triiodothyronine (fT3) to free thyroxine (fT4) ratio has been reported as a risk factor for coronary artery disease, but its prognostic value in euthyroid patients with myocardial infarction with nonobstructive coronary arteries (MINOCA) remains unclear.

METHODS

A total of 1162 euthyroid patients with MINOCA were enrolled and divided according to decreased tertiles of fT3/fT4 ratio. The study endpoint was major adverse cardiovascular events (MACE), including all-cause death, nonfatal MI, nonfatal stroke, revascularization, and hospitalization for unstable angina or heart failure. Kaplan-Meier, Cox regression, and receiver-operating characteristic analyses were performed.

RESULTS

Patients with lower fT3/fT4 tertile levels had a significantly higher incidence of MACE (10.0%, 13.9%, 18.2%; p=0.005) over the median follow-up of 41.7 months. The risk of MACE increased with the decreasing fT3/fT4 tertiles even after multivariate adjustment (tertile1 as reference, tertile2: HR 1.58, 95% CI: 1.05-2.39, p=0.030; tertile3: HR 2.06, 95% CI: 1.17-3.11, p=0.006). Lower level of fT3/fT4 ratio remained a robust predictor of MACE in overall (HR 1.64, 95% CI: 1.18-2.29, p=0.003) and in subgroups. When adding fT3/fT4 ratio [area under the curve (AUC) 0.61] into the thrombolysis in myocardial infarction (TIMI) risk score (AUC 0.69), the combined model (AUC 0.74) yielded a significant improvement in discrimination for MACE (ΔAUC 0.05, p=0.023).

CONCLUSIONS

Low level of fT3/fT4 ratio was strongly associated with a poor prognosis in euthyroid patients with MINOCA. Routine assessment of fT3/fT4 ratio may facilitate risk stratification in this specific population.

The Differential Effects of Propylthiouracil and Methimazole as Graves' Disease Treatment on Vascular Atherosclerosis Markers: A Randomized Clinical Trial

BACKGROUND

Hyperthyroidism is related to vascular atherosclerosis. Propylthiouracil (PTU) and methimazole, other than their antithyroid effects, may have different mechanisms in preventing atherogenesis in Graves' disease.

OBJECTIVE

This study aimed to investigate the effect of antithyroid drugs on markers of vascular atherosclerosis in Graves' hyperthyroidism.

METHODS

This study was a single-blind, randomized clinical trial conducted on 36 patients with Graves' disease in Cipto Mangunkusumo General Hospital, Jakarta, Indonesia, from June 2019 until July 2020. Graves' disease was diagnosed from clinical manifestation of hyperthyroidism with diffuse goiter and then confirmed by thyroid stimulation hormone (TSH), free T4 (fT4), and TSH-receptor antibody (TRAb) measurements. Participants were randomly assigned to either a PTU or a methimazole treatment group and followed up for 3 months. Markers of vascular atherosclerosis were represented by adhesion molecules [intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin], carotid artery stiffness [pulse wave velocity (PWV)], and thickness [carotid intima media thickness (cIMT)].

RESULTS

By the end of the study, 24 participants reached euthyroid condition (13 from the PTU group and 11 from the methimazole group). After 3 months of follow-up, in the PTU group, we noticed an improvement of ICAM-1 [pretreatment: 204.1 (61.3) vs. posttreatment: 141.6 (58.4) ng/ml; p = 0.001], VCAM-1 [837 (707-977) vs. 510 (402-630) ng/ml; p < 0.001] and E-selectin [32.1 (24.1-42.7) vs. 28.2 (21.6-36.8) ng/ml; p = 0.045] in the PTU group. In the methimazole group, only VCAM-1 improvement [725 (565-904) vs. 472 (367-590); p = 0.001] was observed. Meanwhile, we found no significant changes in PWV or cIMT in either group.

CONCLUSION

Antithyroid treatment in Graves' disease leads to improvement in adhesion molecules, with a lesser effect on methimazole, whereas there were no significant changes in PWV or cIMT. PTU may have a better mechanism compared with methimazole in terms of improving adhesion molecules.

The Association of Overt and Subclinical Hyperthyroidism with the Risk of Cardiovascular Events and Cardiovascular Mortality: Meta-Analysis and Systematic Review of Cohort Studies

BACKGROUND

Whether hyperthyroidism is an independent risk factor for cardiovascular events remains controversial. We aimed to evaluate the association of overt and subclinical hyperthyroidism with the risk of ischemic heart disease (IHD), stroke, heart failure, and cardiovascular mortality.

