[Laboratory diagnosis of osteoporosis]

Bone is biologically a highly active tissue whose cells are embedded in a complex network of systemically acting hormones and local mediators. The mechanisms of action involved are as yet only partially understood. With the increase in life expectancy and the resultant change of the population's age structure, diseases of the musculoskeletal system and bones have increased in importance. Thus, research is directed to a greater extent toward bone metabolism and the most frequent bone disease, osteoporosis. Until a few decades ago, the diagnosis of a bone disease was based principally on clinical and radiological methods. Laboratory methods only included the measurement of total alkaline phosphatase activity and calcium and phosphate balance. The development and introduction of new biochemical markers of bone metabolism in recent years led to a considerable increase in available laboratory methods. To evaluate the activity of osteoblastic synthesis, alkaline phosphatase and other bone-forming markers with higher tissue specificity such as bone alkaline phosphatase, osteocalcin, and several collagen propeptides are used. Bone degradation (calcium and hydroxyproline were the only markers until several years ago) can now be detected quickly and reliably with many new serological and urinary markers. Pyridinium derivatives and telopeptides as products of the metabolic activity of osteoclasts have been proved efficacious in diagnosis and therapy control.