Objective: Osteoprotegerin (OPG) is a recently identified inhibitor of bone resorption. Recent studies indicated that OPG also acts as an important regulatory molecule in the vasculature. The purpose of this study was to investigate the change of OPG and its associations with endothelial function before and after exercise training in Hashimoto's thyroiditis (HT) with euthyroidism.The study subjects included 62 newly diagnosed sedentary Chinese Han HT women with euthyroidism and 28 sedentary Chinese Han female healthy subjects. All individuals participated in an exercise training of 6 months. Plasma OPG concentrations were measured in duplicate by a sandwich enzyme-linked immunosorbent assay, and high resolution ultrasound was used to measure brachial artery diameter at rest, after reactive hyperemia, and after sublingual glyceryltrinitrate.
Results: The OPG concentration in HT patients with euthyroidism before exercise was 3.0±0.81 ng/L, which was significantly higher than that in control subjects (2.44±0.24 ng/L, p<0.001). After 6 months of exercise, OPG levels decreased markedly (2.40±0.61 ng/L, p<0.001). Flow-mediated dilation (FMD) in HT patients with euthyroidism before exercise was 4.06±0.78%, which was significantly lower than that in control subjects (5.54±0.61%, p<0.001), and it improved markedly after 6 months of exercise (5.0±0.79, p<0.001). The absolute changes in OPG showed significant correlation with the changes in FMD (r= - 0.432, p=0.001), TBARS (r= - 0.370, p=0.004) and CRP (r= - 0.503, p<0.001).
Conclusion: The current study demonstrates that plasma OPG levels increased significantly at baseline, decreased dramatically after 6 months regular aerobic exercise training, and are correlated with endothelium-dependent arterial dilation in HT patients with euthyroidism.
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