Role of hormonal changes in the pathogenesis of osteoporosis in men

It is clear that age-related changes in sex-steroid production and availability likely play an important role in mediating bone loss in elderly men. Estrogen appears to be particularly important in regulating bone resorption, probably on cancellous and endocortical surfaces, whereas testosterone may have its major effect on periosteal surfaces. There also appears to be a significant role for age-related changes in growth hormone and IGF-I production in mediating age-related bone loss, in part through possible effects of IGF-I on SHBG production, resulting in alterations in sex steroid bioavailability. Perhaps somewhat surprisingly, the hormonal changes in young and middle-aged men with idiopathic osteoporosis appear to be paralleling those seen in aging men, although only a small number of men with idiopathic osteoporosis have been studied in detail. A more complete understanding of the hormonal factors leading to bone loss in both groups of men is likely to lead not only to insights on the mechanisms of sex-steroid action on bone, but also to more rational, mechanism-based therapeutic approaches.