Aromatase inhibitors and bone

The decrease in estrogen levels with the use of aromatase inhibitors results in an increase in the rate of bone remodelling. This result in an acceleration of bone loss, and probably to an increase in the risk of fractures. The risk of fracture is particularly high in the older woman and in the woman with a low bone mineral density. We have a number of proven treatments for the treatment of postmenopausal osteoporosis and it is likely that some of these, particularly bisphosphonates, could be effective at preventing bone loss with aromatase inhibitors.     

Estrogens and women's health: interrelation of coronary heart disease, breast cancer and osteoporosis

The determinants of blood levels of estrogen, estrogen metabolites, and relation to receptors and post-transitional effects are the likely primary cause of breast cancer. Very high risk women for breast cancer can now be identified by measuring bone mineral density and hormone levels. These high risk women have rates of breast cancer similar to risk of myocardial infarction. They are candidates for SERM therapies to reduce risk of breast cancer. The completion of the Women's Health Initiative and other such trials will likely provide a definite association of risk and benefit of both estrogen alone and estrogen-progesterone therapy, coronary heart disease, osteoporotic fracture, and breast cancer. The potential intervention of hormone replacement therapy, obesity, or weight gain and increased atherogenic lipoproteinemia may be of concern and confound the results of clinical trials. Estrogens, clearly, are important in the risk of bone loss and osteoporotic fracture. Obesity is the primary determinant of postmenopausal estrogen levels and reduced risk of fracture. Weight reduction may increase rates of bone loss and fracture. Clinical trials that evaluate weight loss should monitor effects on bone. The beneficial addition of increased physical activity, higher dose of calcium or vitamin D, or use of bone reabsorption drugs in coordination with weight loss should be evaluated. Any therapy that raises blood estrogen or metabolite activity and decreases bone loss may increase risk of breast cancer. Future clinical trials must evaluate multiple endpoints such as CHD, osteoporosis, and breast cancer within the study. The use of surrogate markers such as bone mineral density, coronary calcium, carotid intimal medial thickness and plaque, endothelial function, breast density, hormone levels and metabolites could enhance the evaluation of risk factors, genetic-environmental intervention, and new therapies.     

Contribution of bone mineral density and bone turnover markers to the estimation of risk of osteoporotic fracture in postmenopausal women

In osteoporosis, the main cause for concern is the increase in the risk of fractures. The level of bone mineral density (BMD) measured by various techniques has been shown to be a strong predictor of fracture risk in postmenopausal women. However, half of patients with incident fractures have BMD value above the diagnostic threshold of osteoporosis defined as a T-score of -2.5 SD or more below the average value of young healthy women. Clearly there is a need for improvement in the identification of patients at risk for fracture. Several prospective studies have shown that an increased bone resorption evaluated by specific biochemical markers was associated with increased risk of the hip, spine and non-vertebral fractures independently of BMD. The use of bone markers in individual patients may be appropriate in some situations, especially in women who are not detected at risk by BMD measurements. For example, in the OFELY study including 668 postmenopausal women followed prospectively over 9 years, we found that among the 115 incident fractures, 54 (47%) actually occurred in non-osteoporotic women. Among these women, the combination of bone markers and history of previous fracture was highly predictive of fracture risk. Thus, bone markers may be used in the assessment of fracture risk in selected cases in which BMD and clinical risk factors are not enough to take a treatment decision. Advances in our knowledge of bone matrix biochemistry, most notably of post-translational modifications in type I collagen, may allow identification of biochemical markers that reflect changes in the material property of bone, which is an important determinant of bone strength. Preliminary in vitro studies indicate that the extent of post-translational modifications of collagen--which can be reflected in vivo by the measurement of the urinary ratio between native and isomerised type I collagen--play a role in determining the mechanical competence of cortical bone, independently of BMD. Further studies in osteoporosis should explore the changes in these biochemical parameters of bone matrix as they may represent a key component of bone quality.     

