Triglyceride Glycemic Index and Triglyceride/HDL Ratio: Can They be Biomarkers for Insulin Resistance in Euthyroid Women with Hashimoto's Thyroiditis, and Are They Related to Thyroid Function Tests?

INTRODUCTION

Hashimoto's thyroiditis (HT) is the most common autoimmune disease. Insulin resistance (IR), independent of thyroid function tests but attributed to thyroid autoantibodies, can be observed in (HT). The most frequently employed method for demonstrating IR is the HOMA-IR index. Recently, the triglyceride-glucose index (TGI) and triglyceride-to-HDL ratio (TG/HDL) have been proposed as novel, practical, and cost-effective indicators of IR. Thus, this study aimed to investigate the relationship between TGI, TG/HDL ratio, and HOMA-IR in euthyroid, normoglycemic women aged 18-45 years with HT.

METHODS

This retrospective study was conducted at a tertiary care center and included 108 women with HT and 62 healthy controls. Parameters recorded for all participants included TSH, free thyroxine (fT4), free triiodothyronine (fT3), anti-thyroglobulin antibody (anti-Tg), anti-thyroid peroxidase antibody (anti-TPO), glucose, triglycerides, HDL, LDL, insulin, HOMA-IR, TGI, and TG/HDL ratio.

RESULTS

Compared to the healthy control group, TGI and TG/HDL were significantly elevated in patients with HT, with respective values of 3.67 vs. 3.55 and 1.83 vs. 1.46 (p=0.001, p=0.005, respectively). Anti-TPO showed a weak positive correlation with HOMA-IR and moderate positive correlations with TGI and TG/HDL (r=0.280, 0.352, and 0.336, respectively). Similarly, anti-Tg correlated positively with HOMA-IR, TGI, and TG/HDL (r=0.274, 0.187, and 0.159, respectively). A moderate, significant positive correlation was found between HOMAIR and both TGI and TG/HDL (r=0.477 and 0.455, respectively). Receiver operating characteristic analysis indicated that TG/HDL (area under the curve (AUC): 0.802, 95% confidence interval (CI): 0.716-0.888, p<0.001) and TGI [AUC: 0.824, 95% CI: 0.741-0.907, p<0.001) had diagnostic value in predicting elevated HOMA-IR. Furthermore, a TG/HDL ratio of ≥1.99 predicted elevated HOMA-IR with 80.6% sensitivity and 70.1% specificity, while a TGI ≥ 3.68 had 87.1% sensitivity and 67.5% specificity.

CONCLUSION

Women with euthyroid, normoglycemic HT exhibit increased HOMA-IR. TGI and TG/HDL are novel, cost-effective, accessible biomarkers that can be used to detect IR early in this patient group and facilitate screening across large populations.