Association between a novel nutritional-inflammatory index and testosterone levels: a cross-sectional study.

Introduction: Testosterone deficiency (TD) has been closely associated with systemic inflammation and metabolic disturbances. The C-reactive protein-albumin-lymphocyte (CALLY) index is a composite biomarker integrating inflammatory, nutritional, and immune parameters. However, its association with TD remains unclear. This study aimed to investigate the relationship between the CALLY index and TD in adult men. Methods: This multicenter cross-sectional study included 434 adult men recruited from urology and andrology outpatient clinics between December 2024 and February 2026. The CALLY index was calculated using serum albumin, lymphocyte count, and C-reactive protein levels. TD was operationally defined as a morning total testosterone (TT) concentration <300 ng/dL in the presence of relevant clinical symptoms. Calculated free testosterone (cFT) was estimated from TT, SHBG, and albumin using the Vermeulen equation, and cFT-based sensitivity analyses were performed. Multivariable logistic regression was performed after adjustment for age, body mass index, smoking status, alcohol use, regular exercise, hypertension, diabetes, total cholesterol, and triglycerides. Receiver operating characteristic (ROC) curve analysis was conducted to evaluate discriminative performance. Results: Among the participants, 198 (45.6%) were classified as having TD. The prevalence of TD decreased progressively across increasing quartiles of the CALLY index (70.6% in Q1 vs. 23.2% in Q4; Discussion: These findings indicate that the CALLY index is associated with TD and provides moderate discrimination. It may serve as a readily accessible composite marker of the inflammatory and nutritional milieu associated with TD; however, external validation is required before any clinical application can be considered.