METHODS

Studies regarding the association between hyperthyroidism and cardiovascular events were searched on PubMed and Embase databases. The cardiovascular disease (CVD) risk was classified as high and low, based on pre-existing diseases, including history of coronary, cerebral, or peripheral artery disease; heart failure; atrial fibrillation; diabetes mellitus; or chronic kidney disease.

RESULTS

Thirty-seven cohort studies were included in this meta-analysis. The pooled hazard ratio for subjects with overt hyperthyroidism compared with the control group was 1.11 (95% confidence interval [CI], 1.03 to 1.19) for IHD, 1.35 (95% CI, 1.03 to 1.75) for stroke, and 1.20 (95% CI, 1.00 to 1.46) for cardiovascular mortality. For subjects with subclinical hyperthyroidism, the pooled hazard ratio was 1.24 (95% CI, 1.07 to 1.45) for IHD, when compared with the control group. Subgroup analysis by CVD risk showed that the risk of stroke in overt hyperthyroidism was increased in the low CVD risk group; however, these association was not observed in the high CVD risk group. Similarly, the risk of IHD in subjects with subclinical hyperthyroidism was significantly increased in the low CVD risk group.

CONCLUSION

Overt hyperthyroidism is associated with increased risk of IHD, stroke, and cardiovascular mortality, and subclinical hyperthyroidism is associated with increased risk of IHD. These associations were particularly observed in the low risk CVD group without underlying CVD.

Magnesium Sulfate Improves Some Risk Factors for Atherosclerosis in Patients Suffering from One or Two Coronary Artery Diseases: A Double-blind Clinical Trial Study

Purpose

Given the beneficial effect of MgSO₄ on the cardiovascular system, this study was designed to investigate the effect of MgSO₄ administration on suppressing some atherosclerotic risk factors in moderate coronary artery disease patients with one or two atherosclerotic vessels.

Patients and Methods

In a randomized double-blind placebo-controlled clinical trial study, 64 patients with moderate coronary artery disease (55–69% stenosis) were selected according to angiography findings. Patients were divided into four groups including patients with one or two atherosclerotic vessels treated with MgSO₄ (Mg-treated-VR1, Mg-treated-VR2, respectively), placebo treated patients with one or two atherosclerotic vessels (Control-VR1, Control-VR2, respectively). The patients received either placebo or MgSO₄ supplement capsule containing 300 mg MgSO₄ for six months on a daily basis. ESR, Ca/Mg ratio, urine Mg level, serum Mg, fibrinogen, homocysteine, uric acid, Na, K, Ca, CRP, T3, T4, TSH, BUN, and Cr concentrations were measured at baseline and every three months.

Results

Serum T3, Ca, K, homocysteine, CRP, and Mg concentrations were significantly improved in Mg-treated groups compared to placebo groups.

Conclusion

The results of this study showed that despite the slight change in serum magnesium level, oral administration of MgSO₄for six months could slightly reduce the serum levels of some inflammatory and vascular factors in moderate coronary artery disease patients.

Insulin‑receptor substrate 1 protects against injury in endothelial cell models of ox‑LDL‑induced atherosclerosis by inhibiting ER stress/oxidative stress‑mediated apoptosis and activating the Akt/FoxO1 signaling pathway

