1-alpha-OH-cholecalciferol (1-alpha-OHD3) and low phosphate diet in predialysis chronic renal failure: effects on renal function and on secondary hyperparathyroidism.

The effect of 1-alpha-OHD3 on the rate of decline of renal function was studied in 18 patients with predialytic chronic renal failure. 9 patients with serum creatinine 4.19 +/- 1.63 mg/dl, were treated with 1-alpha-OHD3 0.4 +/- 0.11 micrograms/day and a low phosphate diet and 9 patients, with serum creatinine 3.69 +/- 1.24 mg/dl, received the low phosphate diet alone. In the first group retrospectively in 8 patients up to 3-44 months and prospectively in all patients reciprocal values of serum creatinine levels fell linearly with time. Comparison of the slopes of the regression lines before and following the start of treatment did not show statistical differences in 6 cases, in 1 case the decline of renal function improved significantly and in 1 case it became positive. Serum calcium increased significantly (p less than 0.025), alkaline phosphatase decreased (p less than 0.005) and serum iPTH decreased in 6 of 8 cases. In the low phosphate diet group, serum calcium, alkaline phosphatase did not change while iPTH increased in 8 of 9 cases. The rate of decline of renal function before treatment in 3 cases did not improve after the institution of the diet. In conclusion improvement or prevention of secondary hyperparathyroidism in predialytic chronic renal failure can be achieved with daily doses of less than or equal to 0.5 micrograms 1-alpha OHD and a low phosphate diet. The small increment in serum calcium levels induced by the treatment did not accelerate the deterioration of renal function while showing a better control of alkaline phosphatase and serum iPTH than the low phosphate diet alone.