The Relationships Between the Degree of β-Isomerization of Type I Collagen Degradation Products in the Urine and Aging, Menopause and Osteoporosis with Fractures
We have evaluated the effect of aging, menopause and osteoporosis on the measurements of both nonisomerized type I collagen C-telopeptide breakdown products (α-CTx) by radioimmunoassay (RIA) and β-isomerized type I collagen C-telopeptide breakdown products (β-CTx) by enzyme-linked immunosorbent assay (ELISA). In 86 premenopausal healthy women (PRE), 144 postmenopausal healthy women (POST), 74 patients with vertebral fractures (VX) and 61 patients with hip fractures (HX), urinary CTx excretion was measured by both ELISA and RIA assays. Samples were collected more than 6 months after fracture in the VX group and within 48 h after fracture in the HX group. In all subjects a highly significant correlation was found between α-CTx and β-CTx (r= 0.85). The values of β-CTx in the POST group greatly increased compared with those in the PRE group (% mean increase: 82%), while the values of α-CTx in the POST group moderately increased compared with those in the PRE group (% mean increase: 47%). The values of both α-CTx and β-CTx in the HX group were significantly higher than those in the other groups, but particularly the increase in mean α-CTx (211% for HX versus POST) was very high compared with the increase in mean β-CTx (68% for HX versus POST). Moreover, the α-CTx/β-CTx ratio in the HX group was significantly higher than in the other groups. These results suggest that both assays well reflect the increase in bone resorption associated with high bone turnover, especially, in osteoporotic patients with hip fracture. However, there was a difference between the urinary excretion of α-CTx and β-CTx in patients with hip fracture, so the α-CTx/β-CTx radio might be a good indicator reflecting the characteristics of bone metabolism for osteoporosis with hip fracture.
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