Metabolic and Atherogenic Thresholds in the Severity of Erectile Dysfunction: The Dominant Role of the Triglyceride-Glucose Index

Background: This study aimed to investigate the association between metabolic and atherogenic indices and erectile dysfunction (ED) severity, and to compare their diagnostic performance in predicting severe ED. Methods: This retrospective study included 221 men with ED between January 2025 and January 2026. ED severity was assessed using the International Index of Erectile Function-5 (IIEF-5). The triglyceride–glucose (TyG) index, atherogenic index of plasma (AIP), Castelli Risk Index-1 and -2, and atherogenic coefficient (AC) were calculated from routine laboratory parameters. Correlation, logistic regression, and ROC analyses were performed. Results: Patients with severe ED (n = 57) had significantly higher triglyceride, fasting glucose, TyG, and AIP levels and lower high-density lipoprotein cholesterol (HDL) levels than those with mild-to-moderate ED (all p < 0.05). TyG (ρ = 0.369, p < 0.001) and AIP (ρ = 0.359, p < 0.001) were positively correlated with severe ED. In the multivariable model, the TyG index remained associated with severe ED after adjustment for AIP, age, BMI, total testosterone, and the TyG-by-testosterone interaction (OR: 4.354, 95% CI: 1.668–11.364; p = 0.003). Total testosterone was not independently associated with severe ED (p = 0.510), and the TyG-by-testosterone interaction was not significant (p = 0.281). ROC analysis showed that TyG had the best predictive performance (AUC: 0.743). Conclusions: The TyG index showed discrimination for IIEF-5-defined severe ED and may have value as a complementary metabolic risk-stratification parameter.