Association between triglyceride glucose-waist height ratio index and incident thyroid nodules: a prospective cohort study

BACKGROUND: Insulin resistance is associated with thyroid nodule formation. The triglyceride-glucose (TyG) index is a widely recognized surrogate for insulin resistance, and its clinical value increases when integrated with adiposity indices. We tested whether an elevated triglyceride glucose-waist height ratio (TyG-WHtR) is independently associated with incident thyroid nodules. METHODS: This prospective cohort study recruited 65,347 participants between January and December 2021, with follow-up surveys conducted between January and December 2025. We examined associations of baseline and cumulative TyG-WHtR quartiles with thyroid nodule occurrence using multivariable binary logistic regression. Restricted cubic spline (RCS) models tested nonlinear trends in the association between thyroid nodules and TyG-WHtR. Receiver operating characteristic (ROC) curves were generated to compare the area under the curve (AUC) across four metabolic metrics: baseline TyG, WHtR, TyG-WHtR, as well as cumulative TyG-WHtR, with thyroid nodule status as the outcome. We also conducted subgroup and sensitivity analyses, which collectively confirmed the robustness of our observed associations. RESULTS: During a mean follow-up of 4.08 ± 0.27 years, 4,029 participants (15.8%) were diagnosed with thyroid nodules by 2025. In fully adjusted models, the highest versus lowest quartile of baseline TyG-WHtR showed an OR of 1.57 (95% CI: 1.22-2.02), and cumulative TyG-WHtR yielded an OR of 1.57 (95% CI: 1.25-1.96). Each 1-SD increment in baseline and cumulative TyG-WHtR corresponded to ORs of 1.15 (1.05-1.26) and 1.17 (1.07-1.27), respectively. RCS analyses confirmed linear dose-response relationships for both (P for nonlinearity > 0.05). ROC curve analysis demonstrated that cumulative TyG-WHtR had the highest AUC (0.539) for thyroid nodules. CONCLUSIONS: TyG-WHtR is independently associated with thyroid nodule risk, with cumulative TyG-WHtR showing a stronger association than baseline TyG-WHtR. Maintaining favorable TyG and waist circumference levels over time may reduce thyroid nodule risk in this Chinese population.