Vitamin D and osteoporosis-related fracture

The age-related decline in mass and quality of bone (osteoporosis) and muscle (sarcopenia) leads to an exponential increased risk for osteoporosis-related fracture with advancing age in older adults. As vitamin D inadequacy plausibly causally contributes to these declines, optimization of vitamin D status might reduce the deterioration of bone and muscle function with age. Putative mechanisms by which vitamin D inadequacy may increase fracture risk include both direct and indirect effects on bone and muscle. However, controversy currently clouds the role(s) of vitamin D in osteoporosis-related fracture, the amount of vitamin D required and the optimal 25-hydroxyvitamin D level. This review provides an overview of current knowledge and suggests a clinical approach to vitamin D status in older adults with, or at risk for, osteoporosis-related fracture. These recommendations are likely to evolve as additional data becomes available.     

Nouveaux marqueurs biologiques du remodelage osseux dans l’ostéoporose

Current biological markers of bone turnover have proven useful in improving fracture risk assessment and monitoring treatment efficacy in postmenopausal osteoporosis. Progress in the characterization of important biological pathways regulating bone cell activity and the organic components of bone matrix has led to the development of new biochemical markers. These include the non collagenous protein, bone sialoproteine, the resorption-mediated osteocalcin fragments, the osteoclastic enzymes (isoenzyme 5b of tartrate-resistant acid phosphatase and cathepsin K), the regulators of osteoclastic (osteoprotegerine, RANK-L) and osteoblastic (Wnt signaling molecules) activity and the post-translational modifications of matrix molecules. One of the most interesting developments has been the demonstration that the non-enzymatic modifications of bone collagen, including glycation-mediated crosslinks and the isomerization of aspartic acid, contribute to fracture resistance independent of bone mineral density (BMD). Systemic levels of the glycated crosslink pentosidine and the urinary ratio between native (αCTX) and isomerized (βCTX) type I collagen C-telopeptide are associated with fracture risk in postmenopausal women independent of BMD and may respond differently to the different anti-resorptive therapies and parathyroid hormone. The identification of bone-specific post-translational modifications of bone matrix proteins that influence bone fracture resistance should lead to the development of new biological markers that will be useful in assessing the contribution of changes in bone matrix properties to fracture risk in untreated and treated patients with osteoporosis.     

Management of osteoporosis

Osteoporosis or osteopenia occurs in about 44 million Americans, resulting in 1.5 million fragility fractures per year. The consequences of these fractures include pain, disability, depression, loss of independence, and increased mortality. The burden to the healthcare system, in terms of cost and resources, is tremendous, with an estimated direct annual USA healthcare expenditure of about $17 billion. With longer life expectancy and the aging of the baby-boomer generation, the number of men and women with osteoporosis or low bone density is expected to rise to over 61 million by 2020. Osteoporosis is a silent disease that causes no symptoms until a fracture occurs. Any fragility fracture greatly increases the risk of future fractures. Most patients with osteoporosis are not being diagnosed or treated. Even those with previous fractures, who are at extremely high risk of future fractures, are often not being treated. It is preferable to diagnose osteoporosis by bone density testing of high risk individuals before the first fracture occurs. If osteoporosis or low bone density is identified, evaluation for contributing factors should be considered. Patients on long-term glucocorticoid therapy are at especially high risk for developing osteoporosis, and may sustain fractures at a lower bone density than those not taking glucocorticoids. All patients should be counseled on the importance of regular weight-bearing exercise and adequate daily intake of calcium and vitamin D. Exposure to medications that cause drowsiness or hypotension should be minimized. Non-pharmacologic therapy to reduce the non-skeletal risk factors for fracture should be considered. These include fall prevention through balance training and muscle strengthening, removal of fall hazards at home, and wearing hip protectors if the risk of falling remains high. Pharmacologic therapy can stabilize or increase bone density in most patients, and reduce fracture risk by about 50%. By selecting high risk patients for bone density testing it is possible to diagnose this disease before the first fracture occurs, and initiate appropriate treatment to reduce the risk of future fractures.     

