Thyroid Function Within the Normal Range, Subclinical Hypothyroidism, and the Risk of Atrial Fibrillation

Association of Serum Thyroxine and Atrial Fibrillation in Patients on Levothyroxine

INTRODUCTION

Excess thyroid hormone is a well-documented risk factor for the development of atrial fibrillation (AF). The purpose of the study is to assess incidence of AF in patients taking levothyroxine for hypothyroidism and correlate it with biochemical thyroid function.

MATERIALS AND METHODS

This was a retrospective cohort study of patients aged 18 years and older who were treated with levothyroxine. Exclusion criteria were pre-existing diagnosis of AF and use of amiodarone in the prior year. Patients were followed 2012 through 2019 and stratified into 4 groups based on mean thyroid-stimulating hormone (TSH) value or mean fT4 value in 2012. Primary outcome was incidence of AF. Rates of AF between groups were assessed via Poisson regression with control of underlying confounders.

RESULTS

Of 21,035 patients, 1091 (5.2%) developed AF during follow-up. Thyroid-stimulating hormone at baseline was not significantly associated with incident AF. Higher fT4 levels at baseline were associated with increased AF risk in age- and sex-adjusted analyses (hazard ratio 1.22; 95% CI, 1.03-1.44) for the highest quartile versus the lowest quartile of fT4.

CONCLUSIONS

In hypothyroid patients treated with levothyroxine, higher circulating fT4 levels are associated with increased risk of incident AF. There is no association of serum TSH with risk of AF. In patients at risk for AF, consideration should be given to avoiding fT4 levels in the highest quartile.

Serum protein profiling reveals mechanism of activated thrombus formation in patients with stroke and atrial fibrillation

Stroke is an acute cerebrovascular disease in which blood flow to the brain is suddenly disrupted, causing damage to nerve cells. It involves complex and diverse pathophysiological processes and the treatment strategies are also diverse. The treatment for patients with stroke and atrial fibrillation (AF) is aimed at suppressing thrombus formation and migration. However, information regarding the protein networking involved in different thrombus formation pathways in patients with AF and stroke is insufficient. We performed protein profiling of patients with ischemic stroke with and without AF to investigate the mechanisms of thrombus formation and its pathophysiological association while providing helpful information for treating and managing patients with AF. These two groups were compared to identify the protein networks related to thrombus formation in AF. We observed that patients with ischemic stroke and AF had activated inflammatory responses induced by C-reactive protein, lipopolysaccharide-binding protein, and alpha-1-acid glycoprotein 1. In contrast, thyroid hormones were increased due to a decrease in transthyretin and retinol-binding protein 4 levels. The mechanism underlying enhanced cardiac activity, vasodilation, and the resulting thrombosis pathway were confirmed in AF. These findings will play an essential role in improving the prevention and treatment of AF-related stroke.

Effect of Radioiodine Treatment on Quality of Life in Patients with Subclinical Hyperthyroidism: A Prospective Controlled Study

Radioiodine treatment (RIT) has a high success rate in both the treatment of hyperthyroidism and improving the quality of life (QoL) of symptomatic patients. In asymptomatic patients with subclinical hyperthyroidism thyroid related QoL outcomes are less well known.

METHODS

Study aim was to evaluate thyroid-related QoL in patients with subclinical hyperthyroidism mostly due to toxic nodular goitre undergoing RIT, compared to a control group of euthyroid subjects. Study design was monocentric, prospective, controlled. Fifty control subjects were enrolled and 51 RIT patients. Most subjects were examined at least twice at an interval of 6 months, with visits immediately before and 6 months after treatment in the RIT group. QoL was estimated with the ThyPRO questionnaire, using its composite scale as primary outcome. Treatment effect was the mean adjusted difference (MAD) between groups over time, using repeated? measures mixed? effects models.

RESULTS

TSH concentrations were lower in the RIT group prior to treatment and recovered thereafter slightly above the level of the control group. Correspondingly, QoL improved significantly after 6 months from a worse level in the RIT group, compared to controls (MAD -10.3 [95% CI -14.9, -5.7], p<0.001). QoL improvements were strong for general items, but less pronounced for the hyperthyroid domain. Compared to controls, thyroid volume, thyroid functional capacity (SPINA-GT) and deiodinase activity (SPINA-GD) were significantly reduced in the RIT group.

CONCLUSION

Patients with subclinical hyperthyroidism improve both biochemically and in their QoL after RIT, compared to controls. QoL assessment should have a wider role in clinical practice to complement biochemical tests and help with treatment decisions.

Long-term Effect of Thyrotropin-binding Inhibitor Immunoglobulin on Atrial Fibrillation in Euthyroid Patients

OBJECTIVE

Individuals with hyperthyroidism are at an increased risk of atrial fibrillation (AF), but the association between autoantibodies and AF or cardiovascular mortality in individuals who have returned to normal thyroid function remains unclear.

METHODS

The study utilized electronic medical records from National Taiwan University Hospital between 2000 and 2022. Each hyperthyroidism patient had at least 1 thyrotropin-binding inhibiting immunoglobulin (TBII) measurement. The relationship between TBII levels and the risk of AF and cardiovascular mortality was assessed using multivariable Cox regression models and Kaplan-Meier survival analysis.

RESULTS

Among the 14 618 enrolled patients over a 20-year timeframe, 173 individuals developed AF, while 46 experienced cardiovascular mortality. TBII values exceeding 35% were significantly associated with an elevated risk of AF for both the first TBII (hazard ratio {HR} 1.48 [1.05-2.08], P = .027) and mean TBII (HR 1.91 [1.37-2.65], P < .001). Furthermore, after free T4 levels had normalized, a borderline association between first TBII and AF (HR 1.59 [0.99-2.56], P = .056) was observed, while higher mean TBII increased AF (HR 1.78 [1.11-2.85], P = .017). Higher first and mean TBII burden continued to significantly impact the incidence of cardiovascular mortality (HR 6.73 [1.42-31.82], P = .016; 7.87 [1.66-37.20], P = .009). Kaplan-Meier analysis demonstrated that elevated TBII levels increased the risk of AF and cardiac mortality (log-rank P = .035 and .027, respectively).

CONCLUSION

In euthyroid individuals following antithyroid treatment, elevated circulating TBII levels and burden are associated with an elevated risk of long-term incident AF and cardiovascular mortality. Further reduction of TBII level below 35% will benefit to clinical outcomes.

Thyroid function effect on cardiac structure, cardiac function, and disease risk: Evidence of causal associations in European ancestry

BACKGROUND

Thyroid hormones play a crucial role in cardiovascular physiology. Subclinical thyroid dysfunction has been associated with adverse cardiovascular outcomes, but evidence is mixed regarding causality.

OBJECTIVE

The purpose of this study was to investigate the potential causal relationships of thyroid-stimulating hormone (TSH), free thyroxine, hypothyroidism, and hyperthyroidism with cardiovascular outcomes, including atrial fibrillation (AF), coronary artery disease, myocardial infarction, heart failure, and ischemic stroke, as well as their effect on cardiac structure and function assessed by cardiac magnetic resonance imaging.

METHODS

A comprehensive 2-sample Mendelian randomization analysis was performed using summary data from large-scale meta-analyses of European ancestry individuals.

RESULTS

Genetically determined lower TSH levels (odds ratio 0.928; 95% confidence interval 0.884-0.974; P = .003) and genetic risk of hyperthyroidism (odds ratio 1.049; 95% confidence interval 1.016-1.083; P = .003) were associated with increased AF risk. These associations remained significant even after adjusting for cardiovascular risk factors. Colocalization and multivariable Mendelian randomization revealed height as a key mediator between TSH/hyperthyroidism and AF. These findings were further corroborated in the independent FinnGen cohort. However, no clear evidence was found for relationships between thyroid function and other cardiovascular outcomes and cardiac structure and function.

CONCLUSION

Our study shows that reduced TSH levels and hyperthyroidism heighten AF risk, with height serving as an important mediator in these associations. The primary focus of thyroid management in cardiovascular health should be on preventing and treating arrhythmias, particularly AF. Our research highlights the importance of routine screening and timely treatment of thyroid dysfunction to optimize the prevention and management of arrhythmias.

Subclinical Hypothyroidism Predicted Adverse Cardiovascular Events in Patients with Ejection Fraction Preserved Heart Failure

Background

Subclinical hypothyroidism (SH) increases the risk of cardiovascular events, however the influence of SH on prognosis of ejection fraction preserved heart failure (HFpEF) is not fully understood.

Methods

In this prospective observational study, patients with HFpEF were divided into euthyroidism group (n = 413) and SH group (n = 79). Patients were followed up for at least 30 months to examine the association between SH and cardiovascular events in patients with HFpEF. The primary end point was composite cardiovascular events (cardiovascular death and re-hospitalization). The patients underwent flow-mediated dilation (FMD) measurement by ultrasound in order to value endothelial function.

Results

The rate of composite cardiovascular events was higher in SH group than in euthyroidism group (54.49% and 26.36%, respectively; p < 0.001). The higher risk of cardiovascular events in SH group was primarily due to a higher risk of re-hospitalization compared to euthyroidism group (45.56% and 20.58%, respectively; p < 0.001). The rate of cardiovascular death was higher in SH group than in euthyroidism group (13.92% and 5.81%, respectively; p = 0.017). Cox proportional hazards regression showed that SH (hazard ratios [HR] 1.921, 95% confidence interval [CI] 1.139-3.240), level of TSH (HR 1.025, 95% CI 1.010-1.054), age (HR 1.017, 95% CI 1.002-1.034), LVEF (HR 0.975, 95% CI 0.953-0.996), atrial fibrillation (HR 1.581, 95% CI 1.083-2.307), eGFR (HR 0.987, 95% CI 0.978-0.997), and NYHA cardiac function (HR 2.342, 95% CI 1.649-3.326) were independent predictors of cardiovascular events in patients with HFpEF (all P < 0.05).

