Association between C-reactive protein-triglyceride glucose index and testosterone levels among adult men: analyses of NHANES 2015-2016 data.

Background: The C-reactive protein-triglyceride glucose index (CTI) is a recently introduced index designed to simultaneously assess inflammation (via CRP) and insulin resistance (via the triglyceride-glucose index, TyG), both of which are recognized risk factors for declining testosterone levels in men.

Aim: This study investigates the association between CTI and low testosterone levels in American adult men, aiming to evaluate CTI as a predictor of low testosterone level.

Methods: Data from the 2015-2016 NHANES were used in this cross-sectional study, including men aged 20 and older. Multivariate linear and logistic regression models were employed to analyze the relationship between CTI, total testosterone levels, and the risk of low testosterone level. Receiver operating characteristic (ROC) curves were generated to assess the predictive performance of CTI for low testosterone level.

Outcomes: The primary outcome was testosterone levels, with low testosterone level defined as a serum testosterone level below 300 ng/dL in adult men.

Results: Among 878 participants, 189 had low testosterone level. The mean CTI was significantly higher in the low testosterone level group (9.39 ± 0.09) compared to the non- low testosterone level group (8.62 ± 0.05; P < .0001). After adjusting for covariates, higher CTI was significantly associated with lower total testosterone levels (β = -44.6, 95% CI: -66.34, -22.87, P < .001) and increased low testosterone level risk (OR = 1.84, 95% CI: 1.31, 2.57, P = .002). ROC analysis showed that CTI (AUC = 0.7357, 95% CI: 0.6975, 0.7739) outperformed TyG and VAI in predicting low testosterone level, highlighting its potential clinical value in assessing low testosterone status.

Clinical implications: Timely monitoring of testosterone levels in individuals with elevated CTI is clinically significant. Additionally, for those with TD, regular assessment of CTI may help in preventing future cardiovascular complications.

Strengths and limitations: This study is the first to explore the relationship between CTI and low testosterone using a large sample from the NHANES database. However, due to the cross-sectional design, causal inference regarding CTI and low testosterone level cannot be drawn.

Conclusions: CTI appears to be a more effective predictor of low testosterone level than TyG, CRP, or VAI, suggesting its usefulness as a simple, low-cost indicator for early TD risk assessment. Further research is needed to verify its clinical applicability across diverse populations.