Several factors are involved in determining bone quality including bone density, bone turnover, the extent of trabecular bone connectivity, cortical porosity and geometry. Metabolically active and in a continuous process of remodeling, approximately 20% of bone tissue is renewed annually. Bone turn over markers (BTM) are frequently used in clinical trials and to provide valid information about the effectiveness of osteoporosis treatment, reflecting the state of bone metabolism and its response to treatment, although they are not useful alone to estimate bone loss. In this review the behavior of BTM from different clinical trials or different osteoporotic drugs will be addressed. Arq Bras Endocrinol Metab. 2014;58(5):504-13 Keywords Bone markers; osteoporosis; bone density
ReSumoDiversos fatores estão envolvidos na determinação da qualidade óssea, incluindo a densidade óssea, a remodelação óssea, a extensão da conectividade do osso trabecular, porosidade cortical e geometria. Metabolicamente ativo e, em um processo contínuo de remodelação, cerca de 20% do tecido ósseo é renovado anualmente. Por sua vez, marcadores de turnover ósseo (BTM) são frequentemente utilizados em estudos clínicos e fornecem informações válidas sobre a eficácia do tratamento da osteoporose, o que reflete o metabolismo ósseo e sua resposta ao tratamento, embora eles não sejam úteis somente para estimar a perda óssea. Nesta revisão, o comportamento dos BTM em ensaios clínicos diferentes e com diferentes drogas osteoporóticas será abordado. one is a specific type of tissue composed primarily of type I collagen impregnated with minerals in the form of hydroxyapatite crystals. Several factors are involved in determining bone quality including bone density, bone turnover, the extent of trabecular bone connectivity, cortical porosity and geometry (Figure 1) (1). Metabolically active and in a continuous process of remodeling, approximately 20% of bone tissue is renewed annually (2). This complex process begins at birth and is maintained throughout life. The active cellular participants in this process, often configured as multiple multicellular units, are osteoclasts, osteoblasts and osteocytes.The system is highly regulated by many factors. For example, osteoprotegerin (OPG) (osteoprotegerin), receptor activator of NF-kappaB (RANK) and its cognate ligand, (RANKL), form a metabolic regulatory system focused upon bone resorption (3). Additionally there are other factors that influence bone turnover, such as parathyroid hormone (PTH), 1,25-dihydroxyvitamin D (calcitriol), prostaglandin E2 and interleukins (4). The process of bone turnover leads to the release of factors that give highly relevant information on rates of bone formation and resorption (Figure 2).
