Objective: Impairment of flow-mediated endothelium-dependent arterial dilation (FMD) exists in patients with subclinical hypothyroidism (sHT). Several studies showed that exercise training can improve FMD in patients with type 1 and type 2 diabetes. Therefore, we hypothesized that exercise training can also improve FMD in subjects with sHT. The purpose of the study was to test this hypothesis.
Research design and methods: We selected 30 sedentary women with sHT and 27 sedentary healthy women with euthyroid. All individuals participated in an exercise training of 6 months. Before and after exercise training, high resolution ultrasound was used to measure FMD.
Results: At baseline, FMD among subjects with sHT was 3.87%, which was significantly lower than that in controls (5.98%; P<0.001). After 6 months of exercise, there was a remarkable increase in FMD (31.3%) and VO(2) max (36.7%; P<0.01), and significant decreases in total cholesterol (20%), low-density lipoprotein cholesterol (LDL; 29%), triglycerides (TG; 47.6%), and C-reactive protein (CRP; 61.5%; P<0.05) were observed over the exercise in patients with sHT. The absolute changes in FMD showed significant correlation with changes in LDL (r=-0.596), TG (r=-0.532), and CRP (r=-0.511; P<0.01), and multiple regression analysis showed changes of LDL, TG, CRP were significant determinants of changes of FMD in sHT patients during exercise course.
Conclusion: Regular aerobic exercise improves FMD in sHT patients, and changes of lipids and inflammation during the exercise period may partially contribute to the improvement of endothelial function.