Effects of reproduction on sexual dimorphisms in rat bone mechanics

Osteoporosis most commonly affects postmenopausal women. Although men are also affected, women over 65 are 6 times more likely to develop osteoporosis than men of the same age. This is largely due to accelerated bone remodeling after menopause; however, the peak bone mass attained during young adulthood also plays an important role in osteoporosis risk. Multiple studies have demonstrated sexual dimorphisms in peak bone mass, and additionally, the female skeleton is significantly altered during pregnancy/lactation. Although clinical studies suggest that a reproductive history does not increase the risk of developing postmenopausal osteoporosis, reproduction has been shown to induce long-lasting alterations in maternal bone structure and mechanics, and the effects of pregnancy and lactation on maternal peak bone quality are not well understood. This study compared the structural and mechanical properties of male, virgin female, and post-reproductive female rat bone at multiple skeletal sites and at three different ages. We found that virgin females had a larger quantity of trabecular bone with greater trabecular number and more plate-like morphology, and, relative to their body weight, had a greater cortical bone size and greater bone strength than males. Post-reproductive females had altered trabecular microarchitecture relative to virgins, which was highly similar to that of male rats, and showed similar cortical bone size and bone mechanics to virgin females. This suggests that, to compensate for future reproductive bone losses, females may start off with more trabecular bone than is mechanically necessary, which may explain the paradox that reproduction induces long-lasting changes in maternal bone without increasing postmenopausal fracture risk.     

经皮椎体成形术治疗骨质疏松性椎体压缩骨折的临床疗效及术后邻近椎体骨折的危险因素分析

摘要 目的：观察骨质疏松性椎体压缩骨折（OVCFs）患者以经皮椎体成形术（PVP）治疗后的临床疗效,并分析术后邻近椎体骨折的危险因素。方法：选取我院2018年6月~2020年9月期间收治的OVCFs患者180例,给予PVP治疗,观察其治疗效果、骨水泥渗漏情况、术后邻近椎体骨折发生情况,采用单因素及多因素Logistic回归分析术后邻近椎体骨折的危险因素。结果：OVCFs患者术前~术后6个月功能障碍指数（ODI）、疼痛视觉模拟评分（VAS）、活动能力评分（LAS）均呈降低趋势（P＜0.05）。随访期间,180例患者中,15例（8.33%）出现了骨水泥渗漏,但均不需要进一步处理。32例（17.78%）出现了术后邻近椎体骨折,148例未出现术后邻近椎体骨折,并以此进行分组。再骨折组、未再骨折组在年龄、骨折病史、骨密度、Cobb角、椎体高度恢复、骨水泥渗漏情况、使用抗骨质疏松药物方面对比有明显差异（P<0.05）。年龄>70岁、骨水泥渗漏、骨密度<-2.5SD、未使用抗骨质疏松药物、Cobb角<15°、椎体高度恢复率>87%均是PVP术后邻近椎体骨折的危险因素（P<0.05）。结论：PVP治疗OVCFs疗效较好,可缓解患者疼痛、减轻功能障碍、改善活动能力,术后邻近椎体骨折的发生受年龄、骨密度、Cobb角等多种因素影响,临床可针对这些因素给予对应的干预措施。     

The role of statins as potential targets for bone formation

Inhibitors of the 3-hydroxy-3-methylglutaryl coenzyme A reductase enzyme have recently been shown to stimulate bone formation in rodents both in vitro and in vivo. In bone cells, these inhibitors increase the gene expression of bone morphogenetic protein-2, which is an autocrine-paracrine factor for osteoblast differentiation.The findings that statins increase bone formation and bone mass in rodents suggest a potential new action for these compounds, which may be beneficial in patients with established osteoporosis where marked bone loss has occurred. Recent clinical data suggest that they may reduce the risk of fracture in patients taking these drugs.     

Biomarkers for osteoporosis management: utility in diagnosis, fracture risk prediction and therapy monitoring

