The relationships between the degree of beta-isomerization of type I collagen degradation products in the urine and aging, menopause and osteoporosiswith fractures

We have evaluated the effect of aging, menopause and osteoporosis on the me asurements of both nonisomerized type I collagen C-telopeptide breakdown pr oducts (alpha-CTx) by radioimmunoassay (RIA) and beta-isomerized type I col lagen C-telopeptide breakdown products (beta-CTx) by enzyme-linked immunoso rbent assay (ELISA). In 86 premenopausal healthy women (PRE), 144 postmenop ausal healthy women (POST), 74 patients with vertebral fractures (VX) and 6 1 patients with hip fractures (HX), urinary CTx excretion was measured by b oth ELISA and RIA assays. Samples were collected more than 6 months after f racture in the VX group and within 48 h after fracture in the HX group. In all subjects a highly significant correlation was found between alpha-CTx a nd beta-CTx (r = 0.85). The values of beta-CTx in the POST group greatly in creased compared with those in the PRE group (% mean increase: 82%), while the values of alpha-CTx in the POST group moderately increased compared wit h those in the PRE group (% mean increase: 47%). The values of both alpha-C Tx and beta-CTx in the HX group were significantly higher than those in the other groups, but particularly the increase in mean alpha-CTx (211% for HX versus POST) was very high compared with the increase in mean beta-CTx (68 % for HX versus POST). Moreover, the alpha-CTx/beta-CTx ratio in the HX gro up was significantly higher than in the other groups. These results suggest that both assays well reflect the increase in bone resorption associated w ith high bone turnover, especially, in osteoporotic patients with hip fract ure. However, there was a difference between the urinary excretion of a-CTx and beta-CTx in patients with hip fracture, so the alpha-CTx/beta-CTx radi o might be a good indicator reflecting the characteristics of bone metaboli sm for osteoporosis with hip fracture.