Epidemiology of osteoporosis.

Osteoporosis is defined as a reduction in bone mass and disruption of bone architecture, resulting in reduced bone strength and increase of bone fractures and it is responsible for more than 1.5 million fractures annually, including 300,000 hip fractures, approximately 700,000 vertebral fractures, 250,000 wrist fractures, and more than 300,000 fractures at other sites. The lifetime risk for any fragility fractures in Caucasian women at age 50 years approaches 40% and 13% in men. During childhood and adolescence there is a rapid linear and appositional skeletal growth with a peak bone mass attained during the third decade of life. During adult life the mechanical integrity of the skeleton is maintained by the process of bone remodeling, in which old bone is removed by osteoclasts and subsequently replaced by new bone, formed by osteoblasts. In recent years, we have come to appreciate that the close association between bone and vasculature plays a pivotal role in the regulation of bone remodeling and fracture repair. Vitamin D, OPG/RANK/ RANK-L system, Matrix Gla-proteins (Mgp) and Fetuin-A/calcium phosphate mineral phase complex play an important role in the regulation of bone homeostasis and vascular calcifications. A greater understanding of the biological linkages may lead to new dual-purpose therapies that may ultimately prevent the adverse outcomes of osteoporosis and atherosclerosis.