Osteoporosis is a systemic disease characterized by low bone mass and microarchitectural deterioration of bone tissue, resulting in an increased risk of fracture. While the level of bone mass can be estimated by measuring bone mineral density (BMD) using dual X-ray absorptiometry (DXA), its measurement does not capture all the risk factors for fracture. Quantitative changes in skeletal turnover can be assessed easily and non-invasively by the measurement of serum and urinary biochemical markers; the most sensitive markers include serum osteocalcin, bone specific alkaline phosphatase, the N-terminal propeptide of type I collagen for bone formation, and the crosslinked C- (CTX) and N- (NTX) telopeptides of type I collagen for bone resorption. Advances in our knowledge of bone matrix biochemistry, most notably of post-translational modifications in type I collagen, are likely to lead to the development of new biochemical markers that reflect changes in the material property of bone, an important determinant of bone strength. Among those, the measurement of the urinary ratio of native (alpha) to isomerized (beta) CTX - an index of bone matrix maturation - has been shown to be predictive of fracture risk independently of BMD and bone turnover.In postmenopausal osteoporosis, levels of bone resorption markers above the upper limit of the premenopausal range are associated with an increased risk of hip, vertebral, and nonvertebral fracture, independent of BMD. Therefore, the combined use of BMD measurement and biochemical markers is helpful in risk assessment, especially in those women who are not identified as at risk by BMD measurement alone. Levels of bone markers decrease rapidly with antiresorptive therapies, and the levels reached after 3-6 months of therapy have been shown to be more strongly associated with fracture outcome than changes in BMD. Preliminary studies indicate that monitoring changes of bone formation markers could also be useful to monitor anabolic therapies, including intermittent parathyroid hormone administration and, possibly, to improve adherence to treatment. Thus, repeated measurements of bone markers during therapy may help improve the management of osteoporosis in patients.     

Osteoporosis: combination therapy for better or worse

Osteoporosis is a condition that is associated with an increased susceptibility for fractures. In the past few years, several drugs have become available that can reduce the incidence of fractures in patients with osteoporosis. Since these drugs work through different cellular mechanisms, combining agents of different classes may have an additive or multiplicative effect on fracture risk reduction. Combination treatments that have been evaluated in clinical trials include bisphosphonates with estrogen, raloxifene or PTH/ bisphosphonates and PTH/ estrogen. In general, these trials have shown increases in bone mineral density over that observed with each agent alone. However, whether anti-fracture efficacy is improved, or worsened remains to be established. This article reviews the combination treatments that have been evaluated in clinical trials, with a discussion of the potential benefits and risks that those treatments entail. Integrating safety and cost issues will eventually determine whether those combinations will become the standard of care.     

Overview of osteoporosis.

Osteoporosis is a common age-related disorder manifested clinically by skeletal fractures, especially fractures of the vertebrae, hip, and distal forearm. The major cause of these fractures is low bone mass, although an increase in trauma due to falls in the elderly also contributes. There are multiple causes for the low bone mass which, in any given individual, may contribute differently to the development of the osteopenia. The most important groups of causes are failure to achieve adequate peak bone mass, slow bone loss due to processes relating to aging, the menopause in women, and a variety of sporadic behavioral, nutritional, and environmental factors that affect bone mass in some but not in other individuals. The most important approach is prevention. Drugs and behavioral factors known to cause bone loss should be eliminated and perimenopausal women should be evaluated for possible preventive administration of estrogen. For patients with fractures due to established osteoporosis, the only drugs approved by the Food and Drug Administration are the antiresorptive agents calcium, estrogen, and calcitonin. Formation-stimulating regimens, however, are being developed and may be available for clinical use in the foreseeable future. These regimens may be capable of increasing bone mass to above the fracture threshold, thereby resulting in a clinical cure of the osteoporosis.     

Recommendations on the management of fragility fracture risk in women younger than 70 years

The risk for fragility fracture represents a problem of enormous magnitude. It is estimated that only a small fraction of women with this risk take the benefit of preventive measures. The relationship between estrogen and bone mass is well known as they are the other factors related to the risk for fracture. There are precise diagnostic methods, including a tool to diagnose the risk for fracture. Yet there continues to be an under-diagnosis, with the unrecoverable delay in instituting preventive measures. Women under the age of 70 years, being much more numerous than those older, and having risk factors, are a group in which it is essential to avoid that first fragility fracture. Today it is usual not to differentiate between the treatment and the prevention of osteoporosis since the common aim is to prevent fragility fractures. Included in this are women with osteoporosis or with low bone mass and increased risk for fracture, for whom risk factors play a primary role. There is clearly controversy over the type of treatment and its duration, especially given the possible adverse effects of long-term use. This justifies the concept of sequential treatment, even more so in women under the age of 70, since they presumably will need treatment for many years. Bone metabolism is age-dependent. In postmenopausal women under 70 years of age, the increase in bone resorption is clearly predominant, related to a sharp drop in estrogens. Thus a logical treatment is the prevention of fragility fractures by hormone replacement therapy (HRT) and, in asymptomatic women, selective estradiol receptor modulators (SERMs). Afterwards, there is a period of greater resorption, albeit less intense but continuous, when one could utilise anti-resorptive treatments such as bisphosphonates or denosumab or a dual agent like strontium ranelate. Bone formation treatment, such as parathyroid hormone (PTH), in women under 70 years will be uncommon. That is because it should be used in cases where the formation is greatly diminished and there is a high risk for fracture, something found in much older women.     

