Metabolic burden is independently and linearly associated with lower testosterone levels: evidence from NHANES

OBJECTIVES: Testosterone deficiency and metabolic dysfunction frequently coexist in aging men; however, whether metabolic impairment is associated with a progressive decline in testosterone across the metabolic spectrum remains unclear. METHODS: We analyzed 2,192 U.S. men aged ≥40 years from the National Health and Nutrition Examination Survey (NHANES). Metabolic burden was assessed using the triglyceride-glucose (TyG) index. Survey-weighted linear regression models were used to evaluate the association between TyG and log-transformed total testosterone after adjustment for age, HDL cholesterol, diabetes, and smoking. Dose-response relationships were further examined using quartiles and restricted cubic spline analyses. RESULTS: Higher TyG levels were independently associated with lower testosterone concentrations. In fully adjusted models, each 1-unit increase in TyG was associated with an approximately 12 % decrease in testosterone (p<0.001). Compared with the lowest TyG quartile, men in the highest quartile had approximately 19 % lower testosterone levels. Spline analysis demonstrated a consistent inverse association without significant nonlinearity (p for nonlinearity=0.21), supporting a graded and continuous relationship across the metabolic spectrum. CONCLUSIONS: Higher metabolic burden was independently associated with lower total testosterone levels in middle-aged and older men. However, due to the cross-sectional design and absence of SHBG/free testosterone measurements, these findings should be interpreted cautiously and require confirmation in longitudinal studies.