Bone Turnover and the Development of Osteoporosis
Throughout life, bone is metabolically active. Once skeletal growth is complete, bones are continuously remodeled resulting in an annual turnover of about 10%. The remodeling of bone requires the cyclical actions of the osteoclasts to remove aged bone, and the osteoblasts to generate new bones.
Bone mineral density (BMD) accounts for 70% of fracture risk in osteoporosis; the remaining 30% is affected by bone micro-architecture. Greater bone resorption and not enough bone formation result in net bone loss and lower bone density. Even though normal bone density may be achieved when treated with common anti-resorption drugs, abnormal bone micro-architecture may still be present resulting in brittle bones.
Typically, osteoporosis is a disease of aging. Bone mass begins to decline an average of 0.7% per year after age 35 and the rate of loss increases after menopause. Some women have osteoporosis as early as perimenopause and many more have osteopenia. As a healthcare provider, the key is proactive intervention.