The clinical application of serial bone mass measurements

Although the short-term precision of various bone mineral content (BMC) measurements is known, questions about the clinical use of serial BMC measurements remain: how frequently should BMC be measured? When is it appropriate to calculate bone loss rates? How are estimates of loss rate interpreted? This paper discusses both biological and technical sources of uncertainty, and the estimation of confidence limits for measured bone loss rates. For many, possibly most, patients, calculation of bone loss rate may not be necessary; however, repeated measures of BMC can still be useful for re-evaluating fracture risk. Indications for repeating BMC measurements may include low initial BMC (moderate to high fracture risk), anticipation of rapid bone loss (e.g., menopause, estrogen discontinuation), and verification of treatment efficacy.     

How drugs decrease fracture risk: lessons from trials

In women with osteoporosis, each 1% improvement in spine BMD (by DXA) is expected to reduce vertebral fracture risk by about 4%. However, randomized trials of antiresorptive agents show that 1 to 6% improvements in spine BMD reduce vertebral fracture risk by 35 to 50%. Less 20% of the decreased spine fracture risk produced by alendronate or raloxifene be explained by improvement in spine BMD. The discrepancy is even greater during the first year or two of treatment when 1 to 4% improvements in BMD are associated with 65-68% decreases in spine fracture risk. Bisphosphonates continue to increase BMD but the reduction in fracture risk wanes to 20 to 45%. DXA underestimates the change in bone density of spinal trabecular bone and this might explain part of the discrepancy between expected and observed reductions in spine fracture risk. Even more accurate measurement of BMD would not explain the rapid onset and later waning of effect despite gradually increasing BMD. The biomechanical effects inhibiting bone resorption could explain the early onset but not the waning effectiveness. The waning effectiveness of antiresorptives raises concerns that prolonged inhibition of remodeling may weaken bone by allowing microdamage to accumulate. The effect of drugs on nonspine fracture risk is more complex and cannot be predicted from changes in DXA BMD. For example, Beck showed that long-term users of estrogen increase section modulus vs. nonusers with a net increase in section modulus and predicted femoral neck strength despite losing about 0.4% per year in femoral neck BMD. PTH reduces spine fracture risk and this effect is more completely explained by improvement in spine BMD. This suggests that sustaining the increased BMD produced by PTH may maintain long-term reductions in fracture risk.     

Dose dependent response of symptoms,pituitary, and bone to transdermal oestrogen in postmenopausal women.

The effect of the plasma oestradiol concentration on climacteric symptoms, gonadotrophin release, and bone resorption was studied in three groups of postmenopausal women given 0.025 mg, 0.05 mg, or 0.1 mg transdermal oestradiol daily. There was a dose related reduction in symptoms, plasma follicle stimulating hormone concentration, and urinary calcium and hydroxyproline excretion. The relation of the response to plasma oestradiol values was similar for each variable with an initial large reduction and little change in response to increases in the plasma oestradiol concentration above 150 pmol/l (41 pg/ml). Hormone replacement therapy producing an effect equivalent to higher oestradiol concentrations is likely to increase the risk of side effects without conferring any additional benefit.     

