Early Cardiovascular Changes in Subclinical Hypothyroidism: Evidence from Clinical and Echocardiographic Evaluation

Abstract

Background: Subclinical hypothyroidism (SCH) is characterized by elevated thyroid-stimulating hormone (TSH) levels with normal free thyroid hormone concentrations and is increasingly recognized as a risk factor for cardiovascular dysfunction. This study aimed to evaluate early cardiovascular changes in SCH using clinical, biochemical, electrocardiographic, and echocardiographic parameters.
Methods: A hospital-based cross-sectional observational study was conducted over two years (2019–2021) at the Department of General Medicine, Veer Surendra Sai Institute of Medical Sciences and Research (VIMSAR), Burla, Odisha. A total of 210 adults with SCH were enrolled and categorized into mild SCH (TSH 4.5–9.9 mIU/L; n=170) and severe SCH (TSH >10 mIU/L; n=40). Clinical assessment, lipid profile, inflammatory markers, electrocardiography (ECG), and two-dimensional echocardiography were performed. Statistical analysis was carried out using SPSS version 11.5.
Results: Severe SCH patients showed significantly higher serum creatinine, anti-thyroid peroxidase positivity, and elevated C-reactive protein levels compared to mild SCH (p<0.05). Significant dyslipidemia was observed in severe SCH with increased total cholesterol, triglycerides, LDL, and VLDL levels (p=0.001). ECG abnormalities such as ST-segment depression, low-voltage complexes, prolonged QT interval, and conduction defects were more frequent in severe SCH. Echocardiographic evaluation revealed significantly reduced ejection fraction, increased posterior wall thickness, reduced E velocity, decreased E/A ratio, and prolonged isovolumetric relaxation time in severe SCH, indicating both systolic and diastolic dysfunction.
Conclusion: Severe SCH is associated with significant metabolic abnormalities and early cardiovascular dysfunction, including electrophysiological and echocardiographic alterations. Early cardiovascular evaluation in SCH patients may help identify high-risk individuals and prevent future cardiovascular complications.