Osteocalcin

Osteocalcin is a small, non-collagenous protein primarily synthesized by osteoblasts, the cells responsible for bone formation. It is the most abundant non-collagenous protein in bone and serves as a key marker of bone turnover. Beyond its well-established role in bones, research has revealed its crucial involvement as a hormone regulating various physiological processes throughout the body. These include insulin secretion and sensitivity, glucose metabolism, energy expenditure, and aspects of male fertility. It circulates in the bloodstream in both carboxylated (Gla-osteocalcin) and uncarboxylated (ucOC) forms. While both forms are present, the uncarboxylated form is increasingly recognized for its endocrine functions. Vitamin K, particularly K2, plays an important role in the carboxylation of osteocalcin, which is essential for its proper function in bone mineralization. The total circulating level of osteocalcin is often used in clinical settings as a biomarker for bone formation activity. Its half-life in circulation is relatively short, approximately one hour, reflecting its dynamic involvement in these biological systems. (PubChem, NIH ODS)