Thyroid Hormone and Cardioprotection

Low T3 syndrome predicts more adverse events in patients with hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is a common cardiac genetic disorder that clinically manifests with sudden death and progressive heart failure. Moreover, thyroid dysfunction is associated with increased cardiovascular morbidity and mortality risks. Therefore, this study aimed to clarify whether thyroid hormones could serve as an independent predictor of adverse events in patients with HCM.

METHODS

The cohort consisted of 782 patients with HCM who had thyroid hormones baseline data and were admitted to the Affiliated Hospital of Jiaxing University. Patients were divided into two groups according to serum levels of free triiodothyronine (fT3): the normal fT3 and low triiodothyronine (T3) syndrome groups. Low T3 syndrome was defined as fT3 < 2.43 pmol/L with a normal thyroid-stimulating hormone (TSH) level. Patients whose TSH levels were abnormally high or abnormally low were excluded from this study. The primary endpoint was the occurrence of sudden cardiac death (SCD) events, and the secondary endpoint was a composite of worsening heart failure (WHF) events, including heart failure death, cardiac decompensation, hospitalization for heart failure, and HCM-related stroke. The Kaplan-Meier and Cox regression were performed for the survival analysis.

RESULTS

After a median follow-up of 52 months, 75 SCD events and 134 WHF events were recorded. The Kaplan-Meier survival curves showed that the cumulative incidence of SCD events and WHF events were significantly higher in patients with low T3 syndrome (log-rank p = .02 and log-rank p = .001, respectively). Furthermore, multivariate Cox regression analysis demonstrated that low T3 syndrome is a strong predictor of SCD events and WHF events (adjusted hazard ratio [HR: 1.53, 95% confidence interval [CI]: 1.13-2.24, p < .01; HR: 3.87, 95% CI: 2.91-4.98, p < .001, respectively).

CONCLUSIONS

Low T3 syndrome is highly prevalent among patients with HCM and was independently associated with an increased risk of SCD events and WHF events. The routine assessment of serum fT3 levels may provide risk stratification in this population.

Low T3 syndrome is associated with 30-day mortality in adult patients with fulminant myocarditis

Background

Fulminant myocarditis (FM) is a critical disease with high early mortality. Low triiodothyronine syndrome (LT3S) was a strong predictor of poor prognosis of critical diseases. This study investigated whether LT3S was associated with 30-day mortality in FM patients.

Methods

Ninety-six FM patients were divided into LT3S (n=39, 40%) and normal free triiodothyronine (FT3) (n=57, 60%) groups based on serum FT3 level. Univariable and multivariable logistic regression analyses were performed to identify independent predictors of 30-day mortality. Kaplan-Meier curve was used to compare 30-day mortality between two groups. Receiver operating characteristic (ROC) curve and decision curve analysis (DCA) were used to assess the value of FT3 level for 30-day mortality prediction.

Results

Compared to normal FT3 group, LT3S group had higher incidence of ventricular arrhythmias, worse hemodynamics, worse cardiac function, more severe kidney impairment, and higher 30-day mortality (48.7% vs. 12.3%, P<0.001). In univariable analysis, LT3S (odds ratio [OR]:6.786, 95% confidence interval [CI]:2.472-18.629, P<0.001) and serum FT3 (OR:0.272, 95%CI:0.139-0.532, P<0.001) were significant strong predictors of 30-day mortality. After adjustment for confounders in multivariable analysis, LT3S (OR:3.409, 95%CI:1.019-11.413, P=0.047) and serum FT3 (OR:0.408, 95%CI:0.199-0.837, P=0.014) remained independent 30-day mortality predictors. The area under the ROC curve of FT3 level was 0.774 (cut-off: 3.58, sensitivity: 88.46%, specificity: 62.86%). In DCA, FT3 level showed good clinical-application value for 30-day mortality prediction.

Conclusion

In FM patients, LT3S could independently predict 30-day mortality. FT3 level was a strong 30-day mortality predictor and a potentially useful risk-stratification biomarker.