Conclusion

Subclinical hypothyroidism was associated with increased cardiovascular events and death in patients with HFpEF.

Thyroid cancer and cardiovascular diseases: a Mendelian randomization study

Background

Multiple observational studies have shown associations between thyroid cancer (TC) and cardiovascular diseases (CVDs). However, the results were inconsistent, and the potential causal genetic relationship remains unclear.

Methods

The genetic instruments of TC and CVDs were derived from data obtained through genome-wide association studies (GWAS). We performed the two-sample Mendelian randomization(MR) methods to investigate the causality of TC on CVDs. Summary-level statistics for CVDs, including heart failure (HF), atrial fibrillation (AF), coronary artery disease (CAD), myocardial infarction (MI), ischemic stroke (IS) and venous thromboembolism (VTE). The primary method employed in this MR analysis was the Inverse Variance Weighted (IVW) approach, and four additional algorithms were used: MR-Egger, weighted median, simple mode, and weighted mode. Additionally, we assessed the reliability of the causal relationship through pleiotropy, heterogeneity and leave-one-out sensitivity analysis.

Results

In this MR analysis, we only detected causality of genetically predicted TC on HF (IVW method, odds ratio (OR) = 1.00134, 95% confidence interval (CI): 1.00023-1.00244, p = 0.017). However, There were no causal associations of TC with CAD, MI, AF, IS, and VTE.

Conclusion

Our results confirmed the causal association between TC and HF. It is crucial to closely monitor the incidence of HF in TC patients and give comprehensive clinical intervention based on conventional treatment.

Thyroid dysfunction in nonvalvular atrial fibrillation and clinical outcomes

BACKGROUND

Thyroid dysfunction's effects on those who have been diagnosed with atrial fibrillation have not been well investigated. We looked at how thyroid function among patients with pre-existing atrial fibrillation related to thromboembolic risk and clinical outcomes.

METHODS

We gathered the medical information of patients diagnosed with nonvalvular atrial fibrillation (NVAF) between 2016 and 2020 at Dongguan People's Hospital. We then assessed the correlation between thyroid dysfunction and thrombotic risk (CHA2DS2-VASc) as well as the occurrence of clinical composite endpoint (all-cause death, heart failure, systemic embolism and hemorrhage events).

RESULTS

Of 1329 patients were admitted, 82.6% were euthyroid, 7.4% had subclinical hyperthyroidism, 4.2% had subclinical hypothyroidism, and 6.7% had low triiodothyronine (T3) syndrome. Lower levels of total triiodothyronine (TT3) were linked to an increased risk of thromboembolism (P < 0.005). During a median follow-up period of 1.84 years, there were 608 clinical composite endpoint occurrences. In the adjusted model, Low T3 syndrome was linked to a higher risk of the clinical composite endpoint (HR, 1.68; 95% CI, 1.20-2.37; P < 0.05) in comparison to euthyroidism. Specifically, low T3 syndrome was linked to a higher risk of heart failure (HR, 1.52; 95%CI, 1.01-2.30; P < 0.05) and all-cause death (HR, 3.34; 95% CI, 1.76-6.36; P < 0.001).

CONCLUSION

Low T3 syndrome are linked to an increased risk of heart failure and all-cause death in individuals with NVAF. And Patients with NVAF and low TT3 levels have a higher risk of thromboembolism.

Subclinical hypothyroidism and clinical outcomes after cardiac surgery: A systematic review and meta-analysis

Background

Subclinical hypothyroidism (SCH) is associated with major adverse cardiovascular events. Despite the recognized negative impact of SCH on cardiovascular health, research on cardiac postoperative outcomes with SCH has yielded conflicting results, and patients are not currently treated for SCH before cardiac surgery procedures.

Methods

We performed a study-level meta-analysis on the impact of SCH on patients undergoing nonurgent cardiac surgery, including coronary artery bypass grafting and valve and aortic surgery. The primary outcome was operative mortality. Secondary outcomes were hospital length of stay (LOS), intensive care unit (ICU) stay, postoperative atrial fibrillation (POAF), intra-aortic balloon pump (IABP) use, renal complications, and long-term all-cause mortality.

Results

Seven observational studies, with a total of 3445 patients, including 851 [24.7%] diagnosed with SCH and 2594 [75.3%] euthyroid patients) were identified. Compared to euthyroid patients, the patients with SCH had higher rates of operative mortality (odds ratio [OR], 2.57; 95% confidence interval [CI], 1.09-6.04; P = .03), prolonged hospital LOS (standardized mean difference, 0.32; 95% CI, 0.02-0.62; P = .04), a higher rate of renal complications (OR, 2.53; 95% CI, 1.74-3.69; P < .0001), but no significant differences in ICU stay, POAF, or IABP use. At mean follow-up of 49.3 months, the presence of SCH was associated with a higher rate of all-cause mortality (incidence rate ratio, 1.82; 95% CI, 1.18-2.83; P = .02).

Conclusions

Patients with SCH have higher operative mortality, prolonged hospital LOS, and increased renal complications after cardiac surgery. Achieving and maintaining a euthyroid state prior to and after cardiac surgery procedures might improve outcomes in these patients.

Epidemiology, prognosis, and challenges in the management of hyperthyroidism-related atrial fibrillation

Atrial fibrillation (AF) is a common condition with a global estimated prevalence of 60 million cases, and the most common cardiac complication of hyperthyroidism, occurring in 5-15% of overtly hyperthyroid patients. Additionally, subclinical hyperthyroidism and high-normal free T4 have been associated with an increased risk in the development of AF. Hyperthyroidism-related AF is a reversible cause of AF, and the majority of patients spontaneously revert to sinus rhythm in 4-6 months during or after restoration of euthyroidism. Therefore, restoring thyroid function is an indispensable element in hyperthyroidism-related AF management. Rate control with beta-blockers consists another first-line therapy, reserving rhythm control in cases of persistent hyperthyroidism-related AF. It is still controversial whether hyperthyroidism is an independent risk factor of stroke in nonvalvular AF. As a result, initiating anticoagulation should be guided by the clinical thromboembolic risk score CHA2DS2-VASc score in the same way it is applied in patients with non-hyperthyroidism-related AF. Treatment with the novel direct oral anticoagulants appears to be as beneficial and may be safer than warfarin in patients with hyperthyroidism-related AF. In this review, we address the epidemiology, prognosis, and diagnosis of hyperthyroidism-related AF, and we discuss the management strategies and controversies in patients with hyperthyroidism-related AF.

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.

Association between the oxidative balance score and thyroid function: Results from the NHANES 2007-2012 and Mendelian randomization study

BACKGROUND

Oxidative stress is a significant contributor to the development of various diseases, and the oxidative balance score (OBS) is a valuable tool for assessing the impact of dietary and lifestyle factors on oxidative stress in humans. Nevertheless, the precise relationship between OBS and thyroid function in adults remains elusive.

METHODS

This cross-sectional study comprised 6222 adult participants drawn from the National Health and Nutrition Examination Survey (NHANES) conducted from 2007 to 2012. Employing weighted multivariable linear regression modeling, the study estimated the connection between OBS quartiles and thyroid functions. The causal relationship between OBS components and thyroid function was analyzed by Mendelian randomization (MR).

RESULTS

We found a significant negative correlation between OBS and free thyroxine (FT4) and total thyroxine (TT4). Univariate and multivariate MR Analyses showed a causal relationship between BMI and FT4. Copper, smoking, and riboflavin showed a causal relationship with FT4 after moderation.

CONCLUSION

We found that a lifestyle high in antioxidant exposure reduced FT4 and TT4 levels in the population. We suggest that BMI, Copper, and Riboflavin are important factors in the regulation of FT4 levels.

Thyroid dysfunction and mortality in cardiovascular hospitalized patients

Background

Thyroid dysfunction (TD) is associated with increased cardiovascular morbidity and mortality. Early detection may influence the clinical management.

Objective

To determine the prevalence, predictors, and prognostic value of TD among hospitalized cardiac patients.

Methods

A retrospective analysis of a 12-year database consisting of nonselectively adult patients admitted to a Cardiology Department and who were all screened for serum thyroid-stimulation-hormone (TSH) levels . Statistical analysis of demographic and clinical characteristics, mortality and length of hospital stay (LOS) was performed.

Results

A total of 14369 patients were included in the study; mean age was 67 years, 38.3% females. 1465 patients (10.2%) had TD. The most frequent type of TD was mildly elevated TSH (5.4%) followed by mildly reduced TSH (2.1%), markedly elevated TSH (1.5%), and markedly reduced TSH (1.2%). Female gender, history of hypothyroidism, heart failure, atrial fibrillation, renal failure and amiodarone use were significantly associated with TD. During follow-up 2975 (20.7%) patients died. There was increased mortality in the mildly reduced TSH subgroup (hazard ratio [HR] =1.44), markedly elevated TSH subgroup (HR=1.40) and mildly elevated TSH subgroup (HR=1.27). LOS was longer for patients with TD; the longest stay was observed in the markedly elevated TSH subgroup (odds ratio=1.69).

