Association between lifetime endogenous estrogen exposure and body composition metrics in postmenopausal women: findings from the Tehran Lipid and Glucose Study.

Background: The role of endogenous estrogen exposure (EEE) in shaping body composition and its implications for cardiometabolic health remain understudied despite its potential significance. This cross-sectional study aimed to investigate the association between EEE and body composition indices among postmenopausal women.

Methods: Data were obtained from the Tehran Lipid and Glucose Study (TLGS), including 960 women aged over 40 years. EEE was calculated based on reproductive events, and participants were categorized into tertiles. Anthropometric measurements and body composition were assessed using standardized protocols. Linear regression models were employed to evaluate associations, adjusting for potential confounders.

Results: It was revealed significant differences in body composition indices across EEE tertiles, with increasing EEE associated with decreased fat mass, skeletal muscle mass, and fat-free mass. Moreover, women with higher EEE exhibited lower anthropometric and body composition measurements compared to those with lower EEE, even after adjusting for confounding factors. Specifically, for each year of increasing EEE, fat mass decreased by 0.12 kg, skeletal muscle mass by 0.04 kg, fat-free mass by 0.07 kg, and fat mass ratio decreased by 0.003. Comparing tertiles, women with the highest EEE demonstrated significantly lower anthropometric and body composition measurements compared to those with the lowest EEE.

Conclusion: These findings suggest a link between EEE and favorable changes in body composition, highlighting the importance of considering reproductive history in health assessment.