Independent Association of Thyroid Dysfunction and Inflammation Predicts Adverse Events in Patients with Heart Failure via Promoting Cell Death

Thyroid dysfunction and inflammation are individually implicated in the increased risk of heart failure. Given the regulatory role of thyroid hormones on immune cells, this study aimed to investigate their joint association in heart failure. Patients with pre-existing heart failure were enrolled when hospitalized between July 2019 and September 2021. Thyroid function and inflammatory markers were measured at the enrollment. The composite of all-cause mortality or rehospitalization for heart failure were studied in the following year. Among 451 participants (mean age 66.1 years, 69.4% male), 141 incident primary endpoints were observed during a median follow-up of 289 days. TT3 and FT3 levels were negatively correlated with BNP levels (r: −0.40, p < 0.001; r: −0.40, p < 0.001, respectively) and NT-proBNP levels (r: −0.39, p < 0.001; r: −0.39, p < 0.001). Multivariate COX regression analysis revealed that FT3 (adjusted HR: 0.677, 95% CI: 0.551−0.832) and NLR (adjusted HR: 1.073, 95% CI: 1.036−1.111) were associated with adverse event, and similar results for TT3 (adjusted HR: 0.320, 95% CI: 0.181−0.565) and NLR (adjusted HR: 1.072, 95% CI: 1.035−1.110). Restricted cubic splines analysis indicated a linear relationship between T3 level and adverse events. Mechanistically, primary cardiomyocytes showed strong resistance to TNF-α induced apoptosis under optimal T3 concentrations, as evidenced by TUNEL staining, flow cytometry analysis, and LDH release assay as well as increased expression of Bcl-2. Thyroid dysfunction and inflammation are independently associated with cardiovascular risk in heart failure patients, which may concurrently contribute to the ongoing cardiomyocyte loss in the disease progression.

Association Between Thyroid Dysfunction and Incidence of Atrial Fibrillation in Patients With Hypertrophic Obstructive Cardiomyopathy

OBJECTIVE

To explore the correlation between the incidence of atrial fibrillation (AF) and thyroid dysfunction in patients with hypertrophic obstructive cardiomyopathy (HOCM).

METHODS

Thyroid function testing in 755 consecutive patients with HOCM were examined at the National Center for Cardiovascular Diseases (China) from October 2009 to December 2013. Patients were divided into four groups according to the TSH levels: TSH<0.55 mIU/L(n=37)、0.55~2.49 mIU/L (n=490)、2.50~9.9 mIU/L (n=211) and >10.00mIU/L(n=17).

RESULTS

A total of 107 patients were diagnosed with AF (14%).(1) Compared to HOCM patients without AF,HOCM patients with AF have older age (P<0.001), higher NT-proBNP (P=0.002), higher Cr (P=0.005), larger left atrial diameter(P=0.001), lower FT3 (P=0.046), higher FT4 (P=0.004).(2) In the four groups according to the TSH levels: TSH<0.55 mIU/L, 0.55~2.49mIU/L, 2.50~9.9mIU/L and ≥10.00mIU/L, the incidence of AF was 27.02%(10/37),10.20%(50/490), 19.43%(41/211), and 35.29%(6/17), respectively. Both high and low TSH levels were associated with an increased incidence of AF. After adjusting for the common risk factor (age, NT-proBNP, and so on), stepwise multiple logistic regression analysis revealed that TSH levels were significantly related to AF incidence.Compared to patients with TSH 0.55~2.49 mlU/L, the adjusted odds ratio of AF for TSH<0.55, 2.50~9.99, ≥10.00 mIU/L were 1.481 (95% CI 0.485~4.518,P=0.490), 1.977 (95%CI 1.115~3.506, p=0.02), 4.301 (95%CI 1.059~17.476, P=0.041), respectively.

CONCLUSION

Our results suggested that thyroid dysfunction was associated with an increased risk of AF in patients with HOCM.