Conclusion

The prevalence of TD in hospitalized cardiac patients is 10.2%. TD is associated with an increased mortality rate and LOS. Consequently, routine screening for thyroid function in this population is advisable, particularly for selected high-risk subgroups. Future studies are needed to determine whether optimizing thyroid function can improve survival in these patients.

Low-normal free triiodothyronine as a predictor of post-operative atrial fibrillation after surgical coronary revascularization

Background

Recent studies have focused on the association between thyroid function within normal range and cardiovascular diseases, especially on free triiodothyronine (FT3) levels. This study aims to evaluate the effects of normal FT3 level on new-onset atrial fibrillation (AF) in patients with surgical coronary revascularization.

Methods

The patients who underwent surgical coronary revascularization were enrolled in the retrospective study. Thyroid function was tested after an overnight fast on the first morning of hospitalization. Serum FT3 level was divided into quartile groups within the normal range. Hazards ratios (HRs) of FT3 level for AF were analyzed by COX proportional hazard model.

Results

This study included 503 patients with a mean [standard deviation (SD)] age of 63 (±9) years, and 396 (78.73%) were male. Post-operative AF (POAF) occurred in 120 (23.86%) patients at a median of two days after surgical coronary revascularization. The cumulating incidence of AF was significantly higher in the FT3 quartile 1 (Q1) group especially in older patients as evidenced by Kaplan-Meier analysis. Additionally, the patients who experienced AF had longer hospital stays, the same result was also found in the FT3 Q1 group. Further study demonstrated that low-normal FT3 was an independent predictor of POAF [HR =1.52, 95% confidence interval (CI): 1.01, 2.28, P=0.045].

Conclusions

Low-normal FT3 is associated with an increased risk of POAF and is an independent predictor of POAF. Patients who experienced AF have longer hospital stays. The findings may help to identify patients with surgical coronary revascularization at a higher risk for the development of AF.

2024 Heart Disease and Stroke Statistics: A Report of US and Global Data From the American Heart Association

BACKGROUND

The American Heart Association (AHA), in conjunction with the National Institutes of Health, annually reports the most up-to-date statistics related to heart disease, stroke, and cardiovascular risk factors, including core health behaviors (smoking, physical activity, nutrition, sleep, and obesity) and health factors (cholesterol, blood pressure, glucose control, and metabolic syndrome) that contribute to cardiovascular health. The AHA Heart Disease and Stroke Statistical Update presents the latest data on a range of major clinical heart and circulatory disease conditions (including stroke, brain health, complications of pregnancy, kidney disease, congenital heart disease, rhythm disorders, sudden cardiac arrest, subclinical atherosclerosis, coronary heart disease, cardiomyopathy, heart failure, valvular disease, venous thromboembolism, and peripheral artery disease) and the associated outcomes (including quality of care, procedures, and economic costs).

METHODS

The AHA, through its Epidemiology and Prevention Statistics Committee, continuously monitors and evaluates sources of data on heart disease and stroke in the United States and globally to provide the most current information available in the annual Statistical Update with review of published literature through the year before writing. The 2024 AHA Statistical Update is the product of a full year's worth of effort in 2023 by dedicated volunteer clinicians and scientists, committed government professionals, and AHA staff members. The AHA strives to further understand and help heal health problems inflicted by structural racism, a public health crisis that can significantly damage physical and mental health and perpetuate disparities in access to health care, education, income, housing, and several other factors vital to healthy lives. This year's edition includes additional global data, as well as data on the monitoring and benefits of cardiovascular health in the population, with an enhanced focus on health equity across several key domains.

RESULTS

Each of the chapters in the Statistical Update focuses on a different topic related to heart disease and stroke statistics.

CONCLUSIONS

The Statistical Update represents a critical resource for the lay public, policymakers, media professionals, clinicians, health care administrators, researchers, health advocates, and others seeking the best available data on these factors and conditions.

Prospective Study of Risk Factors for Postoperative Atrial Fibrillation After Cardiac Surgery

INTRODUCTION

To examine risk factors for new-onset postoperative atrial fibrillation (POAF) after cardiac surgery.

METHODS

Patients enrolled in the Cardiothoracic Surgical Trials Network multicenter, randomized trial of rate control versus rhythm control for POAF were included. Predictors of POAF were determined using multivariable logistic regression.

RESULTS

Among the 2104 patients who were enrolled preoperatively, 695 developed POAF (33.0%). Rates of POAF were 28.1% after isolated coronary artery bypass grafting (CABG), 33.7% after isolated valve repair or replacement, and 47.3% after CABG plus valve repair or replacement. Baseline characteristics associated with an increased risk of POAF identified on multivariable analysis included older age (odds ratio [OR] 1.57; 95% confidence interval [CI] 1.42-1.73, per 10 y), White race or non-Hispanic ethnicity (OR 1.52; CI: 1.11-2.07), history of heart failure (OR 1.55; CI: 1.16-2.08), and history of hypothyroidism (OR 1.42; CI 1.04-1.94). The type of cardiac procedure was associated with an increased risk of POAF with both isolated valve repair or replacement (OR 1.33, CI 1.08-1.64) and combined CABG plus valve repair or replacement (OR 1.64, CI 1.24-2.17) having increased risk of POAF compared to isolated CABG. No preoperative cardiac medication was associated with POAF.

CONCLUSIONS

In this prospective cohort of patients, older age, a history of hypothyroidism, a history of heart failure, and valve repair or replacement, with or without CABG, and White non-Hispanic race were associated with an increased risk of POAF.

Association of radioactive iodine treatment in differentiated thyroid cancer and cardiovascular death: a large population-based study

PURPOSE

The risk of cardiovascular diseases' death (CVD) in patients with differentiated thyroid cancer (DTC) treated with radioactive iodine (RAI) after surgery has not been adequately studied.

METHODS

Data of DTC patients who received RAI after surgery were retrieved from the Surveillance, Epidemiology, and End Result (SEER) database (2004-2015). Standardized mortality rate (SMR) analysis was used to evaluate the CVD risk in patients with RAI vs general population. A 1:1 propensity score matching (PSM) was applied to balance inter-group bias, and Pearson's correlation coefficient was used to detect collinearity between variables. The Cox proportional hazard model and multivariate competing risk model were utilized to evaluate the impact of RAI on CVD. At last, we curved forest plots to compare differences in factors significantly associated with CVD or cancer-related deaths.

RESULTS

DTC patients with RAI treatment showed lower SMR for CVD than general population (RAI: SMR = 0.66, 95% CI 0.62-0.71, P < 0.05). After PSM, Cox proportional hazard regression demonstrated a decreased risk of CVD among patients with RAI compared to patients without (HR = 0.76, 95% CI 0.6-0.97, P = 0.029). However, in competing risk regression analysis, there was no significant difference (adjusted HR = 0.82, 95% CI 0.66-1.01, P = 0.11). The independent risk factors associated with CVD were different from those associated with cancer-related deaths.

CONCLUSION

The CVD risk between DTC patients treated with RAI and those who did not was no statistical difference. Noteworthy, they had decreased CVD risk compared with the general population.

Prognostic implications of thyroid disease in patients with atrial fibrillation

Atrial fibrillation (AF) is often accompanied by thyroid disease (THD). This study aimed to explore the relationship between THD and the occurrence of significant clinical outcomes in patients with AF. This post hoc analysis utilized data from the MISOAC-AF trial (NCT02941978), which enrolled hospitalized patients with AF. Patients were categorized based on their THD history into hyperthyroidism, hypothyroidism, or euthyroidism. Cox regression models were employed to calculate unadjusted and adjusted hazard ratios (aHRs). The primary outcomes of interest included all-cause mortality, cardiovascular death, and hospitalizations during the follow-up period. The study included 496 AF patients (mean age 73.09 ± 11.10 years) with available THD data, who were followed-up for a median duration of 31 months. Among them, 16 patients (3.2%) had hyperthyroidism, 141 (28.4%) had hypothyroidism, and 339 (68.4%) had no thyroid disease. Patients with hypothyroidism exhibited higher rates of hospitalization during follow-up (aHR: 1.57, 95% CI 1.12 to 2.20, p = 0.025) compared to the euthyroid group. Elevated levels of thyroid-stimulating hormone (TSH) were correlated with an increased risk of cardiovascular mortality (aHR: 1.03, 95% CI 1.01 to 1.05, p = 0.007) and hospitalizations (aHR: 1.06, 95% CI 1.01 to 1.12, p = 0.03). Conversely, lower levels of triiodothyronine (T3) were associated with higher risks of all-cause mortality (aHR: 0.51, 95% CI 0.31 to 0.82, p = 0.006) and cardiovascular mortality (aHR: 0.42, 95% CI 0.23 to 0.77, p = 0.005). Among patients with AF, hypothyroidism was associated with increased hospitalizations. Furthermore, elevated TSH levels and decreased T3 levels were linked to higher cardiovascular and all-cause mortality risks, respectively.

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.

Association of thyroid dysfunction in individuals ≥ 65 years of age with subclinical cardiac abnormalities

CONTEXT

The relationship between thyroid dysfunction and measures of myocardial disease in older individuals remains to be defined.

OBJECTIVE

To evaluate the impact of thyroid dysfunction on structure and function of the left-heart chambers and blood markers of cardiac disease.

