Association between allostatic load and thyroid function in U.S. adults: a cross-sectional study based on NHANES data

Chronic stress may contribute to endocrine dysregulation. The allostatic load (AL), an indicator of cumulative physiological burden across multiple systems, has unclear associations with thyroid function. We analyzed 5525 adults (2678 men and 2847 women) from NHANES 2007-2010. The participants were categorized into allostatic load score (ALS) quartiles: Q1 (n = 2582), Q2 (n = 1394), Q3 (n = 1003), and Q4 (n = 546). The ALS was constructed from eight cardiovascular, metabolic, and inflammatory biomarkers. Thyroid function was assessed (TSH, FT3, FT4, TgAb, and TPOAb) and categorized as thyroid dysfunction. Survey-weighted multivariable linear and logistic models estimated associations; trend tests and restricted cubic splines (RCS) assessed linearity. Subgroup and interaction analyses examined effect modification, and sensitivity analyses evaluated robustness. ALS was positively associated with higher TSH (β = 0.038, 95% CI: 0.019-0.057, p = 0.001) and FT3 (β = 0.005, 95% CI: 0.003-0.008, p < 0.001). No significant associations were observed for FT4, TPOAb, or TgAb. TSH increased linearly across ALS quartiles (p-trend < 0.001). Restricted cubic splines indicated no overall departure from linearity; in sex-stratified analyses, the association was linear in women and nonlinear in men. Significant interactions with age and race (p < 0.05) indicate that the ALS-TSH association differs by demographics. The results were consistent across the subgroup and sensitivity analyses. Our study suggested a significant positive association between AL and TSH levels. Further research is needed to clarify the mechanisms linking stress and thyroid function.