Bone resorption in healthy and osteoporotic postmenopausal women: comparison markers for serum carboxy-terminal telopeptide of type I collagen and urinary pyridinium cross-links.

We compared two highly specific markers for bone resorption-pyridinium cross-links (pyridinoline (PYR) and deoxypyridinoline (DPR)) in urine and carboxy-terminal telopeptide of type I collagen (ICTP) in serum-in 63 healthy postmenopausal women and 63 women with osteoporosis characterized by more bone resorption than bone formation. The ICTP, PYR and DPR levels were all higher, by 24% (p = 0.001), 16% (p = 0.05) and 25% (p = 0.004), respectively, in the osteoporotic women. For the merged groups, there were significant correlations between serum ICTP concentration and urinary PYR (r = 0.667, p < 0.0001) and DPR (r = 0.452, p < 0.0001) excretion; for the osteoporotic and normal women separately, the r values were 0.73 (p < 0.01) and 0.45 (p < 0.01) for PYR and 0.51 (p < 0.01) and 0.22 (p = 0.08) for DPR versus ICTP respectively. Weak correlations in linear regression between ICTP and various indices of bone formation (osteocalcin, bone-specific alkaline phosphatase and carboxy-terminal propeptide of type I procollagen) disappeared when the correlation between ICTP and pyridinolines was accounted for by calculation of partial correlation coefficients in multiple regression analysis. Serum ICTP concentration appears to discriminate between groups of normal and osteoporotic women as well as urinary pyridinium cross-links, which is thus far the most sensitive method for assessing bone resorption.