Thyroid hormone and cardiovascular disease

Diagnosis and management of thyroid disorders and thyroid hormone supplementation in adult horses and foals

Equine thyroid disorders pose a diagnostic challenge in clinical practice because of the effects of nonthyroidal factors on the hypothalamic-pituitary-thyroid axis, and the horse's ability to tolerate wide fluctuations in thyroid hormone concentrations and survive without a thyroid gland. While benign thyroid tumours are common in older horses, other disorders like primary hypothyroidism or hyperthyroidism in adult horses and congenital hypothyroidism in foals are rare. There is a common misunderstanding regarding hypothyroidism in adult horses, especially when associated with the clinical profile of obesity, lethargy, and poor performance observed in dogs and humans. Low blood thyroid hormone concentrations are often detected in horses as a secondary response to metabolic and disease states, including with the nonthyroidal illness syndrome; however, it is important to note that low thyroid hormone concentrations in these cases do not necessarily indicate hypothyroidism. Assessing equine thyroid function involves measuring thyroid hormone concentrations, including total and free fractions of thyroxine (T4) and triiodothyronine (T3); however, interpreting these results can be challenging due to the pulsatile secretion of thyroid hormones and the many factors that can affect their concentrations. Dynamic testing, such as the thyrotropin-releasing hormone stimulation test, can help assess the thyroid gland response to stimulation. Although true hypothyroidism is extremely rare, thyroid hormone supplementation is commonly used in equine practice to help manage obesity and poor performance. This review focuses on thyroid gland pathophysiology in adult horses and foals, interpretation of blood thyroid hormone concentrations, and evaluation of horses with thyroid disorders. It also discusses the use of T4 supplementation in equine practice.

Changes of serum TSH, FT3, and FT4 levels in infants received surgical correction of congenital heart disease under cardiopulmonary bypass

OBJECTIVE

This study aimed to explore the fluctuations and clinical relevance of serum thyrotropin (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) levels in infants undergoing surgical correction for congenital heart disease (CHD) using cardiopulmonary bypass (CPB).

METHODS

In a retrospective design, 58 infants who underwent CHD surgical correction under CPB between January 2021 and January 2022 at our institution were incorporated. These infants were categorized into two groups: simple CHD (n = 34) and complex CHD (n = 24). TSH, FT3, and FT4 serum concentrations were assessed at four intervals: 24 h pre-surgery (T0) and 24 h (T1), 48 h (T2), and 72 h (T3) post-surgery.

RESULTS

The simple CHD group displayed a significantly reduced CPB duration compared to the complex CHD group (P < 0.001). Both groups exhibited a notable decline in serum thyroid hormone concentrations at T1 compared to T0. However, from T1 to T3, an upward trend in hormone levels was observed. By T3, though the levels in both groups had risen notably from T1, they remained significantly diminished from T0 (P < 0.01). In both the simple and complex CHD cohorts, significant fluctuations in thyroid hormone levels (TSH, FT3, FT4) were noted across the different timepoints (T0, T1, T3) (P < 0.01). While no significant disparities were found between the two groups' hormone concentrations at T0 and T1 (P > 0.05), at T2 and T3, the simple CHD group manifested higher TSH, FT3, and FT4 levels compared to the complex CHD group (P < 0.05).

CONCLUSIONS

Infants undergoing CHD surgical correction under CPB experience significant declines in TSH, FT3, and FT4 serum levels. The post-surgery thyroid hormone recovery was more pronounced in infants with simple CHD compared to those with complex CHD. As such, vigilant monitoring of thyroid hormone levels during the perioperative phase is imperative, and timely intervention measures should be employed when necessary.

Decrease of thyroid function after ischemic stroke is related to stroke severity

BACKGROUND

Thyroid hormones are of fundamental importance for brain function. While low triiodothyronine levels during acute ischemic stroke (AIS) are associated with worse clinical outcomes, dynamics of thyroid function after AIS remains unknown. Thus, we longitudinally evaluated thyroid hormones after stroke and related them to stroke severity.

METHODS

We prospectively traced thyroid stimulating hormone (TSH), free triiodothyronine (fT3), and free thyroxin (fT4) levels from the hyper-acute (within 24 h) to acute (3-5 days) and chronic (3-6 months) stages of ischemic stroke using a mixed regression model. Then, we analyzed whether stroke severity at presentation, expressed by National Institute of Health Stroke Scale (NIHSS), is associated with change in thyroid function.

RESULTS

Forty-five patients were evaluated in hyper-acute and acute stages, while 29 were followed through chronic stage. TSH levels decreased from hyper-acute (2.91 ± 0.65 μIU/mL) to acute (2.86 ± 0.46 μIU/mL) and chronic stages of stroke (1.93 ± 0.35 μIU/m, p = 0.95). fT3 levels decreased from hyper-acute (2.79 ± 0.09 pg/ml) to acute (2.37 ± 0.07 pg/ml) stages, but recovered in chronic stage (2.78 ± 0.10 pg/ml, p < 0.01). fT4 levels decreased from hyper-acute (1.64 ± 0.14 ng/dl) to acute (1.13 ± 0.03 ng/dl) stages, and increased in the chronic stage (1.16 ± 0.08 ng/dl, p = 0.02). One-unit increase in presenting NIHSS was associated with 0.04-unit decrease of fT3 from hyper-acute to the acute stage (p < 0.01).

CONCLUSION

There is a transient decrease of thyroid hormones after ischemic stroke, possibly driven by stroke severity. Larger studies are needed to validate these findings. Correction of thyroid function in acute stroke may be investigated to improve stroke outcomes.

Cardiothyreosis: Epidemiological, clinical and therapeutic approach

Introduction

Cardiothyreosis corresponds to the cellular effects of free thyroid hormones on the vascular wall and the myocardium. We aim to describe the clinical, para-clinical and therapeutic aspects of cardiothyreosis and to detail prognostic factors.

Methods

We conducted a descriptive retrospective study at the Endocrinology-Diabetology Department of the Hedi Chaker University Hospital in Sfax-Tunisia. We collected medical records of 100 patients with cardiothyreosis between January 1999 and December 2019. We included patients with cardiothyreosis who underwent adequate cardiac evaluation. We excluded patients with cardiac abnormalities related to conditions other than hyperthyroidism, patients who died and patients without cardiothyreosis.

Results

We included 100 adult patients (43 men and 57 women). The mean age was 49.3 ±12.9 years (20-79 years). The diagnosis of cardiothyreosis was concomitant with that of hyperthyroidism in 72% of cases. Weight loss and palpitations were the two most frequently reported signs in 91% of cases each. Hypertension was systolic in 15 patients. The average heart rate was 103.1 beats/min (52-182 bpm). The mean TSH and FT4 levels were 0.042 μIU/ml and 59.6 pmol/l, respectively. Rhythm disorders and heart failure were the most common cardiac complications with 81 and 56 cases, respectively. Cardiac ultrasound showed dilatation of the left atrium in 28.3% of patients. Pulmonary arterial hypertension was present in 43% of cases. 57 patients had been treated with benzylthiouracil at a mean dose of 157.45 mg/day. Radical treatment with radioactive iodine was indicated in 81 patients. The evolution of cardiothyreosis was favourable in 58 patients.

Conclusion

Cardiothyreosis is a serious complication of hyperthyroidism. Future prospective studies will be of great help to better characterise and manage cardiothyreosis.

