Comparison of serum and urinary C-terminal telopeptide of type I collagen in aging, menopause and osteoporosis.

BACKGROUND: Urinary C-terminal telopeptide of type I collagen (u-CTx) has been reported to be a sensitive biochemical marker of bone turnover. There have been two assays for urinary CTx, which are alpha-CTx and beta-CTx. A newly developed immunoassay for serum CTx (s-CTx) is now available for assessment of bone resorption. We evaluated the effects of aging, menopause, and osteoporosis on the measurements of serum CTx and compared them to urinary CTx assays. Methods: In 79 premenopausal healthy women, 80 postmenopausal healthy women, 61 osteoporotic patients with vertebral fractures and 34 osteoporotic patients with hip fractures, s-CTx and urinary beta-CTx (u-betaCTx) were measured by ELISAs, and urinary alpha-CTx (u-alphaCTx) was measured by an RIA. RESULTS: In all subjects, s-CTx significantly correlated with both u-alphaCTx (r=0.54) and u-betaCTx (r=0.51). There was no significant difference among s-CTx, u-alphaCTx and u-betaCTx in the T-scores of the postmenopausal group over the premenopausal group. These findings indicate that the value of s-CTx, as well as urinary CTxs, reflected the increase of bone resorption associated with menopause with a high degree of sensitivity. Patients with vertebral fractures had moderately increased concentrations of bone resorption markers compared to age-matched healthy postmenopausal women (T-score; s-CTx: 0.8, u-alphaCTx: 0.9, u-betaCTx: 0.7), whereas bone resorption markers in hip fracture patients were greatly increased compared to healthy postmenopausal women (T-score; s-CTx: 1.1, u-alphaCTx: 1.3 u-betaCTx: 1.3). The T-scores of u-CTxs against the postmenopausal group in vertebral fracture group and in hip fracture group were not significantly different from those of s-CTx. CONCLUSIONS: s-CTx, as well as urinary CTxs, reflects the increase of bone resorption in patients with vertebral fractures and hip fractures.