TyG–BMI as a Marker of Metabolic Status and Its Association with Bone Quality and Mineral Metabolism: A Sex-Specific Analysis

Background: Insulin resistance (IR) is a major pathogenic factor in metabolic syndrome and related diseases. It is challenging to accurately measure IR due to high cost and technical complexity. TyG-derived indices have been proposed as simple and reliable surrogates for assessing insulin resistance. The present study aimed to investigate the association between TyG-derived indices and indicators of mineral metabolism and bone quality and to examine sex-specific differences. Methods: This cross-sectional study included 330 adults aged 18–65 years. Age-adjusted partial correlation analyses and multivariable linear regression models were performed to examine the associations between TyG indices and several metabolic parameters, minerals, and QUS bone indices. Results: TyG–BMI was strongly correlated with triglycerides (females: r = 0.51; males: r = 0.54, both p < 0.001), glucose (females: r = 0.54, p < 0.001), and hip circumference (females: r = 0.77; males: r = 0.58, both p < 0.001). HDL showed inverse associations (females: r = −0.41, p < 0.001). In females, TyG–BMI demonstrated modest positive correlations with bone parameters, including BQI (r = 0.21, p = 0.002), T-score and Z-score (r = 0.21, p = 0.002 for both), SOS (r = 0.19, p = 0.007), and BUA (r = 0.18, p = 0.010), whereas no significant associations were observed in males. In multivariable models, TyG–BMI in females remained independently associated with glucose (β = 9.77, p < 0.001), waist circumference (β = 2.94, p < 0.001), and HDL (β = −26.6, p < 0.001), but not with mineral or bone parameters. Conclusions: The TyG-derived indices, most notably TyG–BMI, are useful indicators of metabolic status that correlate with bone quality yet exhibit sex-specific associations. These findings support the role of TyG-derived indices as accessible surrogate markers of metabolic status and demonstrate sex-specific associations with bone quality parameters.