BIOCHEMICAL MARKERS OF BONE-RESORPTION COMPARED WITH ESTIMATES OF BONE-RESORPTION FROM RADIOTRACER KINETIC-STUDIES IN OSTEOPOROSIS

The pyridinium cross-links of collagen pyridinoline (Pyd) and deoxypyr idinoline (Dpd) are released during bone resorption and are neither me tabolized nor absorbed from the diet. The aim of this study was to val idate their use in osteoporosis, We studied 19 women with osteoporosis and estimated the bone resorption rate from a combined calcium balanc e/kinetics technique without (R) and with partial (R(H)) and ''complet e'' (Res) correction for long-term exchange. The strongest correlation was observed between the bone-specific marker (Dpd) and with complete correction for long-term exchange (Res) (r = 0,71, p < 0.001). The in tercept was not different from zero, suggesting that bone was the majo r source for Dpd, The crude ratio of Dpd to Res in the 19 women was 54 .5; but the regression coefficient relating Dpd as the dependent varia ble to Res was 31.8 (95% CI 15.6-48.0), which was higher, but not sign ificantly, than the ratio between Dpd and calcium (16.4) in 10 bone sa mples (cortical and trabecular bone). The weakest correlations between a biochemical marker and a kinetic index were those between hydroxypr oline (a nonspecific marker of bone resorption) and R or R(H). Treatme nt with hormone replacement therapy (HRT) or HRT and parathyroid hormo ne peptide 1-38 in seven women over 1 year resulted in similar percent changes in the biochemical markers and estimates of bone resorption, We conclude that the measurement of Dpd provides a reasonably accurate assessment of bone resorption in osteoporosis, and in the context of several repeat 24-h collections of urine offers measurement precision that is similar to that obtainable with methods depending on the use o f radioisotopic tracers and the assessment of metabolic calcium balanc e.