title: Influence of long-term postmenopausal hormone-replacement therapy on estimated structural bone strength: a study in discordant monozygotic twins.
abstract: Although postmenopausal hormone-replacement therapy (HRT) is known to prevent fractures, knowledge on the influence of long-term HRT on bone strength and its determinants other than areal bone mineral density is scarce. This study used a genetically controlled design with 24 monozygotic female twin pairs aged 54 to 72 years in which one cotwin was using HRT (mean duration 8 years) and the other had never used HRT. Estimated bone strength, cross-sectional area, volumetric bone mineral density, bone mineral mass, and cross-sectional density and mass distributions were assessed in the tibial shaft, distal tibia, and distal radius with peripheral computed tomography (pQCT). In the tibial shaft, HRT users had 9% [95% confidence interval (CI) 3%-15%] higher estimated bending strength than their nonusing cotwins. Larger cortical area and higher cortical bone mineral density accounted for this difference. The cortex was larger in the HRT users in the endocortical region. In the distal tibia, estimated compressive strength was 24% (95% CI 9%-40%) higher and in the distal radius 26% (95% CI 11%-41%) higher in the HRT users than in their nonusing cotwins owing to higher volumetric bone mineral density. No difference between users and nonusers was observed in total bone cross-sectional area in any measured bone site. The added mineral mass in the HRT users was distributed evenly within and between bone sites. In postmenopausal women, long-term HRT preserves estimated bone strength systemically by preventing bone mineral loss similarly in body weight-loaded and non-weight-loaded bone.
authors.affiliation: Department of Health Sciences, University of Jyväskylä, Jyväskylä, Finland. tuija.m.mikkola@jyu.fi
authors.forename: Tuija M
authors.initials: TM
authors.lastname: Mikkola
authors.forename: Ari
authors.initials: A
authors.lastname: Heinonen
authors.forename: Vuokko
authors.initials: V
authors.lastname: Kovanen
authors.forename: Sulin
authors.initials: S
authors.lastname: Cheng
authors.forename: Urho M
authors.initials: UM
authors.lastname: Kujala
authors.forename: Harri
authors.initials: H
authors.lastname: Suominen
authors.forename: Markku
authors.initials: M
authors.lastname: Alén
authors.forename: Jukka
authors.initials: J
authors.lastname: Puolakka
authors.forename: Carina
authors.initials: C
authors.lastname: Ankarberg-Lindgren
authors.forename: Paula H A
authors.initials: PH
authors.lastname: Ronkainen
authors.forename: Markku
authors.initials: M
authors.lastname: Koskenvuo
authors.forename: Jaakko
authors.initials: J
authors.lastname: Kaprio
authors.forename: Taina
authors.initials: T
authors.lastname: Rantanen
authors.forename: Sarianna
authors.initials: S
authors.lastname: Sipilä
mesh_terms: D000368:Aged; D000886:Anthropometry; D001823:Body Composition; D015519:Bone Density / Q000502:physiology; D001842:Bone and Bones / Q000033:anatomy & histology* / Q000502:physiology*; D018483:Diaphyses / Q000473:pathology / Q000502:physiology; D015914:Estrogen Replacement Therapy; D005260:Female; D006728:Hormones / Q000097:blood; D006801:Humans; D008875:Middle Aged; D009929:Organ Size; D057566:Self Report; D013997:Time Factors; D014430:Twins, Monozygotic / Q000097:blood
chemical_list: D006728:Hormones