Calcium metabolism in patients with chronic non-dialytic renal disease

Calcium metabolism was evaluated in 81 patients with chronic non-dialytic renal disease. Bone mineral content measured by photon absorptiometry was significantly lower than in normals, and serum alkaline phosphatase levels higher than in normals. However, the differences were small indicating that the calcium-metabolic disturbance was moderate. None of the patients suffered from overt osteomalacia. The mean serum level of 25-hydroxy-cholecalciferol (25-OH-D₃) was slightly, but significantly higher than in normals studied at the same time of the year, but some patients and subnormal 25-OH-D₃ levels. One such patient was given a daily dose of 1200 U of vitamin D₃ by mouth for 3 weeks. Hereafter, the serum 25-OH-D₃ concentration rose progressively to high normal values. These two observations would suggest that the hepatic 25-hydroxylation in such patients is unimpaired. The results are in accordance with the existence of a subclinical vitamin D deficiency in patients with non-dialytic renal disease, due to an impaired production of 1,25-(OH)₂D₃. It is an open question whether such patients should be given (prophylactic) treatment with 1α-hydroxycholecalciferol.