When I was a young intern in internal medicine, osteoporosis was defined mainly as a fracture occurring in elderly people. However, although plain X-ray examination was recognized as an insensitive way to detect osteoporosis, hypodense bone was already considered as the reflection of the disease. Over the past 20 years, con- siderable progress has been accomplished. In terms of prevalence, incidence, risk factors, and the burden of osteoporosis and...