Triiodothyronine maintains cardiac transverse-tubule structure and function

Subclinical hypothyroidism and low T3 syndrome are commonly associated with an increased risk of cardiovascular disease (CVD) and mortality. We examined effects of T3 on T-tubule (TT) structures, Ca²⁺ mobilization and contractility, and clustering of dyadic proteins. Thyroid hormone (TH) deficiency was induced in adult female rats by propyl-thiouracil (PTU; 0.025%) treatment for 8 weeks. Rats were then randomized to continued PTU or triiodo-L-thyronine (T3; 10 μg/kg/d) treatment for 2 weeks (PTU + T3). After in vivo echocardiographic and hemodynamic recordings, cardiomyocytes (CM) were isolated to record Ca²⁺ transients and contractility. TT organization was assessed by confocal microscopy, and STORM images were captured to measure ryanodine receptor (RyR2) cluster number and size, and L-type Ca²⁺ channel (LTCC, Ca_v1.2) co-localization. Expressed genes including two integral TT proteins, junctophilin-2 (Jph-2) and bridging integrator-1 (BIN1), were analyzed in left ventricular (LV) tissues and cultured CM using qPCR and RNA sequencing. The T3 dosage used normalized serum T3, and reversed adverse effects of TH deficiency on in vivo measures of cardiac function. Recordings of isolated CM indicated that T3 increased rates of Ca²⁺ release and re-uptake, resulting in increased velocities of sarcomere shortening and re-lengthening. TT periodicity was significantly decreased, with reduced transverse tubules but increased longitudinal tubules in TH-deficient CMs and LV tissue, and these structures were normalized by T3 treatment. Analysis of STORM data of PTU myocytes showed decreased RyR2 cluster numbers and RyR localizations within each cluster without significant changes in Ca_v1.2 localizations within RyR clusters. T3 treatment normalized RyR2 cluster size and number. qPCR and RNAseq analyses of LV and cultured CM showed that Jph2 expression was T3-responsive, and its increase with treatment may explain improved TT organization and RyR-LTCC coupling.

Cardioprotection by post-conditioning with exogenous triiodothyronine in isolated perfused rat hearts and isolated adult rat cardiomyocytes

Ischemic post-conditioning (iPoCo) by coronary re-occlusion/reperfusion during immediate reperfusion after prolonged myocardial ischemia reduces infarct size. Mechanical manipulation of culprit lesions, however, carries the risk of coronary microembolization which may obscure iPoCo's cardioprotection. Pharmacological post-conditioning with exogenous triiodothyronine (T3) could serve as an alternative conditioning strategy. Similar to iPoCo, T3 may activate cardioprotective prosurvival pathways. We aimed to study T3's impact on infarct size and its underlying signal transduction. Hearts were isolated from male Lewis rats (200-380 g), buffer-perfused and subjected to 30 min/120 min global zero-flow ischemia/reperfusion (I/R). In additional hearts, either iPoCo (2 × 30 s/30 s I/R) was performed or T3 (100-500 µg/L) infused at reperfusion. Infarct size was demarcated with triphenyl tetrazolium chloride staining and calculated as percent of ventricular mass. Infarct size was reduced with iPoCo to 16 ± 7% vs. 36 ± 4% with I/R only. The maximum infarct size reduction was observed with 300 µg/L T3 (14 ± 2%). T3 increased the phosphorylation of protein kinase B and mitogen extracellular-regulated-kinase 1/2, both key enzymes of the reperfusion injury salvage kinase (RISK) pathway. Pharmacological RISK blockade (RISK-BL) during reperfusion abrogated T3's cardioprotection (35 ± 10%). Adult ventricular cardiomyocytes were isolated from buffer-perfused rat hearts and exposed to 30 min/5 min hypoxia/reoxygenation (H/R); reoxygenation was initiated without or with T3, respectively, and without or with RISK-BL, respectively. Maximal preservation of viability was observed with 500 µg/L T3 after H/R (27 ± 4% of all cells vs. 5 ± 3% in time-matched controls). Again, RISK-BL abrogated protection (11 ± 3%). Mitochondria were isolated at early reperfusion from buffer-perfused rat hearts without or with iPoCo or 300 µg/L T3, respectively, at reperfusion. T3 improved mitochondrial function (i.e.: increased respiration, adenosine triphosphate production, calcium retention capacity, and decreased reactive oxygen species formation) to a similar extent as iPoCo. T3 at reperfusion reduces infarct size by activation of the RISK pathway. T3's protection is a cardiomyocyte phenomenon and targets mitochondria.

Ignoring a basic pathophysiological mechanism of heart failure progression will not make it go away

A link between heart failure (HF) and low thyroid hormone (TH) function has been known for over a century. Nonetheless, there is a general belief that TH treatment of patients with HF may not be worth the risk. This is largely based on two clinical trials where heart patients were treated with excessive doses of TH analogs, not actual THs. Further complicating the matter is the fact that normalization of THs in noncardiac patients can often be challenging. This issue is not going away as noted by a steady increase in TH-HF citations in recent years. In this article, we discuss what we know and how we may move the field forward.

