This test helps in making a differential diagnosis and monitoring responsiveness to treatment for several diseases, such as osteoporosis and Paget’s disease.
Throughout our lifetime, our bones undergo constant transformation (known as turnover) as bone tissue is continuously being destroyed and renewed in a process we call bone remodelling (or bone metabolism). This process takes place in two phases: the first phase (resorption) is the “destruction” of a small part of mature bone tissue, and it is followed by the second phase (formation), which involves its replacement by new bone tissue. In patients with osteoporosis, the bones are weakened because the resorption process takes place at a faster rate than the formation process. In Paget’s disease, both phases take place very quickly, causing pain and bone deformities.
Osteocalcin is a protein released during bone formation and it is part of the bone structure. Small amounts of osteocalcin are found in the bloodstream during bone resorption. Osteocalcin levels reflect both bone formation and bone resorption activity. There are other specific markers for resorption activity (C-telopeptide) and formation activity (P1NP). The measurement of osteocalcin is ordered as a second-line test when a physician suspects specific bone metabolism abnormalities (particular cases of osteoporosis, rickets and osteomalacia, hyperparathyroidism, and so on).