DESIGN

Cross-sectional analysis.

SETTING

The Cardiovascular Health Study, a community-based cohort of older individuals recruited from four urban areas in the United States.

PATIENTS

Of 3163 participants studied, 2477 were euthyroid, 465 had subclinical hypothyroidism (SCH), 47 overt hypothyroidism (OH), 45 endogenous (endo) subclinical hyperthyroidism (endo-SCT), and 129 had exogenous (exo) SCT due to thyroid hormone supplementation.

INTERVENTIONS

Clinical evaluation, blood sampling and biomarker measurement, 2-dimensional and speckle-tracking echocardiography.

MAIN OUTCOME MEASURE(S)

Left heart myocardial deformation, circulating biomarkers of diastolic overload (NT-proBNP), fibrosis (sST2, gal-3), and cardiomyocyte injury (hs-cTnT).

RESULTS

SCH was associated with higher NT-proBNP (beta = 0.17, p = 0.004), whereas OH was associated with higher hs-cTnT (beta = 0.29, p = 0.005). There were also suggestive associations of SCH with higher sST2, as well as endo-SCT with higher gal-3 and lower (worse) left atrial reservoir strain. Left ventricular longitudinal strain and end-diastolic strain rate did not differ significantly from euthyroid participants in SCH, OH, or exo-SCT.

CONCLUSIONS

In this free-living elderly cohort, subclinical and overt hypothyroidism were associated with abnormalities of blood biomarkers consistent with diastolic overload and myocardial necrosis respectively, whereas subclinical hyperthyroidism tended to be associated with myocardial fibrosis and decreased left atrial strain. Our findings could represent stage B heart failure and illuminate distinct aspects of the pathobiology of heart disease related to thyroid gland dysfunction with potential clinical implications.

Subclinical thyroid dysfunction and the risk of incident atrial fibrillation: A systematic review and meta-analysis

BACKGROUND

Thyroid hormones act on the cardiovascular system directly by modulating its function and indirectly by transcriptional regulation of gene expression in the heart and the vasculature. Studies have shown associations between overt and subclinical thyroid disorders and cardiovascular outcomes. The aim of this study was to perform a systematic review and meta-analysis to assess the potential relationships between subclinical hyper- and hypothyroidism and risk of atrial fibrillation (AF), and post-operative AF.

METHODS

MEDLINE and Scopus databases were searched from inception to 18th February 2023 for randomised controlled trials, case-control studies, and cohort studies which assessed the relationship between subclinical thyroid dysfunction and incident AF events. Risk of bias and the quality of evidence were assessed using the RoBANS tool and GRADE approach, respectively. Meta-analysis was conducted in Review Manager 5.4 using the Mantel-Haenszel statistical method and a random-effects model. Data are presented as risk ratios with 95% confidence intervals. Statistical heterogeneity amongst studies was assessed by the chi-squared (χ2) test and I2 statistic. p≤0.05 were considered significant.

RESULTS

A total of 6467 records were identified, of which 10 cohort studies met the inclusion criteria. Both subclinical hyperthyroidism and subclinical hypothyroidism were associated with an increased risk of incident AF (risk ratio (RR), 1.99; 95% confidence interval (CI), 1.43-2.77; n = 5 studies; p<0.0001 and RR, 1.19; CI, 1.03-1.39; n = 7 studies; p = 0.02, respectively). Subgroup analysis for post-operative AF revealed marked heterogeneity between studies (I2 = 84%) and association with subclinical hypothyroidism was not significant (RR, 1.41; CI, 0.89-2.22; n = 3 studies; p = 0.15).

CONCLUSIONS

The current evidence suggests that both subclinical hyperthyroidism and subclinical hypothyroidism are associated with increased risk of incident AF. Further investigation is required to determine potential causal links that would guide future clinical practice.

Atrioventricular block in patients with hyperthyroidism: a narrative review

Atrioventricular block (AVB) is a rare cardiac manifestation of hyperthyroidism (HTH). The scientific literature contains multiple reports of AVB in patients with HTH, ranging from subclinical to overt HTH and even thyroid storm. However, much remains unknown about the true prevalence, clinical course, optimal management, and outcomes of AVB in patients with HTH. Such patients are possibly overtreated with pacemakers because of a lack of understanding that AVB might be secondary to the hyperthyroid state and thus reversible. This narrative review discusses the pathophysiology of AVB in patients with HTH in the context of the available evidence.

Takayasu arteritis and hyperthyroidism: A secondary hypertension case report

INTRODUCTION

Renovascular disease and hyperthyroidism are secondary hypertension. Takayasu arteritis (TAK) is a chronic, progressive, nonspecific great vasculitis involving the aorta and its major branches. It is one of the causes of renal artery stenosis. Hyperthyroidism is an endocrine disease caused by improper continuous synthesis and secretion of excessive thyroid hormone by the thyroid gland. Both diseases can raise blood pressure (BP).

CASE PRESENTATION

we present a case of 18-year-old. Female, after exercise, fatigue palpitations. The maximum BP was 190/87 mm Hg, ankle-brachial index was <0.9. C-reactive protein and erythrocyte sedimentation rate were elevated. Imaging revealed multiple vascular stenosis. Triiodothyronine, tetraiodothyroxine, serum-free triiodothyronine, serum-free thyroxine, thyroid peroxidase antibody and thyroid stimulating receptor antibody were elevated. TSH reduced. She was diagnosed with TAK and hyperthyroidism. After treatment, the BP was normal, the thyroid function gradually returned to normal, and the symptoms improved.

CONCLUSION

It is suggested that the BP of both upper limbs should be measured in newly diagnostic hypertension. If BP is not measured in both upper limbs, it is likely to be missed diagnosis. The cause of vascular stenosis needs to be identified, otherwise interventional treatment may lead to aggravation of the condition. Few cases of TAK complicated with hyperthyroidism have been reported. Both diseases are related to the immune system, whether there is any correlation between the 2 diseases, further research is needed. Early diagnosis, early treatment, the earlier intervention, the better prognosis.

Association Between Serum Thyroid Measurements and Hyperhomocysteinemia in Euthyroid Subjects: A Retrospective Cross-Sectional Study

Objective

The objective of this study was to investigate the association between serum thyroid measurements and homocysteine (HCy) in euthyroid participants.

Methods

This retrospective study was based on Hospital Information Systems. After excluding participants with thyroid dysfunction and those who had recently taken medications that affected serum HCy, 775 participants were enrolled. We compared the serum thyroid function measurements of patients with or without hyperhomocysteinemia (HHCy) and analyzed the effect of thyroid indicators on HHCy prevalence and HCy levels. Multivariate regression analysis was utilized to analyze the association of thyroid-stimulating hormone (TSH) and thyroid peroxidase (TPOAb) with HCy.

Results

The serum TSH level (2.10 ± 1.06 mIU/L) of HHCy patients (n = 98) was significantly higher than controls (n = 677) (1.65 ± 0.90 mIU/L) (p < 0.05), as was the positive rate of TPOAb (19.4% vs 10.0%, p < 0.05). The serum HCy levels in subjects with TSH within the highest quartile were significantly higher than those in the lowest quartile (13.49 ± 7.78 vs 9.81 ± 3.59 μmol/L, p < 0.05). HCy was also significantly higher in TPOAb-positive patients than in negative subjects (14.06 ± 8.89 vs 11.48 ± 5.47 μmol/L, p < 0.05). Among the TSH quartiles, the prevalence of HHCy showed a similar significant upward trend to that described above. The prevalence of HHCy was also significantly higher in TPOAb-positive patients. The results of multivariate regression analysis suggested that both TSH elevation and TPOAb positivity were independent risk factors for HCy elevation and HHCy prevalence. However, we found no definitive association between linear increases in TPOAb titers and HCy concentrations or HHCy prevalence.

Conclusion

Patients with HHCy had significantly higher TSH levels and positive rates of TPOAb. Elevated TSH and positive TPOAb levels were independent risk factors for elevated HCy concentrations and HHCy risk.

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.

Cardiovascular outcomes in subclinical thyroid disease: an update

PURPOSE OF REVIEW

Subclinical thyroid disease is defined by a thyroid stimulating hormone (TSH) level outside of the normal range with normal circulating thyroid hormone levels. Excess adverse cardiovascular outcomes have been observed in certain patient populations with subclinical hypothyroidism (SCH) and hyperthyroidism (SCHr). The role of thyroid hormone and antithyroid treatments for subclinical thyroid disease remains debated.

RECENT FINDINGS

Cardiovascular disease appears to be a major mediator of all-cause mortality in patients with SCH, in particular those aged at least 60 years of age. In contrast, pooled clinical trial results did not find that levothyroxine reduced the incidence of cardiovascular events or mortality in this patient population. The association between SCHr and atrial fibrillation is well established; however, a 5-year follow-up of older patients with mild (TSH 0.1-0.4 mIU/l) SCHr found no increased incidence of atrial fibrillation. Separately, SCHr was associated with derangements in endothelial progenitor cell function that may underlie vascular disease independent from effects on cardiac function.

SUMMARY

The impact of treatment of subclinical thyroid disease on cardiovascular outcomes remains uncertain. Additional prospective and trial data are needed to evaluate treatment effects on cardiovascular outcomes in younger populations.

Iodine-Induced Hyperthyroidism and Long-term Risks of Incident Atrial Fibrillation and Flutter

CONTEXT

Although iodine-induced hyperthyroidism is a potential consequence of iodinated radiologic contrast administration, its association with long-term cardiovascular outcomes has not been previously studied.

OBJECTIVE

To investigate the relationships between hyperthyroidism observed after iodine contrast administration and incident atrial fibrillation/flutter.

METHODS

Retrospective cohort study of the U.S. Veterans Health Administration (1998-2021) of patients age ≥18 years with a normal baseline serum thyrotropin (TSH) concentration, subsequent TSH <1 year, and receipt of iodine contrast <60 days before the subsequent TSH. Cox proportional hazards regression was employed to ascertain the adjusted hazard ratio (HR) with 95% CI of incident atrial fibrillation/flutter following iodine-induced hyperthyroidism, compared with iodine-induced euthyroidism.

RESULTS

Iodine-induced hyperthyroidism was observed in 2500 (5.6%) of 44 607 Veterans (mean ± SD age, 60.9 ± 14.1 years; 88% men) and atrial fibrillation/flutter in 10.4% over a median follow-up of 3.7 years (interquartile range 1.9-7.4). Adjusted for sociodemographic and cardiovascular risk factors, iodine-induced hyperthyroidism was associated with an increased risk of atrial fibrillation/flutter compared with those who remained euthyroid after iodine exposure (adjusted HR 1.19, 95% CI 1.06-1.33). Females were at greater risk for incident atrial fibrillation/flutter than males (females, HR 1.81, 95% CI 1.12-2.92; males, HR 1.15, 95% CI 1.03-1.30; P for interaction = .04).

CONCLUSION

Hyperthyroidism following a high iodine load was associated with an increased risk of incident atrial fibrillation/flutter, particularly among females. The observed sex-based differences should be confirmed in a more sex-diverse study sample, and the cost-benefit analysis of long-term monitoring for cardiac arrhythmias following iodine-induced hyperthyroidism should be evaluated.

The determinants of thyroid function among vegetable farmers with primary exposure to chlorpyrifos: A cross-sectional study in Central Java, Indonesia

Objectives

Occupational pesticide exposure, chlorpyrifos (CPF) in particular, may adversely affect the thyroid. The purpose of this study was to evaluate the determinants of thyroid function as indicated by the serum concentration of thyroid-stimulating hormone (TSH) among Indonesian vegetable farmers with primary exposure to CPF.

Methods

A total of 151 vegetable farmers participated in this study. The sociodemographic and occupational characteristics of the participants were obtained using a structured interviewer-administered questionnaire. A validated quantitative method was used to estimate the cumulative exposure level (CEL). Serum TSH, thyroglobulin (Tg), free thyroxine (FT4), and urinary iodine excretion (UIE) were measured in the laboratory. The difference in TSH concentrations according to CEL and other characteristics were analysed using the Mann-Whitney U test. A multiple linear regression model was used to evaluate the potential determinants of TSH.

Results

The mean age was 50 (SD 9.4) years. The median concentrations of TSH, FT4, and Tg/FT4 ratio were 1.46 mIU/L, 1.17 ng/dL, and 6.23 × 10², respectively. We observed that higher TSH concentrations were found among those with a higher Tg/FT4 ratio, were classified as high CEL, and had lower UIE or FT4.

Conclusions

Our findings show that Tg/FT4 ratio, CEL, FT4, UIE concentrations, and post-spraying days were determinants of TSH concentrations among farmers with primary exposure to CPF. These results indicate that farmers are exposed to agents with thyroid-disrupting properties, thus supporting previous evidence showing the potential for thyroid disorders in agricultural populations exposed to pesticides.

Biomarkers of Atrial Fibrillation Recurrence in Patients with Paroxysmal or Persistent Atrial Fibrillation Following External Direct Current Electrical Cardioversion

Atrial fibrillation (AF) is associated with atrial remodeling, cardiac dysfunction, and poor clinical outcomes. External direct current electrical cardioversion is a well-developed urgent treatment strategy for patients presenting with recent-onset AF. However, there is a lack of accurate predictive serum biomarkers to identify the risks of AF relapse after electrical cardioversion. We reviewed the currently available data and interpreted the findings of several studies revealing biomarkers for crucial elements in the pathogenesis of AF and affecting cardiac remodeling, fibrosis, inflammation, endothelial dysfunction, oxidative stress, adipose tissue dysfunction, myopathy, and mitochondrial dysfunction. Although there is ample strong evidence that elevated levels of numerous biomarkers (such as natriuretic peptides, C-reactive protein, galectin-3, soluble suppressor tumorigenicity-2, fibroblast growth factor-23, turn-over collagen biomarkers, growth differential factor-15) are associated with AF occurrence, the data obtained in clinical studies seem to be controversial in terms of their predictive ability for post-cardioversion outcomes. Novel circulating biomarkers are needed to elucidate the modality of this approach compared with conventional predictive tools. Conclusions: Biomarker-based strategies for predicting events after AF treatment require extensive investigation in the future, especially in the presence of different gender and variable comorbidity profiles. Perhaps, a multiple biomarker approach exerts more utilization for patients with different forms of AF than single biomarker use.

The role of amiodarone in post-operative hypothyroidism patient with factitious thyrotoxicosis and atrial fibrillation: A case report

INTRODUCTION

Factitious thyrotoxicosis includes all causes of thyrotoxicosis from the short or long-term ingestion of thyroid hormone, of which one of the complications is atrial fibrillation.

CASE PRESENTATION

A woman, 71 years old, complained of chest palpitations. She had a medical history of thyroidectomy, hypertension, and dyslipidemia. In addition, she took Levothyroxine, amlodipine and simvastatin regularly. On physical examination, the general status was weak, with vital signs showing blood pressure (BP) of 170/100 mmHg, heart rate (HR) of 130-150 bpm, irregular rhythm, respiratory rate (RR) of 20×/min, axillary temperature of 36.8 °C, and oxygen saturation (SpO2) 98 % with room air. The abnormal laboratory found were significant increase in total T4, total T3, FT4, and low levels of TSH. The first electrocardiogram (ECG) showed AF and Burch Watorfsky's score was 45. The AF was treated with a loading dose of amiodarone 150 mg in 10 min and decreased gradually. She had received a high-calorie, protein and low-salt diet of 2100 kcal/day, termination Levothyroxine usage, propranolol of 10 mg/8 h, amlodipine of 5 mg/day, and lisinopril of 5 mg/day. Treatment for AF was continued with a maintenance dose of amiodarone IV 300 mg in 6 h, then 600 mg in 18 h, warfarin tablet 2 mg/day (according to treatment from a cardiologist), and atorvastatin 20 mg/day at night. After 6 days of treatment, the patient experienced improvement and continued discharge. The patient improved on an outpatient basis and was monitored periodically.

DISCUSSION

Monitored treatment of thyrotoxicosis and AF management with 3 principles can minimize complication severity.

CONCLUSION

Early, effective and monitored treatment of thyrotoxicosis is vital to manage AF in achieving a better outcome.

The Etiology of Abnormal TSH in Veterans Cared by a VA Medical Center - One High Serum Thyrotropin is Associated with Higher 5-Years Mortality

Objective

By analyzing the etiology of abnormal TSH in randomly selected veteran patients, we set our heart on improving future clinical care/management of the clinical/subclinical hyper- and hypothyroidism in the aging veteran population.

Methods

A total of 1100 patients' charts in alphabetical order were selected. Excluded cases of insufficient information, 897 patients' charts were reviewed and analyzed for causes of abnormal TSH. Among them, 602 for the cause of low TSH (below 0.55 uU/mL) and 295 for high TSH (above 4.78 uU/mL) were reviewed retrospectively.

Findings

Among the 1100 patients selected, 680 (61.8%) were 60 y or older (female=44, 6.8%); 420 were under 60 y (female=80, 19.0%); significantly more female patients were found in the younger age group (P<0.001). After excluding patients with insufficient data, the most common cause of suppressed TSH is iodine-induced, CT iodinated contrast and betadine use caused 35.0% in the older group (n=126) compared to 23.6% in the younger group(n=57) (P = 0.027). The significant difference is that older veterans received more contrast CTs (P < 0.05 compared to the younger group). In both age groups with concurrent FT4 study, we found four high FT4 among 90 studies, 4.4% overt hyperthyroidism. The second most common cause of suppressed TSH is due to thyroid hormone (TH) replacement in the older group (119 patients, 33.1%) with age > 60y, significantly more frequent compared to the younger group, P<0.001. There is significantly more overt hyperthyroidism, 27.8/%, than the iodine-load induced suppression of TSH, P<0.001, due to 17 patients on TSH suppression therapy after total thyroidectomy for thyroid cancer. Among the 295 patients with elevated TSH, the most common cause of high TSH was due to hypothyroidism on T4 replacement: a total of 128 (59.3%) in the older group (N=216) is, similar to 47 (59.5%) in the younger group (N=79). In both age groups, there were 139 patients with concomitant FT4 measurement; 17 overt hypothyroidism were found, 12.2%. No significant difference is seen in the two age groups. The next most common causes of elevated TSH are CT contrast infusion, 23 (10.6%) in the older group and 7 (8.9%) in the younger group. We find high TSH is associated with a higher death rate of 101/238 (42.4%) in a 5-year follow-up (from 2016 to 2021), as compared to low TSH of 68/238 (28.6%), in the older age group, p<0.03； both were significantly higher than the age- and sex-matched general US population, 19.7%, P<0.01.

Conclusion

Even though most, ~ 90%, were subclinical, the suppressed and elevated TSH are associated with severe consequences in CV/CNS and immune-suppression complications in aging veterans. Therefore, cautious use (and more frequent check of TSH) of TH replacement and CT contrast in aging veterans is recommended. The alarming increase in 5 years death rate in older patients with elevated TSH deserves further study.

Heart Disease and Stroke Statistics-2023 Update: A Report From the American Heart Association

BACKGROUND

The American Heart Association, in conjunction with the National Institutes of Health, annually reports the most up-to-date statistics related to heart disease, stroke, and cardiovascular risk factors, including core health behaviors (smoking, physical activity, diet, and weight) and health factors (cholesterol, blood pressure, and glucose control) that contribute to cardiovascular health. The Statistical Update presents the latest data on a range of major clinical heart and circulatory disease conditions (including stroke, congenital heart disease, rhythm disorders, subclinical atherosclerosis, coronary heart disease, heart failure, valvular disease, venous disease, and peripheral artery disease) and the associated outcomes (including quality of care, procedures, and economic costs).

METHODS

The American Heart Association, through its Epidemiology and Prevention Statistics Committee, continuously monitors and evaluates sources of data on heart disease and stroke in the United States to provide the most current information available in the annual Statistical Update with review of published literature through the year before writing. The 2023 Statistical Update is the product of a full year's worth of effort in 2022 by dedicated volunteer clinicians and scientists, committed government professionals, and American Heart Association staff members. The American Heart Association strives to further understand and help heal health problems inflicted by structural racism, a public health crisis that can significantly damage physical and mental health and perpetuate disparities in access to health care, education, income, housing, and several other factors vital to healthy lives. This year's edition includes additional COVID-19 (coronavirus disease 2019) publications, as well as data on the monitoring and benefits of cardiovascular health in the population, with an enhanced focus on health equity across several key domains.

RESULTS

Each of the chapters in the Statistical Update focuses on a different topic related to heart disease and stroke statistics.

CONCLUSIONS

The Statistical Update represents a critical resource for the lay public, policymakers, media professionals, clinicians, health care administrators, researchers, health advocates, and others seeking the best available data on these factors and conditions.

Association between sensitivity to thyroid hormones and risk of arrhythmia in patients with coronary heart disease: a RCSCD-TCM study in China

BACKGROUND

Thyroid dysfunction is closely related to arrhythmia. However, the relationship between sensitivity to thyroid hormone and risk of arrhythmia remains unknown. This study aimed to investigate the association between the thyroid system complex index and risk of arrhythmia in patients with coronary heart disease (CHD).

METHODS

This large, multicenter study included 28,413 patients with CHD. Central sensitivity to thyroid hormone was assessed by calculating the thyroid feedback quantile-based index (TFQI). Logistic regression was used to analyze the relationship between sensitivity to thyroid hormone and risk of arrhythmia. This study also assessed the relationship between sensitivity to thyroid hormone and risk of arrhythmia in different sexes, ages, and glucose regulation and blood lipid states.

RESULTS

Of the 28,413 participants, 8935 (31.4%) patients with CHD had arrhythmia. There was a remarkable association between TFQI and risk of arrhythmia (odds ratio [OR]: 0.783; 95% confidence interval [CI], 0.735-0.836). Furthermore, the association between the TFQI and risk of arrhythmia in women (OR: 0.731; 95% CI: 0.667-0.802) was stronger than that in men (OR: 0.894; 95% CI: 0.816-0.910), as well as higher in elder (OR: 0.779; 95% CI: 0.721-0.843) than middle-aged (OR: 0.789; 95% CI: 0.703-0.886) patients. Furthermore, the association was strong in the state of diabetes (OR: 0.635; 95% 0.569-0.709) and dyslipidemia (OR: 0.706; 95% CI: 0.644-0.774).

CONCLUSION

There is a remarkable association between sensitivity to thyroid hormone and risk of arrhythmia in patients with CHD, which is more pronounced among women and the elderly. The association is also stronger in CHD patients with dyslipidemia or diabetes.

A one-health lens offers new perspectives on the importance of endocrine disorders in the equine athlete

Endocrine disorders are associated with joint pain and tendon injury in humans, but the effects in the horse are only starting to be understood. Similar patterns of clinical signs and injury appear to affect horses and humans for both orthopedic and endocrine disorders, supporting the use of a one-health approach to tackle these issues. In this Currents in One Health, we will discuss common equine endocrinopathies, current testing recommendations, dietary management, genetic predispositions, and endocrine disorders' effects on performance. Our aim is to use a one-health lens to describe current comparative research so that veterinarians can employ cutting-edge preventative, diagnostic, and therapeutic recommendations. Identified key gaps in knowledge include whether equine metabolic osteoarthritis exists, if steroid joint injections are safe in horses with endocrine disorders, and if the return to performance percentage improves with concurrent treatment of endocrine and musculoskeletal disorders. Key takeaways include that the relationship between endocrine disorders and musculoskeletal disease in the horse goes beyond laminitis to include lameness, muscle atrophy, suspensory ligament degeneration, osteochondritis dissecans, and potentially metabolic osteoarthritis. Approaches learned from human and equine comparative studies can offer insight into injury recognition and management, thus mitigating the impact of endocrine disorders on performance in both species. Readers interested in an in-depth description of current and future research involving pathophysiology, novel interventions, and multiomic approaches to identify individuals with athletic limitations induced by endocrine disorders are invited to read the companion Currents in One Health by Manfredi et al, AJVR, February 2023.

Hydrogen sulfide alleviates hypothyroidism-induced myocardial fibrosis in rats through stimulating autophagy and inhibiting TGF-β1/Smad2 pathway

Hypothyroidism alone can lead to myocardial fibrosis and result in heart failure, but traditional hormone replacement therapy does not improve the fibrotic situation. Hydrogen sulfide (H₂S), a new gas signaling molecule, possesses anti-inflammatory, antioxidant, and anti-fibrotic capabilities. Whether H₂S could improve hypothyroidism-induced myocardial fibrosis are not yet studied. In our study, H₂S could decrease collagen deposition in the myocardial tissue of rats caused by hypothyroidism. Furthermore, in hypothyroidism-induced rats, we found that H₂S could enhance cystathionine-gamma-lyase (CSE), not cystathionine β-synthase (CBS), protein expressions. Finally, we noticed that H₂S could elevate autophagy levels and inhibit the transforming growth factor-β1 (TGF-β1) signal transduction pathway. In conclusion, our experiments not only suggest that H₂S could alleviate hypothyroidism-induced myocardial fibrosis by activating autophagy and suppressing TGF-β1/SMAD family member 2 (Smad 2) signal transduction pathway, but also show that it can be used as a complementary treatment to conventional hormone therapy.

The occurrence of early atrial fibrillation after cardiac valve operation and the establishment of a nomogram model

Background

Postoperative atrial fibrillation (POAF) is a common complication after cardiac surgery, which is associated with age and massive bleeding. However, whether thyroid hormone (TH) level can affect POAF remains controversial.

Aim

To investigate the occurrence and risk factors of POAF, in particular, the preoperative TH level of patients was introduced into this study as a variable for analysis, and a column graph prediction model of POAF was constructed.

Methods

Patients who underwent valve surgery in Fujian Cardiac Medical Center from January 2019 to May 2022 were retrospectively analyzed and divided into POAF group and NO-POAF group. Baseline characteristics and relevant clinical data were collected from the two groups of patients. Independent risk factors for POAF were screened using univariate analysis and binary logistic regression analysis, and a column line graph prediction model was established based on the regression analysis results, and the diagnostic efficacy and calibration of the model were evaluated using the Receiver Operating Characteristic Curve (ROC) and calibration curve.

Results

A total of 2,340 patients underwent valve surgery, excluding 1,751 patients, a total of 589 patients were included, including 89 patients in POAF group and 500 patients in NO-POAF group. The total incidence of POAF was 15.1%. The results of the Logistics regression analysis showed that gender, age, leukocytes and TSH were risk factors of POAF. The area under the ROC curve of the nomogram prediction model for POAF was 0.747 (95% CI: 0.688-0.806, P < 0.001), with a sensitivity of 74.2% and specificity of 68%. Hosmer-Lemeshow test showed χ ²= 11.141, P = 0.194 > 0.05, the calibration curve was well fitted.

Conclusion

The results of this study show that gender, age, leukocyte and TSH are risk factors of POAF, and the nomogram prediction model has a good prediction effect. Due to the limited sample size and included population, more studies are needed to validate this result.

An elevated parametric thyroid feedback quantile-based index is associated with atrial fibrillation

INTRODUCTION

Atrial fibrillation is associated with hyperthyroidism. Within the euthyroid range, it is also associated with high thyroxine (fT4), but not with thyrotropin (TSH). We aim to describe differences in thyroid regulation, measured by the Parametric Thyroid Feedback Quantile-Based Index (PTFQI), between patients with atrial fibrillation and the general population.

MATERIALS AND METHODS

Thyroid parameters (PTFQI, TSH, and fT4) of a sample of 84 euthyroid subjects with atrial fibrillation (cases) were compared to a reference sample of euthyroid healthcare patients (controls). We calculated age and sex adjusted ORs for atrial fibrillation across tertiles of these parameters. Also, within cases, we studied thyroid parameters association with clinical characteristics of the atrial fibrillation.

