The effect of thyroid function on clinical outcome in patients with heart failure

Subclinical hypothyroidism predicts outcome in heart failure: insights from the T.O.S.CA. registry

Subclinical hypothyroidism (SH), defined as increased serum thyroid-stimulating hormone (TSH) with normal free T4 (fT4) levels, is frequently observed in the general population. Prevalence ranges from 0.6% to 1.8% in the adult population, depending on age, sex, and iodine intake. Several studies reported a worse prognosis in patients with heart failure with reduced ejection fraction (HFrEF) and SH, but they considered heterogeneous populations suffering mainly from severe SH. Aim of this study was to evaluate if SH was independently associated with the occurrence of cardiovascular death considering 30 months of follow-up. 277 HFrEF patients enrolled in the prospective, multicenter, observational T.O.S.CA. (Terapia Ormonale Scompenso CArdiaco) registry, were included in this analysis. Patients were divided into two groups according to the presence of SH (serum TSH levels > 4.5 mIU/L with normal fT4 levels). Data regarding clinical status, echocardiography, and survival were analyzed. Twenty-three patients displayed SH (87% mild vs 13% severe), while 254 were euthyroid. No differences were found in terms of age, sex, HF etiology, and left ventricular ejection fraction. When compared with the euthyroid group, SH patients showed higher TSH levels (7.7 ± 4.1 vs 1.6 ± 0.9, p < 0.001), as expected, with comparable levels of fT4 (1.3 ± 0.3 vs 1.3 ± 0.3, p = NS). When corrected for established predictors of poor outcome in HF, the presence of SH resulted to be an independent predictor of cardiovascular mortality (HR: 2.96; 5-95% CI:1.13-7.74; p = 0.03). Since thyroid tests are widely available and inexpensive, they should be performed in HF patients to detect subclinical disorders, evaluate replacement therapy, and improve prognosis.

Evaluation of thyroid congestion in patients with heart failure using shear wave elastography: An observational study

Shear wave elastography (SWE) is a noninvasive method for measuring organ stiffness. Liver stiffness measured using SWE reflects hepatic congestion in patients with heart failure (HF). However, little is known about the use of SWE to assess other organ congestions. This study aimed to evaluate the utility of SWE for assessing not only the liver but also thyroid congestion in patients with HF. This prospective study included 21 patients with HF who have normal thyroid lobes (age: 77.0 ± 11.0, men: 14). Thyroid and liver stiffness were measured by SWE using the ARIETTA 850 ultrasonography system (Fujifilm Ltd., Tokyo, Japan). SWE of the thyroid was performed on B-mode ultrasonography; a target region was identified within a region of interest. SWE was performed in each lobe of the thyroid gland. Five measurements were taken at the same location and the averages were recorded for comparison. We investigated the relationship between SWE for evaluating thyroid stiffness and the clinical characteristics of patients with HF. SWE of the thyroid was significantly correlated with SWE of the liver (R = 0.768, P < .001), thyroid stimulation hormone (R = 0.570, P = .011), free thyroxine (R = 0.493, P = .032), estimated right atrial pressure (RAP; R = 0.468, P = .033), and composite congestion score (R = 0.441, P = .045). SWE may be useful for evaluating thyroid stiffness and assessing the degree of thyroid congestion. Thyroid congestion may reflect the elevation of RAP and cause thyroid dysfunction through organ congestion.

The effect of preoperative TSH levels on perioperative complications in patients undergoing pituitary surgery

INTRODUCTION

Pituitary surgery involves special conditions for the anaesthetist due to the anatomical localisation and the role of the pituitary gland in hormonal balance. The aim of this study was to retrospectively investigate the effect of TSH levels on perioperative complication rates in patients undergoing pituitary surgery.

METHODS

In this study, patients who underwent pituitary surgery at Izmir Katip Celebi University Ataturk Training and Research Hospital between January 2017 and November 2022 were retrospectively screened. Two patients out of the 137 were excluded from the study as they underwent simultaneous aneurysm surgery along with pituitary tumor surgery. A total of 135 patients meeting the criteria were analyzed. Patients were divided into three groups according to TSH levels. Perioperative complication rates and mortality rates were compared between the three groups.

FINDINGS

The study included a total of 135 patients, with an age range of 16-76 years. Among the groups with low-normal-high TSH levels, there were no statistically significant difference observed, in postoperative complications, such as epistaxis, rhinorrhea, postoperative nausea/vomiting, seizures, hypertension, and hypotension. When looking at the incidence of postoperative diabetes insipidus, a significant difference was found between the groups. When examining the mortality rates on the 28th day, a significant difference was found between the groups, with a mortality rate of 25% in the high TSH group (p < 0.5).

CONCLUSIONS

The risk of perioperative mortality is higher in patients with TSH levels above normal.

Effects of levothyroxine in subclinical hypothyroidism and heart failure with reduced ejection fraction: An open-label randomized trial

We report a randomized, multicenter, open-label trial (ClinicalTrials.gov: NCT03096613) to investigate the clinical benefits of levothyroxine (L-T4) administration in subclinical hypothyroidism (SCH) patients with heart failure with reduced ejection fraction (HFrEF). Overall, 117 patients were enrolled and received L-T4 plus standard HFrEF treatment (experimental group, N = 57) or standard HFrEF therapy alone (control group, N = 60). The change of 6-min walk test distance in the experimental group was significantly higher than that in the control group at 24 weeks (70.08 ± 85.76 m vs. 27.73 ± 82.00 m, mean difference [95% confidence interval (CI)] 46.90 [12.90, 80.90], p < 0.001). Improvements in New York Heart Association (NYHA) classification (p = 0.033) and thyroid function were significant. Adverse event incidence was similar between groups (risk ratio [95% CI]: 0.942 1.053 (0.424, 2.616); p = 0.628). L-T4 addition to HFrEF treatment improved activity tolerance, NYHA class, and thyroid function within 6 months, suggesting its potential for combined therapy in HFrEF patients with SCH. Future double-blind, placebo-controlled trials should be performed to confirm these results.

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

Background and aims

Hyperthyroidism is an endocrine disease with multiple etiologies and manifestations. Heart failure (HF) is a common, costly, and deadly medical condition in clinical practice. Numerous studies have suggested that abnormal thyroid function can induce or aggravate the development of heart disease. However, no study has demonstrated a causal relationship between hyperthyroidism and heart failure. Therefore, the purpose of this study was to explore the causal link between hyperthyroidism and HF.

