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Biomedical subjects

Steven Boonen

Publications and source records attributed to Steven Boonen.

At least 19 recordsLinked to original sources
PubMed2007

The diagnosis and treatment of male osteoporosis: Defining, assessing, and preventing skeletal fragility in men.

Male osteoporosis is associated with a significant burden in terms of morbidity, mortality, and economic cost. Despite recent advances in the understanding of the male osteoporotic syndrome, the evaluation and treatment of men suffering from osteoporosis remains a clinical challenge. In men with osteoporosis, it remains particularly critical to exclude underlying pathological causes as these are much more likely to be present than in women. There is increasing evidence that the approaches developed to diagnose and treat the disorder in women may be equally useful in men. The available evidence suggests that the anti-fracture efficacy of treatment with alendronate, risedronate, or teriparatide is similar in both sexes. Additional research is warranted to prospectively address the usefulness of BMD measurements to predict fracture risk, to identify those men who are likely to benefit the most from therapy, and to monitor individual responses to therapy.

Journal Article↗
PubMed2007

Impact of androgens, growth hormone, and IGF-I on bone and muscle in male mice during puberty.

UNLABELLED: The interaction between androgens and GH/IGF-I was studied in male GHR gene disrupted or GHRKO and WT mice during puberty. Androgens stimulate trabecular and cortical bone modeling and increase muscle mass even in the absence of a functional GHR. GHR activation seems to be the main determinant of radial bone expansion, although GH and androgens are both necessary for optimal stimulation of periosteal growth during puberty. INTRODUCTION: Growth hormone (GH) is considered to be a major regulator of postnatal skeletal growth, whereas androgens are considered to be a key regulator of male periosteal bone expansion. Moreover, both androgens and GH are essential for the increase in muscle mass during male puberty. Deficiency or resistance to either GH or androgens impairs bone modeling and decreases muscle mass. The aim of the study was to investigate androgen action on bone and muscle during puberty in the presence and absence of a functional GH/insulin-like growth factor (IGF)-I axis. MATERIALS AND METHODS: Dihydrotestosterone (DHT) or testosterone (T) were administered to orchidectomized (ORX) male GH receptor gene knockout (GHRKO) and corresponding wildtype (WT) mice during late puberty (6-10 weeks of age). Trabecular and cortical bone modeling, cortical strength, body composition, IGF-I in serum, and its expression in liver, muscle, and bone were studied by histomorphometry, pQCT, DXA, radioimmunoassay and RT-PCR, respectively. RESULTS: GH receptor (GHR) inactivation and low serum IGF-I did not affect trabecular bone modeling, because trabecular BMD, bone volume, number, width, and bone turnover were similar in GHRKO and WT mice. The normal trabecular phenotype in GHRKO mice was paralleled by a normal expression of skeletal IGF-I mRNA. ORX decreased trabecular bone volume significantly and to a similar extent in GHRKO and WT mice, whereas DHT and T administration fully prevented trabecular bone loss. Moreover, DHT and T stimulated periosteal bone formation, not only in WT (+100% and +100%, respectively, versus ORX + vehicle [V]; p < 0.05), but also in GHRKO mice (+58% and +89%, respectively, versus ORX + V; p < 0.05), initially characterized by very low periosteal growth. This stimulatory action on periosteal bone resulted in an increase in cortical thickness and occurred without any treatment effect on serum IGF-I or skeletal IGF-I expression. GHRKO mice also had reduced lean body mass and quadriceps muscle weight, along with significantly decreased IGF-I mRNA expression in quadriceps muscle. DHT and T equally stimulated muscle mass in GHRKO and WT mice, without any effect on muscle IGF-I expression. CONCLUSIONS: Androgens stimulate trabecular and cortical bone modeling and increase muscle weight independently from either systemic or local IGF-I production. GHR activation seems to be the main determinant of radial bone expansion, although GHR signaling and androgens are both necessary for optimal stimulation of periosteal growth during puberty.

Androgens↗
PubMed2006

Effects of whole body vibration training on postural control in older individuals: a 1 year randomized controlled trial.

This randomized controlled trial investigated the effects of a 12 month whole body vibration training program on postural control in healthy older adults. Two hundred and twenty people were randomly assigned to a whole body vibration group (n=94), a fitness group (n=60) or a control group (n=66). The whole body vibration and fitness groups trained three times a week for 1 year. The vibration group performed exercises on a vibration platform and the fitness group performed cardiovascular, strength, balance and stretching exercises. Balance was measured using dynamic computerized posturography at baseline and after 6 and 12 months. Whole body vibration training was associated with reduced falls frequency on a moving platform when vision was disturbed and improvements in the response to toes down rotations at the ankle induced by the moving platform. The fitness group showed reduced falls frequency on the moving surface when vision was disturbed. Thus, whole body vibration training may improve some aspects of postural control in community dwelling older individuals.

Accidental Falls↗
PubMed2006

Relative impact of androgen and estrogen receptor activation in the effects of androgens on trabecular and cortical bone in growing male mice: a study in the androgen receptor knockout mouse model.

UNLABELLED: The relative importance of AR and ER activation has been studied in pubertal male AR knockout and WT mice after orchidectomy and androgen replacement therapy, either with or without an aromatase inhibitor. AR activation dominates normal trabecular bone development and cortical bone modeling in male mice. Moreover, optimal periosteal bone expansion is only observed in the presence of both AR and ER activation. INTRODUCTION: Androgen receptor (AR)-mediated androgen action has traditionally been considered a key determinant of male skeletal growth. Increasing evidence, however, suggests that estrogens are also essential for normal male bone growth. Therefore, the relative importance of AR-mediated and estrogen receptor (ER)-mediated androgen action after aromatization remains to be clarified. MATERIALS AND METHODS: Trabecular and cortical bone was studied in intact or orchidectomized pubertal AR knockout (ARKO) and male wildtype (WT) mice, with or without replacement therapy (3-8 weeks of age). Nonaromatizable (dihydrotestosterone [DHT]) and aromatizable (testosterone [T]) androgens and T plus an aromatase inhibitor (anastrazole) were administered to orchidectomized ARKO and WT mice. Trabecular and cortical bone modeling were evaluated by static and dynamic histomorphometry, respectively. RESULTS: AR inactivation or orchidectomy induced a similar degree of trabecular bone loss (-68% and -71%, respectively). Both DHT and T prevented orchidectomy-induced bone loss in WT mice but not in ARKO mice. Administration of an aromatase inhibitor did not affect T action on trabecular bone. AR inactivation and orchidectomy had similar negative effects on cortical thickness (-13% and -8%, respectively) and periosteal bone formation (-50% and -26%, respectively). In orchidectomized WT mice, both DHT and T were found to stimulate periosteal bone formation and, as a result, to increase cortical thickness. In contrast, the periosteum of ARKO mice remained unresponsive to either DHT or T. Interestingly, administration of an aromatase inhibitor partly reduced T action on periosteal bone formation in orchidectomized WT mice (-34% versus orchidectomized WT mice on T), but not in ARKO mice. This effect was associated with a significant decrease in serum IGF-I (-21% versus orchidectomized WT mice on T). CONCLUSIONS: These findings suggest a major role for AR activation in normal development of trabecular bone and periosteal bone growth in male mice. