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      Increased vertebral morphometric fracture in patients with postsurgical hypoparathyroidism despite normal bone mineral density

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          Abstract

          Background

          The mechanism behind parathyroid hormone (PTH) activation of bone remodeling is intimately dependent on the time of exposure of bone cells to hormone levels. Sustained high PTH levels trigger catabolism, while transitory elevations induce anabolism. The effects of hypoparathyroidism (PhPT) on bone are unknown. The objective was to study the impact of PhPT on bone mineral density (BMD), on the frequency of subclinical vertebral fracture and on mandible morphometry.

          Methods

          The study comprised thirty-three postmenopausal women, 17 controls (CG) and 16 with PhPT (PhPTG) matched for age, weight and height. Bone mineral density (BMD) of lumbar spine, total hip and 1/3 radius, radiographic evaluation of vertebral morphometry, panoramic radiography of the mandible, and biochemical evaluation of mineral metabolism and bone remodeling were evaluated in both groups.

          Results

          There were no significant differences in lumbar spine or total hip BMD between groups. There was marked heterogeneity of lumbar spine BMD in PhPTG (high = 4, normal = 9, osteopenia = 1, and osteoporosis = 2 patients). BMD was decreased in the 1/3 radius in PhPTG P < 0.005). The PhPTG group exhibited an increased frequency of morphometric vertebral fractures and decreased mandible cortical thickness.

          Conclusion

          The study suggests that vertebral fragility occurs in PhPT despite normal or even high BMD. The current results encourage further studies to evaluate the use of panoramic radiography in the identification of osteometabolic disorders, such as PhPT and the development of a more physiological treatment for PhPT.

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          Most cited references31

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          Atypical subtrochanteric and diaphyseal femoral fractures: report of a task force of the American Society for Bone and Mineral Research.

          Reports linking long-term use of bisphosphonates (BPs) with atypical fractures of the femur led the leadership of the American Society for Bone and Mineral Research (ASBMR) to appoint a task force to address key questions related to this problem. A multidisciplinary expert group reviewed pertinent published reports concerning atypical femur fractures, as well as preclinical studies that could provide insight into their pathogenesis. A case definition was developed so that subsequent studies report on the same condition. The task force defined major and minor features of complete and incomplete atypical femoral fractures and recommends that all major features, including their location in the subtrochanteric region and femoral shaft, transverse or short oblique orientation, minimal or no associated trauma, a medial spike when the fracture is complete, and absence of comminution, be present to designate a femoral fracture as atypical. Minor features include their association with cortical thickening, a periosteal reaction of the lateral cortex, prodromal pain, bilaterality, delayed healing, comorbid conditions, and concomitant drug exposures, including BPs, other antiresorptive agents, glucocorticoids, and proton pump inhibitors. Preclinical data evaluating the effects of BPs on collagen cross-linking and maturation, accumulation of microdamage and advanced glycation end products, mineralization, remodeling, vascularity, and angiogenesis lend biologic plausibility to a potential association with long-term BP use. Based on published and unpublished data and the widespread use of BPs, the incidence of atypical femoral fractures associated with BP therapy for osteoporosis appears to be very low, particularly compared with the number of vertebral, hip, and other fractures that are prevented by BPs. Moreover, a causal association between BPs and atypical fractures has not been established. However, recent observations suggest that the risk rises with increasing duration of exposure, and there is concern that lack of awareness and underreporting may mask the true incidence of the problem. Given the relative rarity of atypical femoral fractures, the task force recommends that specific diagnostic and procedural codes be created and that an international registry be established to facilitate studies of the clinical and genetic risk factors and optimal surgical and medical management of these fractures. Physicians and patients should be made aware of the possibility of atypical femoral fractures and of the potential for bilaterality through a change in labeling of BPs. Research directions should include development of animal models, increased surveillance, and additional epidemiologic and clinical data to establish the true incidence of and risk factors for this condition and to inform orthopedic and medical management. © 2010 American Society for Bone and Mineral Research.
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            Molecular and cellular mechanisms of the anabolic effect of intermittent PTH.