Methods

Summary data for genetically predicted hyperthyroidism were obtained from a genetic association study. The data examined for genetically determined all-cause heart failure came from 218,208 individuals from the FinnGen Consortium. Two-sample Mendelian randomization (MR) analysis was used to estimate the causal link between hyperthyroidism and heart failure. Statistical analyses were conducted using the inverse variance-weighted, weighted median, simple median, weighted mode, MR-PRESSO (number of distribution = 5000), MR-Egger, and leave-one-out.

Results

The results of the inverse-variance weighted analysis indicated a causal association between hyperthyroidism and an increased risk of all-cause heart failure (IVW: β=0.048, OR=1.049, 95%CI: [1.013 to 1.087], P=0.007). Similarly, the weighted median approach demonstrated a positive correlation between hyperthyroidism and all-cause heart failure (OR=1.049, [95% CI, 1.001-1.100]; P=0.044). Additionally, no horizontal pleiotropy or heterogeneity was observed. The leave-one-out analysis revealed that the majority of the SNP-driven associations were not influenced by a single genetic marker.

Conclusion

Our study observed a causal relationship between hyperthyroidism and all-cause heart failure. Hyperthyroidism may associate with heart failure genetically.

The effect of over- and undertreatment of hypothyroidism on hospitalization outcomes of patients with decompensated heart failure

The effect of over- and undertreatment of hypothyroidism on hospitalization outcomes of patients with acute decompensated heart failure (HF) has not been evaluated yet. We conducted retrospective cohort analyses of outcomes among 231 consecutive patients with treated hypothyroidism who were admitted to internal medicine departments of Shamir Medical Center with HF (2011-2019). Patients were divided into three groups according to their thyroid-stimulating hormone (TSH) levels: well treated (TSH: 0.4-4 mIU/L), overtreated (TSH: <0.4 mIU/L), and undertreated (TSH: >4 mIU/L). The main outcomes were mortality and recurrent hospitalization within 3 months. Among 231 patients, 106 were euthyroid, 14 were overtreated, and 111 undertreated. Patients' mean age was 79.8 ± 9.4 years. In-hospital mortality occurred in 4.7% in euthyroid patients, 14.3% in the overtreated group, and 10.7% in the undertreated group (p = 0.183). Differences in 30-day (p = 0.287) and 90-day (p = 0.2) mortality or recurrent hospitalization (p = 0.438) were not significantly different as well. However, in patients who were markedly undertreated and overtreated (TSH: >10 mIU/L or below 0.4 mIU/L) compared with 0.4-10 mIU/L, a significant increase in 90-day mortality was observed (33.3% vs 15.1% p = 0.016). Treatment status was independently associated with 90-day mortality after controlling for confounders with an adjusted odds ratio of 3.55 (95% confidence interval: 1.39-9.06). Although mild under- or overtreatment of hypothyroidism does not have a significant detrimental effect on hospitalization outcomes of patients with acute decompensated HF, markedly under- and overtreatment are independently associated with rehospitalizations and 90-day mortality. Larger cohorts are needed to establish the relationship between treatment targets and hospitalization outcomes of patients at risk for HF hospitalization.

Thyroid-stimulating hormone regulates cardiac function through modulating HCN2 via targeting microRNA-1a

Previous studies have found microRNA-1 (miR-1) and hyperpolarization-activated cyclic nucleotide-gated channel 2 (HCN2) may be involved in the pathogenesis of thyroid hormone (TH) induced cardiac hypertrophy. However, little is known about the role of miR-1 and HCN2 in thyroid stimulation hormone (TSH)-induced cardiac dysfunction. In order to investigate the molecular mechanisms of TSH induced cardiac dysfunction and the role of miR-1/HCN2 in that process, we evaluated the expression of miR-1a/HCN2 in the ventricular myocardium of hypothyroid mice and in TSH-stimulated H9c2 cardiomyocytes. Our data revealed that hypothyroidism mice had smaller hearts, ventricular muscle atrophy, and cardiac contractile dysfunction compared with euthyroid controls. The upregulation of miR-1a and downregulation of HCN2 were found in ventricular myocardium of hypothyroid mice and TSH-stimulated H9c2 cardiomyocytes, indicating that miR-1a and HCN2 may be involved in TSH-induced cardiac dysfunction. We also found that the regulation of miR-1a and HCN2 expression and HCN2 channel activity by TSH requires TSHR, while the regulation of HCN2 expression and HCN2 channel function by TSH requires miR-1a. Thus, our data revealed the potential mechanism of TSH-induced cardiac dysfunction and might shed new light on the pathological role of miR-1a/HCN2 in hypothyroid heart disease.

High-TSH Subclinical Hypothyroidism Is Associated With Postoperative Mortality in Acute Type A Aortic Dissection

BACKGROUND

Subclinical hypothyroidism can negatively affect the cardiovascular system and increase the risk of mortality, especially for individuals with thyroid-stimulating hormone (TSH) levels above 10 mU/L. We investigated the relationship between high-TSH subclinical hypothyroidism and postoperative mortality in acute type A aortic dissection (ATAAD) patients.

METHOD

We enrolled 146 patients with ATAAD who underwent aortic surgery in Beijing Anzhen Hospital from July 2016 to November 2018. Thyroid hormone levels were obtained before surgery, and participants were divided into a ≥10mU/L TSH level group and a <10mU/L level group. Cox proportional hazard regression and subgroup analysis were conducted to examine the association of preoperative high-TSH subclinical hypothyroidism with postoperative mortality.

RESULT

Participants with preoperative high-TSH (≥10mU/L) subclinical hypothyroidism tended to have longer hospitalization stays after surgery [16.0 (IQR 11.0-21.0) days vs 12.5 (IQR 8.0-16.0) days, P=0.001]. During the first 30 days after operation, 15 of 146 patients died (10.3%); during a median of 3.16 (IQR 1.76-4.56) years of follow-up, 24 patients died (16.4%). Cox proportional hazard regression showed that preoperative high-TSH subclinical hypothyroidism was independently associated with 30-day mortality (HR=6.2, 95% CI, 1.7-22.0, P=0.005) and postoperative mortality after adjusting for age, sex, BMI, hypertension, ejection fraction, diabetes and history of PCI (HR=3.4, 95% CI, 1.4-8.0, P=0.005).

CONCLUSION

This study showed that preoperative high-TSH subclinical hypothyroidism was an independent predictor of postoperative mortality in ATAAD patients who underwent aortic surgery.

