Introduction.Graves’ disease is the most common cause of hyperthyroidism. The mortality rate increases by 20% in hyperthyroid patients; cardiac problems are the leading cause of death and arrhythmia is the most common cardiac complication. Our study aimed to evaluate the corrected QT interval (QTc), the Tpeak-Tend interval (Tp-e), and the Tp-e/QTc ratio to predict arrhythmia risk in patients with Graves’ disease. Methods. The study included 64 patients with Graves’ disease and 57 euthyroid controls. The 12-lead electrocardiograms of the individuals under study were evaluated. The QTc interval, the Tp-e interval, and the Tp-e/QTc ratio of all participants were determined and statistically evaluated with thyroid stimulating hormone (TSH), free triiodothyronine (fT3) and free thyroxine (fT4) values. Results. Tp-e (p < 0.001) and QTc (p < 0.05) were significantly prolonged in the group of patients with Graves’ disease as compared to the control group. Heart rate was higher in patients with Graves’ disease as well (p < 0.05). Correlation analysis in patients with hyperthyroidism demonstrated that Tp-e (r=0.372, p=0.002), QTc (r=0.291, p=0.020), and fT3 levels were significantly and positively correlated. Similarly, Tp-e (r=0.271, p=0.030), QTc (r=0.259, p=0.039), and fT4 levels were significantly and positively correlated. Conclusions. We observed a significant prolongation of the Tp-e and QTc intervals with the increase in fT3 and fT4 levels. On the other hand, our study demonstrated that the sensitivity and specificity of Tp-e in the prediction of hyperthyroidism were 70.3% and 70.1%, respectively (AUC=0.724 (CI: 0.629-0.818)), the optimal cut-off value=83.5 ms). The Tp-e interval, which has recently been used as one of the arrhythmogenicity indices, may be an indicator of arrhythmia risk in patients with Graves’ disease.

Introduction and aim. Thyroid hormones play an important role in glucose metabolism as in many metabolic events. The aim of our study is to evaluate the relationship between subclinical hypothyroidism (SCH) and insulin resistance, especially in obese women. Material and methods. Newly diagnosed SCH patients with body mass index (BMI) ≥30 who applied to our outpatient clinic between March 2021 and October 2021, and euthyroid obese women who applied for routine control were included in the study. In this study, we used homeostasis model assessment of insulin resistance (HOMA-IR) and triglyceride glucose (TyG) indexes, which are noninvasive, simple and useful methods for evaluating insulin sensitivity. Results. The study included 78 female patients between the ages of 19 and 64. A correlational analysis was performed between thyroid stimulating hormone (TSH) and HOMA-IR, TyG, and BMI. The results showed that TSH levels were positively correlated with HOMA-IR (R=0.297, p=0.008), TyG (R=0.316, p=0.005) and BMI (R=0.307, p=0.006). This relationship was stronger for TyG compared to the other variables. As another finding, BMI was positively correlated with HOMA-IR (R=0.359, p=0.001) and TyG (R=0.404, p<0.001). This relationship was stronger for TyG than HOMA-IR. Conclusion. These results show that patients with SCH are at risk of developing diseases that accompany insulin resistance, such as metabolic syndrome and cardiovascular disorders. The most important finding of our study is that the TyG index gives more significant results than HOMA-IR, especially in obese women.