[Therapeutic strategies in osteoporosis: whom and when to treat]

Postmenopausal bone loss can be efficiently prevented by compounds which inhibit bone resorption, but they can not induce a sustained and relevant bone gain. The initial increase in bone volume observed within the first year of treatment is due to a transient uncoupling between bone resorption and formation: the first is suddenly blocked whereas bone formation decreases slowly within several months; bone is gained until the previously resorbed cavities are refilled. This net increase in bone mass is completely lost as soon as treatment is withdrawn. Since these antiresorptive agents can only be used in order to prevent bone loss, they should be given for several years. Thus, the choice of the drug is also conditioned by its cost and long-term compliance. Estrogen replacement is very convenient, from these points of view in most patients immediately after the menopause. Afterwards, parenteral calcitonin has been, up to now, the sole available alternative with convincing evidence of effectiveness, at least in the medium term. Its cost and the scarce compliance to injections have strongly limited its extensive use. There is increasing evidence that oral bisphosphonates are very effective and therefore they might represent, in the near future, an effective and convenient alternative to estrogen replacement therapy.