Association of Thyroid-Stimulating Hormone (TSH) Levels With the Prognosis of Patients Undergoing Heart Transplantation: A Retrospective Study

Purpose: To investigate the impact of TSH levels using a more stringent cutoff of subclinical hypothyroidism (i.e., TSH > 2.5 mIU/L) on the short-term complications and long-term prognosis in patients who underwent heart transplantation (HTx). Methods: This is a retrospective study of consecutive patients with end-stage heart failure (HF) who underwent HTx. They were divided into three groups: thyroid-stimulating hormone (TSH) ≤ 2.50 mIU/L (L-TSH), 2.50 < TSH ≤ 4.91 mIU/L (M-TSH), and TSH > 4.91 mIU/L (H-TSH). The outcomes are all-cause death and cardiogenic death. Results: There are 63 (70%) males and 27 (30%) females. Nine (10%) patients died within 1 month after surgery, including five cardiogenic deaths. By 1 year, a total of 19 patients total were dead. The survival rate in the M-TSH group was significantly higher than that of the L-TSH group (P = 0.017). After adjusted by variables of sex, age, BMI, diabetes history, hypertension history, the multivariable Cox analysis showed that body mass index (HR = 0.804, 95%CI: 0.680-0.951, P = 0.011), and L-TSH (HR = 8.757, 95%CI: 1.786-42.948, P = 0.007 vs. M-TSH), and H-TSH (HR = 6.427, 95%CI: 1.137-36.327, P = 0.035 vs. M-TSH) were independently associated with all-cause death. The multivariable Cox analysis showed that body mass index (HR = 0.703, 95%CI: 0.564-0.878, P = 0.002), and L-TSH (HR = 17.717, 95%CI: 1.907-164.607, P = 0.011 vs. M-TSH) were independently associated with cardiogenic death. Conclusion: For patients with end-stage HF undergoing HTx, low and high baseline TSH levels are independently associated with 1-year all-cause death and low baseline TSH levels with cardiogenic death.

The association of presystolic wave with subclinical left-ventricular dysfunction in patients with subclinical hypothyroidism

PURPOSE

Subclinical hypothyroidism (SCH) patients develop left-ventricular dysfunction (LVD) in an earlier stage. LVD could be detected with myocardial performance index (MPI), left -ventricular global longitudinal strain (LVGLS), and conventional and tissue-Doppler imaging (TDI). A presystolic wave (PSW) detected on late diastole is associated with LVD. We aimed to determine whether there is an association between PSW and subclinical LVD assessed by different echocardiographic methods in SCH patients.

METHODS

We prospectively enrolled 105 patients diagnosed with SCH in this study. Patients were divided into two groups based on the presence of PSW. Both groups were compared with respect to demographic, clinical, and echocardiographic properties. Multivariable regression analysis was performed to detect predictors of subclinical LVD.

RESULTS

The study included 70 PSW-positive patients (66%, mean age: 50.2) and 35 PSW-negative patients (34%, mean age: 46.5). PSW-positive patients had a lower platelet and a higher RDW level compared to PSW-negative patients. PSW-positive patients had more frequent subclinical LVD, which was assessed by MPI, by conventional and TDI parameters, and by LVGLS. PSW velocity was significantly correlated with MPI velocity (r = 0.31, p = 0.009), TSH level (r = 0.44, p < 0.001), and with LVGLS (r = 0.33, p = 0.005). The presence of PSW was an independent predictor of subclinical LVD in multivariable logistic regression analysis detected with MPI, LVGLS, and TDI parameters (OR = 5.409, p = 0.03; OR = 4.872, p = 0.005; OR = 5.632, p = 0.014, respectively).

CONCLUSION

PSW prevalence was 66% in SCH patients. PSW velocity was significantly correlated with MPI and LVGLS. The presence of PSW was independently associated with subclinical LVD in SCH patients.

Evaluation of Thyroid Function in Patients Hospitalized for Acute Heart Failure

BACKGROUND

Thyroid hormones (TH) are crucial for cardiovascular homeostasis. Recent evidence suggests that acute cardiovascular conditions, particularly acute heart failure (AHF), significantly impair the thyroid axis. Our aim was to evaluate the association of thyroid function with cardiovascular parameters and short- and long-term clinical outcomes in AHF patients.

METHODS

We performed a single-centre retrospective cohort study including patients hospitalized for AHF between January 2012 and December 2017. We used linear, logistic, and Cox proportional hazard regression models to analyse the association of thyroid-stimulating hormone (TSH) and free thyroxine (FT4) with inpatient cardiovascular parameters, in-hospital mortality, short-term adverse clinical outcomes, and long-term mortality. Two models were used: (1) unadjusted, and (2) adjusted for age and sex.

RESULTS

Of the 235 patients included, 59% were female, and the mean age was 77.5 (SD 10.4) years. In the adjusted model, diastolic blood pressure was positively associated with TSH [β = 2.68 (0.27 to 5.09); p = 0.030]; left ventricle ejection fraction (LVEF) was negatively associated with FT4 [β = -24.85 (-47.87 to -1.82); p = 0.035]; and a nonsignificant trend for a positive association was found between 30-day all-cause mortality and FT4 [OR = 3.40 (0.90 to 12.83); p = 0.071]. Among euthyroid participants, higher FT4 levels were significantly associated with a higher odds of 30-day all-cause death [OR = 4.40 (1.06 to 18.16); p = 0.041]. Neither TSH nor FT4 levels were relevant predictors of long-term mortality in the adjusted model.

CONCLUSIONS

Thyroid function in AHF patients is associated with blood pressure and LVEF during hospitalization. FT4 might be useful as a biomarker of short-term adverse outcomes in these patients.

Treatment of subclinical hypothyroidism: assessing when treatment is likely to be beneficial

Introduction: Subclinical hypothyroidism (SCH) is a common condition diagnosed in up to 16% of the population. SCH is diagnosed when serum TSH is high and circulating thyroid hormones are within the reference range. SCH is considered to be a mild form of thyroid failure by some due to the log-linear relationship between TSH and thyroid hormones. Nevertheless, it is unclear whether the treatment of SCH with thyroid hormones is beneficial, and hence, it is not surprising that expert opinions and recommendations from societies differ in their opinions on how best to manage SCH.Areas covered: This article reviews the currently available evidence pertaining to SCH and provides recommendations as to when treatment of SCH should be considered. An electronic search of PubMed from 1970 to 2019 was performed and systematically reviewed studies assessing the effects of treatment in SCH. The main areas that are considered are the effects of treatment on symptoms and quality of life, and important clinical consequences including psychocognitive outcomes and cardiovascular events.Expert opinion: Treatment of SCH with thyroid hormones is debated and the current literature in this area lacks clarity. We provide an evidence-based recommendation for when treatment of SCH with thyroid hormones should be considered.