RESULTS

After adjusting for age and sex, fT4 and PTFQI were higher in subjects with atrial fibrillation when compared to the general sample (p<0.01 and p=0.01, respectively). Atrial fibrillation ORs of the third versus the first PTFQI tertile was 1.88(95%CI 1.07,3.42), and there was a gradient across tertiles (p trend=0.02). Among atrial fibrillation patients, we observed that higher PTFQI was associated with sleep apnea/hypopnea syndrome (OSAS) (p=0.03), higher fT4 was associated with the presence of an arrhythmogenic trigger (p=0.02) and with heart failure (p<0.01), and higher TSH was also associated with OSAS (p<0.01).

CONCLUSIONS

Euthyroid subjects with atrial fibrillation have an elevation of the pituitary TSH-inhibition threshold, measured by PTFQI, with respect to the general population. Within atrial fibrillation patients, high PTFQI was associated with OSAS, and high fT4 with heart failure. These results hint of the existence of a relationship between thyroid regulation and atrial fibrillation.

Cardiovascular and Neuronal Consequences of Thyroid Hormones Alterations in the Ischemic Stroke

Ischemic stroke is one of the leading global causes of neurological morbidity and decease. Its etiology depends on multiple events such as cardiac embolism, brain capillaries occlusion and atherosclerosis, which ultimately culminate in blood flow interruption, incurring hypoxia and nutrient deprivation. Thyroid hormones (THs) are pleiotropic modulators of several metabolic pathways, and critically influence different aspects of tissues development. The brain is a key TH target tissue and both hypo- and hyperthyroidism, during embryonic and adult life, are associated with deranged neuronal formation and cognitive functions. Accordingly, increasing pieces of evidence are drawing attention on the consistent relationship between the THs status and the acute cerebral and cardiac diseases. However, the concrete contribution of THs systemic or local alteration to the pathology outcome still needs to be fully addressed. In this review, we aim to summarize the multiple influences that THs exert on the brain and heart patho-physiology, to deepen the reasons for the harmful effects of hypo- and hyperthyroidism on these organs and to provide insights on the intricate relationship between the THs variations and the pathological alterations that take place after the ischemic injury.

Endocrinopathy After Treatment for Medulloblastoma: Results From the SJMB03 Trial of Risk-Adapted Radiation Therapy

PURPOSE

The objective of this study was to estimate the cumulative incidence of endocrinopathy in pediatric patients treated for medulloblastoma with surgery, risk-adapted photon craniospinal irradiation, and dose-intensive chemotherapy.

METHODS AND MATERIALS

Children and adolescents (n = 156) treated between 2003 and 2013 were evaluated for evidence of endocrinopathy. Clinical information and mean radiation dose to hypothalamus and thyroid were calculated and used to estimate cumulative incidence of growth hormone deficiency, hypothyroidism, adrenal insufficiency, hypogonadism, and precocious puberty.

RESULTS

The 5-year cumulative incidences were estimated for growth hormone deficiency, 68.9% (60.9%, 75.6%); hypothyroidism, 48.4% (95% confidence interval (CI), 40.2%-56.1%); adrenal insufficiency, 13.0% (95% CI, 8.3%-18.9%); hypogonadism, 33.9% (95% CI, 25.2%-42.7%); and precocious puberty, 2.0% (95% CI, 0.6%-5.4%). Growth hormone deficiency was associated with increased hypothalamus dose (hazard ratio [HR], 1.035; 95% CI, 1.010-1.061; P = .0055) in average-risk patients and cerebrospinal fluid shunt (HR, 2.532; 95% CI, 1.325-4.838; P = .0049) in high-risk patients. In average-risk patients, hypothyroidism was associated with younger age (HR, 0.902; 95% CI, 0.842-0.973; P = .0070), hypothalamus dose (HR, 1.039; 95% CI, 1.004-1.075; P = .0273), and thyroid dose (HR, 1.070; 95% CI, 1.008-1.136; P = .0263). In high-risk patients, hypothyroidism was associated with increased hypothalamus dose (HR, 1.068; 95% CI, 0.995-1.147; P = .0671) and thyroid dose (HR, 1.050; 95% CI, 1.000-1.104; P = .0515). Adrenal insufficiency was associated with increased hypothalamus dose (HR, 1.112; 95% CI, 1.058-1.170; P < .0001). Growth hormone deficiency incidence was higher when comparing patients treated with cerebrospinal fluid shunt versus those not having a shunt/extraventricular drain placed during initial surgery (HR, 1.712; 95% CI, 1.109-2.643).

CONCLUSIONS

Incidence and time to onset of clinically significant endocrinopathy after photon craniospinal irradiation for pediatric medulloblastoma is influenced by radiation dose to target organs and patient age at time of treatment. Advanced radiation therapy methods and dose-reduction strategies are needed to reduce the incidence of endocrinopathy.

Reduced Sensitivity to Thyroid Hormones Is Associated With High Remnant Cholesterol Levels in Chinese Euthyroid Adults

CONTEXT

It remains unclear whether the thyroid system could regulate the atherogenic remnant cholesterol (RC) levels in euthyroid status.

OBJECTIVE

We aimed to investigate the relationship between sensitivity to thyroid hormones and RC levels in Chinese euthyroid population.

METHODS

This study included 18 766 euthyroid adults. High RC levels were defined as the upper quartile of RC levels. The thyroid hormone sensitivity indices, including thyroid feedback quantile-based index (TFQI), thyroid-stimulating hormone index (TSHI), thyrotrophic thyroxine resistance index (TT4RI), and free triiodothyronine to free thyroxine (FT3/FT4) ratio were calculated. Linear and binary logistic regression analysis were applied to determine the associations between those composite indices with RC levels by genders.

RESULTS

Both females and males with high RC levels exhibited co-existing higher TSH and FT4 levels. Linear regression analysis revealed that TFQI, TSHI, and TT4RI were positively, while FT3/FT4 ratio levels were negatively associated with serum RC levels. The odds ratios (ORs) (95% CI) for high RC levels were increased with rising TFQI quartiles (Q) [females: Q3 1.41 (1.22-1.63), Q4 1.61 (1.39-1.86); males: Q3 1.25 (1.09-1.45), Q4 1.38 (1.19-1.59), all P for trend < 0.001] after full adjustment, with Q1 as the reference. TSHI and TT4RI yielded similar results. By contrast, the ORs (95% CI) for high RC levels were decreased with increasing FT3/FT4 ratio quartiles in both genders (P for trend < 0.001).

CONCLUSION

In euthyroid adults, reduced sensitivity to thyroid hormones was associated with high RC levels. Our results suggested an additive cardiometabolic risk of euthyroid population with thyroid hormones insensitivity.

Mechanisms and Management of Thyroid Disease and Atrial Fibrillation: Impact of Atrial Electrical Remodeling and Cardiac Fibrosis

Atrial fibrillation (AF) is the most common cardiac arrhythmia associated with increased cardiovascular morbidity and mortality. The pathophysiology of AF is characterized by electrical and structural remodeling occurring in the atrial myocardium. As a source of production of various hormones such as angiotensin-2, calcitonin, and atrial natriuretic peptide, the atria are a target for endocrine regulation. Studies have shown that disorders associated with endocrine dysregulation are potential underlying causes of AF. The thyroid gland is an endocrine organ that secretes three hormones: triiodothyronine (T3), thyroxine (T4) and calcitonin. Thyroid dysregulation affects the cardiovascular system. Although there is a well-established relationship between thyroid disease (especially hyperthyroidism) and AF, the underlying biochemical mechanisms leading to atrial fibrosis and atrial arrhythmias are poorly understood in thyrotoxicosis. Various animal models and cellular studies demonstrated that thyroid hormones are involved in promoting AF substrate. This review explores the recent clinical and experimental evidence of the association between thyroid disease and AF. We highlight the current knowledge on the potential mechanisms underlying the pathophysiological impact of thyroid hormones T3 and T4 dysregulation, in the development of the atrial arrhythmogenic substrate. Finally, we review the available therapeutic strategies to treat AF in the context of thyroid disease.

Impact of thyroid function screening in a large cohort of patients admitted to an emergency department

BACKGROUND

Thyroid dysfunctions are highly prevalent and can worsen underlying cardiopathies, but despite that the routine screening of thyroid function in the Emergency Department (ED) setting is not generally recommended.

OBJECTIVE

To understand if staff training and implementation of rapid TSH screening (rTSH) could improve the management of patients arrived in the ED. Specifically, we aimed at evaluating the prevalence of undiagnosed thyroid diseases among ED patients; the effects of educational meetings in the clinical decision-making process; the usefulness of rTSH, in terms of variation of either the clinical work out or the existing treatment.

DESIGN

Retrospective case-control study of 9227 patients managed in the ED of an academic institution. rTSH was routinely available for all patients, who were divided into rTSH-YES and rTSH-NO groups.

RESULTS

We included 4243 and 4984  patients in the rTSH-YES and rTSH-NO group, respectively. Trained personnel uncovered a high prevalence of undiagnosed thyroid dysfunction (7%). The diagnosis in the ED of heart failure, history of thyroid diseases, contrast media/amiodarone administration and female gender were independently associated with an increased likelihood to have thyroid dysfunction. The rTSH improved the clinical outcome by (a) appropriate treatment of an underlying clinical condition causing ED entrance, (b) appropriate prophylaxis in patients requiring contrast media, (c) uncovering incorrect treatments, with 60% of patients on levothyroxine requiring a dose reduction.