Oxidized low‑density lipoprotein (ox‑LDL)‑induced endothelial cell (EC) injury is a risk factor for atherosclerosis. Therefore, the present study aimed to investigate the effects of insulin‑receptor substrate 1 (IRS‑1) on injury to ox‑LDL‑exposed ECs. For this purpose, thoracic aorta tissues were isolated from rats and cultured to obtain ECs, which were then identified using immunohistochemical staining. IRS‑1 overexpression plasmid (pcDNA3.1‑IRS‑1) and IRS‑1‑small interfering RNA were synthesized and transfected into ECs pre‑exposed to ox‑LDL. MTT and TUNEL assays were performed to evaluate the cell proliferative activity and apoptosis. Intracellular reactive oxygen species (ROS) production was determined by a flow cytometry assay. Reverse transcription‑quantitative PCR was conducted to measure the peroxisome proliferator‑activated receptor gamma co‑activator 1 alpha (Ppargcla), phosphoenolpyruvate carboxykinase 1 (Pck1) and glucose‑6‑phosphatase catalytic subunit (G6pc) gene transcription levels. Western blot analysis was then performed to determine the IRS‑1, forkhead box O1 (FoxO1), phosphorylated (p‑)FoxO1, 78‑kDa glucose‑regulated protein (GRP78), p‑eukaryotic translation initiation factor 2A (eIF2α), CHOP, Akt and p‑Akt expression levels. Immunofluorescence staining was used to evaluate p‑FoxO1 nuclear localization. The results indicated that IRS‑1 significantly enhanced the proliferative activity, whereas it inhibited the apoptosis of ECs in a model of ox‑LDL‑induced atherosclerosis compared with ECs without IRS‑1 treatment (P<0.05). IRS‑1 significantly decreased the p‑FoxO1/FoxO1 ratio compared with ECs without ox‑LDL treatment (P<0.05). IRS‑1 significantly downregulated the expression of ER stress biomarkers, including GRP78, CHOP and the p‑eIF2α/eIF2α ratio in ox‑LDL‑exposed ECs compared with ECs without ISR‑1 treatment (P<0.05). IRS‑1 significantly reduced the intracellular ROS levels in the EC models of ox‑LDL‑induced atherosclerosis compared with ECs without IRS‑1 treatment (P<0.05). Moreover, IRS‑1 promoted the phosphorylation of Akt in the EC models of ox‑LDL‑induced atherosclerosis. IRS‑1 also significantly suppressed the transcription of atherosclerosis‑associated genes in ox‑LDL‑exposed ECs compared with ECs without IRS‑1 treatment (P<0.05). Furthermore, IRS‑1 significantly increased the cytoplasmic localization of p‑FoxO1 in EC models of ox‑LDL‑induced atherosclerosis. On the whole, the findings of the present study demonstrate that IRS‑1 exerts protective effects in an EC model of ox‑LDL‑induced atherosclerosis by inhibiting ER stress/oxidative stress‑mediated apoptosis and activating the Akt/FoxO1 signaling pathway.

Thyroid Function Affects the Risk of Stroke via Atrial Fibrillation: A Mendelian Randomization Study

CONTEXT

Observational studies suggest that variations in normal range thyroid function are associated with cardiovascular diseases. However, it remains to be determined whether these associations are causal or not.

OBJECTIVE

To test whether genetically determined variation in normal range thyroid function is causally associated with the risk of stroke and coronary artery disease (CAD) and investigate via which pathways these relations may be mediated.

DESIGN, SETTING, AND PARTICIPANTS

Mendelian randomization analyses for stroke and CAD using genetic instruments associated with normal range thyrotropin (TSH) and free thyroxine levels or Hashimoto's thyroiditis and Graves' disease. The potential mediating role of known stroke and CAD risk factors was examined. Publicly available summary statistics data were used.

MAIN OUTCOME MEASURES

Stroke or CAD risk per genetically predicted increase in TSH or FT4 levels.

RESULTS

A 1 standard deviation increase in TSH was associated with a 5% decrease in the risk of stroke (odds ratio [OR], 0.95; 95% confidence interval [CI], 0.91-0.99; P = 0.008). Multivariable MR analyses indicated that this effect is mainly mediated via atrial fibrillation. MR analyses did not show a causal association between normal range thyroid function and CAD. Secondary analyses showed a causal relationship between Hashimoto's thyroiditis and a 7% increased risk of CAD (OR, 1.07; 95% CI, 1.01-1.13; P = 0.026), which was mainly mediated via body mass index.

CONCLUSION

These results provide important new insights into the causal relationships and mediating pathways between thyroid function, stroke, and CAD. We identify variation in normal range thyroid function and Hashimoto's thyroiditis as risk factors for stroke and CAD, respectively.

Incidence and Mortality of Myocardial Infarction and Stroke in Patients with Hyperthyroidism: A Nationwide Cohort Study in Korea