Brain nuclear receptors and cardiovascular function

Brain-heart interaction has raised up increasing attentions. Nuclear receptors (NRs) are abundantly expressed in the brain, and emerging evidence indicates that a number of these brain NRs regulate multiple aspects of cardiovascular diseases (CVDs), including hypertension, heart failure, atherosclerosis, etc. In this review, we will elaborate recent findings that have established the physiological relevance of brain NRs in the context of cardiovascular function. In addition, we will discuss the currently available evidence regarding the distinct neuronal populations that respond to brain NRs in the cardiovascular control. These findings suggest connections between cardiac control and brain dynamics through NR signaling, which may lead to novel tools for the treatment of pathological changes in the CVDs.

Anomalies cardiaques associées à l'hyperthyroïdie : étude clinique, structurelle et rythmique

INTRODUCTION

The prevalence and nature of cardiac complications associated with hyperthyroidism vary considerably in the literature depending on the population studied and the means of investigation used to detect them. The aim of this study was to determine the structural, functional, and rhythmic cardiac abnormalities associated with hyperthyroidism and to identify their risk factors.

METHODS

It is a cross-sectional study conducted in thirty adult patients with overt or subclinical hyperthyroidism. Each patient underwent a clinical cardiovascular examination, a cardiac Doppler ultrasound, a pulmonary ultrasound and a 24-hours rhythm holter. The diagnosis of cardiothyreosis (thyrotoxic heart disease) was retained if an arrhythmia, heart failure (HF) and/or pulmonary arterial hypertension (PAH) were noted following the investigations carried out.

RESULTS

The mean age of the patients was 44.8 ± 14.4 years. The sex ratio (M/F) was 0.3. Five patients (17%) had subclinical hyperthyroidism and 25 (83%) had overt hyperthyroidism. Thirteen patients (43%) had cardiothyreosis. It consisted of a rhythm disorder in three patients (10%), PAH in twelve patients (40%) and HF in eight patients (27%). An age over 50 years and toxic nodular etiology were associated with atrial fibrillation (AF), p = 0.041 and p = 0.004 respectively. Tachycardia and a higher number of atrial extrasystoles were associated with HF, p = 0.039 and p = 0.007 respectively. A lower TSH, tachycardia and a higher number of atrial extrasystoles were associated with the presence of PAH, p = 0.004, p = 0.011 and p = 0.007 respectively.

CONCLUSION

Cardiac complications should be sought in all patients with hyperthyroidism, especially in elderly and tachycardic patients. Specialized investigations such as echocardiography or 24 hours rhythmic holter should be requested in these cases.

A Prolonged QTc Interval Leads to the Diagnosis of Hyperthyroidism in an Adolescent Boy

BACKGROUND

Syncope is a common cause of pediatric emergency department visits and carries a broad differential diagnosis, which includes a few rare but critical cardiac conditions.

CASE REPORT

We review the case of an adolescent boy who presented to the emergency department after a syncopal event. He was found to have a prolonged QTc interval on electrocardiogram (ECG), without personal or family history or known risk factors. He was screened for thyroid dysfunction on a second ED visit for presyncope and was subsequently diagnosed with hyperthyroidism. The patient was treated with methimazole for 2 weeks and a repeat ECG showed normalization of the QTc interval with a QTc reduction of more than 100 ms; routine thyroid studies showed correction of thyroid stimulating hormone and free thyroxine levels shortly thereafter. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: This case and review of the medical literature should raise awareness for the emergency physician to consider evaluation of thyroid function in pediatric patients with QT interval prolongation and vice versa, potentially averting dangerous dysrhythmias.

Thyroid hormones regulate cardiac repolarization and QT-interval related gene expression in hiPSC cardiomyocytes

Prolongation of cardiac repolarization (QT interval) represents a dangerous and potentially life-threatening electrical event affecting the heart. Thyroid hormones (THs) are critical for cardiac development and heart function. However, little is known about THs influence on ventricular repolarization and controversial effects on QT prolongation are reported. Human iPSC-derived cardiomyocytes (hiPSC-CMs) and multielectrode array (MEA) systems were used to investigate the influence of 3,3',5-triiodo-L-Thyronine (T3) and 3,3',5,5'-tetraiodo-L-Thyronine (T4) on corrected Field Potential Duration (FPDc), the in vitro analog of QT interval, and on local extracellular Action Potential Duration (APD). Treatment with high THs doses induces a significant prolongation of both FPDc and APD, with the strongest increase reached after 24 h exposure. Preincubation with reverse T3 (rT3), a specific antagonist for nuclear TH receptor binding, significantly reduces T3 effects on FPDc, suggesting a TRs-mediated transcriptional mechanism. RNA-seq analysis showed significant deregulation in genes involved in cardiac repolarization pathways, including several QT-interval related genes. In conclusion, long-time administration of high THs doses induces FPDc prolongation in hiPSC-CMs probably through the modulation of genes linked to QT-interval regulation. These results open the way to investigate new potential diagnostic biomarkers and specific targeted therapies for cardiac repolarization dysfunctions.

Development of Triiodothyronine Polymeric Nanoparticles for Targeted Delivery in the Cardioprotection against Ischemic Insult

Ischemic heart disease is the main cause of death globally. Cardioprotection is the process whereby mechanisms that reduce myocardial damage, and activate protective factors, contribute to the preservation of the heart. Targeting these processes could be a new strategy in the treatment of post-ischemic heart failure (HF). Triiodothyronine (T3) and thyroxine (T4), which have multiple effects on the heart, prevent myocardial damage. This study describes the formulation, and characterization, of chemically modified polymeric nanoparticles incorporating T3, to target the thyroid hormone receptors. Modified T3 was conjugated to polylactide-co-glycolide (PLGA) to facilitate T3 delivery and restrict its nuclear translocation. Modified T3 and PLGA-T3 was characterized with ¹H-NMR. The protective role of synthesized phosphocreatine (PCr) encapsulated PLGA-T3 nanoparticles (PLGA-T3/PCr NPs) and PLGA-T3 nanoparticles (PLGA-T3 NPs) in hypoxia-mediated cardiac cell insults was investigated. The results showed that PLGA-T3/PCr NPs represent a potentially new therapeutic agent for the control of tissue damage in cardiac ischemia and resuscitation.

Free Triiodothyronine Connected With Metabolic Changes in Patients With Coronary Artery Disease by Interacting With Other Functional Indicators

This study aims to evaluate the association between free triiodothyronine (FT3) and outcomes of coronary artery disease (CAD) patients, as well as to assess the predictive power of FT3 and related functional markers from the perspective of potential mechanism. A total of 5104 CAD patients with an average follow-up of three years were enrolled into our study. Multivariate Cox regression was used to evaluate the associations between FT3, FT4 (free thyroxin), FT3/FT4 and death, MACE. We developed and validated an age, biomarker, and clinical history (ABC) model based on FT3 indicators to predict the prognosis of patients with CAD. In the multivariable Cox proportional hazards model, FT3 and FT3/FT4 were independent predictors of mortality (Adjusted HR = 0.624, 95% CI = 0.486–0.801; adjusted HR = 0.011, 95% CI = 0.002–0.07, respectively). Meanwhile, emerging markers pre-brain natriuretic peptide, fibrinogen, and albumin levels are significantly associated with low FT3 (p < 0.001). The new risk death score based on biomarkers can be used to well predict the outcomes of CAD patients (C index of 0.764, 95% CI = 0.731–0.797). Overall, our findings suggest that low levels of FT3 and FT3/FT4 are independent predictors of death and MACE risk in CAD patients. Besides, the prognostic model based on FT3 provides a useful tool for the death risk stratification of CAD patients.