CONCLUSIONS

The rTSH in the ED revealed a high prevalence of untreated thyroid disorders with a major impact on following interventions. The training of a multidisciplinary team is crucial in driving the correct decision-making process.

Associations of Warfarin Use with Risks of Ischemic Cerebrovascular Events and Major Bleeding in Patients with Hyperthyroidism-Related Atrial Fibrillation

The use of oral anticoagulants for patients with new-onset hyperthyroidism-related atrial fibrillation (AF) is controversial. We aimed to evaluate the clinical benefits of warfarin therapy in this population. This retrospective cohort study used a data-cut of Taiwan Health and Welfare Database between 2000 and 2016. We compared warfarin users and nonusers among AF patients with hyperthyroidism. We used 1:2 propensity score matching to balance covariates and Cox regression model to calculate hazard ratios (HRs). The primary outcome was risk of ischemic stroke/transient ischemic attack (TIA), and the secondary outcome was major bleeding. After propensity score matching, we defined 90 and 168 hyperthyroidism-related AF patients with mean (SD) age of 59.9 ± 13.5 and 59.2 ± 14.6 in the warfarin-treated group and untreated group separately. The mean (SD) CHA2DS2-VASc scores for the two groups were 2.1 ± 1.6 and 1.8 ± 1.5, respectively. Patients with hyperthyroidism-related AF receiving warfarin had no significant risk of ischemic stroke/TIA (adjusted HR: 1.16, 95% confidence interval [CI]: 0.52-2.56, p = 0.717) compared to nonusers. There was a comparable risk of major bleeding between those receiving warfarin or not (adjusted HR: 0.91, 95% CI: 0.56-1.47, p = 0.702). The active-comparator design also demonstrated that warfarin use had no significant association with the risk of stroke/TIA versus aspirin use (adjusted HR: 2.43; 95% CI: 0.68-8.70). In conclusion, anticoagulation therapy did not have a statistically significant benefit on ischemic stroke/TIA nor risk of bleeding, among patients with new-onset hyperthyroidism-related AF under a low CHA2DS2-VASc score, by comparing those without use.

Non-medicalization of medical science: Rationalization for future

As we delve into the intricacies of human disease, millions of people continue to be diagnosed as having what are labelled as pre-conditions or sub-clinical entities and may receive treatments designed to prevent further progression to clinical disease, but with debatable impact and consequences. Endocrinology is no different, with almost every organ system and associated diseases having subclinical entities. Although the expansion of these “grey” pre-conditions and their treatments come with a better understanding of pathophysiologic processes, they also entail financial costs and drug adverse-effects, and lack true prevention, thus refuting the very foundation of Medicine laid by Hippocrates “Primum non nocere” (Latin), i.e., do no harm. Subclinical hypothyroidism, prediabetes, osteopenia, and minimal autonomous cortisol excess are some of the endocrine pre-clinical conditions which do not require active pharmacological management in the vast majority. In fact, progression to clinical disease is seen in only a small minority with reversal to normality in most. Giving drugs also does not lead to true prevention by changing the course of future disease. The goal of the medical fraternity thus as a whole should be to bring this large chunk of humanity out of the hospitals towards leading a healthy lifestyle and away from the label of a medical disease condition.

Redefinition of Successful Treatment of Patients With Hypothyroidism. Is TSH the Best Biomarker of Euthyroidism?

In recent years evidence has accumulated supporting a revised view of the nature of euthyroidism and the biomarkers of thyroid function. Within the normal range, variations in thyroid hormone levels are associated with variations in clinical parameters and outcomes. There are therefore no readily identified individually specific optimum levels of thyroid hormones for any individual. Levels around the middle of the normal population range may best reflect euthyroidism. These levels may have evolutionary advantages on the basis that adverse outcomes often increase with divergence from such levels, and physiological processes tend to minimise such inter-individual and intra-individual divergence. In populations of predominantly untreated individuals, levels of thyroid hormones and in particular levels of free thyroxine (FT4) correlate more often with clinical parameters than do levels of thyrotropin (TSH). Levels of thyroid hormones may therefore be regarded as the best available biomarkers of euthyroidism and dysthyroidism. It follows that 'subclinical hypothyroidism' (normal FT4/raised TSH levels), rather than being an accurate marker of peripheral tissue hypothyroidism is more a marker of decreased thyroid reserve and prognosis. The recent evidence suggests that treatment of hypothyroxinemia, regardless of the TSH level, and monitoring therapy using FT4 and/or triiodothyronine levels, depending on the replacement regime, may result in more successful treatment of hypothyroidism than relying on thyrotropin levels for patient selection and subsequent treatment monitoring. The equivalents of mid-range levels of thyroid hormones (especially FT4), adjusted by individual comorbidity concerns, may be rational general replacement targets. These implications of the new evidence may create opportunities for novel trials of thyroid replacement therapy.

The bidirectional relationship of thyroid disease and atrial fibrillation: Established knowledge and future considerations

Atrial fibrillation (AF) tends to occur frequently in patients with thyroid disease, primarily hyperthyroidism. In hyperthyroidism, increased levels of thyroid hormones, via intra- and extranuclear mechanisms, have profound effects on cardiac electrophysiology. Hypothyroidism carries a lower risk for AF and is mainly associated with the overtreatment of hypothyroid patients. New-onset AF is frequently the only manifestation of thyroid disease, which renders screening for thyroid dysfunction in that scenario clinically useful. Managing thyroid disease and comorbid AF is essential. This includes thyroid hormones control along with conventional AF therapy. However, there are several open issues with this comorbid duo. The optimal management of thyroid disease and its impact on AF burden remains obscure. There is scanty information on clear-cut benefits for therapy of subclinical thyroid disease and screening of asymptomatic patients. Furthermore, the immunogenetic overlap between the autoantibodies in Graves' disease and AF genesis may lead to novel therapeutic implications. The objective of this review is to summarize the up-to-date epidemiology, pathogenesis, pathophysiology and management of interacting thyroid disease and AF.

Effects of thyroid dysfunction and thyroid stimulating hormone levels on the Atrial fibrillation risks: a systematic review and dose-response meta-analysis from cohort studies

OBJECTIVE

To explore the relationship between thyroid dysfunction, thyroid stimulating hormone (TSH) levels and risks of atrial fibrillation (AF) in studies as well as to conduct a dose-response meta-analysis on the correlation between TSH levels and AF risks.

METHODS

13 studies from five databases with 649,293 subjects (mean age 65.1 years) were included. The dose-response meta-analysis was conducted by comparing the Risk Ratios (RRs) and 95% Confidence Intervals (CI) for incident AF associated with different levels of TSH (vs TSH=0 mU/L) across studies. Data were collected until Oct 25, 2021.

RESULTS

Subclinical hyperthyroidism, subclinical hypothyroidism, clinical hyperthyroidism were associated with the increased risk of AF respectively (RR=1.70, 95% CI: 1.11-2.62; RR=1.23, 95% CI:1.05-1.44; RR=2.35, 95% CI:1.07-5.16), while clinical hypothyroidism was not found associated with the significantly increased risk of AF (RR=1.20, 95% CI: 0.72-1.99). A non-linear relationship was observed in two models (crude model: P_nonlinear<0.001; adjusted model: P_nonlinear =0.0391) between the TSH concentrations and the risks of AF.

CONCLUSIONS

Our study indicated that subclinical hyperthyroidism, subclinical hypothyroidism, clinical hyperthyroidism were associated with the risk of AF, and the results for TSH levels and AF risk were mixed which showed a U-shaped relationship.

The impact of the management strategies for patients with subclinical hypothyroidism on long-term clinical outcomes: An umbrella review

AIM

This umbrella review summarises and compares synthesised evidence on the impact of subclinical hypothyroidism and its management on long-term clinical outcomes.

METHODS

We conducted comprehensive searches on MEDLINE, EMBASE, Scopus, Web of Science, Cochrane Database of Systematic Reviews, JBI Evidence Synthesis, the PROSPERO register, Epistemonikos Database and PDQ Evidence from inception to February and July 2021 using keywords on subclinical hypothyroidism, treatment with levothyroxine, monitoring and primary outcomes (all-cause mortality, cardiovascular events, stroke, frailty fractures and quality of life). Only systematic reviews and meta-analyses on adult patient populations were considered. Study selection, data extraction and quality appraisal using AMSTAR-2 were done independently by two reviewers and discrepancies were resolved through discussion. Overlap across the selected reviews was also assessed, followed by a narrative synthesis of findings.

RESULTS

A total of 763 studies were identified from literature searches; 20 reviews met inclusion criteria. Methodological quality ratings were high (n = 8), moderate (n = 7), and low (n = 5), but no reviews were excluded on this basis. Though there was slight overlap across all reviews, some pairwise comparisons had high corrected covered area scores. Compared to euthyroidism, untreated subclinical hypothyroidism was associated with a higher risk of cardiovascular events or death if Thyroid Stimulating Hormone was above 10mIU/L at baseline. Treatment was associated with a lower risk of death from all causes for patients younger than 70 years and possibly better cognitive and quality of life scores than untreated individuals. Evidence on the risk of strokes and fractures was inconclusive.

CONCLUSION

In the long term, treatment of subclinical hypothyroidism may be beneficial for some patient groups. However, the findings of this review are negatively impacted by the relative sparseness and poor quality of available evidence. Additional large and adequately powered studies are needed to investigate this topic further.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO (CRD42021235172).

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.