Background: Hyperthyroidism is associated with various cardiovascular risk factors. However, the relationship between hyperthyroidism and myocardial infarction (MI) or stroke has not been fully elucidated; only a few studies have investigated the association of hyperthyroidism with survival after MI or stroke. Methods: We included 59,021 hyperthyroid patients and a control cohort with 1,180,420 age- and sex-matched subjects from the Korean National Health Insurance database. Blood pressure, body mass index (BMI), glucose and cholesterol levels, and smoking history were obtained during National Health screening examination. We compared the incidence of MI, stroke, and survival after cardiovascular events between subjects with hyperthyroidism and the control cohort. Results: Subjects with hyperthyroidism had higher blood pressure, fasting glucose, and smoking rate, but lower cholesterol levels and a lower obesity rate compared with the control cohort. After adjusting these differences, as well as atrial fibrillation, hyperthyroidism was associated with increased risk of MI and ischemic stroke. Adjusted hazard ratios (HRs) for MI and ischemic stroke with hyperthyroidism was 1.16 [95% confidence interval, CI 1.03-1.30] and 1.12 [CI 1.04-1.20], respectively. In age-, sex-, and BMI-stratified analyses, an increased risk of MI and ischemic stroke remained significant in females, the older age group (≥50 years), and nonobese subjects (BMI <25 kg/m²), but not in males, the younger age group (<50 years), and obese subjects (BMI ≥25 kg/m²). The risk of hemorrhagic stroke was not different between subjects with hyperthyroidism and controls. Adjusted HRs for mortality in subjects with hyperthyroidism who developed MI, ischemic stroke, and hemorrhagic stroke were 1.11 ([CI 0.86-1.43], p = 0.44), 0.89 ([CI 0.75-1.05], p = 0.16), and 1.13 ([CI 0.88-1.47], p = 0.34), respectively. Conclusions: Hyperthyroidism is associated with increased risk of MI and ischemic stroke, independent of cardiovascular risk factors. This association is prominent in subjects with age ≥50 years, in females, and in the nonobese group. Hyperthyroidism did not significantly affect the mortality secondary to cardiovascular events.

TAK1-AMPK Pathway in Macrophages Regulates Hypothyroid Atherosclerosis

PURPOSE

Hypothyroidism (HT) is associated with accelerated atherosclerosis (AS). The efficacy of traditional strategies of hypothyroid AS remains controversial. Here, we aimed to deepen the understanding of the HT-induced acceleration of AS, to decrease the residual risk of coronary artery disease (CAD) and to find a new therapeutic target.

METHODS

We collected peripheral venous blood samples from 20 patients and divided them into 4 groups, namely, the normal group, the HT group, the CAD group and the HT + CAD group. Then we performed mRNA microarray analysis and bioinformatics analysis to screen the differentially expressed genes and pathways, and we also conducted validations on ApoE knockout mice models and Raw264.7 cell models.

RESULTS

In short, (1) in the analysis between the CAD group and the HT + CAD group, we found a total of 1218 differentially expressed genes, 11 upregulated pathways and 40 downregulated pathways. (2) We validated that patients with HT and CAD had a significantly decreased expression of MAP3K7 (encoding transforming growth factor-β-activated kinase 1, TAK1) gene than normal subjects. (3) In animal and cell experiments, we found the decreased expression of TAK1 and the reduced phosphorylation of AMP-activated protein kinase (AMPK) under the hypothyroid and atherosclerotic condition. (4) Changes in the expressions of TAK1 may affect the progression of AS.

CONCLUSION

Taken together, these data suggest that the accelerated AS in hypothyroid patients may be due to the suppression of TAK1-AMPK pathway in macrophages. This new finding may become a novel therapeutic target in hypothyroid AS.

The Genetic Basis of Thyroid Function: Novel Findings and New Approaches

CONTEXT

Genetic factors are major determinants of thyroid function. Over the last two decades, multiple genetic variants have been associated with variations in normal range thyroid function tests. Most recently, a large-scale genome-wide association study (GWAS) doubled the number of known variants associated with normal range thyrotropin (TSH) and free thyroxine (FT4) levels.

EVIDENCE ACQUISITION

This review summarizes the results of genetic association studies on normal range thyroid function and explores how these genetic variants can be used in future studies to improve our understanding of thyroid hormone regulation and disease.

EVIDENCE SYNTHESIS

Serum TSH and FT4 levels are determined by multiple genetic variants on virtually all levels of the hypothalamus-pituitary-thyroid (HPT) axis. Functional follow-up studies on top of GWAS hits has the potential to discover new key players in thyroid hormone regulation, as exemplified by the identification of the thyroid hormone transporter SLC17A4 and the metabolizing enzyme AADAT. Translational studies may use these genetic variants to investigate causal associations between thyroid function and various outcomes in Mendelian Randomization (MR) studies, to identify individuals with an increased risk of thyroid dysfunction, and to predict the individual HPT axis setpoint.

CONCLUSIONS

Recent genetic studies have greatly improved our understanding of the genetic basis of thyroid function, and have revealed novel pathways involved in its regulation. In addition, these findings have paved the way for various lines of research that can improve our understanding of thyroid hormone regulation and thyroid diseases, as well as the potential use of these markers in future clinical practice.