Euthyroid sick syndrome in paediatric and adult patients requiring extracorporeal circulatory support and the role of thyroid hormone supplementation: a review

Non-thyroid disorders may modify thyroid hormone metabolism, resulting in an 'euthyroid sick syndrome'. Studies determining the association of cardiopulmonary bypass to thyroid function showed changes in line with this euthyroid sick syndrome. In some cases, cardiovascular dysfunction after cardiac surgery with cardiopulmonary bypass is comparable to that noticed in hypothyroidism associated with low cardiac output and elevated systemic vascular resistance. Numerous lines of research have proposed that triiodothyronine can behave acutely as a positive inotropic and vasodilator agent. The aim of this review is to present an update on the current literature about in what clinical situations the use of thyroid supplementation during the perioperative period of extracorporeal circulation in the adult and paediatric populations may impact outcome to any appreciable degree. The contribution of thyroid function in patients undergoing a ventricular assist device implantation is additionally reviewed and future study directions are proposed. This is a narrative review, where the search strategy consisted on retrieving the articles through an extensive literature search performed using electronic databases from January 1978 up to September 2019. All controlled trials randomly allocating to perioperative thyroid hormone administration in children and adults undergoing extracorporeal circulation for cardiac surgery were considered. Thyroid hormone supplementation may be recommended particularly in selected paediatric sub-populations. There is currently no firm evidence regarding the benefits of routine use of thyroid hormone administration in cardiac adult patients. Further studies are required to assess the beneficial effect of thyroid hormone on patients with end-stage heart failure supported by ventricular assist devices.

Posttraumatic stress disorder and incidence of thyroid dysfunction in women

BACKGROUND

Abnormal thyroid function is prevalent among women and has been linked to increased risk of chronic disease. Posttraumatic stress disorder (PTSD) has been linked to thyroid dysfunction in some studies; however, the results have been inconsistent. Thus, we evaluated trauma exposure and PTSD symptoms in relation to incident thyroid dysfunction in a large longitudinal cohort of civilian women.

METHODS

We used data from 45 992 women from the ongoing Nurses' Health Study II, a longitudinal US cohort study that began in 1989. In 2008, history of trauma and PTSD were assessed with the Short Screening Scale for Diagnostic and Statistical Manual of Mental Disorders, fourth edition, PTSD, and incident thyroid dysfunction was determined by participants' self-report in biennial questionnaires of physician-diagnosed hypothyroidism and Graves' hyperthyroidism. The study period was from 1989 to 2013. Proportional hazard models were used to estimate multivariable-adjusted hazard ratios and 95% confidence intervals (CIs) for incident hypothyroidism and Graves' hyperthyroidism.

RESULTS

In multivariable-adjusted models, we found significant associations for PTSD only with hypothyroidism [p-trend <0.001; trauma with no PTSD symptoms, 1.08 (95% CI 1.02-1.15); 1-3 PTSD symptoms, 1.12 (95% CI 1.04-1.21); 4-5 PTSD symptoms, 1.23 (95% CI 1.13-1.34); and 6-7 PTSD symptoms, 1.26 (95% CI 1.14-1.40)]. PTSD was not associated with risk of Graves' hyperthyroidism (p-trend = 0.34). Associations were similar in sensitivity analyses restricted to outcomes with onset after 2008, when PTSD was assessed.

CONCLUSIONS

PTSD was associated with higher risk of hypothyroidism in a dose-dependent fashion. Highlighted awareness for thyroid dysfunction may be especially important in women with PTSD.

Cardiothyreosis: Prevalence and risk factors

Cardiothyreosis (CT) or thyrotoxic heart disease is associated with higher morbidity and mortality than the other forms of hyperthyroidism. Its risk factors have been analyzed in a limited number of studies. The aims of our study were to investigate the prevalence of CT and its risk factors in patients with hyperthyroidism.

METHODS

We identified 538 patients with a hospital discharge diagnosis of hyperthyroidism from January 2000 to December 2015. Among them, 35 patients were diagnosed as having CT. Their demographic, clinical and biological characteristics were studied and compared with those of 72 controls (patients admitted for hyperthyroidism without CT) randomly selected using univariate and multivariate analysis.

RESULTS

The prevalence of CT in patients hospitalized with overt hyperthyroidism was 6.5%. The cardiac complications seen were atrial fibrillation (AF) in 33 cases (6.1%) and cardiac heart failure (CHF) in 11 cases (2%). The risk factors of CT were age greater than 50 years (OR=13.1; 95% CI [4.9-34.4]), low socioeconomic status (OR=2.8; 95% CI [1.2-6.7]), low educational level (OR=3.1; 95% CI [1.2-8.3]), personal history of hypertension (OR=3.5; 95% CI [1.1-11.2]) and a multinodular toxic goiter as the etiology of hyperthyroidism (OR=4.6; 95% CI [1.6-13.9]). After multivariate analysis, age greater than 50 years was the only independent risk factor of CT (adjusted OR=11.6; 95% CI [2.7-49.5]). Severe biological hyperthyroidism (FT4 >3 times normal) was associated with a lower risk of CT (adjusted OR=0.2; 95% CI [0.1-0.9]).

CONCLUSIONS

The prevalence of CT in patients with overt hyperthyroidism was relatively low. Cardiac complications were AF and CHF with a clear predominance of AF. Advanced age was the only independent risk factor of CT. Cardiac complications may be seen even if hyperthyroidism is not biologically severe.

Efficient Mining Template of Predictive Temporal Clinical Event Patterns From Patient Electronic Medical Records

Exploring the temporal relationship among events in patient electronic medical records (EMR) is an important problem in biomedical informatics and the results can reveal patients' impending disease conditions. In this paper, we investigate the problem of mining patterns from a sequence of point events, i.e., we only have the information on when the event happens but no duration or numerical value available. We propose a whole pipeline, including event preprocessing, pattern mining, and outcome analysis to mine the patterns and evaluate their effectiveness and discriminative power. Finally, we treat those mined patterns as additional features and evaluate them in a predictive modeling task for the early detection of congestive heart failure. On a real-world EMR data warehouse, we found that by adding those sequential pattern features, the prediction performance could be significantly improved approximately 0.1.

Environmental pollutant hexachlorobenzene induces hypertension in a rat model

Hexachlorobenzene (HCB) is a dioxin-like environmental pollutant, widely distributed in the environment. New research links exposure to high levels of persistent organic environmental toxicants to cardiovascular disease, however little is known about the effect of HCB on vascular function and on blood pressure. The purpose of the present study was to evaluate biochemical and cardiovascular changes resulting from subchronic HCB exposure. Adult female Sprague-Dawley rats were treated with vehicle or HCB (5 or 500 mg/kg b.w) for 45 days. Systolic blood pressure (BP), recorded by tail cuff plethysmography, was significantly increased at 35, 40 and 45 days of 500 mg/kg HCB-treatment. HCB (500 mg/kg) increased arterial thickness, while both 5 and 500 mg/kg HCB decreased proliferating cell nuclear antigen (PCNA) protein levels and cellular nuclei in abdominal aortas indicating a hypertrophic process. Also, aortas from both groups of HCB-treated rats presented higher sensitivity to noradrenalin (NA) and a significant decrease in maximum contractile response. Arteries from 500 mg/kg HCB-treated rats showed a significant increase in the levels of transforming growth factor-β1 (TGF-β1) mRNA and angiotensin II type1 receptor (AT₁), and a significant decrease in estrogen receptor alpha (ERα), endothelial nitric oxidide synthase (eNOS) protein expression and deiodinase II (DII) mRNA levels. In conclusion, we have demonstrated for the first time that subchronic HCB administration significantly increases BP and alters associated cardiovascular parameters in rats. In addition, HCB alters the expression of key vascular tissue molecules involved in BP regulation, such as TGF-β1, AT1, ERα, eNOS and DII.