Relation Between Thyroid Function and Mortality in Patients With Chronic Heart Failure

Thyroid dysfunction is common in patients with chronic heart failure (CHF), but there is conflicting evidence regarding its prognostic significance. We investigated the relation between thyroid function and prognosis in a large, well characterized cohort of ambulatory patients with CHF. Heart failure was defined as signs and symptoms of the disease and either left ventricular systolic dysfunction (LVSD) mild or worse (heart failure with reduced ejection fraction [HFrEF]), or no LVSD and raised amino-terminal pro-B-type natriuretic peptide (NT-proBNP) levels (>125 ng/L; heart failure with normal ejection fraction [HFnEF]). Euthyroid state was defined as a thyroid-stimulating hormone (TSH) level between 0.35 and 4.70 mIU/l, hypothyroidism as TSH >4.70 mIU/l, and hyperthyroidism as TSH <0.35 mIU/l. 2997 patients had HFrEF and 1995 patients had HFnEF. 4491 (90%) patients were euthyroid, 312 (6%) were hypothyroid, and 189 (4%) were hyperthyroid. In univariable analysis, both hypothyroid patients (hazard ratio [HR] 1.25, 95% confidence interval [CI] 1.08 to 1.45) and hyperthyroid patients (HR 1.21, 95% CI 1.01 to 1.46) had a greater risk of death compared with euthyroid patients. There was a U-shaped relation between TSH and outcome. Increasing TSH was a predictor of mortality in univariable analysis (HR 1.02, 95% CI 1.01 to 1.03), but the association disappeared in multivariable analysis. The three strongest predictors of adverse outcome were increasing age, increasing NT-proBNP, and higher NYHA class. In conclusion, although thyroid dysfunction is associated with worse survival in patients with CHF, it is not an independent predictor of mortality.

[Use of thyroid hormones in the treatment of cardiovascular diseases: literature review]

Cardiovascular diseases remain the leading cause of death all over the world. Thyroid hormones play a significant role in the regulation of cardiac function. According to a number of researches, patients with cardiovascular diseases usually have a decrease in the concentration of thyroid hormones in the blood serum, which may be associated with a poor prognosis. Today it still remains unclear whether the change in the bioavailability of thyroid hormones in the myocardium is a favorable physiological mechanism or a replication of an adaptation disorder. Experimental researches suggest that thyroid hormone therapy may be applied in clinical cardiology. This review describes the results of researches examining the use of thyroid hormones in patients with cardiovascular diseases, as well as experiment data on animal models. The available data on the use of thyroid hormones in patients with acute myocardial infarction and heart failure allow us to suggest that normalization of thyroid hormone levels is a safe and potentially effective treatment method in the group of patients with cardiovascular disease. At the same time, the data on the use of thyroid hormones in patients who have undergone an open-heart surgery or heart transplantation are limited. However, at present, it is difficult to draw unambiguous conclusions about the benefits, as well as about the possible risk of using thyroid hormones in the described conditions. Large-scale clinical researches are required to confirm the safety and evaluate the effectiveness of such therapy. Moreover, it is necessary to set parameters for evaluating the safety and effectiveness and understand which hormone (thyroxine or triiodothyronine), what dosage and at what stage of the disease should be applied. Until we do not have answers for these questions, thyroid hormone therapy in patients with cardiovascular diseases should remain within the research field.

Congestive Heart Failure and Thyroid Dysfunction: The Role of the Low T3 Syndrome and Therapeutic Aspects

Background:

Both the morbidity and mortality rates from congestive heart failure (CHF) remain elevated despite the medical and non-medical management of the disease, thus suggesting the existence of residual risk factors such as thyroid dysfunction. Particularly, the 15-30% of patients with CHF, especially those with severe ventricular dysfunction, display the so-called low T3 syndrome (LT3S), which seems to negatively affect the cardiovascular prognosis.

Objective:

Only a few clinical trials have been carried out to verify both the safety and the efficacy of thyroid replacement in the LT3S, aiming to ameliorate the prognosis of CHF, and most of the results were controversial.

Methods:

Since the aim of the present review was to briefly overview both the indication and contraindication of triiodothyronine replacement in CHF and LT3S, the authors searched PubMed using the medical subject headings (MeSH) related to the following terms: “congestive heart failure” and “low T3 syndrome” or “euthyroid sick syndrome” or “non-thyroidal sick syndrome”. The research study only focused on the narrative and systematic reviews, randomized clinical trials and meta-analysis studies which were conducted before June 2019.

Results:

Studies conducted in both animal models and humans provided controversial information about the effectiveness and safety of the T3 replacement for improving ventricular dysfunction, particularly in the long-term.

Conclusion:

Further clinical trials are needed to better explore the role of LT3S in patients with CHF and its consequent therapeutic strategy in this clinical setting.

Thyroid Disorders and Prognosis in Chronic Heart Failure: A Long-Term Follow-Up Study

BACKGROUND

Thyroid disorders may have a negative impact on the prognosis of patients affected by chronic heart failure (CHF).

OBJECTIVE

The aim of the current study was to evaluate the prognostic role of all thyroid disorders over a long term follow-up in a single centre large sample of CHF outpatients.

METHODS

In all patients, the function of the thyroid was evaluated at the enrolment and during the follow- up. On the basis of free triiodothyronine (T3), free thyroxine (fT4) and thyroid-stimulating hormone (TSH) serum levels, patients were classified into one of the following four categories: euthyroid subjects, patients affected by hypothyroidism, low T3 (LT3) syndrome and hyperthyroidism. During the follow-up, death for all causes was assessed as primary end-point, whereas time to the first hospitalization for heart failure worsening was the secondary end-point analyzed.

RESULTS

Among 762 patients, 190 patients were affected by hypothyroidism (Hypo). LT3 syndrome was diagnosed in 15 patients and 59 patients were affected by hyperthyroidism (Hyper). During a long term follow-up (5.1±3.7 years), 303 patients died. Patients with Hypo showed an increased risk of death as well as of hospitalization due to heart failure worsening at univariate regression analysis. At multivariate regression analysis, Hypo remained associated with hospitalization after correction for age >75 years, ischemic aetiology, diabetes, therapy with ACE-inhibitors or ARBs, therapy with betablockers and with aldosterone antagonists, NYHA class 3, systolic arterial pressure <95 mmHg, left ventricular ejection fraction <30%, estimated glomerular filtration rate <60 ml/min, hyponatremia and NTproBNP> 1000 pg/ml. At multivariate analysis, the independent association with death was significant only for the subgroup of patients with TSH >10 mIU/L. LT3 was independently associated with both heart failure hospitalization and death, whereas Hyper was not associated with any of the two considered end-points.

