[Osteocalcin, marker of bone metabolism].

The recent development of biochemical markers gives the opportunity to assess bone metabolism. Osteocalcin is a non collagenous protein of the bone matrix specifically synthesized by osteoblasts. The concentration of osteocalcin in serum reflects osteoblastic function and bone turnover. It has emerged as a more specific index of bone metabolism than serum alkaline phosphatase activity. Great care must be taken in blood sampling, processing and storage to avoid protein degradation. Inasmuch, we have shown in human clinical settings, the interest of this marker in patients with bone metabolic disorders characterized by increased bone turnover such as primary and secondary hyperparathyroidism or postmenopausal osteoporosis. Conversely, exogenous or endogenous high levels of corticosteroids rapidly induced a reversible decrease in osteocalcin levels.