Thyroid hormones and cardiac remodeling

Thyroid hormones have many cardioprotective actions expressed mainly through the action of T3 on thyroid receptors α1 and β1. They are procontractile anti-apoptotic, anti-inflammatory, and anti-fibrotic, promote angiogenesis and regeneration, and have beneficial effects on microRNA profiles. They have proven to be anti-remodeling in numerous animal studies, mostly in rodents; a specific action on the border zone has been described. Studies in humans with DIPTA have been in conclusion. Remodeling can be defined as an increase of ≥20 % of the end-diastolic or end-systolic volume, together with a return to the fetal phenotype. An overview of animal and clinical studies is given.

Fatigue is associated with excess mortality in the general population: results from the EPIC-Norfolk study

BACKGROUND

Significant fatigue is a frequent reason for seeking medical advice in the general population. Patients, however, commonly feel their complaint is ignored. This situation may be because clinicians perceive fatigue to be benign, unrelated to traditional biomedical outcomes such as premature mortality. The present study aimed to investigate whether an association between significant fatigue and mortality actually exists, and, if so, to identify potential mechanisms of this association.

METHODS

A population-based cohort of 18,101 men and women aged 40-79 years who completed a measure of fatigue (Short Form 36 vitality domain, SF36-VT) in addition to providing information on possible confounding factors (age, sex, body mass index, marital status, smoking, education level, alcohol consumption, social class, depression, bodily pain, diabetes, use of β blockers, physical activity and diet) and mechanisms (haemoglobin, C-reactive protein and thyroid function) were followed up prospectively for up to 20 years. Mortality from all causes, cancer and cardiovascular disease was ascertained using death certification linkage with the UK Office of National Statistics.

RESULTS

During 300,322 person years of follow-up (mean 16.6 years), 4397 deaths occurred. After adjusting for confounders, the hazard ratio (HR) for all-cause mortality was 1.40 (95 % confidence interval [CI] 1.25-1.56) for those reporting the highest fatigue (bottom SF36-VT quartile) compared with those reporting the lowest fatigue (top SF36-VT quartile). This significant association was specifically observed for those deaths related to cardiovascular disease (HR 1.45, 95 % CI 1.18-1.78) but not cancer (HR 1.09, 95 % CI 0.90-1.32). Of the considered mechanisms, thyroid function was most notable for attenuating this association. The risk of all-cause mortality, however, remained significant even after considering all putative confounders and mechanisms (HR 1.26, 95 % CI 1.10-1.45).

CONCLUSIONS

High levels of fatigue are associated with excess mortality in the general population. This commonly dismissed symptom demands greater evaluation and should not automatically be considered benign.

Combined Open-Heart Coronary Artery Bypass Surgery and Subtotal Thyroidectomy in a 54-year-old patient: A Case Report

Background

Combined open-heart surgery and thyroidectomy is a rare procedure. However, some difficulties will occur for cardiac surgery when thyromegaly extends into the retrosternal space.

Case Details

A 54-year-old woman suffering from dyspnea, chest pain and decreased left ventricular function (EF=40%) was diagnosed with coronary artery disease (3 vessel disease) and became candidate for coronary artery bypass grafting (CABG). Also, she had multinodular goiter with normal thyroid function test. After midsternotomy, a huge goiter was seen in the upper mediastinum. Because the mass had covered the ascending aorta and involved the posterior aspect of the innominate vein making access to aorta impossible, thyroidectomy was performed at first followed by CABG. Post-operation course was satisfactory. Fourteen months later, the patient was euthyroid and in NYHA class 1.

Conclusion

The evidence of the case showed that combined CABG and thyroidectomy can be performed safely.

The corrected QT (QTc) prolongation in hyperthyroidism and the association of thyroid hormone with the QTc interval

Purpose

Ventricular repolarization is assessed using the QT interval corrected by the heart rate (QTc) via an electrocardiogram (ECG). Prolonged QTc is associated with an increased risk of arrhythmias and cardiac mortality. As there have been few reports regarding the effects of hyperthyroidism on ventricular repolarization, we studied the association between serum free thyroxine (free T4 [fT4]) and thyroid stimulating hormone (TSH) levels and the QTc interval.

Methods

Thirty-eight patients with hyperthyroidism (<30 years old) were included, and we used their clinical records and available ECGs (between August 2003 and August 2011) to evaluate the association between their fT4 and TSH levels and their QTc interval. In addition, we studied the ECGs of 72 age-matched patients with no hyperthyroidism (control group) and compared their data with that from the patients group.

Results

The QTc duration in patients with hyperthyroidism was significantly prolonged compared to that in the control subjects (P<0.001). In addition, the number of hyperthyroid patients with abnormal prolonged QTc was significantly higher than that in the control group (P<0.001). Among the patients with hyperthyroidism, patients with prolonged QTc and borderline QTc had higher fT4 levels and there was positive correlation between their fT4 levels and their QTc interval (P<0.05). However, no correlation was observed between their TSH levels and their QTc interval.

Conclusion

We report that hyperthyroidism is associated with QTc prolongation. The correlation between the fT4 levels and the QTc interval suggests that thyroid status is associated with QTc values and the risk of cardiac mortality.

New Look at BTEX: Are Ambient Levels a Problem?

Benzene, toluene, ethylbenzene, and xylene (BTEX) are retrieved during fossil fuel extraction and used as solvents in consumer and industrial products, as gasoline additives, and as intermediates in the synthesis of organic compounds for many consumer products. Emissions from the combustion of gasoline and diesel fuels are the largest contributors to atmospheric BTEX concentrations. However, levels indoors (where people spend greater than 83% of their time) can be many times greater than outdoors. In this review we identified epidemiological studies assessing the noncancer health impacts of ambient level BTEX exposure (i.e., nonoccupational) and discussed how the health conditions may be hormonally mediated. Health effects significantly associated with ambient level exposure included sperm abnormalities, reduced fetal growth, cardiovascular disease, respiratory dysfunction, asthma, sensitization to common antigens, and more. Several hormones including estrogens, androgens, glucocorticoids, insulin, and serotonin may be involved in these health outcomes. This analysis suggests that all four chemicals may have endocrine disrupting properties at exposure levels below reference concentrations (i.e., safe levels) issued by the U.S. Environmental Protection Agency. These data should be considered when evaluating the use of BTEX in consumer and industrial products and indicates a need to change how chemicals present at low concentrations are assessed and regulated.

Prediction of infarct severity from triiodothyronine levels in patients with ST-elevation myocardial infarction

BACKGROUND/AIMS

The aim of the present study was to evaluate the relationship between thyroid hormone levels and infarct severity in patients with ST-elevation myocardial infarction (STEMI).

METHODS

We retrospectively reviewed thyroid hormone levels, infarct severity, and the extent of transmurality in 40 STEMI patients evaluated via contrast-enhanced cardiac magnetic resonance imaging.

RESULTS

The high triiodothyronine (T3) group (≥ 68.3 ng/dL) exhibited a significantly higher extent of transmural involvement (late transmural enhancement > 75% after administration of gadolinium contrast agent) than did the low T3 group (60% vs. 15%; p = 0.003). However, no significant difference was evident between the high- and low-thyroid-stimulating hormone/free thyroxine (FT4) groups. When the T3 cutoff level was set to 68.3 ng/dL using a receiver operating characteristic curve, the sensitivity was 80% and the specificity 68% in terms of differentiating between those with and without transmural involvement. Upon logistic regression analysis, high T3 level was an independent predictor of transmural involvement after adjustment for the presence of diabetes mellitus (DM) and the use of glycoprotein IIb/IIIa inhibitors (odds ratio, 40.62; 95% confidence interval, 3.29 to 502; p = 0.004).

