Relation between serum calcium, phosphate, parathyroid hormone and 'nondipper' circadian blood pressure variability profile in patients with normal renal function.

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 x phosphate (Ca x 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 x 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 (beta = 0.43, p = 0.001) and phosphate (beta = 0.9, p = 0.03).

CONCLUSION

We demonstrate a graded independent relation between higher levels of phosphate, PTH, Ca x P product and the risk of nondipping in hypertensive patients with an estimated GFR of >60 ml/min and normal mineral metabolism.