The field of bone turnover markers has developed considerably in the past decade. Biochemical monitoring of bone metabolism depends upon measurement of enzymes and proteins released during bone formation and of degradation products produced during bone resorption. Various biochemical markers are now available that allow a specific and sensitive assessment of the rate of bone formation and bone resorption of the skeleton. Although these markers are not recommended for use in diagnosis of osteoporosis yet, they appear to be useful for the individual monitoring of osteoporotic patients treated with antiresorptive agents Osteoporosis is a silent disease with no symptoms, but its clinical consequences can be debilitating. Common sites for osteoporotic fractures include the spine, wrist, and hip. The aging population, as well as lifestyle changes, have led to an increase in the disease's prevalence and the incidence of fractures. In fact, fractures account for the majority of osteoporosis-associated health costs, with hip fractures causing the most morbidity and mortality and accounting for a large proportion of the cost. In the U.S., the annual cost of osteoporotic fractures has risen from $17 billion in 2006 to approximately $20 billion today, and it is predicted to rise to $25 billion by 2025.