Relative role of T-tubules disruption and decreased SERCA2 on contractile dynamics of isolated rat ventricular myocytes

AIMS

Ventricular myocytes (VM) depolarization activates L-type Ca2+ channels (LCC) allowing Ca2+ influx (ICa) to synchronize sarcoplasmic reticulum (SR) Ca2+ release, via Ca2+-release channels (RyR2). The resulting whole-cell Ca2+ transient triggers contraction, while cytosolic Ca2+ removal by SR Ca2+ pump (SERCA2) and sarcolemmal Na+/Ca2+ exchanger (NCX) allows relaxation. In diseased hearts, extensive VM remodeling causes heterogeneous, blunted and slow Ca2+ transients. Among remodeling changes are: A) T-tubules disorganization. B) Diminished SERCA2 and low SR Ca2+. However, those often overlap, hindering their relative contribution to contractile dysfunction (CD). Furthermore, few studies have assessed their specific impact on the spatiotemporal Ca2+ transient properties and contractile dynamics simultaneously. Therefore, we sought to perform a quantitative comparison of how heterogeneous and slow Ca2+ transients, with different underlying determinants, affect contractile performance.

METHODS

We used two experimental models: A) formamide-induced acute "detubulation", where VM retain functional RyR2 and SERCA2, but lack T-tubules-associated LCC and NCX. B) Intact VM from hypothyroid rats, presenting decreased SERCA2 and SR Ca2+, but maintained T-tubules. By confocal imaging of Fluo-4-loaded VM, under field-stimulation, simultaneously acquired Ca2+ transients and shortening, allowing direct correlations.

KEY FINDINGS

We found near-linear correlations among key parameters of altered Ca2+ transients, caused independently by T-tubules disruption or decreased SR Ca2+, and shortening and relaxation, SIGNIFICANCE: Unrelated structural and molecular alterations converge in similarly abnormal Ca2+ transients and CD, highlighting the importance of independently reproduce disease-specific alterations, to quantitatively assess their impact on Ca2+ signaling and contractility, which would be valuable to determine potential disease-specific therapeutic targets.

Adverse transverse-tubule remodeling in a rat model of heart failure is attenuated with low-dose triiodothyronine treatment

Abstract

Pre-clinical animal studies have shown that triiodothyronine (T3) replacement therapy improves cardiac contractile function after myocardial infarction (MI). We hypothesized that T3 treatment could prevent adverse post-infarction cardiomyocyte remodeling by maintaining transverse-tubule (TT) structures, thus improving calcium dynamics and contractility.

Methods

Myocardial infarction (MI) or sham surgeries were performed on female Sprague-Dawley rats (aged 12 wks), followed by treatment with T3 (5μg/kg/d) or vehicle in drinking water for 16 wks (n = 10–11/group). After in vivo echocardiographic and hemodynamic analyses, left ventricular myocytes were isolated by collagenase digestion and simultaneous calcium and contractile transients in single cardiomyocytes were recorded using IonOptix imaging. Live cardiomyocytes were stained with AlexaFluor-488 conjugated wheat germ agglutinin (WGA-488) or di-8-ANEPPS, and multiple z-stack images per cell were captured by confocal microscopy for analysis of TT organization. RTqPCR and immunoblot approaches determined expression of TT proteins.

Results

Echocardiography and in vivo hemodynamic measurements showed significant improvements in systolic and diastolic function in T3- vs vehicle-treated MI rats. Isolated cardiomyocyte analysis showed significant dysfunction in measurements of myocyte relengthening in MI hearts, and improvements with T3 treatment: max relengthening velocity (Vmax, um/s), 2.984 ± 1.410 vs 1.593 ± 0.325, p < 0.05 and time to Vmax (sec), 0.233 ± 0.037 vs 0.314 ± 0.019, p < 0.001; MI + T3 vs MI + Veh, respectively. Time to peak contraction was shortened by T3 treatment (0.161 ± 0.021 vs 0.197 ± 0.011 s., p < 0.01; MI + T3 vs MI + Veh, respectively). Analysis of TT periodicity of WGA- or ANEPPS-stained cardiomyocytes indicated significant TT disorganization in MI myocytes and improvement with T3 treatment (transverse-oriented tubules (TE%): 9.07 ± 0.39 sham, 6.94 ± 0.67 MI + Veh and 8.99 ± 0.38 MI + T3; sham vs MI + Veh, p < 0.001; MI + Veh vs MI + T3, p < 0.01). Quantitative RT-PCR showed that reduced expression of BIN1 (Bridging integrator-1), Jph2 (junctophilin-2), RyR2 (ryanodine receptor) and Ca_v1.2 (L-type calcium channel) in the failing myocardium were increased by T3 and immunoblot analysis further supporting a potential T3 effect on the TT-associated proteins, BIN1 and Jph2.

