5 - Biochemical Markers of Bone Turnover

Abstract

Biochemical indices that are available to the general practitioner, as well as to the specialty physician who manages osteoporotic patients, reflect the ongoing bone remodeling process. These biochemical markers are based on the measurement of blood or urine levels of either enzymatic activities produced by bone cells, or bone matrix components which pass into the circulation during bone apposition or resorption. Biochemical markers of bone turnover with established or promising clinical relevance are presented in the chapter. In most metabolic bone diseases, and in particular osteoporosis, bone formation and resorption are coupled, that is both processes are increased, decreased, or normal. This explains why it is extremely difficult to establish, on a clinical basis, whether one biochemical marker is indeed a pure indicator of one particular phase of bone remodeling. In addition, matrix products can be released into the circulation during their synthesis (bone formation) and breakdown (bone resorption). Thus, in most cases each biochemical marker has to be considered as being prevalently associated with either bone formation or resorption.