Clinical Utility of the Triglyceride-Glucose Index in Assessing Hepatic Steatosis Severity Within the MASLD Spectrum

Background/Objectives: The global increase in metabolic dysfunction-associated steatotic liver disease underscores the need for accessible and reliable markers to assess hepatic steatosis. The triglyceride-glucose (TyG) index, derived from fasting plasma glucose and triglyceride levels, has emerged as a practical surrogate marker of insulin resistance and has been increasingly associated with metabolic liver involvement. This study aimed to evaluate the relationship between the TyG index and the severity of hepatic steatosis assessed by ultrasonography. Methods: This retrospective cross-sectional study included 480 adult patients without a prior diagnosis of diabetes mellitus or hypertension who underwent fasting laboratory testing and abdominal ultrasonography between January 2024 and May 2025. Fasting plasma glucose and triglyceride levels were obtained on the same day as ultrasonographic evaluation. Hepatic steatosis was assessed by a single experienced radiologist using standardized ultrasonographic criteria, and patients were categorized into three groups according to steatosis grade (grade 0, grade 1, and grade 2-3; n = 160 for each group). Demographic data and laboratory parameters, including glucose, triglycerides, HbA1c, platelet count, neutrophils, lymphocytes, monocytes, ALT, AST, and total cholesterol levels, were recorded. The TyG index was calculated using the formula: TyG = ln[(fasting triglycerides × fasting glucose)/2]. Results: A total of 480 patients (30.6% male) were included in the analysis. Mean fasting glucose, triglyceride, and TyG index values were 94.20 ± 11.15 mg/dL, 146.91 ± 83.94 mg/dL, and 8.70 ± 0.55, respectively. Metabolic and inflammatory parameters increased significantly with advancing steatosis grades (all p < 0.05). The TyG index demonstrated a clear stepwise increase from grade 0 (8.29 ± 0.42) to grade 1 (8.74 ± 0.42) and grade 2-3 steatosis (9.07 ± 0.49) (p < 0.001), with all pairwise comparisons remaining statistically significant. Receiver operating characteristic (ROC) analysis showed good discriminative performance of the TyG index for hepatic steatosis (AUC = 0.829), and an optimal cutoff value of 7.90 was identified using the Youden index, yielding high sensitivity for detection. In multivariable logistic regression analysis, the TyG index remained the strongest independent predictor of hepatic steatosis (adjusted OR 11.41, 95% CI 6.10-21.34; p < 0.001). Conclusions: The TyG index increased progressively with the severity of hepatic steatosis and showed strong associations with metabolic and inflammatory parameters. These findings support the TyG index as a simple and accessible marker reflecting metabolic dysfunction and hepatic steatosis, with potential value for early risk stratification in clinical practice.