Objectives: Vitamin D deficiency and high parathyroid hormone (PTH) levels have been linked with hypertension. Nondipper hypertension is associated with increased morbidity and mortality. We aimed to investigate the relationship of vitamin D and PTH levels with nondipper hypertension and nocturnal decline in untreated hypertensive patients.
Patients and methods: This cross-sectional study included a total of 73 hypertensive and 34 normotensive participants. Each patient underwent 24-hour ambulatory blood pressure monitoring, routine biochemical tests, vitamin D, and PTH analysis.
Results: The study population was divided into three groups according to ambulatory blood pressure monitoring records: 40 nondippers (mean age; 59.8±10.8 years, 24 women and 16 men), 33 dipper hypertensives (mean age; 58±11.8 years, 13 women and 20 men), and 34 normotensives (mean age; 56.9±11.7 years, 19 women and 15 men). Nondipper hypertensives showed lower levels of vitamin D than dippers and normotensives (9.7±6.1 vs. 14.9±10.1 vs. 16.4±9.5 ng/ml, P=0.001, for both) and higher levels of PTH than dippers (74.8±34.7 vs. 53.3±19.9 ng/ml, P=0.001). A significant positive correlation was observed between vitamin D and nocturnal decline (r=0.34, P=0.001), whereas a significant negative correlation was present between PTH and nocturnal decline(r=-0.26, P=0.006). In multivariate analysis, PTH level was correlated independently with nocturnal decline (β=-0.07, 95% confidence interval: -0.114-0.025, P=0.003).
Conclusion: In this study, vitamin D levels were significantly lower and PTH levels were significantly higher in nondippers. The vitamin D level was correlated positively and the PTH level was correlated negatively with nocturnal decline. In addition, PTH level was associated independently with nocturnal decline in hypertension.