Triglyceride-glucose index a good surrogate for insulin resistance

The novel triglyceride-glucose (TyG) index may serve as a good surrogate marker for insulin resistance (IR) in assessing the link between IR and thyroid function, a recent Korea study has found.

Researchers conducted a cross-sectional analysis of 1,482 nondiabetic, euthyroid adults in whom serum insulin, thyrotropin (TSH), and free thyroxine (fT4) levels were measured. Fasting levels of triglycerides and plasma glucose (FPG) were also measured for the calculation of the TyG index.

Both sexes were equally represented in the study sample with no significant difference in age at baseline (men vs women: 42.0±14.7 vs 41.3±14.6 years; p=0.334). FT4, FPG, insulin, triglycerides, cholesterol, glycated haemoglobin, and other such markers were significantly elevated in men. The same was true for TyG index (4.71±0.32 vs 4.48±0.27; p<0.001).

The TyG index was significantly correlated with the homeostatic model assessment for IR (HOMA-IR) in both men (r, 0.311; p<0.001) and women (r, 0.381; p<0.001). In men, TyG was likewise significantly and inversely correlated with fT4 levels even after adjusting for confounders (β, –0.094; p=0.009), though no such interaction was found between TyG and TSH.

In women, the TyG shared an inverse correlation with fT4, but only in the unadjusted model (r, –0.116; p=0.002; adjusted p=0.163). A significant association with TSH was also observed (β, 0.078; p=0.018).

“[T]his study shows that low-normal thyroid function was associated with a higher TyG index in euthyroid Korean adults,” the researchers said. “[T]he relationship between the different components of low-normal thyroid function and the TyG index were found to differ according to sex, namely fT4 in men and TSH in women.”

“Our findings suggest that the TyG index is a good surrogate marker of IR in evaluating its relationship with thyroid function,” they added.