In conclusion, low dose T3 treatment initiated immediately after myocardial infarction attenuated adverse TT remodeling, improved calcium dynamics and contractility, thus supporting the potential therapeutic utility of T3 treatment in heart failure.

Uridine phosphorylase 1 associates to biological and clinical significance in thyroid carcinoma cell lines

Thyroid cancer incidence has been continuity increasing worldwide. Uridine phosphorylase 1 (UPP1) is a protein-coding gene and has been detected that UPP1 was the higher expression in many solid malignancies, just as head and neck cancers, breast cancer, compared with paired normal tissue. But the act of UPP1 in thyroid cancer is not explicit. In this article, we investigate the function of UPP1 expression in thyroid cancer. The Cancer Genome Atlas (TCGA) unpaired thyroid cancer and normal RNA-seq data were downloaded, and our paired thyroid cancer and normal samples were analysed by a polymerase chain reaction. The expression of UPP1 was regulated by transfected small interfering RNA, and the function of UPP1 was determined via migration, invasion and cell proliferation assays. Western blot assay was achieved to determine the UPP1 expression correlates with the function of 5-FU regulate epithelial-mesenchymal transition. The significant upregulation of UPP1 in thyroid cancer tissues compared with normal thyroid tissues was revealed by our data and TCGA data. UPP1 overexpression was significantly correlated with lymph node metastasis, tumour stage and tumour size. In the cell, experiments showed that UPP1 low expression significantly suppressed the migration, invasion and proliferation. Western blot assay proves the effect of UPP1 expression on 5-FU regulates epithelial-mesenchymal transition pathway. UPP1 plays a crucial oncogene in thyroid cancer. Our findings indicate that UPP1 might be a biomarker of thyroid cancer and may act by regulating epithelial-mesenchymal transition (EMT).

Association Between 3-Iodothyronamine (T1am) Concentrations and Left Ventricular Function in Chronic Heart Failure

CONTEXT

Thyroid hormone metabolites might affect the heart. The endogenous aminergic metabolite 3-iodothyronamine (T1am) reduces left ventricular ejection fraction (LVEF) in rodents.

OBJECTIVE

To investigate concentration of T1am and its association with LVEF and biomarkers of heart function in patients with chronic heart failure (CHF) without thyroid disease, including patients with cardiac cachexia (nonedematous weight loss >5% over 6 months).

METHODS

Cross-sectional study. CHF was characterized by LVEF <45% and symptoms. Three groups were included (n = 19 in each group, matched on age, sex, and kidney function): patients with cachexia (CAC), patients without (non-CAC), and control (C) patients with prior myocardial infarction and LVEF >45%. T1am was measured by a monoclonal antibody-based chemiluminescence immunoassay. N-amino terminal pro-BNP (NT-proBNP) concentrations were also analyzed.

RESULTS

Mean (SD) LVEF: CAC, 32 ± 9%; non-CAC, 38 ± 8%; and C, 60 ± 8% (P < 0.0001). TSH, T4, and T3 levels did not differ between groups and did not correlate to T1am. Serum T1am (nmol/L) concentrations were higher in CHF: CAC (mean ± SD), 12.4 ± 6.6; non-CAC, 9.1 ± 5; and C, 7.3 ± 2.9. A negative association between T1am and LVEF was present after adjusting for sex, age, T3, and estimated glomerular filtration rate (P = 0.03). Further, serum T1am levels tended to be associated with NT-proBNP (P = 0.053).

CONCLUSION

Serum T1am levels were increased in patients with CHF and numerically highest (although nonsignificant) in patients with cardiac cachexia. Increasing T1am concentrations were independently associated with reduced LVEF, suggesting a direct effect on the human heart.

