24 patients with chronic renal failure in the predialytic stage were treated with 1, 24 R-dihydroxycholecalcif erol (1, 24D3) in doses of 0. 5-1. 5μg/day for 22.3±10.6 weeks. All patients had abnormally high serum levels of alkaline phosphatase and/or parathyroid hormone at the start of treatment. The levels of alkaline phosphatase were decreased significantly during treatment, and in 7 patients fell into normal range. In contrast, the serum levels of PTH did not show any significant decrease. The rate of deterioration of renal function was determined by serial measurements of serum creatinine and plotting the reciprocal of them against time. The slope of regression lines before and during the treatment were compared in 16 patients. The renal functions in 7 cases showed the significant acceleration of the detrioration rate. The cases with serum creatinine level over 4, 1mg/dl were prone to the acceleration compared with the cases with creatinine level under 4, 0mg/dl. In conclusion, 1, 24D3 is proved to have some beneficial effect on renal osteodystrophy, especially to control the level of alkaline phsphatase. However, it is potentially dangerous to renal function, and the routine prophylactic use is probably not warranted.
