Short-term effects of varying doses of 1 alpha-hydroxyvitamin D3 on blood and urine chemistry and calcium absorption of osteoporotic patients.

During a period of 4-7 days, synthetic 1 alpha-hydroxyvitamin D3 (1alpha-OH-D3) was given to osteoporotic patients with hip fractures in 3 different dose levels, viz. 1 microgram, 2 microgram, and 4 microgram, in combination with calcium. The increase in serum calcium level was more prominent during treatment with 2 microgram and 4 microgram doses of 1 alpha-OH-D3 and was also dependent on the duration of treatment. The level of serum phosphate was only slightly elevated. The urinary calcium excretion increased, while the urine phosphate and hydroxyproline excretion decreased. The intestinal absorption of calcium increased in rate during treatment with 1 alpha-OH-D3. On discontinuation of treatment, values did not normalize within 6 days. The administration of small doses of 1 alpha-OH-D3 did not seem to expose osteoporotic patients to the risks of hypercalcemia. The efficiency of vitamin D metabolites in the treatment of osteoporosis requires further investigation.