Preoperative oral thyroid hormones to prevent euthyroid sick syndrome and attenuate myocardial ischemia-reperfusion injury after cardiac surgery with cardiopulmonary bypass in children: A randomized, double-blind, placebo-controlled trial

BACKGROUND

Both euthyroid sick syndrome and myocardial ischemia-reperfusion injury are common and have been significantly associated with morbidity and mortality after pediatric cardiac surgery with cardiopulmonary bypass. This single-center, prospective, double-blind, randomized placebo-controlled clinical pilot trial was designed to assess if preoperative oral thyroid hormone therapy could prevent the occurrence of euthyroid sick syndrome (ESS) and attenuate myocardial ischemia-reperfusion injury (IRI) after cardiac surgery with cardiopulmonary bypass (CPB) in children.

METHODS

Forty children aged 3 to 12 year, scheduled for elective congenital heart disease repair surgery with CPB, were randomized into 2 groups of equal size to receive the following treatments in a double-blind manner: placebo (control group) and thyroid tablet 0.4 mg/kg (trial group) taken orally once a day for 4 days before surgery. The perioperative serum thyroid hormone levels and hemodynamic variables were determined. The extubation time, duration of intensive care unit (ICU) stay, and use of inotropic drugs in the ICU were recorded. The myocardial expressions of heat shock protein 70 (HSP70), myosin heavy chain (MHC) mRNA, and thyroid hormone receptor (TR) mRNA were detected. The serum creatine kinase-MB (CK-MB) activity and troponin I (TnI) positive ratio at 24 hour after surgery were assessed.

RESULTS

There were no significant differences in hemodynamic variables at all observed points, extubation time, and duration of ICU stay between groups. As compared with baselines on administration, serum triiodothyronine (T3) and free T3 (FT3) levels on the first, second, and fourth postoperative day, and serum thyrotropic-stimulating hormone (TSH), tetraiodothyronine (T4), and free T4 (FT4) levels on the first postoperative day were significantly decreased in the 2 groups. Serum T3, FT3, and T4 levels on the first and second postoperative day, and serum FT4 level on the first postoperative day were significantly higher in the trial group than in control group. As compared with the control group, the number of patients requiring inotropic drugs in the ICU, serum CK-MB activity, serum positive TnI ratio, and myocardial expression of MHCβ mRNA were significantly decreased, and myocardial expressions of both HSP70 and MHCα mRNA were significantly increased in the trial group.

CONCLUSIONS

In children undergoing cardiac surgery with CPB, preoperative oral small-dose thyroid hormone therapy reduces severity of postoperative ESS and provides a protection against myocardial IRI by increasing HSP70 and MHCα expression.

Association between free thyroid hormones values and the lipid profile in middle-aged women with chronic symptoms

AIMS

To determine the association between the thyroid hormones(FT3, FT4 and TSH) and the lipid profile markers(HDL-c, LDL-c and triglycerides) values in middle-aged women with no metabolic disorders and recurrent chronic symptomatology.

MATERIALS AND METHODS

We carried out an analytical cross-sectional study in euthyroid women with recurrent chronic symptoms of at least six months with no apparent diagnosis who attended the endocrinological gynaecology outpatient service of a private clinic in Lima-Peru during 2012-2014. Participants who met the eligibility criteria were evaluated according to their thyroid hormones(FT3, FT4 and TSH) and lipid profile markers(HDL-c, LDL-c and triglycerides) values. We elaborated univariate/multivariate linear regression models to evaluate the association between the thyroid markers and the lipid profile levels. The reported association measure was the beta coefficient(β) with its respective p-value.

RESULTS

We analyzed 211 participants, the average age was 44.9 ± 14.0(SD) years, the FT3 and FT4 mean levels were 3.2 ± 0.4 pg/mL and 1.2 ± 0.2 ng/dL respectively, while the TSH median was 2.8(IQR:1.9-4.0) μU/mL. The mean or median levels of LDL-c, HDL-c and triglycerides were of 137.5 ± 37.9 mg/dL, 54.0 ± 15.0 mg/dL and 118.5(IQR:79.5-169.5) mg/dL respectively. In the multivariate linear regression model between the FT3 and LDL-c levels, we found that for each increase in a FT3 unit, the LDL-c values decreased on average 30.85 mg/dL(p < 0.01). We found no statistically significant associations in the other multivariate models of linear regression, among the other thyroid hormones and lipid markers.

