Effect of fluoride therapy on nondialyzable urinary hydroxyproline,serum alkaline phosphatase,parathyroid hormone,and 25-hydroxyvitamin D

The effect of sodium fluoride therapy was studied in 40 osteoporotic male subjects, aged 50–80 yr. Twenty patients were treated with sodium fluoride (20–40 mg/day) and 20 received placebo for 107 wk. A marked increase (53%; p < 0.001) in the nondialyzable fraction of urinary hydroxyproline was found in the fluoridetreated group. Total urinary hydroxyproline levels were unchanged. The increased fraction of urinary hydroxyproline is suggestive of increased bone collagen synthesis and is consistent with the finding of a diminished rate of bone loss in the fluoride-treated group (per cent change in bone density after 107 wk was ?0.14 ± 5.28 versus ?5.24 ± 7.62 for the placebo-treated group; p < 0.02). Serum alkaline phosphatase levels were elevated in the fluoride-treated group (38%; p < 0.001) after 107 wk of treatment. This change, as well as the increased fraction of urinary hydroxyproline persisted for at least 6 mo after cessation of fluoride treatment and was not temporally related to serum fluoride levels. No significant changes in serum parathyroid hormone, 25-hydroxyvitamin D, serum calcium, and phosphorus were found after 1 yr of fluoride treatment. These findings suggest that fluoride does not alter serum 25-hydroxy-vitamin D and that the mechanism by which fluoride increases the rate of bone formation does not involve hyperparathyroidism.