title: Low Normal TSH levels are Associated with Impaired BMD and Hip Geometry in the Elderly.
abstract: Subclinical hyperthyroidism is known to be associated with the risk of fractures in elderly people. However, there are few studies assessing whether low normal thyroid-stimulating hormone (TSH) levels affect bone density and geometry. Here, we aimed to assess the influence of the TSH level on bone mineral density (BMD) and geometry in elderly euthyroid subjects. This was a cross-sectional cohort study. A total of 343 men and 674 women with euthyroidism were included and analyzed separately. The subjects were divided into tertiles based on the serum TSH level. The BMD and geometry were measured using dual-energy X-ray absorptiometry and a hip structural analysis program. Multiple regression analysis was used to compute the odds ratios of osteoporosis in the lower TSH tertile group and the association between geometry parameters and the TSH level. We found that the femoral neck and total hip BMDs were lower in the lower TSH tertile group. In women, the cross-sectional area and cortical thickness of the femur were negatively associated with the TSH level in all three regions (the narrow neck, intertrochanter, and femoral shaft); however, in men, these geometry parameters were significantly associated with the TSH level only in the intertrochanter region. The buckling ratio, a bone geometry parameter representing cortical instability, was significantly higher in the lower TSH tertile group in all three regions in women, but not in men. Our results indicated that lower TSH levels in the euthyroid range are related to lower BMD and weaker femoral structure in elderly women.
authors.affiliation: 1Department of Internal Medicine, Severance Hospital, Endocrine Research Institute, Yonsei University College of Medicine, Seoul, Korea; 2Department of Internal Medicine, National Health Insurance Service Ilsan Hospital, Goyang, Korea.
authors.forename: Su Jin
authors.initials: SJ
authors.lastname: Lee
authors.affiliation: 3Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
authors.forename: Kyoung Min
authors.initials: KM
authors.lastname: Kim
authors.affiliation: 4Division of Endocrinology and Metabolism, Department of Internal Medicine, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, Korea.
authors.forename: Eun Young
authors.initials: EY
authors.lastname: Lee
authors.affiliation: 5Department of Research Affairs, Biostatistics Collaboration Unit, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Mi Kyung
authors.initials: MK
authors.lastname: Song
authors.affiliation: 6Office of Biostatistics, Ajou University School of Medicine, Suwon, Korea.
authors.forename: Dae Ryong
authors.initials: DR
authors.lastname: Kang
authors.affiliation: 7Department of Preventive Medicine, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Hyeon Chang
authors.initials: HC
authors.lastname: Kim
authors.affiliation: 8Department of Sociology, Yonsei University, Seoul, Korea.
authors.forename: Yoosik
authors.initials: Y
authors.lastname: Youm
authors.affiliation: 5Department of Research Affairs, Biostatistics Collaboration Unit, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Young Mi
authors.initials: YM
authors.lastname: Yun
authors.affiliation: 9Division of Cardiovascular and Rare Diseases, Korea National Institute of Health, Osong, Korea.
authors.forename: Hyun-Young
authors.initials: HY
authors.lastname: Park
authors.affiliation: 10Division of Geriatrics, Department of Internal Medicine, Severance Hospital, Seoul, Korea.
authors.forename: Chang Oh
authors.initials: CO
authors.lastname: Kim
authors.affiliation: 1Department of Internal Medicine, Severance Hospital, Endocrine Research Institute, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Yumie
authors.initials: Y
authors.lastname: Rhee
keywords: TSH; bone density; bone geometry; elderly people; euthyroidism