CONCLUSION

Hypo is associated with a worse prognosis over a long-term follow-up. The association with heart failure hospitalization is not dependent on the baseline TSH levels, whereas the association with death is significant only when TSH >10 mIU/L. Finally, Hyper does not have any association with a worse prognosis.

Novel uses of thyroid hormones in cardiovascular conditions

Thyroid hormone levels are reduced in cardiovascular diseases and this phenomenon is associated with worse outcomes. It is unclear whether the changes in thyroid hormone bioavailability to the affected myocardium are beneficial or if this is a maladaptive response. Experimental studies from animal models of acute myocardial infarction (AMI) suggest that thyroid hormone treatment may be beneficial. There is limited data available on the use of thyroid hormones in patients with AMI and heart failure and this suggests that treatment to normalise thyroid hormone levels may be safe and potentially efficacious. Similarly, evidence of thyroid hormone therapy in patients undergoing cardiac surgery or during cardiac transplantation is limited. It is therefore difficult to draw any firm conclusions about benefits or risks of thyroid hormone treatment in these conditions. Large scale clinical trials of thyroid hormones in patients with cardiac conditions are required to confirm safety and evaluate efficacy. Furthermore, it needs to be elucidated which hormone to administer (thyroxine or triiodothyronine), when in the disease pathway to treat, dose of thyroid hormone to administer, and which parameters to utilise to assess safety and efficacy. Until these important questions are answered thyroid hormone therapy in cardiovascular diseases must remain within the research domain.

New insights into the pathogenesis and treatment of sarcopenia in chronic heart failure

Sarcopenia is an age-related geriatric syndrome that is characterized by a progressive loss of muscle mass, strength and function. Chronic heart failure (CHF), the final stage of various cardiovascular diseases, may be closely correlated with the occurrence of sarcopenia. Accumulating evidence has demonstrated that CHF can promote the development of sarcopenia through multiple pathophysiological mechanisms, including malnutrition, inflammation, hormonal changes, oxidative stress, autophagy, and apoptosis. Additionally, CHF can aggravate the adverse outcomes associated with sarcopenia, including falls, osteoporosis, frailty, cachexia, hospitalization, and mortality. Sarcopenia and CHF are mutually interacting clinical syndromes. Patients with these two syndromes seem to endure a double burden, with no particularly effective way to hinder their progression. However, the combination of physical exercise, nutritional supplements, and drug therapy may counteract the development of these maladies. In this review, we will summarize the latest progress in the pathogenesis and treatment of sarcopenia in patients with CHF.

Subclinical thyroid dysfunction is associated with adverse prognosis in heart failure patients with reduced ejection fraction

BACKGROUND

Subclinical thyroid dysfunction whose typical patterns include subclinical hypothyroidism and subclinical hyperthyroidism, has been indicated to be associated with an increased risk of heart failure (HF). However, the relationship between subclinical thyroid dysfunction and the clinical outcomes of HF patients is uncertain. This meta-analysis was conducted to assess the association between subclinical thyroid dysfunction and the clinical outcomes of HF patients.

METHODS

Pubmed, Embase, Web of Science and Cochrane Central Register of Clinical Trials were searched for eligible studies published up to August 1, 2018 which reported the association between subclinical thyroid dysfunction and the clinical outcomes of HF patients. The pooled hazard ratio (HR) with the corresponding 95% confidence interval (CI) was used to assess the association.

RESULTS

Fourteen studies met the eligibility criteria and a total of 21,221 patients with heart failure were included in the meta-analysis. Compared with HF patients with euthyroidism, the pooled HR of subclinical hypothyroidism for all-cause mortality was 1.45 (95% CI 1.26-1.67) in a randomized effects model with mild heterogeneity (I² = 40.1, P = 0.073). The pooled HR of subclinical hypothyroidism for cardiac death and/or hospitalization was 1.33 (1.17-1.50) in a randomized effects model with moderate heterogeneity (I² = 69.4, P < 0.001). Subclinical hyperthyroid can increase the risk of all-cause mortality without heterogeneity (HR 1.31, 95% CI 1.10-1.55, I² = 25.5%, P = 0.225) but have no influence on the risk of cardiac death and/or hospitalization (HR 1.03, 95% CI 0.87-1.23, I² = 0.0%, P = 0.958). These significant adverse associations were also retained in subgroup analysis. Sensitivity analysis demonstrated the stability of the results of our meta-analysis.

CONCLUSIONS

Both subclinical hypothyroidism and subclinical hyperthyroidism are associated with adverse prognosis in patients with HF. Subclinical thyroid dysfunction may be a useful and promising predictor for the long-term prognosis in HF patients.

Thyroid Function in Patients With a Fontan Circulation

In this study, we tested our hypothesis that thyroid function is impaired and contributes to perturbed hemodynamics in patients after Fontan operation. Cardiac catheterization and blood tests for thyroid function were performed in 37 patients who underwent a Fontan operation. Among them, 12 patients (33%) had subclinical thyroid dysfunction with an elevated thyroid-stimulating hormone level despite normal thyroxine levels. Thyroid-stimulating hormone levels were significantly correlated with central venous pressure (p <0.01, R² = 0.3), and patients with subclinical hypothyroidism showed significantly elevated γ-glutamyltransferase level, an indicator of liver congestion, compared with the other patients (125.6 ± 12.2 vs 67.6 ± 4.6 IU/L, p <0.01). In addition, the levels of free triiodothyronine, an effective thyroid hormone, were significantly lower in patients with subclinical hypothyroidism than in those with normal thyroid function (3.1 ± 0.1 vs 3.5 ± 0.1 pg/dl, p <0.01). The free triiodothyronine level was significantly and negatively correlated with the relaxation time constant (p = 0.03) and brain natriuretic hormone (p <0.01) level and positively correlated with the cardiac index (p = 0.04). In conclusion, venous congestion in Fontan patients may cause thyroid dysfunction, which can be responsible for decreased ventricular function and cardiac output in Fontan patients. Thus, thyroid function should be routinely monitored after Fontan surgery.

