Evolution, aging, and osteoporosis.

Aging is a process whereby organisms lose to the capacity to effectively handle life's stresses. Associated with aging are pathophysiological processes, such as decreases in bone mass, which in the extreme form lead to significant morbidity. Evolutionary theory suggests that these pathophysiological processes are permitted to occur because an organism need only preserve its body against stress only for the amount of time needed for effective reproduction. In this review, an understanding of osteoporosis and bone loss is discussed within the context of aging theory. Specific topics covered include: (1) bone loss as an antagonistically pleiotropic physiological process, (2) age-associated stress accumulation and its negative impact on bone turnover, and (3) the mechanisms whereby gonadal failure, increases in inflammatory cytokines, and cellular bone marrow changes lead to bone loss. This review concludes by examining purported hypotheses in the context of Werner's syndrome, a disease characterized by premature aging. We suggest that future osteoporosis therapy will likely focus on prevention of aging in general as a means to prevent the development of osteoporosis.