Serum vitamin D levels in kidney transplant recipients: The importance of an immunosuppression regimen and sun exposure

Background: Vitamin D deficiency was shown to be prevalent among renal transplant recipients in northern countries, but little is known regarding risk factors. Objectives: To test vitamin D levels in kidney transplant recipients residing closer to the equator, compare them to levels in liver transplant recipients and hemodialysis patients, and identify possible risk factors. Methods: In a cross-sectional study 103 kidney transplant recipients, 27 liver transplant recipients and 50 hemodialysis patients followed at our institute were tested for vitamin D levels. Demographic data, medical history and current treatment were recorded from the medical files. Results: Inadequate vitamin D levels (< 30 ng/ml) were found in 75% of all patients and 75% of all kidney transplant recipients. Vitamin D levels were higher among dialysis patients than transplant recipients, though deficiency rates were similar. No association was found between kidney function and vitamin deficiency. Deficiency was associated with higher prednisone doses, use of mycophenolate sodium, tacrolimus, and iron supplements, or lower doses of vitamin D supplementation. Conclusions: Despite potential higher ultraviolet B exposure, inadequate vitamin D levels were prevalent in our study group. Importantly, some immunosuppressive medications were associated with vitamin D deficiency and high doses of vitamin D were associated with less deficiency.