CONCLUSIONS

The T3 level predicted transmural involvement that was independent of glycoprotein IIb/IIIa inhibitor use and DM positivity.

Cardiac microvascular rarefaction in hyperthyroidism-induced left ventricle dysfunction

OBJECTIVE

The pathophysiology underlying hyperthyroidism-induced left ventricle (LV) dysfunction and hypertrophy directly involves the heart and indirectly involves the neuroendocrine systems. The effects of hyperthyroidism on the microcirculation are still controversial in experimental models. We investigated the effects of hyperthyroidism on the cardiac function and microcirculation of an experimental rat model.

METHODS

Male Wistar rats (170-250 g) were divided into two groups: the euthyroid group (n = 10), which was treated with 0.9% saline solution, and the hyperthyroid group (n = 10), which was treated with l-thyroxine (600 μg/kg/day, i.p.) during 14 days. An echocardiographic study was performed to evaluate the alterations in cardiac function, structure and geometry. The structural capillary density and the expression of angiotensin II AT1 receptor in the LV were analyzed using histochemistry and immunohistochemistry, respectively.

RESULTS

Hyperthyroidism was found to induce profound cardiovascular alterations, such as systolic hypertension, tachycardia, LV dysfunction, cardiac hypertrophy, and myocardial fibrosis. This study demonstrates the existence of structural capillary rarefaction and the down-regulation of the cardiac angiotensin II AT1 receptor in the myocardium of hyperthyroid rats in comparison with euthyroid rats.

CONCLUSIONS

Microvascular rarefaction may be involved in the pathophysiology of hyperthyroidism-induced cardiovascular alterations.

Miscarriage and future maternal cardiovascular disease: a systematic review and meta-analysis

Context

The 2011 American Heart Association guidelines identified pregnancy complications as a risk factor for cardiovascular disease in women. However, miscarriage was not mentioned within the guidelines, and there is no consensus on the association between miscarriage and future risk of cardiovascular disease.

Objective

To confirm or refute the association, a meta-analysis of published papers was conducted.

Data sources

PubMed, Web of Knowledge and Scopus were systematically searched to identify appropriate articles. Reference lists were then hand searched for additional relevant titles.

Study Selection

To be included, articles had to assess the association between miscarriage and subsequent cardiovascular disease in otherwise healthy women. Only women who had miscarriages were considered exposed. Pooled association measures, using random effects meta-analysis, were calculated for coronary heart disease and cerebrovascular disease. Publication bias and between-study heterogeneity were evaluated.

Data Extraction

Two authors individually reviewed all studies and extracted data on patient and study characteristics along with cardiovascular outcomes.

Results

10 studies were identified, with 517 504 individuals included in the coronary heart disease meta-analysis and 134 461 individuals in the cerebrovascular disease analysis. A history of miscarriage was associated with a greater odds of developing coronary heart disease, OR (95% CI) =1.45 (1.18 to 1.78), but not with cerebrovascular disease, OR=1.11 (0.72 to 1.69). There was a strong association between recurrent miscarriage and coronary heart disease OR=1.99 (1.13 to 3.50). Evidence was found for moderate between-study heterogeneity and publication bias in the coronary heart disease analysis.

Conclusions

The meta-analysis indicates that a history of miscarriage or recurrent miscarriage is associated with a greater risk of subsequent coronary heart disease.

Longstanding hyperthyroidism is associated with normal or enhanced intrinsic cardiomyocyte function despite decline in global cardiac function

Thyroid hormones (THs) play a pivotal role in cardiac homeostasis. TH imbalances alter cardiac performance and ultimately cause cardiac dysfunction. Although short-term hyperthyroidism typically leads to heightened left ventricular (LV) contractility and improved hemodynamic parameters, chronic hyperthyroidism is associated with deleterious cardiac consequences including increased risk of arrhythmia, impaired cardiac reserve and exercise capacity, myocardial remodeling, and occasionally heart failure. To evaluate the long-term consequences of chronic hyperthyroidism on LV remodeling and function, we examined LV isolated myocyte function, chamber function, and whole tissue remodeling in a hamster model. Three-month-old F1b hamsters were randomized to control or 10 months TH treatment (0.1% grade I desiccated TH). LV chamber remodeling and function was assessed by echocardiography at 1, 2, 4, 6, 8, and 10 months of treatment. After 10 months, terminal cardiac function was assessed by echocardiography and LV hemodynamics. Hyperthyroid hamsters exhibited significant cardiac hypertrophy and deleterious cardiac remodeling characterized by myocyte lengthening, chamber dilatation, decreased relative wall thickness, increased wall stress, and increased LV interstitial fibrotic deposition. Importantly, hyperthyroid hamsters demonstrated significant LV systolic and diastolic dysfunction. Despite the aforementioned remodeling and global cardiac decline, individual isolated cardiac myocytes from chronically hyperthyroid hamsters had enhanced function when compared with myocytes from untreated age-matched controls. Thus, it appears that long-term hyperthyroidism may impair global LV function, at least in part by increasing interstitial ventricular fibrosis, in spite of normal or enhanced intrinsic cardiomyocyte function.

Thyroid hormone and cardiac disease: from basic concepts to clinical application

Nature's models of regeneration provide substantial evidence that a natural healing process may exist in the heart. Analogies existing between the damaged myocardium and the developing heart strongly indicate that regulatory factors which drive embryonic heart development may also control aspects of heart regeneration. In this context, thyroid hormone (TH) which is critical in heart maturation during development appears to have a reparative role in adult life. Thus, changes in TH -thyroid hormone receptor (TR) homeostasis are shown to govern the return of the damaged myocardium to the fetal phenotype. Accordingly, thyroid hormone treatment preferentially rebuilds the injured myocardium by reactivating developmental gene programming. Clinical data provide further support to this experimental evidence and changes in TH levels and in particular a reduction of biologically active triiodothyronine (T3) in plasma after myocardial infarction or during evolution of heart failure, are strongly correlated with patients morbidity and mortality. The potential of TH to regenerate a diseased heart has now been testing in patients with acute myocardial infarction in a phase II, randomized, double blind, placebo-controlled study (the THiRST study).

Excessive thyroxine enhances susceptibility to apoptosis and decreases contractility of cardiomyocytes

Excessive thyroid hormone induces cardiac hypertrophy and promotes heart failure in patients with hyperthyroidism, but the mechanism remains elusive. Rats were orally administered with levothyroxine (100 microg/kg, T(4)) for 4 weeks to induce hyperthyroidism. The calculated stroke volume decreased and the shortening amplitude-frequency relationship in unloaded contraction of isolated cardiomyocytes was negative in T(4)-treated rats. Apoptotic rates increased and DNA laddering was also detectable in T(4)-treated rat hearts. By contrast, in primary cultured cardiomyocytes, T(3) induced dose-dependent hypertrophy but did not affect the apoptotic rate. Angiotensin II further increased the apoptotic rate of T(3)-induced hypertrophied cardiomyocytes. The apoptotic rate was dependent on the extent of cardiomyocyte hypertrophy. These results suggest that cardiac contractility is enhanced during the early stage of hyperthyroidism, but decreased during the late stage of hyperthyroidism. The hypertrophied cardiomyocytes were also susceptible to apoptotic stimulation by angiotensin II. Depressed cardiac contractility and enhanced apoptosis may lead to heart failure in hypertrophied myocardium.

