Vitamin D in nephrotic syndrome remission: a case-control study

Vitamin D deficiency may contribute to osteoporosis in nephrotic syndrome (NS). A cross-sectional case-control study was performed to investigate 25 hydroxycholecalciferol [25(OH)D] status in 40 patients with NS in remission and 40 healthy controls. Serum levels of 25(OH)D, calcium, phosphate, alkaline phosphatase (ALP), and intact parathyroid hormone (PTH) were assayed. NS patients were segregated by age at onset, current age, type and duration of NS, months since relapse and current drug therapy. Levels of 25(OH)D showed a positive correlation with months elapsed since last NS relapse (r (s) = +0.4, p = 0.012) and were lower in NS patients within 3 months of relapse but similar to that of controls in patients in remission for > 3 months [median 14.23 (interquartile range 12.19-17.63) vs. 19.75 (14.04-28.38) ng/ml, respectively; p = 0.039]. There was no correlation of 25(OH)D levels with other disease characteristics or drug therapy. ALP levels were also lowest after relapse (r (s) = +0.34, p = 0.036). Overall, 25(OH)D levels of < 20 ng/ml occurred in 62.5 % of NS patients + controls, and correlated negatively with age (r (s) = -0.24, p = 0.037) but showed no significant correlation with calcium, phosphate, or PTH levels. In our patients with NS, vitamin D stores remained low for 3 months after NS relapse but showed an increase with longer remission time to control levels. Vitamin D stores were not influenced by disease characteristics or therapy. Longitudinal studies are required to confirm these findings and evaluate the effect of vitamin D on bones, particularly in frequent relapsers.