The Cut-Off Value for the Triglyceride–Glucose Index (TyG) Discriminating Insulin Resistance Based on the SHBG Level and HOMA-IR Values in Women with Polycystic Ovary Syndrome

The triglyceride-glucose (TyG) index was recently suggested as a surrogate marker of liver steatosis and insulin resistance. However, the TyG index cut-off value may be affected by age, sex, and race. Therefore, this study aimed to estimate the cut-off value for the TyG index discriminating insulin resistance based on the previously established cut-offs for HOMA-IR (Homeostatic Model Assessment for Insulin Resistance) and serum level of SHBG (sex hormone-binding globulin) in Caucasian women with polycystic ovary syndrome (PCOS). The medical records of 311 unselected Caucasian women diagnosed with PCOS were included. Finally, due to the exclusion of patients with diabetes and hypertension, a cohort of 264 (84.9%) women with PCOS were analyzed. The following data were retrieved from the medical history: age, body weight, waist circumference, height, serum levels of glucose, triglycerides, insulin, and SHBG. HOMA-IR was calculated with a standard formula. The TyG index was calculated according to the formula TyG = ln(triglycerides[mg/dL] × glucose [mg/dL]/2). The cut-off value for the TyG index was calculated using ROC analysis. The empirical optimal of the TyG index cut-off, corresponding to HOMA-IR ≥ 2.1, was >8.31 (AUC 0.77, accuracy 0.70, sensitivity 61.2%, specificity 75.3%, PPV-positive predictive value 59.4%, NPV-negative predictive value 76.7%). The corresponding TyG index cut-off values for a SHBG level < 41.5 nmol/L was >8.31 (AUC 0.67, accuracy 0.65, sensitivity 54.9%, specificity 73.9%, PPV 64.4%, NPV 65.6%). Our study suggests that the cut-off point for the TyG index in young Caucasian women with PCOS, which discriminates against insulin resistance, is 8.31 (based on both HOMA-IR and SHBG values). In addition, our data confirm the usefulness of the TyG index as an initial assessment of insulin resistance, which should be confirmed by assessing the HOMA-IR value or SHBG concentration.