Abstract
We evaluated the effects of therapy with a small dose (0.5 μg/day) of 1,25-dihydroxyvitamin D3 in 12 previously untreated patients with postmenopausal osteoporosis. Combined radiocalcium kinetic and balance studies showed that at base line, net calcium absorption (mean ± SEM) was low (7 ± 3%), calcium balance was negative (-59 ± 22 mg/day), and bone resorption rate (297 ± 40 mg/day) exceeded bone formation rate (239 ± 36 mg/day). After short-term therapy (6-8 months), calcium absorption was normal (27 ± 3%. P