Thyroid hormone sensitivity, insulin resistance and visceral fat area as determinants of prevalent coronary heart disease in euthyroid patients with type 2 diabetes.

BACKGROUND: Coronary heart disease (CHD) remains a leading cause of morbidity and mortality in patients with type 2 diabetes mellitus (T2DM). Whether thyroid hormone sensitivity indices add value for CHD risk stratification among euthyroid T2DM patients is unclear. METHODS: In this retrospective study, we included 412 euthyroid adults with T2DM hospitalized at a tertiary hospital (112 with CHD and 300 without). We assessed thyroid hormone sensitivity indices (TT4RI, TFQI, TSHI and FT3/FT4 ratio), insulin resistance measures (HOMA-IR and METS-IR) and visceral fat area (VFA). Candidate predictors were screened by univariable logistic regression and collinearity diagnostics. A multivariable logistic regression model for prevalent CHD was developed using a stratified 70/30 train-validation split and evaluated with class-weighted stratified 5-fold cross-validation. RESULTS: In univariable analyses, higher HOMA-IR, VFA, TT4RI, TSH, older age and hypertension were associated with CHD. Because TSH and TT4RI were highly collinear, TSH was excluded and TT4RI retained. In the final model, TT4RI, HOMA-IR, VFA and age remained independent predictors after accounting for hypertension. Discrimination was good (AUC 0.768 in the training set and 0.766 in the validation set; mean cross-validated AUROC 0.750 ± 0.035), with acceptable precision-recall performance (mean AUPRC 0.523 ± 0.074) and reasonable calibration. CONCLUSION: Impaired thyroid hormone sensitivity, increased insulin resistance and greater visceral fat accumulation are independently associated with prevalent CHD in euthyroid patients with T2DM. A simple model incorporating TT4RI, HOMA-IR and VFA may help refine CHD risk stratification in this population.