Osteocalcin is the major non-collagenous protein of bone matrix. Osteocalcin is synthesised in bone by osteoblasts. After production, it is partly incorporated into the bone matrix and partly delivered to the circulatory system. The precise physiological function of osteocalcin is still unclear. A large number of studies have shown that the circulating level of osteocalcin reflects the rate of bone formation. Determination of serum osteocalcin has proved to be valuable as an aid in identifying women at risk of developing osteoporosis, for monitoring bone metabolism during the perimenopause and postmenopause and during anti-resorptive therapy. In other words, this test can be used to estimate the rate of loss of bone tissue. It has been routinely observed that higher serum-osteocalcin levels are relatively well correlated with increases in bone mineral density (BMD) during treatment with anabolic bone formation drugs for osteoporosis, such as Forteo. In many studies, Osteocalcin is used as a preliminary biomarker on the effectiveness of a given drug on bone formation. ELEVATED osteocalcin levels are associated with metabolic bone diseases such as osteoporosis, primary hyperparathyroidism, Paget’s disease, and renal osteodystrophy.