MARKERS OF BONE AND COLLAGEN-METABOLISM - PROBLEMS AND PERSPECTIVES IN PEDIATRICS

This paper gives a short overview of the physiology of biochemical ind ices of bone metabolism, their origins, the problems of interpretation of their activities and the most important clinical applications in c hildhood and adolescence. Markers of bone formation are all osteoblast products that enter the circulation; alkaline phosphatase (bone isofo rm), osteocalcin and type I procollagen peptides. Most of the traditio nal and new markers for bone resorption analyse the matrix (collagen) degradation products in urine from osteoclast activity. These include urinary hydroxyproline, hydroxylysine glycosides, total or free pyridi noline cross-links and cross-linked N- or C-telopeptides. Many studies have shown that both the old and new markers of bone metabolism are u seful tools for basic bone biology research, for defining physiologica l phenomena in clinical studies, or drug trials of growth modifying th erapies (e.g. growth hormone), and for following up individual patient s. For the exact interpretation of bone markers it is necessary to def ine the factors which may influence measurement of the markers, such a s age, sex, puberty, height velocity, circadian rhythms, diet, liver f unction and kidney clearance rates.