Objective: To study the efficacy of synthetic 1,25 dihydroxyvitamin D3 (calcitriol) in the treatment of osteoporosis.
Design: Two-year, double-blind, randomized clinical trial.
Setting: University medical center.
Patients: Fifty postmenopausal women with vertebral fractures recruited by referral.
Intervention: Calcium intake was adjusted to 25 mmol/d (1000 mg/d) at baseline. Patients were then randomized to treatment with either calcitriol or placebo. During the study, calcium intake was reduced to 15 mmol/d (600 mg/d) and the dose of calcitriol was adjusted to maintain serum calcium less than 2.74 mmol/L (less than 11.0 mg/dL) or urine calcium less than 9.96 mmol/d (less than 400 mg/d).
Measurements and main results: After 2 years, the mean dose of calcitriol in the treated group was 0.62 micrograms/d. Bone mineral density of the spine increased 1.94% with calcitriol therapy and decreased 3.92% with placebo (P = 0.001). Total body calcium increased 0.21% with calcitriol therapy and decreased 1.85% with placebo (P = 0.004). Patients receiving placebo had significant decreases in spine density (P = 0.0007) and total body calcium (P = 0.0004). There were no differences in vertebral fracture rates between the groups. Renal function studies were not statistically different between the groups after 2 years.
Conclusion: The treatment of postmenopausal osteoporotic women with synthetic calcitriol for 2 years was associated with increases in spine density and total body calcium. No adverse effects on renal function were seen after long-term calcitriol therapy.