QTc dispersion in hyperthyroidism and its association with pulmonary hypertension

BACKGROUND

Several studies have reported that hyperthyroidism is associated with prolonged QT interval corrected by the heart rate (QTc) and pulmonary hypertension (PHT).

METHODS

Forty-seven patients with newly diagnosed overt hyperthyroidism and 20 healthy people were enrolled in the study. Transthoracic echocardiography, 12-lead surface electrocardiogram, and thyroid hormone levels were studied at the time of enrollment and after achievement of euthyroid state with propylthiouracil treatment.

RESULTS

Baseline clinical characteristics were similar. However, heart rate (90.5+/-19.6 vs 79.2+/-13.7 bpm, P = 0.024), pulmonary artery systolic pressure (PASP) (26.0+/-12.0 vs 10.6+/-4.0 mmHg, P < 0.001), E deceleration time (DT) (191.8+/-25.6 vs 177.0+/-10.7 ms, P = 0.016), isovolumetric relaxation time (IVRT) (91.38+/-12.3 vs 79.6+/-10.5 ms, P < 0.001), and QTc dispersion (QTcD) (50.3+/-17.2 vs 38.9+/-11.6 ms, P = 0.009) were significantly higher in hyperthyroid patients compared to control group. Heart rate (to 74.1+/-13.8, P < 0.001), QTcD (to 37.3+/-10.1 ms, P < 0.001), DT (to 185.3+/-19.7 ms, P = 0.008), IVRT (to 88.6+/-10.3 ms, P = 0.056), and PASP (23.1+/-10.1 mmHg P < 0.001) were significantly decreased after achievement of euthyroid state. Although PHT was present in 16 patients before treatment only six patients still had PHT during euyhyroid state. Compared to patients with normal PASP, QTcD was significantly longer in patients with PHT (56.5+/-15.8 vs 37.9+/-12.8 mmHg P < 0.001). There were also significant correlations between QTcD and presence of PHT (r = 0.516, P < 0.001) and PASP (r = 0.401, P = 0.009).

CONCLUSIONS

Hyperthyroidism is a reversible cause of PHT and diastolic dysfunction. Increased QTcD observed in hyperthyroidism may be associated with PHT and diastolic dysfunction. These abnormal findings in hyperthyroidism often normalize with the achievement of euthyroid state.

Changes in body composition in women following treatment of overt and subclinical hyperthyroidism

OBJECTIVE

To determine changes in weight, body composition, and bone density after treatment of overt hyperthyroidism (OH) and subclinical hyperthyroidism (SCH) in women.

METHODS

Women with OH and SCH referred to the Mayo Clinic Thyroid Clinic were recruited. Hyperthyroid patients and euthyroid control women were matched for age (within decade) and body mass index. Patients with OH and SCH were treated to normalize thyroid function test results and were restudied after 6 months of normal thyroid function. Baseline and posttreatment studies included measurement of height, weight, bone density, lean mass, fat mass, and thigh muscle cross-sectional area. All participants had normal thyroid function test results for at least 6 months before completion of the posttreatment studies.

RESULTS

Twenty-four patients with OH, 21 patients with SCH, and 36 control patients were studied. In the OH group, fat-free mass increased from a mean of 36.8 kg (95% confidence interval [CI], 34.8-38.8) to 40.4 kg (95% CI, 38.5-42.3); in the SCH group, fat-free mass increased from a mean of 40.3 kg (95% CI, 38.1-42.5) to 42.2 kg (95% CI, 39.7-44.7). In both groups, fat mass increased to approximately the same extent, and both groups experienced significant weight gain with no change in percent body fat. Thigh muscle cross-sectional area increased in both groups -- from 100.6 cm(2) (95% CI, 92.7-108.5) to 113.3 cm(2) (95% CI, 105.5-121.1) in the OH group and from 106.1 cm(2) (95% CI, 96.7-115.5) to 112.2 cm(2) (95% CI, 102.0-122.4) in the SCH group. Bone density increased in patients with OH (P<.01) and in patients with SCH (P<.05).

CONCLUSIONS

Treatment of OH and SCH leads to increases in muscle area and bone density. Weight gain reflects increases in both fat and fat-free mass. While these results provide some support for actively treating SCH in women, further prospective studies are needed to determine whether the changes documented translate into real patient benefit.

Synthesis and biological evaluation of a series of liver-selective phosphonic acid thyroid hormone receptor agonists and their prodrugs

Phosphonic acid (PA) thyroid hormone receptor (TR) agonists were synthesized to exploit the poor distribution of PA-based drugs to extrahepatic tissues and thereby to improve the therapeutic index. Nine PAs showed excellent TR binding affinities (TRbeta(1), K(i) < 10 nM), and most of them demonstrated significant cholesterol lowering effects in a cholesterol-fed rat (CFR) model. Unlike the corresponding carboxylic acid analogue and T(3), PA 22c demonstrated liver-selective effects by inducing maximal mitochondrial glycerol-3-phosphate dehydrogenase activity in rat liver while having no effect in the heart. Because of the low oral bioavailability of PA 22c, a series of prodrugs was synthesized and screened for oral efficacy in the CFR assay. The liver-activated cyclic 1-(3-chlorophenyl)-1,3-propanyl prodrug (MB07811) showed potent lipid lowering activity in the CFR (ED(50) 0.4 mg/kg, po) and good oral bioavailability (40%, rat) and was selected for development for the treatment of hypercholesterolemia.

Higher serum free thyroxine levels are associated with coronary artery disease

Thyroid hormone has many effects on the heart and cardiovascular system. Thyrotoxicosis is associated with increased cardiovascular morbidity and mortality, primarily due to heart failure and thromboembolism. However, the relationship between thyroid hormone excess and the cardiac complications of angina pectoris and myocardial infarction remains largely speculative. Moreover, few studies have been reported on the effect of thyroid hormone levels within normal range on coronary artery disease (CAD). Therefore we examined the association of thyroid function with coronary artery diseases in euthyroid angina patients. Total 192 subjects (mean age; 60.8 yrs) were enrolled in which coronary angiograms were performed due to chest pain. We measured free thyroxine (FT(4)), thyroid stimulating hormone (TSH), serum lipid levels and high-sensitivity C-reactive protein (hsCRP) levels and analyzed their association with the presence of CAD. Serum FT(4) levels were higher in patients with CAD compared with the patients without CAD (1.31 +/- 0.30 vs 1.20 +/- 0.23, p = 0.006), and high FT(4) level was associated with the presence of multi-vessel disease. Multivariate analysis showed that age (odds ratio (OR) 1.04; 95% confidence interval (CI) 1.01-1.07, p = 0.007), hypertension (OR 2.04; 95% CI 1.06-3.90, p = 0.036) and FT(4) (OR 4.23; 95% CI 1.12-15.99, p = 0.033), were the determinants for CAD. The relative risk (RR) for CAD in highest tertile of FT(4) showed increased risk compared with the lowest tertile (RR 1.98; 95% CI 0.98-3.99, p<0.001). Our study showed that FT(4) levels were associated with the presence and the severity of CAD. Also, this study suggests that elevated serum FT(4) levels even within normal range could be a risk factor for CAD. Further studies will be necessary to confirm the relationship of thyroid function and CAD.