Objectives, design and main findings until 2020 from the Rotterdam Study

The Rotterdam Study is an ongoing prospective cohort study that started in 1990 in the city of Rotterdam, The Netherlands. The study aims to unravel etiology, preclinical course, natural history and potential targets for intervention for chronic diseases in mid-life and late-life. The study focuses on cardiovascular, endocrine, hepatic, neurological, ophthalmic, psychiatric, dermatological, otolaryngological, locomotor, and respiratory diseases. As of 2008, 14,926 subjects aged 45 years or over comprise the Rotterdam Study cohort. Since 2016, the cohort is being expanded by persons aged 40 years and over. The findings of the Rotterdam Study have been presented in over 1700 research articles and reports. This article provides an update on the rationale and design of the study. It also presents a summary of the major findings from the preceding 3 years and outlines developments for the coming period.

Clinical Associations of Thyroid Hormone Levels with the Risk of Atherosclerosis in Euthyroid Type 2 Diabetic Patients in Central China

BACKGROUND

Thyroid function is associated with the etiology and pathogenesis of type 2 diabetes (T2D) and potentially contributes to the development of the complications of T2D. The association of thyroid hormones with atherosclerosis in euthyroid T2D patients is not clear.

PURPOSE

To investigate the association of thyroid hormone levels with the risk of developing atherosclerosis in euthyroid T2D patients in Central China.

METHODS

This cross-sectional study recruited 910 euthyroid T2D patients from Henan Provincial People's Hospital, China. Association among hemoglobin A1c (HbA1c), thyroid hormones, and the prevalence of atherosclerosis was assessed by multivariable Cox models after adjusting for covariates including age, BMI, duration of T2D, smoking status, SBP, TC, family history of T2D, and medications on hyperlipidemia.

RESULTS

Among all 910 subjects, 373 were diagnosed with atherosclerosis. There were 523 females and 387 males included in this study. The mean age was 51.9 years. The average BMI was 25.3 kg/m². Low-normal serum-free triiodothyronine (FT3) levels (3.50-4.17 pmol/L) were associated with a high prevalence of atherosclerosis. Comparing with low-normal FT3, the prevalence ratio in patients with mid- (4.17-4.83 pmol/L) and high-normal FT3 level (4.83-6.50 pmol/L) is 0.74 (95% CI 0.56 to 0.97, p=0.029) and 0.63 (95% CI 0.46 to 0.87, p=0.005) after adjusting for covariates. High level of free thyroxine (FT4) also had decreased risk for atherosclerosis. Thyroid-stimulating hormone (TSH) and FT3 to FT4 ratio did not show significant association with the development of atherosclerosis.

CONCLUSION

T2D patients with low but clinically normal FT3 level are more likely to develop macrovascular complications comparing with those with mid- and high-normal FT3 level.

Thyroxine Alleviates Energy Failure, Prevents Myocardial Cell Apoptosis, and Protects against Doxorubicin-Induced Cardiac Injury and Cardiac Dysfunction via the LKB1/AMPK/mTOR Axis in Mice

Background

Previous studies have demonstrated that energy failure is closely associated with cardiac injury. Doxorubicin (DOX) is a commonly used clinical chemotherapy drug that can mediate cardiac injury through a variety of mechanisms. Thyroxine is well known to play a critical role in energy generation; thus, this study is aimed at investigating whether thyroxine can attenuate DOX-induced cardiac injury by regulating energy generation.

Methods

First, the effect of DOX on adenosine diphosphate (ADP) and adenosine triphosphate (ATP) ratios in mice was assessed. In addition, thyroxine was given to mice before they were treated with DOX to investigate the effects of thyroxine on DOX-induced cardiac injury. Furthermore, to determine whether the liver kinase b1 (LKB1)/adenosine 5′-monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) axis mediated the effect of thyroxine on DOX-induced cardiac injury, thyroxine was given to DOX-treated LKB1 knockout (KO) mice.

Results

DOX treatment time- and dose-dependently increased the ADP/ATP ratio. Thyroxine treatment also reduced lactate dehydrogenase (LDH) and creatine kinase myocardial band (CK-MB) levels in both serum and heart tissue and alleviated cardiac dysfunction in DOX-treated mice. Furthermore, thyroxine reversed DOX-induced reductions in LKB1 and AMPK phosphorylation; mitochondrial complex I, III, and IV activity; and mitochondrial swelling and reversed DOX-induced increases in mTOR pathway phosphorylation and myocardial cell apoptosis. These effects of thyroxine on DOX-treated mice were significantly attenuated by LKB1 KO.

Conclusions

Thyroxine alleviates energy failure, reduces myocardial cell apoptosis, and protects against DOX-induced cardiac injury via the LKB1/AMPK/mTOR axis in mice. Thyroxine may be a new agent for the clinical prevention of cardiac injury in tumor patients undergoing chemotherapy with DOX.