Biochemical markers of bone turnover in osteoporosis.

Postmenopausal osteoporosis is characterized by an increased frequency of activation of bone remodeling units and by a relative increase in bone resorption. Biochemical markers for bone turnover are simple noninvasive tools for evaluating these changes. Some are enzymes produced by osteoblasts or osteoclasts, whereas others are components of the bone matrix that are released in the bloodstream during bone formation or resorption. The most effective in osteoporosis are serum bone alkaline phosphatase and osteocalcin for bone formation, and urinary pyridinoline and deoxypyridinoline for bone resorption. In addition to being sensitive, these markers have shown evidence in recent experimental studies of contributing usefully to the evaluation of the osteoporosis or fracture risk and to the monitoring of treatments for osteoporosis.