Myocardial protection in man--from research concept to clinical practice

Myocardial protection aims at preventing myocardial tissue loss: (a) In the acute stage, i.e., during primary angioplasty in acute myocardial infarction. In this setup, the attenuation of reperfusion injury is the main target. As a "mechanical" means, post-conditioning has already been tried in man with encouraging results. Pharmacologic interventions that could be of promise are statins, insulin, peptide hormones, including erythropoietin, fibroblast growth factor, and many others. (b) The patient with chronic coronary artery disease offers another paradigm, with the target of avoidance of further myocyte loss through apoptosis and inflammation. Various pharmacologic agents may prove useful in this context, together with exercise and "mechanical" improvement of cardiac function with attenuation of myocardial stretch, which by itself is a noxious influence. A continuous effort toward acute and chronically preserving myocardial integrity is a concept concerning both the researcher and the clinician.

When the storm passes unnoticed—A case series of thyroid storm

INTRODUCTION

Thyroid crisis is an acute manifestation of thyrotoxicosis. Approximately 1-2% of patients progress to a thyroid storm, often precipitated by a physiologically stressful event. If unrecognized or left untreated, thyroid storm may result in cardiovascular collapse and death.

AIM

We describe three patients who presented to the Emergency Department of Singapore General Hospital in a thyroid storm. They had complications of thyrocardiac disease with heart failure and arrhythmias.

METHODS

An analysis of case records of patients presenting to the emergency department of Singapore General Hospital with a primary diagnosis of thyrotoxicosis was made over the period of 2004-2005. Three patients with thyroid storm were identified. All the patients presented heart failure and cardiac arrhythmias (1 atrial flutter, 2 atrial fibrillation).

DISCUSSION AND CONCLUSION

Thyroid storm is a rare manifestation of thyrotoxicosis, usually occurring in females during the third to sixth decades of life. Serious complications such as heart failure and hypotension resulting in cardiovascular collapse and death may occur. Our case series consists of young males presenting with thyrocardiac failure. One patient was treated with beta-blockers and another with calcium channel blockers. Both developed cardiovascular collapse. The third patient was managed with digoxin with a good outcome. The current pathophysiology and therapeutic options are explored. A high index of suspicion should be maintained in young males presenting with heart failure and arrhythmia.

Endocrine function is not impaired in patients with a continuous MicroMed–DeBakey axial flow pump

OBJECTIVES

Pulsatile blood flow has been regarded to be of importance for the regulation of endocrine organs. A new generation of continuous flow mechanical blood pumps is now available for clinical application. Patients with implanted MicroMed-DeBakey axial pumps show nonphysiologic low-pulsatile blood flow profiles, and therefore it appeared to be of interest to evaluate their possible effect on the endocrine system.

METHODS

Eight male patients and 1 female patients (mean age, 51 +/- 10 years) with end-stage left-sided heart failure were implanted with a MicroMed-DeBakey axial pump. After a mean period of 67 +/- 19 days, basal pituitary hormone concentrations and their responses to a bolus injection of hypothalamic releasing hormones were tested. In addition, thyroid hormones, testosterone, and plasma and urinary catecholamine levels were measured at baseline.

RESULTS

Administration of the hypothalamic releasing hormones revealed normal responses of all pituitary hormones (adrenocorticotropic hormone, thyroid-stimulating hormone, luteinizing hormone, and prolactin), except for growth hormone, the response of which was slightly impaired (10.2 +/- 6.8 vs 19.9 +/- 6.5 ng/L, P < .05). Also, the cortisol response to the corticotropin-releasing hormone-stimulated adrenocorticotropic hormone release was normal, as were basal concentrations of thyroid hormones (triiodothyronine, thyroxine, free triiodothyronine, and free thyroxine), testosterone, and urinary catecholamines.

CONCLUSIONS

Implantation of a continuous flow axial pump with low-pulsatile blood flow profile appears to have no major effect on the hypothalamic-pituitary-endorgan system and sympathoadrenal functions. This finding is reassuring for the growing number of patients treated with this convenient new pump and could contribute considerably to their prognosis and quality of life.

Cardiogenic shock in hypothyroidism

A patient with minimal coronary artery disease presented in cardiogenic shock when her previously undiagnosed hypothyroid state was complicated by an episode of AV nodal re-entrant tachycardia. She did not respond to multiple pressors, and recovered dramatically after starting thyroid supplementation. Hypothyroidism caused her lack of responsiveness to pressors and perpetuated her hypotension and increased filling pressures long after she reverted to a sinus rhythm. Our case dramatically demonstrates the severe lack of physiologic reserve that can be associated with hypothyroidism.

Investigation of tissue factor and other hemostatic profiles in experimental hypothyroidism

The influence of thyroid failure on hemostasis has been studied and is still not well understood. These patients have high risk for cardiovascular diseases because of the lipid metabolism and procoagulant agents. But the influence of thyroid failure on hemostasis is controversial. Tissue factor (TF) has an important role in the thromboembolic state. Recent experiments have demonstrated that TF-dependent activation of the coagulation cascade plays an important role in the pathophysiology of intravascular thrombus formation. The purpose of the present study was to investigate the contributions of TF, factor VII:C (FVII:C), factor XII:C (FXII:C), and fibrinogen in experimental hypothyroidism. TF was obtained from the thyroid gland and lung tissue of 10 rats following experimental hypothyroidism induced for 30 d and compared with similar tissue from 10 control rats. Significantly increased TF activities were found in hypothyroid rats. By contrast, FVII:C level was significantly decreased when compared with the control group. In this respect it is interesting to note that a hypercoagulable state due to increased thromboplastic activity may occur. Based on those results, elevated tissue factor activities (TFa) of the patients with low thyroid dysfunction may have another risk factor for cardiovascular diseases.

Usefulness of Pulsed-Wave Tissue Doppler Echocardiography for the Assessment of the Left and Right Ventricular Function in Patients with Clinical Hypothyroidism

Clinical hypothyroidism (HT) is often associated with cardiovascular disorders, such as endothelial and myocardial dysfunction. Previous studies have explored left ventricular (LV) function using pulsed-wave tissue Doppler echocardiography (TDE) in HT. However, no study has utilized this technique in the assessment of right ventricular (RV) function in HT. Accordingly, we investigated the effects of clinical HT on LV and RV function by TDE. The study subjects included 35 newly diagnosed HT patients and 32 healthy normal controls. For each subject, serum FT3, FT4, TT3, TT4, and thyroid stimulating hormone (TSH) levels were measured, and standard echocardiography and TDE were performed. No statistically significant difference was found between patients and controls with regard to age, gender, body mass index, heart rate, and blood pressure. Compared to controls, TSH levels were significantly higher, and TT4 and FT4 levels were significantly lower. TDE showed that patients had significantly lower early diastolic tricuspid annular velocity (Ea) and early/late (Ea/Aa) diastolic tricuspid annular velocity ratio (P < 0.001 and P < 0.001, respectively), and significantly longer isovolumetric relaxation time (P < 0.001) than those of the controls. Aa, Sa, isovolumetric contraction time, and ejection time did not significantly differ. In addition, a significant relationship between some TDE indexes, and thyroid hormones (TT4 and FT4) and TSH was observed. We showed that patients with clinical HT are associated with impaired RV diastolic function, in addition to impaired LV diastolic function using TDE.

Thyrotoxic heart disease

Patients with tachyarrythmias as a result of thyroid storm have been typically treated with beta-blockers to decrease the heart rate and alleviate beta-receptor mediated symptoms such as anxiety and tremulousness. We report an unusual case of a previously well young man presenting to the emergency department with atrial flutter and who was clinically hyperthyroid. The patient was treated with propanolol to control his heart rate but suffered cardiovascular collapse. Although the patient was successfully resuscitated, he required inotropic support and intra-aortic balloon pump. The use of propanolol should be carefully considered in patients with thyrotoxic cardiomyopathy especially in those with heart failure because of the risk of exacerbation.