Efficacy and safety of levothyroxine (L-T4) replacement on the exercise capability in chronic systolic heart failure patients with subclinical hypothyroidism: Study protocol for a multi-center, open label, randomized, parallel group trial (ThyroHeart-CHF)

Background

Subclinical hypothyroidism is a common condition in patients with heart failure and is defined as elevated serum thyroid hormone (TSH) with normal circulating free thyroxine (FT4). Evidence on the effect of thyroid hormone treatment is lacking. We designed a randomized controlled trial to compare the efficacy and safety of thyroid hormone supplementation in patients with chronic heart failure complicated with subclinical hypothyroidism.

Methods/design

Eligible participants were identified from the cardiology units of five study centers based on the following criteria: 18 years or older, systolic heart failure with NewYork Heart Association (NYHA) class II–III, left ventricular ejection fraction ≤ 40%, and subclinical hypothyroidism (TSH > 4.78μIU/ml, < 10 μIU/ml + FT4 level within reference range). Eligible patients will be randomly assigned in a 1:1 manner to receive thyroxine replacement therapy plus standard chronic heart failure (CHF) treatment or only standard CHF therapy. Levothyroxine will be administered at an initial dose of 12.5 μg once daily and will be titrated until TSH is within the normal range. The primary endpoints include the difference in distance of the six-minute walk test between 24 weeks and baseline. The secondary endpoints include differences in plasma NT-proBNP levels and serum lipid profiles, changes in the NYHA classification, cardiovascular death, re-hospitalization, differences in echocardiographic and cardiac magnetic resonance imaging measures, and Minnesota Living With Heart Failure Questionnaire (MLHFQ) results between 24 weeks and baseline.

Discussion

ThyroHeart-CHF is designed as a prospective, multi-center, randomized, controlled clinical trial to study the efficacy and safety of thyroid hormone supplementation in patients with chronic heart failure complicated with subclinical hypothyroidism. The study findings will have significant implications for discovering the new therapeutic targets and methods of heart failure.

Trail Registration

ClinicalTrials.gov, NCT03096613. Registered on 30 March 2017.

Subclinical hypothyroidism and the development of heart failure: an overview of risk and effects on cardiac function

The prevalence of subclinical hypothyroidism (SCH) ranges from 5 to 15% of the general population. However, it remains controversial if SCH warrants life-long thyroxine replacement therapy. Patients with a thyroid-stimulating hormone (TSH) level > 10 mIU/L have a higher risk of developing heart failure with reduced ejection fraction as compared to subjects with normal thyroid function. However, abnormally high TSH levels could also be connected with an overall lower metabolic rate and better survival in elderly subjects. The potential mechanisms responsible for diastolic dysfunction of the left ventricle (LV) in SCH are connected with endothelial dysfunction and arterial stiffness, inflammatory state and are driven by TSH apoptosis-derived microparticles. The impact of SCH on LV systolic function is more controversial, and it is connected not only with cardiac remodelling but also with predisposition of patients with SCH to the conditions leading to heart failure. This review presents an overview of processes in the context of potential benefits of thyroxine supplementation therapy.

Hormone treatments in congestive heart failure

The common ultimate pathological feature for all cardiovascular diseases, congestive heart failure (CHF), is now considered as one of the main public health burdens that is associated with grave implications. Neurohormonal systems play a critical role in cardiovascular homeostasis, pathophysiology, and cardiovascular diseases. Hormone treatments such as the newly invented dual-acting drug valsartan/sacubitril are promising candidates for CHF, in addition to the conventional medications encompassing beta receptor blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and mineralocorticoid receptor antagonists. Clinical trials also indicate that in CHF patients with low insulin-like growth factor-1 or low thyroid hormone levels, supplemental treatment with growth hormone or thyroid hormone seems to be cardioprotective; and in CHF patients with volume overload the vasopressin antagonists can relieve the symptoms superior to loop diuretics. Furthermore, a combination of selective glucocorticoid receptor agonist and mineralocorticoid receptor antagonist may be used in patients with diuretic resistance. Finally, the potential cardiovascular efficacy and safety of incretin-based therapies, testosterone or estrogen supplementation needs to be prudently evaluated in large-scale clinical studies. In this review, we briefly discuss the therapeutic effects of several key hormones in CHF.

Dysthyroidism and Chronic Heart Failure: Pathophysiological Mechanisms and Therapeutic Approaches

Among comorbidity in chronic heart failure (CHF), dysthyroidism represents a relevant problem especially in the ageing CHF patients worldwide. Thyroid greatly affects many cardiovascular activities and its dysfunction may worsen a CHF condition. In particular, hypothyroidism has a relative high prevalence in patients with heart failure and it plays a key role in influencing CHF onset, progression and prognosis. Hyperthyroidism, is less frequent in this clinical context but it necessitates of immediate treatment because of its negative effects on cardiovascular balance. Also, it must be considered that dysthyroism may also be iatrogenic and the main responsible drug is Amiodarone.Based on the best available evidence and our cumulative clinical experience, this manuscript analyzes the prevalence, the pathophysiology and the prognostic impact of thyroid disorders in chronic heart failure.

Free Triiodothyronine Level Correlates with Myocardial Injury and Prognosis in Idiopathic Dilated Cardiomyopathy: Evidence from Cardiac MRI and SPECT/PET Imaging

Thyroid dysfunction is associated with poor prognosis in heart failure, but theories of mechanisms are mainly based on animal experiments, not on human level. We aimed to explore the relation between thyroid function and myocardial injuries in idiopathic dilated cardiomyopathy (IDCM) using cardiac magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT) and positron emission tomography (PET). Myocardial fibrosis was detected by late gadolinium enhancement (LGE) MRI, and myocardial perfusion/metabolism was evaluated by ^99mTc-MIBI SPECT /¹⁸F-FDG PET imaging. Across the quartiles of FT3, decreased percentage of segments with LGE and perfusion/metabolism abnormalities were found. As for FT4 and TSH levels, no significant distribution trend of myocardial injuries could be detected. In logistic analysis, FT3 was independently associated with the presence of LGE (OR: 0.140, 95% CI: 0.035-0.567), perfusion abnormalities (OR: 0.172, 95% CI: 0.040-0.738) and metabolism abnormalities (OR: 0.281, 95% CI: 0.081-0.971). After a median follow-up of 46 months, LGE-positive and FT3 < 2.77 pg/mL was identified as the strongest predictor of cardiac events (HR: 8.623, 95% CI: 3.626-16.438). Low FT3 level is associated with myocardial fibrosis and perfusion/metabolism abnormalities in patients with IDCM. The combination of FT3 level and LGE provides useful information for assessing the prognosis of IDCM.

