The quantity and quality of bone tissue renewal are dependent on the generation of new bone (deposition) mediated by osteoblasts and the loss (resorption) mediated by osteoclasts. For each of these processes there are important markers that can be measured in serum or urine. Resorption markers are products of metabolic degradation of bone matrix in particu-lar of the type I collagen (hydroxyproline, pyridinoline and deoxypyridinoline). In addition, the resorptive activity can also be evaluated through the tartrate resistant acid phosphatase (TRAP) and calcium-creatinine ratio in urine. Bone formation markers are collagen proteins (ALP, OCN), non collagen (ONC, OPN, BSP) or fragments of collagen synthesis (procollagen peptides).