Abstract
Serum 25-hydroxyvitamin-D (25-OH-D) was determined in 24 normal subjects and in 60 patients with chronic renal failure (CRF). Mean concentration of 25-OH-D was low (25.4±11.2 ng/ml) in sera from the patients as compared with that (33.9±10.6 ng/ml) of normal controls, although the values in earlier stage of the renal failure were considered to be within normal ranges. In more progressive stage, however, the value decreased extremely (11.3±5.5 ng/ml)e In contrast, the patients receiving regular hem. odialysis 3 times a week showed an almost idetical serum 25-OH-D level (26.4±11.2 ng/ml) to those of another normal controls, the level of which had been measured in winter season. The protein intake by patients with CRF is limited depending upon the degree of disturcance of their renal function, although such a diet therapy was not given to the patients when their chronic hemodialysis was started. The reduction of serum 25-OH-D levels in patients with CRF would be thus attributed to the limitation of vitamin D intake resulting from diet therapy with low protein intake. The estimation of excretion of 25-OH-D in the urine was performed on the urinary samples from 5 normal subjects and these from 24 patients with renal diseases showing proteinuria. Mean urinary excretin of 25-OH-D in 5 control subjects was 4.8±4.7 ng/day whereas those of the patients with light (urinary protein<3.5 g/24h) and heavy (urinary protein>3.5g/24h) proteinuria were 24.3±19.9 ng/day and 75.5±43.9 ng/day respectively. By the administration of 25-OH-D (200 μg) to the same subjects, this tendency became more remarkable. Since concomitant 25-OH-D binding activity appeared in the urine, renal loss of low molecular weight protein (Transcalciferin ?) supposed to be the cause of low circulating serum 25-OH-D levels in heavy proteinnuric patients. The present data suggest that low levels of serm 25-OH-D in patients with CRF might be due to the leakage of 25-OH-D in the urine as well ar due to the diet therapy with low protein intake.
