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.
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 VO2 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.
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.