Bone mineral density, bone remodeling, insulin-like growth factors, hormone replacement therapy, and exercise training in postmenopausal women

Persistent Link:
http://hdl.handle.net/10150/282746
Title:
Bone mineral density, bone remodeling, insulin-like growth factors, hormone replacement therapy, and exercise training in postmenopausal women
Author:
Milliken, Laura Ann, 1970-
Issue Date:
1998
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Osteoporosis is a condition of reduced bone mineral density (BMD) resulting in an increased susceptibility to bone fractures. The purpose of this study was to determine the effects of 12 months of weight bearing and resistance exercise on BMD, bone formation, measured by serum osteocalcin (OC) and bone resorption, measured by urinary excretion of deoxypyridinoline crosslinks (Dpd), in 2 groups of postmenopausal women who were either taking or not taking hormone replacement therapy (HRT). Secondary aims were to characterize the changes in insulin-like growth factors-l and -2 (IGF-l and -2) and IGF binding protein 3 (IGFBP3) in response to exercise training, and to determine the contribution of these growth factors in predicting changes in bone mineral density in the 2 populations of postmenopausal women. Women who were three to ten years postmenopausal and aged 40-65 years were included in the study. Women in HRT and no HRT groups were randomized into the exercise intervention resulting in four groups: (1) women not taking HRT, not exercising; (2) women taking HRT, not exercising; (3) women exercising, not taking HRT; and (4) women exercising, taking HRT. The number of subjects per group after one year was 27, 21, 25, and 16, respectively. Exercise training and HRT increase BMD similarly at most BMD sites whereas the combination of exercise and HRT produced increases in BMD greater than either treatment alone. Bone remodeling was surpressed in the groups taking HRT regardless of exercise status. The bone remodeling response to exercise training in women not taking HRT was not significantly different from those not exercising but the direction of change suggests an elevation in bone remodeling in response to exercise training. Exercise training does not stimulate a change in IGF-1, IGF-2, IGF-1:IGF-2, and IGFBP3. Markers of bone remodeling and IGF-1 are significant predictors of BMD changes but the overall amount of variation in BMD changes accounted for is low. Exercise and HRT status were significant predictors of changes in BMD even after accounting for variation due to bone remodeling indicating that bone changes are regulated by factors not addressed in this study.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Health Sciences, Rehabilitation and Therapy.; Biology, Animal Physiology.; Health Sciences, Recreation.; Health Sciences, Human Development.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Physiological Sciences
Degree Grantor:
University of Arizona
Advisor:
Lohman, Timothy G.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleBone mineral density, bone remodeling, insulin-like growth factors, hormone replacement therapy, and exercise training in postmenopausal womenen_US
dc.creatorMilliken, Laura Ann, 1970-en_US
dc.contributor.authorMilliken, Laura Ann, 1970-en_US
dc.date.issued1998en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractOsteoporosis is a condition of reduced bone mineral density (BMD) resulting in an increased susceptibility to bone fractures. The purpose of this study was to determine the effects of 12 months of weight bearing and resistance exercise on BMD, bone formation, measured by serum osteocalcin (OC) and bone resorption, measured by urinary excretion of deoxypyridinoline crosslinks (Dpd), in 2 groups of postmenopausal women who were either taking or not taking hormone replacement therapy (HRT). Secondary aims were to characterize the changes in insulin-like growth factors-l and -2 (IGF-l and -2) and IGF binding protein 3 (IGFBP3) in response to exercise training, and to determine the contribution of these growth factors in predicting changes in bone mineral density in the 2 populations of postmenopausal women. Women who were three to ten years postmenopausal and aged 40-65 years were included in the study. Women in HRT and no HRT groups were randomized into the exercise intervention resulting in four groups: (1) women not taking HRT, not exercising; (2) women taking HRT, not exercising; (3) women exercising, not taking HRT; and (4) women exercising, taking HRT. The number of subjects per group after one year was 27, 21, 25, and 16, respectively. Exercise training and HRT increase BMD similarly at most BMD sites whereas the combination of exercise and HRT produced increases in BMD greater than either treatment alone. Bone remodeling was surpressed in the groups taking HRT regardless of exercise status. The bone remodeling response to exercise training in women not taking HRT was not significantly different from those not exercising but the direction of change suggests an elevation in bone remodeling in response to exercise training. Exercise training does not stimulate a change in IGF-1, IGF-2, IGF-1:IGF-2, and IGFBP3. Markers of bone remodeling and IGF-1 are significant predictors of BMD changes but the overall amount of variation in BMD changes accounted for is low. Exercise and HRT status were significant predictors of changes in BMD even after accounting for variation due to bone remodeling indicating that bone changes are regulated by factors not addressed in this study.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectHealth Sciences, Rehabilitation and Therapy.en_US
dc.subjectBiology, Animal Physiology.en_US
dc.subjectHealth Sciences, Recreation.en_US
dc.subjectHealth Sciences, Human Development.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplinePhysiological Sciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorLohman, Timothy G.en_US
dc.identifier.proquest9906515en_US
dc.identifier.bibrecord.b3886521xen_US
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