Decrease of arterial stiffness at common carotid artery in hypothyroid patients by normalization of thyroid function

This study examined the effect of hypothyroidism on arterial stiffening and the effect of levothyroxine (l-T4) replacement. The arterial stiffness index beta (stiffness β) and intima-media thickness (IMT), a parameter of arterial stiffening and thickening, respectively, were determined in common carotid artery (CCA) by ultrasonography in 30 hypothyroid patients before and after 1 year of normalization of thyroid function by l-T4 replacement. Baseline CCA stiffness β and IMT was significantly higher in the hypothyroid patients than in age- and sex-matched normal controls [9.46 ± 0.93 vs. 8.02 ± 0.91 (mean ± SE); P < 0.05, 0.635 ± 0.018 mm vs. 0.541 ± 0.019 mm; P < 0.005, respectively]. In multivariate analysis, baseline stiffness β was significantly associated with baseline levels of IMT (r = 0.457, P = 0.0311), FT4 (r = -0.413, P = 0.0169), and a plasma vascular injury marker, von Willebrand factor (vWF) (r = 0.412, P = 0.0261). During 1 year of euthyroidism, 22 and 29 out of 30 patients showed significant decreases of stiffness β and IMT to normal respective level, from 9.46 ± 0.93 to 7.58 ± 0.34 and from 0.635 ± 0.018 to 0.552 ± 0.015 mm, respectively. Change in stiffness β during l-T4 therapy correlated significantly in a negative manner with baseline levels of age (r = -0.465, P = 0.011) and IMT (r = -0.406, P = 0.029). Stiffness β after but not before l-T4 therapy showed a tendency towards a positive correlation with age. This study suggested that increases of arterial thickening, and plasma vWF, and a reduction in serum FT4 might have an important role independently in the increased arterial stiffening in hypothyroid patients. Furthermore, it was demonstrated that sustained euthyroidism might have the potential to reverse arterial stiffening in addition to thickening in hypothyroid patients.