Relation between Serum Calcium, Phosphate, Parathyroid Hormone and ‘Nondipper’ Circadian Blood Pressure Variability Profile in Patients with Normal Renal Function

Abstract

Background and Aims: In patients with renal disease, an association between abnormal circadian blood pressure profile and abnormalities in bone and mineral metabolism, including vascular calcifications, is well known. However, such a link has not yet been reported in hypertensive patients with normal renal function. We aimed to evaluate if higher serum phosphate, calcium, parathyroid hormone (PTH) level and the calcium×phosphate (Ca×P) product would be associated with a nondipper hypertension, in patients with normal renal function and without any PTH disorder. Methods: 190 hypertensive subjects with the following inclusion criteria were enrolled: (1) normal phosphate and PTH levels; (2) glomerular filtration rate (GFR) >60 ml/min, and (3) no history of calcium, phosphate, vitamin D medication and hyperparathyroidism. Results: Of the total population, 76 patients (40%) were classified as dippers and 114 (60%) as nondippers. Nondipper patients had higher levels of phosphate (3.70 ± 0.61 vs. 3.35 ± 0.44 mg/dl, p = 0.001), Ca×P product (35.4 ± 6.5 vs. 31.5 ± 5.0, p = 0.001) and PTH (75.7 ± 28.8 vs. 46.6 ± 17.1 pg/ml, p = 0.000) compared to dipper patients. Independent predictors (multiple regression) for nondipper hypertension were PTH (β = 0.43, p = 0.001) and phosphate (β = 0.9, p = 0.03). Conclusion: We demonstrate a graded independent relation between higher levels of phosphate, PTH, Ca×P product and the risk of nondipping in hypertensive patients with an estimated GFR of >60 ml/min and normal mineral metabolism.