The prognostic impact of thyroid function in pulmonary hypertension

BACKGROUND

Thyroid disease is common in patients with pulmonary hypertension (PH), but its effect on long-term survival remains unknown. We examined the prognostic significance of thyroid hormone levels of free triiodothyronine (fT3) and free thyroxine and thyroid-stimulating hormone (TSH), and thyroid hormone replacement (THR) therapy in PH.

METHODS

We conducted a retrospective analysis of 1,756 patients enrolled in the Giessen PH Registry in 1999 to 2013 with baseline thyroid function data; of these, 355, 533, 498, and 370 had pulmonary arterial hypertension (PAH); including 192 with idiopathic PAH (iPAH), PH due to left heart disease, PH due to lung diseases, and chronic thromboembolic PH (CTEPH), respectively. Thyroid function parameters associated with mortality were identified using Cox regression and Kaplan-Meier analyses.

RESULTS

Transplant-free survival at 1, 3, and 5 years was 86.7%, 65.6%, and 53.0%, respectively. Absence of THR therapy was an independent predictor of death in iPAH (multivariate hazard ratio [HR], 2.50; 95% confidence interval [CI], 1.06-5.75). In patients without THR therapy, TSH levels in the lowest and highest quartiles (compared with the middle 2 quartiles) independently predicted death in iPAH (HR, 1.98; 95% CI, 1.07-3.67), whereas reduced fT3 levels were independently associated with increased death in PAH (HR, 8.30; 95% CI, 2.50-25.00) and CTEPH (HR, 1.79; 95% CI, 1.14-4.20).

CONCLUSIONS

Thyroid hormone levels and THR therapy are prognostic factors in iPAH, PAH, and CTEPH. Prospective studies are warranted to verify the prognostic significance of thyroid function and the effect of THR therapy in PH.

Overexpression myocardial inducible nitric oxide synthase exacerbates cardiac dysfunction and beta-adrenergic desensitization in experimental hypothyroidism

BACKGROUND

Altered nitric oxide synthase (NOS) has been implicated in the pathophysiology of heart failure (HF). Recent evidence links hypothyroidism to the pathology of HF. However, the precise mechanisms are incompletely understood. The alterations and functional effects of cardiac NOS in hypothyroidism are unknown. We tested the hypothesis that hypothyroidism increases cardiomyocyte inducible NOS (iNOS) expression, which plays an important role in hypothyroidism-induced depression of cardiomyocyte contractile properties, [Ca(2+)]i transient ([Ca(2+)]iT), and β-adrenergic hyporesponsiveness.

METHODS AND RESULTS

We simultaneously evaluated LV functional performance and compared myocyte three NOS, β-adrenergic receptors (AR) and SERCA2a expressions and assessed cardiomyocyte contractile and [Ca(2+)]iT responses to β-AR stimulation with and without pretreatment of iNOS inhibitor (1400 W, 10(-5)mol/L) in 26 controls and 26 rats with hypothyroidism induced by methimazole (~30 mg/kg/day for 8 weeks in the drinking water). Compared with controls, in hypothyroidism, total serum T3 and T4 were significantly reduced followed by significantly decreased LV contractility (EES) with increased LV time constant of relaxation. These LV abnormalities were accompanied by concomitant significant decreases in myocyte contraction (dL/dtmax), relaxation (dR/dtmax), and [Ca(2+)]iT. In hypothyroidism, isoproterenol (10(-8)M) produced significantly smaller increases in dL/dtmax, dR/dtmax and [Ca(2+)]iT. These changes were associated with decreased β1-AR and SERCA2a, but significantly increased iNOS. Moreover, only in hypothyroidism, pretreatment with iNOS inhibitor significantly improved basal and isoproterenol-stimulated myocyte contraction, relaxation and [Ca(2+)]iT.

CONCLUSIONS

Hypothyroidism produces intrinsic defects of LV myocyte force-generating capacity and relaxation with β-AR desensitization. Up-regulation of cardiomyocyte iNOS may promote progressive cardiac dysfunction in hypothyroidism.

Prognostic Role of Hypothyroidism in Heart Failure: A Meta-Analysis

Hypothyroidism is a risk factor of heart failure (HF) in the general population. However, the relationship between hypothyroidism and clinical outcomes in patients with established HF is still inconclusive.We conducted a systematic review and meta-analysis to clarify the association of hypothyroidism and all-cause mortality as well as cardiac death and/or hospitalization in patients with HF. We searched MEDLINE via PubMed, EMBASE, and Scopus databases for studies of hypothyroidism and clinical outcomes in patients with HF published up to the end of January 2015. Random-effects models were used to estimate summary relative risk (RR) statistics. We included 13 articles that reported RR estimates and 95% confidence intervals (95% CIs) for hypothyroidism with outcomes in patients with HF. For the association of hypothyroidism with all-cause mortality and with cardiac death and/or hospitalization, the pooled RR was 1.44 (95% CI: 1.29-1.61) and 1.37 (95% CI: 1.22-1.55), respectively. However, the association disappeared on adjustment for B-type natriuretic protein level (RR 1.17, 95% CI: 0.90-1.52) and in studies of patients with mean age <65 years (RR 1.23, 95% CI: 0.88-1.76).We found hypothyroidism associated with increased all-cause mortality as well as cardiac death and/or hospitalization in patients with HF. Further diagnostic and therapeutic procedures for hypothyroidism may be needed for patients with HF.

Thyroid function within the normal range and risk of coronary heart disease: an individual participant data analysis of 14 cohorts

IMPORTANCE

Some experts suggest that serum thyrotropin levels in the upper part of the current reference range should be considered abnormal, an approach that would reclassify many individuals as having mild hypothyroidism. Health hazards associated with such thyrotropin levels are poorly documented, but conflicting evidence suggests that thyrotropin levels in the upper part of the reference range may be associated with an increased risk of coronary heart disease (CHD).

OBJECTIVE

To assess the association between differences in thyroid function within the reference range and CHD risk.

DESIGN, SETTING, AND PARTICIPANTS

Individual participant data analysis of 14 cohorts with baseline examinations between July 1972 and April 2002 and with median follow-up ranging from 3.3 to 20.0 years. Participants included 55,412 individuals with serum thyrotropin levels of 0.45 to 4.49 mIU/L and no previously known thyroid or cardiovascular disease at baseline.

EXPOSURES

Thyroid function as expressed by serum thyrotropin levels at baseline.

