Evaluation of 25-hydroxy Vitamin D and 1,25-dihydroxy Vitamin D Levels in Maintenance Hemodialysis Patients

Introduction. Dysregulated vitamin D metabolism is one of the most important issues in chronic kidney disease- mineral and bone disorder (CKD-MBD). Patients with end-stage kidney disease (ESKD) receive large amounts of calcitriol, i.e., 1,25 -dihydroxy vitamin D [1-25(OH)(2)D], for suppression of parathyroid hormone (PTH). The aim of this study was to evaluate the 1-25(OH)(2)D status in maintenance hemodialysis patients and its correlation with 25(OH) D level and calcitriol consumption and to determine whether the usual practice of administrating large amounts of calcitriol for suppression of PTH may lead to toxic serum levels. Methods. One hundred and fifty-six maintenance hemodialysis patients were enrolled. Demographic data, comorbid conditions and history of medication use (cumulative and current doses) were retrieved from Hemodialysis Data Processor Software previously designed for our center. Predialysis serum samples were measured for serum levels of 25(OH)D and 1-25(OH)(2)D accompanying by markers of mineral bone metabolism and inflammation. Results. Of 156 patients, 66% were male and the mean age was 56.5 +/- 16.3 years. There was no significant correlation between serum level of 25(OH)D and 1,25(OH)(2)D (r = 0.12, P > .05). Only current ingestion of vitamin D was correlated with both 25(OH) D (r = 0.324, P < .001) and 1,25(OH)(2)D serum levels (r = 0.334, P < .001). There was no significant relationship between current or cumulative calcitriol consumption and 1,25(OH)(2)D serum level. 1,25(OH)(2)D/25(OH)D ratio which, represents the degree of vitamin D hydroxylation efficiency was 0.9 pg/ng (expected value in no CKD > 2.2 pg/ng). Conclusion. Calcitriol consumption was not correlated with increased serum 1,25(OH)(2)D level and the practice of hyperparathyroidism treatment with calcitriol may be safely continued, though we are not yet aware of the 1,25(OH)(2)D status at the cellular level.