Disorders in glucose and lipid metabolism have been shown to exert an influence on bone metabolism. The TyG index, which combines measures of glucose and triglycerides, provides insights into the overall metabolic status. However, the investigation of concurrent disturbances in glucose and lipid metabolism and their specific implications for bone metabolism remains limited in the existing research literature. This study aimed to explore the correlation between the TyG index and bone mineral density (BMD) in US adults.In the National Health and Nutrition Examination Survey (NHANES), subjects were classified based on the TyG index into four groups (< 7.97, 7.97-8.39, 8.39-8.85, > 8.86). Linear regression analysis was conducted to determine the β value and 95% confidence interval (CI). Four multivariable models were constructed. Restricted cubic spline analyses and piecewise linear regression were employed to identify the association between the BMD and TyG index. An analysis of subgroups was also conducted in this study.Significant variations in related characteristics were found among the US adult population, who were distributed into four groups based on the quartiles of the TyG index. A negative correlation between the TyG index and lumbar spine BMD was observed. In the multi-adjusted models, compared to Q1 of the TyG index, the β for Q4 of the TyG index for lumbar spine BMD was [β = - 0.008, 95% CI (- 0.017, 0)] in US adults. The association between the TyG index and lumbar spine BMD was found to be nonlinear (all nonlinear p < 0.001), with a threshold value based on restricted cubic spline analyses. Above the threshold point, the β for lumbar spine BMD was - 0.042 (95% CI, - 0.059, - 0.024). Below the threshold points, no significant difference was observed (p > 0.05). No significant interactions were observed among subgroups based on age, gender, presence of diabetes, BMI, and use of antidiabetic and antihyperlipidemic agents. Similar patterns of association were observed in total and subtotal bone density.This study identified a nonlinear association between the TyG index and BMD in the US population. Furthermore, an increased level of the TyG index may indicate a higher risk of osteoporosis among US adults. These findings highlight the importance of considering glucose and lipid metabolism disturbances in understanding bone health and the potential for developing preventive strategies for osteoporosis.© 2023. The Author(s).