Effect of thyroid hormone on the distribution and activity of Na, K-ATPase in ventricular myocardium

Thyroid and Its Ripple Effect: Impact on Cardiac Structure, Function, and Outcomes

Thyroid dysfunction is a widespread and complex issue in the field of endocrine disorders. It has a significant impact on multiple physiological systems, particularly on the heart. This review explores the complex interaction between thyroid dysfunction and cardiac dynamics, examining the detailed network of molecular, cellular, and systemic changes that underlie the close connection between these two physiological areas. Thyroid dysfunction, which includes both hyperthyroidism and hypothyroidism, is a common endocrine condition that affects millions of people worldwide. The thyroid hormones thyroxine and triiodothyronine regulate various metabolic activities essential for maintaining cellular balance. Disruptions in thyroid function result in widespread consequences, affecting the cardiovascular system. Thyroid hormones directly impact cardiac muscle cells, controlling their ability to contract, their electrical properties, and their reaction to hypertrophy. Thyroid dysfunction goes beyond the level of individual cells and involves complex interactions among vascular dynamics, neurohormonal control, and endothelial function. These factors all contribute to the development of cardiovascular illness. The impact of thyroid dysfunction on cardiac structure, function, and outcomes is not limited to a one-way pattern. Instead, it involves a dynamic two-way interaction. The manifestations of this condition can vary from minor changes in the electrical activity of the heart to more obvious structural abnormalities, such as an increase in the size of the heart muscle and a decrease in its ability to relax during the filling phase. Furthermore, the correlation between thyroid dysfunction and adverse cardiovascular outcomes, such as heart failure and arrhythmias, highlights the clinical importance of this connection. This review provides a complete overview of the relationship between thyroid dysfunction and cardiac dynamics by analyzing a wide range of research from clinical, molecular, and epidemiological perspectives. This study seeks to enhance our comprehension of the comprehensive effects of thyroid dysfunction on the anatomy and function of the heart by explaining the complex molecular mechanisms and systemic consequences. The goal is to establish a basis for informed clinical treatment and future research efforts.

Cardiovascular Manifestations in Hyperthyroidism: A Cross-Sectional Study in a Tertiary Care Hospital in South India

Background

The involvement of the heart in hyperthyroidism patients has a considerable prognostic value and causes significant morbidity and mortality. However, very little research, particularly among the Indian population, has addressed the most critical cardiovascular symptoms of hyperthyroidism, so this study aimed to assess the cardiovascular manifestations of hyperthyroidism.

Method

The current cross-sectional investigation involved 140 newly diagnosed and untreated confirmed cases of hyperthyroidism of any etiology for nine months. A structured data collection schedule was used to collect patient-specific and pertinent information during OPD hours or after admission. T4, T3, and TSH were measured in 10 mL of blood from each patient. The information was entered into a Microsoft Excel spreadsheet. All tests were carried out with a 5% level of significance.

Results

The mean age of study subjects was 43.2 years. Females made up 85.0% of the subjects in the current study, while males made up 15.0%. The etiology of hyperthyroidism was primarily due to Grave’s disease (59.3%). Heat intolerance (67.9%) was the most typical presenting symptom among the patients. The most common cardiac symptom was palpitation among 76.4% of subjects in the present study. Upon clinical examination, 80.7% of subjects had tachycardia. The ECG showed atrial fibrillation (AF) in 17.9% of subjects. The echocardiogram (ECHO) findings revealed systolic dysfunction in 17.8% of subjects.

Conclusion

Since cardiovascular manifestations are common in patients with thyroid disease and may be the only manifestation of thyroid disease, it is suggested that all patients with thyroid disorders be checked for cardiovascular manifestations. In addition, thyroid function tests should be performed in all patients with unexplained cardiovascular disease.

Mitochondrial-Respiration-Improving Effects of Three Different Gardeniae Fructus Preparations and Their Components

The processing method for Chinese traditional herbal medicine is "Pao Zhi" in Chinese. This study examined the efficacy of the Pao Zhi on the preparations of Gardeniae Fructus (GF) on a mitochondrial respiratory function in rats. To determine the efficacy of Pao Zhi, we investigated the effects of GF heat processing on mitochondrial respiratory function. To test the GF components, the rats were randomly divided into a geniposide-alone group, crocin-alone group, and combination groups and treated with geniposide and crocin at different ratios. The results showed that a high dose, raw GF was more effective in improving the neurological function, mitochondrial respiratory function, and activities of Na⁺-K⁺-ATPase and Ca²⁺-Mg²⁺-ATPase than the preparations that underwent heating. Moreover, mitochondrial ROS production was the lowest in the raw GF-treated group. In addition, treatments with crocin and GC3 were more effective than geniposide in improving the functional deficit in MCAO rats. In conclusion, our results suggest that raw GF is the most suitable preparation for the treatment of cerebral ischemia, and its underlying mechanisms may be associated with the improvement of mitochondrial respiratory function, increased activities of Na⁺-K⁺-ATPase and Ca²⁺-Mg²⁺-ATPase, and reduced oxidative stress in mitochondria. Our findings suggest that raw GF, especially crocin, could be an ideal therapeutic agent for ischemic stroke.