            Intermittent administration of parathyroid hormone (PTH) stimulates bone formation by increasing osteoblast number, but the molecular and cellular mechanisms underlying this effect are not completely understood. In vitro and in vivo studies have shown that PTH directly activates survival signaling in osteoblasts; and that delay of osteoblast apoptosis is a major contributor to the increased osteoblast number, at least in mice. This effect requires Runx2-dependent expression of anti-apoptotic genes like Bcl-2. PTH also causes exit of replicating progenitors from the cell cycle by decreasing expression of cyclin D and increasing expression of several cyclin-dependent kinase inhibitors. Exit from the cell cycle may set the stage for pro-differentiating and pro-survival effects of locally produced growth factors and cytokines, the level and/or activity of which are known to be influenced by PTH. Observations from genetically modified mice suggest that the anabolic effect of intermittent PTH requires insulin-like growth factor-I (IGF-I), fibroblast growth factor-2 (FGF-2), and perhaps Wnts. Attenuation of the negative effects of PPAR gamma may also lead to increased osteoblast number. Daily injections of PTH may add to the pro-differentiating and pro-survival effects of locally produced PTH related protein (PTHrP). As a result, osteoblast number increases beyond that needed to replace the bone removed by osteoclasts during bone remodeling. The pleiotropic effects of intermittent PTH, each of which alone may increase osteoblast number, may explain why this therapy reverses bone loss in most osteoporotic individuals regardless of the underlying pathophysiology.
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              Predicting risk of osteoporotic fracture in men and women in England and Wales: prospective derivation and validation of QFractureScores

              Objective To develop and validate two new fracture risk algorithms (QFractureScores) for estimating the individual risk of osteoporotic fracture or hip fracture over 10 years. Design Prospective open cohort study with routinely collected data from 357 general practices to develop the scores and from 178 practices to validate the scores. Setting General practices in England and Wales. Participants 1 183 663 women and 1 174 232 men aged 30-85 in the derivation cohort, who contributed 7 898 208 and 8 049 306 person years of observation, respectively. There were 24 350 incident diagnoses of osteoporotic fracture in women and 7934 in men, and 9302 incident diagnoses of hip fracture in women and 5424 in men. Main outcome measures First (incident) diagnosis of osteoporotic fracture (vertebral, distal radius, or hip) and incident hip fracture recorded in general practice records. Results Use of hormone replacement therapy (HRT), age, body mass index (BMI), smoking status, recorded alcohol use, parental history of osteoporosis, rheumatoid arthritis, cardiovascular disease, type 2 diabetes, asthma, tricyclic antidepressants, corticosteroids, history of falls, menopausal symptoms, chronic liver disease, gastrointestinal malabsorption, and other endocrine disorders were significantly and independently associated with risk of osteoporotic fracture in women. Some variables were significantly associated with risk of osteoporotic fracture but not with risk of hip fracture. The predictors for men for osteoporotic and hip fracture were age, BMI, smoking status, recorded alcohol use, rheumatoid arthritis, cardiovascular disease, type 2 diabetes, asthma, tricyclic antidepressants, corticosteroids, history of falls, and liver disease. The hip fracture algorithm had the best performance among men and women. It explained 63.94% of the variation in women and 63.19% of the variation in men. The D statistic values for discrimination were highest for hip fracture in women (2.73) and men (2.68) and were over twice the magnitude of the corresponding values for osteoporotic fracture. The ROC statistics for hip fracture were also high: 0.89 in women and 0.86 for men versus 0.79 and 0.69, respectively, for the osteoporotic fracture outcome. The algorithms were well calibrated with predicted risks closely matching observed risks. The QFractureScore for hip fracture also had good performance for discrimination and calibration compared with the FRAX (fracture risk assessment) algorithm. Conclusions These new algorithms can predict risk of fracture in primary care populations in the UK without laboratory measurements and are therefore suitable for use in both clinical settings and for self assessment (www.qfracture.org). QFractureScores could be used to identify patients at high risk of fracture who might benefit from interventions to reduce their risk.
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                Author and article information

                Journal
                BMC Endocr Disord
                BMC Endocr Disord
                BMC Endocrine Disorders
                BioMed Central
                1472-6823
                2013
                3 January 2013
                : 13
                : 1
                Affiliations
                [1 ]Department of Internal Medicine, School of Medicine of Ribeirão Preto, University of São Paulo, São Paulo, Brazil
                [2 ]Department of Radiology, School of Dentistry of Ribeirão Preto, University of São Paulo, São Paulo, Brazil
                [3 ]Department of Internal Medicine, School of Medicine of Ribeirão Preto, University of São Paulo, Av. Bandeirantes 3900, Ribeirão Preto, SP, 14049-900, Brazil
                Article
                1472-6823-13-1
                10.1186/1472-6823-13-1
                3546901
                23286605
                be5629ca-795b-49b9-a6b9-9f9cf1970818
                Copyright ©2013 Mendonça et al.; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 30 August 2012
                : 27 December 2012
                Categories
                Research Article

                Endocrinology & Diabetes
                postsurgical hypoparathyroidism,osteoporosis,morphometric fracture,parathyroid hormone,panoramic radiography

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