[Calcitonin and bone aging]

There appears to be a consensus that 100 IU/day of nasally administered salmon calcitonin may prevent trabecular bone loss during the first years of the menopause. Strong evidence exists that half that dose may also be sufficient to prevent trabecular bone loss and that higher doses (> or = 200 IU/day) induce a significant increase in spinal bone mineral content. Calcium supplements should be systemically administered when calcitonin is given, particularly at high doses. Rectal calcitonin seems also to be an efficient alternative in prevention of trabecular bone loss. Further studies are required to evaluate the effect of calcitonin in prevention of cortical bone loss. In established osteoporosis, calcitonin may prevent further bone loss at trabecular and cortical sites. A similar benefit is obtained following parenteral or nasal administration of the drug. Long-term administration of nasal salmon calcitonin induces a significant dose-dependent gain of bone at the lumbar spine, whereas discontinuous therapy with a ratio of 1:2 or 2:3 between the treatment and nontreatment periods is the best regimen for cortical bone. Epidemiological, retrospective, and prospective studies provide a convergent network of evidence that calcitonin administration in osteoporosis contributes to reduce significantly the frequency of subsequent fractures, both in the spine and in the hip. Finally, in established osteoporosis, nasal calcitonin possesses a potent analgesic effect, reduces the duration of bed confinement, and decreases the number of concomitant analgesic medications. The well-demonstrated effects of nasal calcitonin permit it to be considered as a highly rational solution for the prevention and the treatment of postmenopausal osteoporosis.