Which thyroid-stimulating hormone level should be sought in hypothyroid patients under L-thyroxine replacement therapy?

We sought to determine whether relationships exist between level of thyroid-stimulating hormone (TSH) suppression and cardiovascular risk parameters such as plasma homocysteine, C-reactive protein (CRP), fibrinogen, D-dimer and serum cholesterol in patients taking L-thyroxine-replacement therapy (LT4-RT). Four hundred and two hypothyroid patients under LT4-RT were cross-sectionally evaluated. Patients were grouped according to their achieved TSH (mIU/l) levels under LT4-RT on an arbitrary manner. Those patients having a TSH value 0.4-2 were defined as group 1 (n = 154), a TSH level of 2 to less than 5.5 were defined as group 2 (n = 176) and a TSH level of 5.5 to less than 20 with a normal free T3 and free T4 level were defined as group 3 (n = 72). The three groups of patients were also compared with overt hypothyroid patients (n = 71) and healthy controls (n = 97). Homocysteine levels (micromol/l) were significantly different between the three groups (10.4 +/- 4 for group 1, 11.3 +/- 3.7 for group 2 and 13.5 +/- 4.7 for group 3; p < 0.01 for all groups). Significant differences in CRP (mg /l) levels were present between the three groups (2.6 +/- 2.6 for group 1, 3.3 +/- 2.9 for group 2 and 4.8 +/- 4.1 for group 3; p < 0.01 for all groups). Univariate analysis showed that both homocysteine and CRP levels significantly correlated with free T4 and TSH level (p < 0.01 for both groups). No statistically significant differences were noticed in respect to fibrinogen and d-dimer levels between three groups. In examining the effect of LT4-RT on lipid parameters, a tendency towards beneficial effects without achieving statistical significance was observed. Practically speaking, a target TSH level of less than 2 might be advisable to lower CRP levels and homocysteine levels, and possibly lipid parameters.

Clinical review: thyroid hormone replacement in children after cardiac surgery--is it worth a try?

Cardiac surgery using cardiopulmonary bypass produces a generalized systemic inflammatory response, resulting in increased postoperative morbidity and mortality. Under these circumstances, a typical pattern of thyroid abnormalities is seen in the absence of primary disease, defined as sick euthyroid syndrome (SES). The presence of postoperative SES mainly in small children and neonates exposed to long bypass times and the pharmacological profile of thyroid hormones and their effects on the cardiovascular physiology make supplementation therapy an attractive treatment option to improve postoperative morbidity and mortality. Many studies have been performed with conflicting results. In this article, we review the important literature on the development of SES in paediatric postoperative cardiac patients, analyse the existing information on thyroid hormone replacement therapy in this patient group and try to summarize the findings for a recommendation.

Blood coagulation, fibrinolytic activity and lipid profile in subclinical thyroid disease: subclinical hyperthyroidism increases plasma factor X activity

BACKGROUND AND OBJECTIVES

Various abnormalities of coagulation and fibrinolysis occur in patients with thyroid diseases, and may range from subclinical laboratory abnormalities to clinically significant disorders of coagulation and, rarely, major haemorrhage or thromboembolism. The influence of subclinical hypothyroidism (SHypo) on haemostasis is controversial, both hypercoagulable and hypocoagulable states have been reported. A hypercoagulable state might be a risk factor for thromboembolic disease in SHypo. On the other hand, subclinical hyperthyroidism (SCHyper) is associated with enhanced cardiovascular risk. In the English literature, there are no studies on changes in coagulation and fibriolytic status in subjects with SCHyper. Therefore, the aim of the present study was to investigate the markers of endogenous coagulation and fibrinolysis, and to evaluate the relationships between serum lipid profile and thyroid hormones and these haemostatic parameters in subclinical thyroid patients.

DESIGN AND METHODS

Various haemostatic parameters were investigated in 30 patients with SHypo and 20 patients with SCHyper and compared to 20 euthyroid controls. Prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen, factors V, VII, VIII, IX and X activities, vWF, antithrombin III (AT III), protein C, protein S, tissue plasminogen activator (t-PA) and tissue plasminogen activator inhibitor-1 (PAI-1), as well as common lipid variables, were measured. The relationships between serum thyroid hormones and these haemostatic parameters were examined.

RESULTS

Compared with the control subjects, only FX activity was significantly increased in patients with SCHyper (P < 0.01). Total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels were significantly higher in patients with SHypo compared with the control group (P < 0.001 and P < 0.01, respectively). TC levels were significantly higher in patients with SCHyper than in controls (P < 0.05). No differences could be found in coagulation/fibrinolysis parameters between subclinical hypothyroid patients and control subjects. In patients with SCHyper, serum TSH level was positively correlated with FX activity (r: 0.58, P < 0.01) and inversely correlated with PAI-1 (r: -0.55. P < 0.05). Serum TG levels were inversely correlated with plasma activities of factors V, VII, VIII, IX, X and vWF (r: -0.83, P < 0.001; r: -0.68, P < 0.05; r: -0.61, P < 0.05; r: -0.77, P < 0.01; r: -0.63, P < 0.05; r: -0.60, P < 0.05, respectively). Serum TC levels were positively correlated with plasma fibrinogen levels (r: 0.72, P < 0.05). Serum HDL-C levels were positively correlated with protein S activity (r: 0.68, P < 0.05) and negatively correlated with F VII activity (r: -0.69, P < 0.05). Also, in patients with SHypo, serum TG levels were positively correlated with serum TSH levels (r: 0.42, P < 0.05), plasma activities of factors V, VII and X (r: 0.42, P < 0.05; r: 0.54, P < 0.01; r: 0.57, P < 0.01, respectively) and negatively correlated with plasma fibrinogen levels (r: -0.41, P < 0.05). Serum TC levels were positively correlated with factors V and X (r: 0.42, P < 0.05; r: 0.58, P < 0.01, respectively) and negatively correlated with t-PA Ag levels (r: -0.44, P < 0.05). Serum HDL-C levels were inversely correlated with F VII activity (r: -0.48, P < 0.05).

INTERPRETATION AND CONCLUSIONS

Some differences were found in the haemostatic parameters and lipid profile between the subclinical thyroid patients and healthy controls. Increased factor X activity in patients with subclinical hyperthyroidism represent a potential hypercoagulable state, which might augment the already existing risk for atheroscleroic complications. Also, subclinical hypothyroid patients exhibit a more atherogenic lipid profile compared with healthy individuals. Therefore, subclinical hypothyroidism is also associated with an increased risk of cardiovascular disease. However, thyroid hormones may play a role at different levels of the complex haemostatic system in subclinical thyroid disease.

Serum-free thyroxine and thyrotropin concentrations in euthyroid patients with decompensated congestive heart failure

We realized a prospective study of 106 consecutive patients hospitalized in an Internal Medicine Service with decompensated CHF. Between the 95 patients with normal serum-free thyroxine and thyrotropin concentrations, patients older than 70 years had a significant higher serum free thyroxine concentration (13.1+/-2.6 vs. 10.1+/-1.5 pmol/l, p=0.006) and a lower, but not significant, serum thyrotropin concentration (1.3+/-1.2 vs. 1.7+/-1.1 mU/l, p=0.11). No correlation was found between the functional class, the echocardiographic ejection fraction or the in-hospital stay and the serum free thyroxine and thyrotropin concentrations. The sex, the presence of systolic dysfunction, diastolic dysfunction, atrial fibrillation or comorbidity did not determine significant differences in the serum-free thyroxine and thyrotropin concentrations.