CONCLUSION

We found an inverse association between the FT3 and LDL-c values in women with chronic gynaecological symptoms.

Comparison of Therapeutic Triiodothyronine Versus Metoprolol in the Treatment of Myocardial Infarction in Rats

BACKGROUND

Beta blockers are standard therapy for myocardial infarction (MI). Preclinical studies have shown efficacy and safety of thyroid hormone (TH) treatment of cardiovascular disorders. Since THs interact with the sympathoadrenergic system, this study aimed to compare triiodothyronine (T3) and metoprolol (Met) in the treatment of rats with MI on pathophysiology and TH-adrenergic signaling.

METHODS

Female Sprague-Dawley rats aged 12 weeks underwent left anterior descending coronary artery ligation (MI) or sham surgeries. T3 (5 μg/kg/day) or Met (100 mg/kg/day) was given in drinking water immediately after surgery for eight weeks. At the terminal of the experiments, the rats were subjected to morphological, functional, and molecular examination.

RESULTS

T3 and Met significantly enhanced left ventricular contractility (left ventricular fractional shortening 21.37 ± 2.58% and 21.14 ± 3.71%, respectively) compared to untreated MI (17.88 ± 1.23%), and decreased the incidence of inducible atrial tachyarrhythmia by 87.5% and 62.5%, respectively. Although both treatments showed efficacy, T3 but not Met showed statistically significant improvements compared to MI in arrhythmia duration, left atrial diameter (T3 vs. MI 4.33 ± 0.63 vs. 5.65 ± 1.32 mm; p < 0.05), fibrosis (6.1 ± 0.6%, 6.6 ± 0.6% vs. 8.2 ± 0.7%, T3, Met vs. MI, respectively), and aortic vasorelaxation responsiveness to acetylcholine (pD2 6.97 ± 0.22, 6.83 ± 0.21 vs. 6.66 ± 0.22, T3, Met vs. MI, respectively). Quantitative polymerase chain reaction showed that T3 and Met attenuated expression of genes associated with inflammation and oxidative stress and restored expression of ion channels and contractile proteins.

CONCLUSION

These results support comparable efficacy of T3 and Met treatments, suggesting that T3 may provide a therapeutic alternative to standard β-receptor blockade, especially for patients intolerant to treatment with β-blockers after MI.

Effects of enteral different-dose levothyroxinesodium pretreatment on serum thyroid hormone levels and myocardial ischemia-reperfusion injury

INTRODUCTION

The available evidence shows that perioperative oral thyroid hormone can significantly attenuate the postoperative decline in the serum hormone level and improve postoperative hemodynamic and prognostic parameters. However, there has been no study assessing the effects of preoperative oral different-dose thyroid hormone on serum hormone levels and myocardial ischemia-reperfusion injury (IRI) after cardiac surgery.

METHODS

Forty-eight healthy Wistar rats, aged 35 days, were randomly allocated into six groups: Group BC, Group C and four pretreatment groups in which the rats were given levothyroxine-sodium of 10 μg, 20 μg, 40 μg and 80 μg/100 g. On the eighth day, the serum thyroid hormone levels were determined and then an isolated heart ischemia-reperfusion model was established with a Langendorff apparatus.

RESULTS

Compared with Groups BC and C, serum thyroid hormone levels on the eighth day did not significantly change in Group 10 μg, but were significantly increased in Groups 20 μg, 40 μg and 80 μg. The cardiac enzyme myocardial-bound creatine kinase levels in the coronary effluent during reperfusion were significantly lower in Groups 10 μg and 20 μg and 40 μg than in Group C. The recovery rates of + dp/dt_max and - dp/dt_max at 30 min during reperfusion were significantly lower in Groups 40 μg and 80 μg than in Groups 10 μg and 20 μg. Compared with Group C, myocardial expressions of heat shock protein 70 and myosin heavy chain α were increased in the four experiment groups and myocardial expression of thyroid hormone receptor α1 was significantly increased in Groups 20 μg, 40 μg and 80 μg.

