25-Hydroxy vitamin D levels and endothelial vasodilator function in normotensive women

Introduction: Vitamin D was shown to be related to endothelial function and blood pressure. Reactive hyperaemia index (RHI) measurement by pulse arterial tonometry is a new method to evaluate vasodilator function of endothelium. We aimed to evaluate the relationship between vitamin D levels and RHI in women. Material and methods: We enrolled 56 normotensive, nonsmoker, normolipidemic and normoglycemic women, (23 with 25-OH-vitamin D levels > 20 mu g/l, and 33 with values lower than 20 mu g/l). The cardiologist who was blind for vitamin D results executed measurements by pulse arterial tonometry. The measurement was performed on the lying patient with pre- and post-occlusion measurements of RHI by digital sensors placed on each index finger, by 5 min intervals. Pulse amplitudes were recorded, pre-occlusion and post-occlusion ratio was compared by the software of device. Stepwise linear regression and multiple regression analyses were performed to evaluate predictors of endothelial function. Results: The low vitamin D group had a lower RHI value than the normal vitamin D group (p = 0.042). In regression analysis, positive predictors of RHI were serum 25-OHD (beta = 0.401; 95% CI 0.010-0.042, p = 0.002), serum albumin (beta = 0.315; 95% CI 0.286-2.350, p = 0.013), and, inversely, serum calcium (beta = -0.247; 95% CI (-1.347)-(-0.010), p = 0.047). Conclusions: Serum 25-hydroxy vitamin D was significantly related to endothelial functions measured as RHI, even in healthy non-smoker women.