Anabolic effect of long-term estrogen replacement on bone collagen in elderly postmenopausal women with osteoporosis

Estrogen has been shown to stimulate osteoblasts in cell culture and increase bone formation in animal models. Such an anabolic effect of estrogen replacement therapy (ERT) would be beneficial to postmenopausal women with osteoporosis. Hence, we assessed the total collagen content and collagen crosslink maturity in iliac crest bone biopsy from 18 such women before and after 6 years of higher-dose ERT. These results were compared with the serum estradiol level and bone mineral density (BMD). Total collagen content of both cortical and cancellous bone increased, showing a median (95% CI) percent change of 6.7 (0.3-14.2) and 25.6 (13.5-33.8), respectively. Increase in collagen synthesis was supported by a rise in intermediate crosslinks in both cortical and cancellous bone, and mature crosslinks in cortical bone only. At the same time, BMD showed a substantial rise both at the lumbar spine and proximal femur with a median (95% CI) percent change of 28.6 (19.8-37.3) and 14.5 (8.4-20.7), respectively. Serum estradiol and BMD results correlated with cortical bone collagen levels. Our results suggest that long-term higher-dose ERT has a therapeutic role due to its anabolic effect on bone in postmenopausal women with osteoporosis.