CONCLUSIONS

The pretreatment with enterally smaller doses levothyroxine-sodium does not significantly affect serum thyroid hormone levels and produces protection against myocardial IRI, whereas pretreatment with enterally larger doses of levothyroxine-sodium can only provide an attenuated or insignificant cardioprotection because of hyperthyroxinemia. Cardioprotection by levothyroxine-sodium pretreatment is probably attributable to increased myocardial expression of heat shock protein 70 and myosin heavy chain α.

Prognostic Value of Free Triiodothyronine Level in Patients With Hypertrophic Obstructive Cardiomyopathy

CONTEXT

Thyroid hormone acts as a fundamental regulator in cardiovascular homeostasis in pathophysiological conditions.

OBJECTIVE

This study aims to determine whether thyroid hormone could be an independent predictor of adverse events in patients with hypertrophic obstructive cardiomyopathy (HOCM).

DESIGN, PATIENTS, AND OUTCOME MEASURES

The original cohort consisted of 965 consecutive patients with HOCM who were admitted to Fuwai Hospital from October 2009 to December 2014, and 756 patients completed thyroid function evaluations. Patients were divided into three groups according to free triiodothyronine (FT3) levels: tertile 1 (<2.81 pg/mL, n = 247), tertile 2 (2.81 to 3.11 pg/mL, n = 250), tertile 3 (3.12 to 4.09 pg/mL, n = 259).

RESULTS

In correlation analysis, FT3 showed significantly positive correlation with left ventricular ejection fraction (r = 0.109, P = 0.003). After a median follow-up of 44 months, a total of 45 (6.0%) endpoints (all-cause mortality or cardiac transplantation) occurred with rates of 13.4%, 3.6%, and 1.2% in tertiles 1, 2, and 3, respectively. Univariate Cox analysis established FT3 as a predictor of endpoint [hazard ratio (HR), 0.111; 95% confidence interval (CI), 0.065, 0.189; P < 0.001]. After adjustment for traditional risk factors, the prognostic value of FT3 level was still significant (HR, 0.216; 95% CI, 0.083, 0.559; P = 0.002). Compared with patients in tertile 3, those in tertile 1 were at a much higher risk of endpoint (HR, 4.918; 95% CI, 1.076, 22.485; P = 0.040).

CONCLUSIONS

FT3 correlated with cardiac function and could serve as an independent predictor of all-cause mortality and cardiac transplantation in patients with HOCM. These results suggest that monitoring thyroid function in HOCM patients is necessary.

Modified Low-Dose Triiodo-L-thyronine Therapy Safely Improves Function Following Myocardial Ischemia-Reperfusion Injury

Background: We have shown that thyroid hormones (THs) are cardioprotective and can be potentially used as safe therapeutic agents for diabetic cardiomyopathy and permanent infarction. However, no reliable, clinically translatable protocol exists for TH treatment of myocardial ischemia-reperfusion (IR) injury. We hypothesized that modified low-dose triiodo-L-thyronine (T3) therapy would confer safe therapeutic benefits against IR injury.

Methods: Adult female rats underwent left coronary artery ligation for 60 min or sham surgeries. At 2 months following surgery and T3 treatment (described below), the rats were subjected to functional, morphological, and molecular examination.

Results: Following surgery, the rats were treated with T3 (8 μg/kg/day) or vehicle in drinking water ad libitum following IR for 2 months. Oral T3 significantly improved left ventricular (LV) contractility, relaxation, and relaxation time constant, and decreased beta-myosin heavy chain gene expression. As it takes rats ~6 h post-surgery to begin drinking water, we then investigated whether modified T3 dosing initiated immediately upon reperfusion confers additional improvement. We injected an intraperitoneal bolus of T3 (12 μg/kg) upon reperfusion, along with low-dose oral T3 (4.5 μg/kg/day) in drinking water for 2 months. Continuous T3 therapy (bolus + low-dose oral) enhanced LV contractility compared with oral T3 alone. Relaxation parameters were also improved compared to vehicle. Importantly, these were accomplished without significant increases in hypertrophy, serum free T3 levels, or blood pressure.

Conclusions: This is the first study to provide a safe cardiac therapeutic window and optimized, clinically translatable treatment-monitoring protocol for myocardial IR using commercially available and inexpensive T3. Low-dose oral T3 therapy supplemented with bolus treatment initiated upon reperfusion is safer and more efficacious.