MAIN OUTCOMES AND MEASURES

Hazard ratios (HRs) of CHD mortality and CHD events according to thyrotropin levels after adjustment for age, sex, and smoking status.

RESULTS

Among 55,412 individuals, 1813 people (3.3%) died of CHD during 643,183 person-years of follow-up. In 10 cohorts with information on both nonfatal and fatal CHD events, 4666 of 48,875 individuals (9.5%) experienced a first-time CHD event during 533,408 person-years of follow-up. For each 1-mIU/L higher thyrotropin level, the HR was 0.97 (95% CI, 0.90-1.04) for CHD mortality and 1.00 (95% CI, 0.97-1.03) for a first-time CHD event. Similarly, in analyses by categories of thyrotropin, the HRs of CHD mortality (0.94 [95% CI, 0.74-1.20]) and CHD events (0.97 [95% CI, 0.83-1.13]) were similar among participants with the highest (3.50-4.49 mIU/L) compared with the lowest (0.45-1.49 mIU/L) thyrotropin levels. Subgroup analyses by sex and age group yielded similar results.

CONCLUSIONS AND RELEVANCE

Thyrotropin levels within the reference range are not associated with risk of CHD events or CHD mortality. This finding suggests that differences in thyroid function within the population reference range do not influence the risk of CHD. Increased CHD risk does not appear to be a reason for lowering the upper thyrotropin reference limit.

Thyroid function on admission and outcome in patients hospitalized for acute decompensated heart failure

BACKGROUND

Although thyroid dysfunction is a known prognostic factor for cardiovascular disease, the relationship between thyroid function and prognosis in patients with acute decompensated heart failure (ADHF) is poorly understood. Herein, we investigated the association between thyroid hormone levels and outcome in patients hospitalized for ADHF.

METHODS

We evaluated 270 hospitalized ADHF patients with thyroid hormone levels measured at admission between April 2007 and May 2012.

RESULTS

The median (interquartile range) thyroid stimulating hormone, free triiodothyronine (fT3), and free thyroxine were 2.79 (1.49-4.96)μU/ml, 2.32 (1.93-2.75)pg/ml, and 14.0 (12.1-15.7)pg/dl, respectively. Receiver operating characteristic (ROC) curve analysis was applied to assess their prognostic value for in-hospital outcome. The fT3 had the most favorable performance, with an area under the ROC curve of 0.791 (optimal cutoff point ≤2.05; sensitivity 85.0%; specificity 72.0%). Although patients in the low fT3 group (≤2.05) had higher age and lower body mass index, there were no significant differences with respect to systolic blood pressure and heart rate between the groups. In multivariate analysis adjusted for various markers of disease severity and amiodarone use, low fT3 level was independently associated with higher in-hospital mortality (odds ratio 14.4; p<0.001). In addition, the probability of 1-year total death among patients with low fT3 was significantly higher than that among patients with normal fT3 (log-rank p<0.001).

CONCLUSIONS

Low fT3 level was associated with adverse outcomes in patients hospitalized for ADHF. Thyroid hormone measurements might be useful in the risk stratification of ADHF patients.

Thyroid hormone replacement therapy attenuates atrial remodeling and reduces atrial fibrillation inducibility in a rat myocardial infarction-heart failure model

BACKGROUND

Heart failure (HF) is associated with increased atrial fibrillation (AF) risk. Accumulating evidence suggests the presence of myocardial tissue hypothyroidism in HF, which may contribute to HF development. In a recent report we demonstrated that hypothyroidism, like hyperthyroidism, leads to increased AF inducibility. The present study was designed to investigate the effect of thyroid hormone (TH) replacement therapy on AF arrhythmogenesis in HF.

METHODS AND RESULTS

Myocardial infarction (MI) was produced in rats by means of coronary artery ligation. Rats with large MIs (>40%) were randomized into L-thyroxine (T4; n = 14) and placebo (n = 15) groups 2 weeks after MI. Rats received 3.3 mg T4 (in 60-day release form) or placebo pellets for 2 months. Compared with the placebo, T4 treatment improved cardiac function and decreased left ventricular internal diameters as well as left atrial diameter. T4 treatment attenuated atrial effective refractory period prolongation (45 ± 1.5 ms in placebo group vs 37 ± 1.6 ms in T4 group; P < .01) and reduced AF inducibility (AF/atrial flutter/tachycardia were inducible in 11/15 rats [73%] in the placebo- vs 4/14 rats [29%] in the T4-treated group; P < .05). Arrhythmia reduction was associated with decreased atrial fibrosis but was not associated with connexin 43 changes.

CONCLUSIONS

To our knowledge this is the first study demonstrating that TH replacement therapy in HF attenuates atrial remodeling and reduces AF inducibility after MI-HF. Clinical studies are needed to confirm such benefits in human patients.

Restoration of thyroid hormone balance: a game changer in the treatment of heart failure?

The link between low thyroid hormone (TH) function and heart failure is reviewed in the present report. The idea that TH dysfunction may contribute to diseases leading to HF has been discussed for over 60 yr. A growing body of evidence from animal and human studies, particularly in recent years, suggests that TH treatment may improve clinical outcomes. Indeed, if a similar amount of positive information were available for a newly developed heart drug, there is little doubt that large-scale clinical trials would be underway with considerable excitement. THs offer the promise of improving ventricular contraction and relaxation, improving coronary blood flow, and inhibiting atherosclerosis, and new results suggest they may even reduce the incidence of arrhythmias in heart diseases. Are the potential clinical benefits worth the risk of possible overdosing? After so many years, why has this question not been answered? Clearly, the concept has not been disproven. This review explores the body of clinical evidence related to TH dysfunction and heart failure, discuss insights into pathophysiological, cellular, and molecular mechanisms provided by animal research, and discuss what is needed to resolve this long-standing issue in cardiology and move forward.

Thyroid hormone and heart failure: from myocardial protection to systemic regulation

Heart failure (HF) is an intriguing model of chronic disease. It starts as an organ disorder developing, in its progression, into a systemic disease in which the dysfunction of other organs plays a relevant clinical and prognostic impact. Furthermore, continuous activation of systemic pathways plays a role in disease progression, switching their effect from protective to harmful. In this combination of organ dysfunction and systemic derangement, thyroid hormone (TH) have an important regulative impact from cardiovascular to systemic level and from molecular/cellular processes to clinical setting. Whether it is accepted to include TH and thyroid stimulating hormone assessment in the clinical HF course, the next challenge will be to ascertain the benefit of TH replacement therapy in HF patients, taking into consideration the type of hormone to administer, dosage and treatment schedule.