A Critical Investigation of Sick Euthyroid Syndrome in Chronic Heart Failure Patients: Addressing the Need for Accurate Thyroid Assessment

Background The body undergoes numerous metabolic changes during severe illness or physiological stress to protect itself by lowering metabolism and reducing overall demands. This evolutionary adaptation dates back to early human development, long before the advent of ICU facilities and advanced treatments. One such protective mechanism is Sick Euthyroid Syndrome (SES), also known as Non-thyroidal Illness Syndrome (NTIS). SES commonly occurs in critically ill patients and is frequently observed in conditions such as heart failure, chronic kidney disease, and severe sepsis. This syndrome is characterized by abnormal thyroid function tests in patients with acute or chronic systemic illnesses who do not have intrinsic thyroid disease. Typically, these patients exhibit low serum levels of triiodothyronine (T3), normal or low levels of thyroxine (T4), and normal or low thyroid-stimulating hormone (TSH) levels. SES is believed to be an adaptive response to illness, aimed at reducing the body's metabolic rate and conserving energy during severe physiological stress. This original article delves into SES's prevalence and clinical impact in these settings. Materials and methods The study aims to determine the prevalence of SES in patients with long-standing heart failure, elucidate the relationship between thyroid function and heart failure severity, and assess its impact on various hematological and clinical parameters. This observational, cross-sectional study was conducted at Dr. D. Y. Patil Medical College, Hospital and Research Centre, Pune, India, a 2011-bed hospital, over one and a half years. This study included 70 patients with chronic heart failure, aged 18 years and above, defined by a left ventricular ejection fraction of 40% or less and a Boston criteria score of 8 or more. Patients were excluded if they had a history of thyroid dysfunction, clinical sepsis, or were taking thyroid-affecting drugs. Results The study provides important insights into the prevalence and impact of SES in long-standing heart failure patients. It found that a significant 44.29% of these patients exhibited low T3 levels, highlighting the substantial occurrence of SES in this population. Additionally, the study revealed a negative correlation between N-terminal pro-b-type natriuretic peptide (NT-proBNP) levels, Boston score, and total T3, suggesting that as indicators of heart failure severity worsen, total T3 levels may decrease further. Another key finding is the high prevalence of anemia among heart failure patients, with a notable gender disparity: 92.11% of male patients were affected compared to 50% of female patients. Conclusion The study concluded that SES is significantly prevalent among long-standing heart failure patients, further indicating that thyroid suppression increases with the severity of heart failure. Recognizing SES can guide tailored treatments, prompting intensive monitoring and optimized heart failure management. Additionally, the study found a high prevalence of anemia, particularly among male patients, highlighting the need for gender-specific considerations in managing heart failure. These findings underscore the importance of routine thyroid function assessments and regular monitoring of anemia in heart failure patients. Future research should focus on improving clinical outcomes through comprehensive management of both thyroid function and anemia in these patients.