title: Effects of current and discontinued estrogen replacement therapy on hip structural geometry: the study of osteoporotic fractures.
abstract: It is assumed that estrogen influences bone strength and risk of fractures by affecting bone mineral density (BMD). However, estrogen may influence the mechanical strength of bones by altering the structural geometry in ways that may not be apparent in the density. Repeated dual energy X-ray absorptiometry (DXA) hip scan data were analyzed for bone density and structural geometry in elderly women participating in the Study of Osteoporotic Fractures (SOF). Scans were studied with a hip structural analysis program for the effects of estrogen replacement therapy (ERT) on BMD and structural geometry. Of the 3,964 women with ERT-use data, 588 used ERT at both the start and end of the approximately 3.5-year study, 1,203 had past use which was discontinued by clinic visit 4, and 2,163 women had never used ERT. All groups lost BMD at the femoral neck, but the reduced BMD among users of ERT was entirely due to subperiosteal expansion and not bone loss, whereas both bone loss and expansion occurred in past or nonusers. BMD increased 0.8%/year at the femoral shaft among ERT users but decreased 0.8%/year among nonusers. Section moduli increased at both the neck and shaft among ERT users but remained unchanged in past and nonusers. Current, but not past, use of estrogen therapy in elderly women seems to increase mechanical strength of the proximal femur by improving its geometric properties. These effects are not evident from changes in femoral neck BMD.
authors.affiliation: Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Beck
authors.forename: K L
authors.initials: KL
authors.lastname: Stone
authors.forename: T L
authors.initials: TL
authors.lastname: Oreskovic
authors.forename: M C
authors.initials: MC
authors.lastname: Hochberg
authors.forename: M C
authors.initials: MC
authors.lastname: Nevitt
authors.forename: H K
authors.initials: HK
authors.lastname: Genant
authors.forename: S R
authors.initials: SR
authors.lastname: Cummings
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000187:drug effects*; D015914:Estrogen Replacement Therapy; D005260:Female; D005269:Femur / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism; D006620:Hip Fractures / Q000378:metabolism* / Q000517:prevention & control*; D006621:Hip Joint / Q000033:anatomy & histology / Q000187:drug effects* / Q000378:metabolism*; D006801:Humans; D015663:Osteoporosis, Postmenopausal / Q000188:drug therapy* / Q000378:metabolism*; D012307:Risk Factors