Relationship between vascular endothelial function and vitamin D and parathyroid hormone levels in women with arterial hypertension

There are few studies indicating a relationship between vitamin D, parathyroid hormone (PTH), and parameters of endothelial function. The aim of the study was to establish the relationship between vascular endothelial function and the level of vitamin D and PTH in women with arterial hypertension (AH). It was a cross-sectional study of 141 women with AH stage II aged 50.8 ±6.0 years. We determined the serum levels of total 25-hydroxyvitamin D (25(OH)D), PTH, endothelin 1, as well as nitrites and nitrates. Endothelial function was measured by impedance rheography. Endothelium-dependent vasodilatation was measured by a reactive hyperemia test. Endothelium-dependent vasodilatation of less than 12% was considered as endothelial dysfunction (ED). Vitamin D deficiency was observed in 53 women (37.6%); insufficiency, in 42 (30.1%); and the optimal level, in 46 (32.3%). ED was determined in 49.6% of the patients. The serum PTH level was 36.6 ±20.1 pg/ml, and it was above the upper limit of the reference range only in 5.5% of the cases. We showed significant correlations between PTH and systolic blood pressure (R = 0.28; P = 0.003), PTH and 25(OH)D (R = -0.27; P = 0.025), and 25(OH)D and SBP (R = -0.23; P = 0.034). In the group with ED, the serum level of endothelin 1 was higher compared with the group without ED (0.57 ±0.18 vs. 0.49 ±0.21 pg/ml; P = 0.032) and that of nitrates and nitrites was lower compared with the group without ED (15.2 [11.1-29.9] vs. 22.8 [16.9-33.0] μmol/l; P = 0.0005). In the group without ED, PTH inversely correlated with endothelin 1 (R = -0.27; P = 0.043). In the group with ED, PTH inversely correlated with nitrates and nitrites (R = -0.48; P = 0.003). In women with AH and without ED, PTH affected the production of a vasoconstrictor, endothelin 1, while in those with ED, PTH was associated with a lower production of vasodilators, nitrates and nitrites, by the vascular endothelium.