Bone Remodeling Increases Substantially in the Years After Menopause and Remains Increased in Older Osteoporosis Patients

Abstract

Bone remodeling rates (Ac.f) were measured in transilial biopsy specimens from 50 healthy premenopausal women before and 1 year after menopause, in 34 healthy women 13 years past menopause, and in 89 women with untreated osteoporosis. Ac.f nearly doubled 1 year after menopause, tripled 13 years after menopause, and remained elevated in women with osteoporosis. Increased bone remodeling rates are associated with increased skeletal fragility independent of bone mass, partially accounting for the age-related increase in fracture risk in women that is independent of bone loss. We examined bone remodeling rates before and after menopause and in women with osteoporosis by measurements of activation frequency (Ac.f, #/year) in transilial bone biopsy specimens. We recruited 75 women, > 46 years old, who had premenopausal estradiol and gonadotropin levels and regular menses. During 9.5 years of observation, 50 women experienced normal menopause and had 2 transilial bone biopsy specimens after tetracycline labeling, one at the beginning of observation and the second 12 months after the last menses, when serum follicle-stimulating hormone (FSH) was > 75 mIU/ml and serum estradiol was < 20 pg/ml. Ac.f was also computed for a group of older healthy postmenopausal women and a group of women with untreated osteoporosis studied earlier by the same biopsy (Bx) and labeling protocol. Median Ac.f rose from 0.13/year to 0.24/year (p < 0.001) across menopause and was greater still in the older normals (p < 0.008) than in the second Bx. Ac.f was not significantly greater in the osteoporosis patients than in the older postmenopausal normals. Bone remodeling rates double at menopause, triple 13 years later, and remain elevated in osteoporosis. This change contributes to increases in age-related skeletal fragility in women.