Serum 25-hydroxyvitamin D and parathyroid hormone in patients with acute renal failure.

Serum 25-hydroxyvitamiu P and parathyroid hormone in patients with acute renal failure. The concentration of 25-hydroxyvitamin D (25-OH-D) in the serum of 18 patients with acute renal failure was measured serially using a sensitive radiocompetitive assay. In normal subjects, the mean concentration of serum 25OH-D was 16.6 ng/ml (range, 7.7 to 36 nglml). In patients with acute renal failure, the mean serum 25-OH-D was 10.8 ng/ml on admission, and after two weeks of oliguria, it decreased to a mean of 6.0 ng/ml. Frequent sampling of blood and the subsequent assay for 25-OFI-D have allowed for determination of the apparent serum half-life of 25-OH-D, which averaged 5.6 days (range, 1.9 to 9.2) in the 18 patients with acute renal failure. After this initial rapid fall, the patients maintained low serum concentrations of 25-OH-D in the course of acute renal failure, with a subsequent increase following the recovery of normal kidney function. Low concentrations of serum calcium, high inorganic phosphate, and slightly increased levels of alkaline phosphatase activity were typically found early in the course of acute renal failure and persisted during oliguria and early polyuria. The serum immunoreactive parathyroid hormone was incrcased 2 to 4 times above the upper normal limit in the first 4 to 8 days after the onset of renal failure, and it further rose to an average of 2.7 nglml in the early polyuric stage, in spite of a slight increase in serum calcium. It is postulated that low concentrations of serum 25-OH-D may be a factor in the development of the hypocalcemia and the secondary hyperparathyroidism of acute renal failure. The significant fall in serum 25OH-D is probably due to an increased mctabolic clearance rate.