EFFECTS OF A SHORT COURSE OF ORAL PHOSPHATE TREATMENT ON SERUM PARATHYROID HORMONE(1-84) AND BIOCHEMICAL MARKERS OF BONE TURNOVER - A DOSE-RESPONSE STUDY

To investigate the possible use of oral phosphate as an activator of bone remodeling in coherence treatment of osteoporosis, 82 postmenopausal females, aged 50-75 years, were randomized to treatment with oral phosphate (750, 1500, or 2550 mg/day) or placebo for 7 days and followed for 4 months thereafter. All patients had sustained at least one previous fracture of the distal forearm and had a bone mineral content of the contralateral forearm or bone mineral density of the lumbar spine lower than normal mean for age. Urinary phosphate/creatinine ratio increased in a dose-dependent fashion during treatment (P < 0.001), whereas no significant changes were seen in serum phosphate or serum calcium. Serum parathyroid hormone (PTH) rose significantly (P < 0.05) during treatment to a maximum of 36 and 33% in the groups receiving 1500 and 2250 mg/day, respectively, whereas serum 1,25-dihydroxycholecalciferol remained unchanged. In the group receiving 1500 mg/day, mean serum osteocalcin was increased in the period from day 1 to day 28 (P < 0.05), but no significant changes were observed in urinary hydroxyproline/creatinine ratio, or serum bone alkaline phosphatase. We conclude that a short course of oral phosphate treatment increases serum PTH considerably. Furthermore, 1500 mg/day but not 2250 mg/day increases serum osteocalcin. No clear biochemical evidence, however, of increased activation of bone remodeling could be demonstrated in either group.