Pathogenesis of osteoporosis

Publisher Summary Pathophysiology of osteoporosis is multifactorial and includes genetic, endocrine, and lifestyle influences. This chapter reviews the role of these factors in the earlier gain and later loss of bone mass, as well as the cellular mechanisms responsible for the latter. During growth, the effect of genes is modulated by hormonal factors, which in themselves may be genetically mediated. However, there is little consistency regarding the magnitude of importance of each of these genes and the extent to which their contribution can be generalized to all populations. Nutrition is an important, modifiable factor that determines peak bone mass (PBM). Several nutrients play key roles in skeletal development, including protein, calcium, phosphorus, and vitamin D. High-impact forces applied to the skeleton appear to confer the greatest benefit. Weight-bearing exercise is associated with higher PBM in both genders. The amount of tissue in the bone mass is the integral of the amount of bone accrued during growth and consolidation and the inevitable loss of bone tissue with aging and menopause in women. Therefore, both peak bone mass, and the rate and duration of bone loss determine fracture risk. Most clinicians consider the process of loss of mass and its accompanying architectural changes to be a prerequisite to the relationship between bone mass and fracture risk in older individuals.