Osteocalcin (also known as bone Gla protein/BGP) is protein found in bone and dentin. Its synthesis involves vitamin K and vitamin D3; newly synthesized osteocalcin is partioally released into the blood stream and the rest incorporatedthe bone matrix. Both osteocalcin (1-49) and its fragments, including osteocalcin (1-43) are released into the blood stream.
Serum osteocalcin (1-43) is also generated by the catabolic breakdown of osteocalcin (1-49) in circulation, liver, and kidney. This process can also occur by in vitro degradation during storage of samples because of a labile 6-amino acid C-terminal sequence that is easily cleaved at room temperature. Several studies have confirmed that measurement of the more stable N-terminal and mid-regional osteocalcin (osteocalcin 1-43/49) as being more clinically useful, which may contribute to a more accurate assessment of the bone turnover rate.
Because osteocalcin is produced by osteoblasts, it is often used as a biochemical marker, or biomarker, for the bone formation process. It has been routinely observed that high serum osteocalcin levels are relatively well correlated with increases in bone mineral density (BMD) during treatment with anabolic bone formation drugs for osteoporosis. In many studies, osteocalcin is used as a preliminary biomarker on the effectiveness of a given drug on bone formation.