Effects of beta-blockers on fracture risk

Laboratory studies make clear that the sympathetic nervous system does impact on bone cell and tissue function. However, these effects are inconsistent between models, possibly reflecting sympathetic effects at different levels, from the central nervous system through to the bone cells. Observational studies of the use of beta-blockers are confounded by the indications for which these drugs are prescribed, and by other medications that are commonly co-prescribed with them. These data are inconsistent, although a recent meta-analysis did conclude that beta-blocker use was associated with a significant decrease in fracture risk. However, the more recent studies cast doubt on this finding, and the limited data regarding fractures in randomized controlled trials certainly do not support this conclusion. Therefore, there is not an adequate evidence base to support using beta-blockers as a treatment for osteoporosis, nor can they be regarded as a discriminating risk factor for fracture assessment. Until there are definitive randomized, controlled trials of beta-blockers, which include fracture as an endpoint, it is unlikely that the current confusing situation will be resolved.     

Bone Health History in Breast Cancer Patients on Aromatase Inhibitors

A cross-sectional study was performed to assess bone health history among aromatase inhibitor (AI) users before breast cancer (BC) diagnosis, which may impact fracture risk after AI therapy and choice of initial hormonal therapy. A total of 2,157 invasive BC patients initially treated with an AI were identified from a prospective cohort study at Kaiser Permanente Northern California (KPNC). Data on demographic and lifestyle factors were obtained from in-person interviews, and bone health history and clinical data from KPNC clinical databases. The prevalence of osteoporosis and fractures in postmenopausal AI users was assessed, compared with 325 postmenopausal TAM users. The associations of bone health history with demographic and lifestyle factors in AI users were also examined. Among all initial AI users, 11.2% had a prior history of osteoporosis, 16.3% had a prior history of any fracture, and 4.6% had a prior history of major fracture. Postmenopausal women who were taking TAM as their initial hormonal therapy had significantly higher prevalence of prior osteoporosis than postmenopausal AI users (21.5% vs. 11.8%, p<0.0001). Among initial AI users, the associations of history of osteoporosis and fracture in BC patients with demographic and lifestyle factors were, in general, consistent with those known in healthy older women. This study is one of the first to characterize AI users and risk factors for bone morbidity before BC diagnosis. In the future, this study will examine lifestyle, molecular, and genetic risk factors for AI-induced fractures.     

Predicting the structural integrity of bone defects repaired using bone graft materials

Bone defects create stress concentrations which can cause fracture under impact or cyclic loading. Defects are often repaired by filling them with a bone graft material; this will reduce the stress concentration, but not completely, because these materials have lower stiffness than bone. The fracture risk decreases over time as the graft material is replaced by living bone. Many new bone graft materials are being developed, using tissue engineering and other techniques, but currently there is no rational way to compare these materials and predict their effectiveness in repairing a given defect. This paper describes, for the first time, a theoretical model which can be used to predict failure by brittle fracture or fatigue, initiating at the defect. Preliminary results are presented, concentrating on the prediction of stress fracture during the crucial post-operative period. It is shown that the likelihood of fracture is strongly influenced by the shape of the defect as well as its size, and also by the level of post-operative exercise. The most important finding is that bone graft materials can be successful in preventing fracture even when their mechanical properties are greatly inferior to those of bone. Future uses of this technique include pre-clinical assessment of bone replacement materials and pre-operative planning in orthopaedic surgery.     

Predicting the structural integrity of bone defects repaired using bone graft materials

Bone defects create stress concentrations which can cause fracture under impact or cyclic loading. Defects are often repaired by filling them with a bone graft material; this will reduce the stress concentration, but not completely, because these materials have lower stiffness than bone. The fracture risk decreases over time as the graft material is replaced by living bone. Many new bone graft materials are being developed, using tissue engineering and other techniques, but currently there is no rational way to compare these materials and predict their effectiveness in repairing a given defect. This paper describes, for the first time, a theoretical model which can be used to predict failure by brittle fracture or fatigue, initiating at the defect. Preliminary results are presented, concentrating on the prediction of stress fracture during the crucial post-operative period. It is shown that the likelihood of fracture is strongly influenced by the shape of the defect as well as its size, and also by the level of post-operative exercise. The most important finding is that bone graft materials can be successful in preventing fracture even when their mechanical properties are greatly inferior to those of bone. Future uses of this technique include pre-clinical assessment of bone replacement materials and pre-operative planning in orthopaedic surgery.