The relationship between vitamin D status and graft function in renal transplant recipients

INTRODUCTION: Bone and mineral metabolism disorders are important potential complications after renal transplantation. The purpose of this study was to demonstrate the relationship between vitamin D, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], calcium, and phosphorus metabolism with graft function in renal transplant recipients.
METHODS: This prospective longitudinal study included 30 renal transplant recipients (10 female, 20 male; mean age: 40.30±12.86 years). Blood and urine samples were collected before and 6 months after transplantation. Serum creatinine, blood urea nitrogen (BUN), calcium, phosphorus, alkaline phosphatase (ALP), glucose, albumin, parathyroid hormone (PTH), 25-hydroxyvitamin D [25(OH)D], and plasma 1,25(OH)2D3 levels were measured. In addition, the urine protein/creatinine (P/C) ratio was calculated. The plasma 1,25(OH)2D3 level was determined using liquid chromatography-tandem mass spectrometry.
RESULTS: The posttransplant level of serum phosphorus, PTH, creatinine, BUN and ALP was found to be significantly decreased (p=0.0001; p=0.011 for ALP). Although the plasma 1,25(OH)2D3 level had significantly increased (p=0.0001) after transplantation, no significant difference in the serum 25(OH)D level was observed. The urine P/C ratio was found to be significantly decreased after transplantation (p=0.007). A deficiency of vitamin D was observed frequently both before (87%) and after (73%) transplantation.
DISCUSSION AND CONCLUSION: Persistent vitamin D deficiency was detected in the recipients even after transplantation, although the serum PTH level decreased. Some studies published to date draw a direct link between serum vitamin D level and graft function; however, evidence for this link was not observed in the present study. Long-term monitoring may be needed to evaluate the correlation between vitamin D level and graft function.