Sex-specific Anthropometric Variations and the Influence of Central Obesity on Thyroid Hormone Regulation: A Cross-sectional Study

BACKGROUND: Thyroid hormones, namely triiodothyronine (T3), thyroxine (T4) and thyroid-stimulating hormone (TSH), serve as pivotal regulators of energy metabolism and are subject to variation based on sex and adiposity. AIMS: This study aimed to elucidate the function of thyroid hormones in metabolic regulation and potential for clinical applications. MATERIALS AND METHODS: A cross-sectional study was performed at the Department of Physiology, Regional Institute of Medical Sciences, Imphal, from September 2023 to June 2024, involving 168 healthy adults aged 20-60 years. Anthropometric parameters such as body mass index (BMI), waist circumference (WC) and waist-hip ratio (WHR) were assessed. Serum concentrations of TSH, T3 and T4 were quantified via enzyme-linked immunosorbent assay. Participants were categorised according to BMI (normal, overweight and obese), WC and WHR thresholds established by World Health Organisation and Asian Indian criteria. Statistical evaluations employed t-tests, ANOVA and Pearson's correlation, with significance established at P < 0.05. RESULTS: Males demonstrated larger body size compared to females, with no significant difference observed in BMI and thyroid hormones. Increased BMI, WC and WHR correlated with higher serum levels of TSH and T3 levels, while T4 showed minimal variation. Strong positive correlations were found between BMI and TSH (r = 0.46, P = 0.00) and T3 (r = 0.60, P = 0.00) across the total cohort. CONCLUSION: This investigation demonstrates a significant correlation between adiposity markers and higher thyroid hormone concentrations, notably TSH and T3, indicating adaptive mechanisms to increased fat mass. These results highlight the necessity of taking into account for sex-specific anthropometric variations and central obesity metrics such as WHR in assessing thyroid function.