Effects of 1alpha-hydroxyvitamin D3 on serum calcium and immunoreactive parathyroid hormone in patients with chronic renal insufficiency.

Six patients with chronic renal failure on regular dialysis treatment were given low doses (0.5--1.0 microgram/day) of 1alpha-hydroxyvitamin D3, monitoring the serum calcium, inorganic phosphate, immunoreactive parathyroid hormone concentration (IPTH) and alkaline phosphatase activity. The serum calcium rose in all patients after 7 days' treatment, in some subjects to hypercalcemic range; this effect persisted 6--14 days after withdrawal of 1alpha-hydroxyvitamin D3. The elevated serum IPTH rose in the first days of treatment, but later decreased to normal values. It is suggested that active vitamin D metabolites are necessary for normal response of parathyroid glands to variation in serum calcium. Low-dose 1alpha-hydroxyvitamin D3 treatment appears to be a promising method of correcting hypocalcemia and secondary hyperparathyroidism in chronic renal failure. Careful control of serum calcium is necessary, as hypercalcemia may occur even after minute doses of 1alpha-hydroxyvitamin D3.