Associations between cardiovascular risk, insulin resistance, β-cell function and thyroid dysfunction: a cross-sectional study in She ethnic minority group of Fujian Province in China

Objective: To investigate the associations between cardiovascular risk, insulin resistance (IR), beta-cell function and thyroid dysfunction in She ethnic minority group in China. Methods: We enrolled 5080 participants of She ethnicity in this analysis eventually. We measured serum TSH and thyroid peroxidase antibody (TPOAb) concentrations, blood glucose and insulin levels in both fasting and 2-h postprandial states, serum lipid levels, blood pressure (BP), brachial-ankle pulse wave velocity (baPWV), electrophysiological parameters, including T-peak-T-end interval (Tp-e), QT interval and height of the R wave in lead aVL (RaVL), and anthropometric parameters. Results: The total prevalence of thyroid dysfunction in this population is 12.1%. Hyperthyroid subjects had shorter Tp-e interval and QT interval in electrocardiogram (ECG), while hypothyroid subjects had shorter Tp-e interval and longer QT interval in ECG than euthyroid subjects. Neither hyperthyroid nor hypothyroid subjects showed significant difference in BP, pulse pressure, and baPWV compared with euthyroid subjects. RaVL was slightly higher in hyperthyroid subjects, though the difference did not reach statistical significance (P=0.08). Subjects with TSH<0.3 mIU/l had higher blood glucose, insulin, homeostasis model assessment of insulin resistance (HOMA-IR), and beta-cell function (HOMA-beta), whereas subjects with TSH>10 mIU/l had lower insulin, HOMA-IR, and HOMA-beta than the reference group. There was a significant negative correlation, albeit weak, between TSH and HOMA-IR, HOMA-beta after adjustment for confounding factors. Conclusions: Hypothyroid subjects may carry higher cardiovascular risk than euthyroid subjects. Moreover, IR and beta-cell function are inversely correlated with TSH, which may be explained by the decreasing insulin-antagonistic effects of thyroid hormones along with increasing TSH.