The hydvoxypyridinium compounds pyridinoline and deoxypyridinoline are specific constituents of mature skeletal collagens. They are released into the circulation and excreted in the urine. Their measurement in urine is a sensitive index of the extent of ongoing bone vesovption. Currently, quantification of collagen crosslinks in urine is achieved by chromatogvaphic techniques, but more convenient immunoassays will make these measurements more widely available in the near future. Clinical applications of hydt-oxypyridinium markers include numer-ous metabolic bone disorders such as osteoporosis, primary hyperpavathyvoidism, Paget’s disease of bone, and metastatic bone disease. Urinary pyridinium crosslinks of collagen also show great promise as markers of therapeutic efficacy in bone disorders associated with accelerated bone t-esouption.(Trends Endocrinol Metab 1992; 3: 263-270)

Diagnosis and therapy of a variety of metabolic bone diseases would be helped enormously by the availability of specific, sensitive, and noninvasive markers of bone resorption. Measurements of the calcium-regulating hormones, paratbyraid hormone, and 1, 25dibydroxyvitamin D are helpful but they do not necessarily reflect bone resorption. Analysis of bone biopsy specimens by quantitative histomorphometry gives a great deal of useful information in this regard, but the technique is invasive and the analysis is time-consuming and expensive.