Frequency of Cardiovascular Manifestation in Patients With Hyperthyroidism

Introduction Cardiovascular manifestations are very common in hyperthyroidism. Various cardiovascular symptoms such as palpitations, exercise intolerance, dyspnea, angina, edema, and congestive heart failure are commonly reported in hyperthyroidism. In this study, we determine the frequency of cardiovascular signs, symptoms, and various conduction disorders associated with hyperthyroidism. Methodology This cross-sectional, observational study was conducted in the cardiology department of a tertiary care hospital in Pakistan in close association with the internal medicine department from August 2019 to December 2019. A total of 100 hyperthyroid patients confirmed based on thyroid stimulating hormone (TSH, also known as thyrotropin), free T₄ (FT₄; thyroxine), and free T₃ (FT₃; triiodothyronine) were enrolled in the study. Results The most common cardiovascular symptom in this study was palpitations identified in 72% of the participants, followed by breathlessness in 41% of the participants. The most common cardiovascular sign was a pulse rate of more than 100 beats per minute found in 72% of the participants. The most common abnormality in electrocardiogram (ECG) was sinus tachycardia in 39% of the participants, followed by atrial fibrillation in 22% of the participants. In echocardiography, 5% of the participants had systolic dysfunction. Conclusion In this study, cardiovascular signs, symptoms, ECG, and echo changes were very frequent in hyperthyroidism. Management of hyperthyroidism should include routine ECG and echo testing, and cardiologists should be involved in thorough cardiovascular examination.

The Effects of Altered Membrane Cholesterol Levels on Sodium Pump Activity in Subclinical Hypothyroidism

BACKGROUND

Metabolic dysfunctions characteristic of overt hypothyroidism (OH) start at the early stage of subclinical hypothyroidism (SCH). Na⁺/K⁺-ATPase (the sodium pump) is a transmembrane enzyme that plays a vital role in cellular activities in combination with membrane lipids. We evaluated the effects of early changes in thyroid hormone and membrane cholesterol on sodium pump activity in SCH and OH patients.

METHODS

In 32 SCH patients, 35 OH patients, and 34 euthyroid patients, sodium pump activity and cholesterol levels in red blood cell membranes were measured. Serum thyroxine (T₄) and thyroid stimulating hormone (TSH) levels were measured using enzyme-linked immunosorbent assays. Differences in their mean values were analysed using post hoc analysis of variance. We assessed the dependence of the sodium pump on other metabolites by multiple regression analysis.

RESULTS

Sodium pump activity and membrane cholesterol were lower in both hypothyroid groups than in control group, OH group exhibiting lower values than SCH group. In SCH group, sodium pump activity showed a significant direct dependence on membrane cholesterol with an inverse relationship with serum TSH levels. In OH group, sodium pump activity depended directly on membrane cholesterol and serum T₄ levels. No dependence on serum cholesterol was observed in either case.

CONCLUSION

Despite the presence of elevated serum cholesterol in hypothyroidism, membrane cholesterol contributed significantly to maintain sodium pump activity in the cells. A critical reduction in membrane cholesterol levels heralds compromised enzyme activity, even in the early stage of hypothyroidism, and this can be predicted by elevated TSH levels alone, without any evident clinical manifestations.

Hyperthyroidism and cardiovascular complications: a narrative review on the basis of pathophysiology

Cardiovascular complications are important in hyperthyroidism because of their high frequency in clinical presentation and increased mortality and morbidity risk. The cause of hyperthyroidism, factors related to the patient, and the genetic basis for complications are associated with risk and the basic underlying mechanisms are important for treatment and management of the disease. Besides cellular effects, hyperthyroidism also causes hemodynamic changes, such as increased preload and contractility and decreased systemic vascular resistance causes increased cardiac output. Besides tachyarrythmias, impaired systolic ventricular dysfunction and diastolic dysfunction may cause thyrotoxic cardiomyopathy in a small percentage of the patients, as another high mortality complication. Although the medical literature has some conflicting data about benefits of treatment of subclinical hyperthyroidism, even high-normal thyroid function may cause cardiovascular problems and it should be treated. This review summarizes the cardiovascular consequences of hyperthyroidism with underlying mechanisms.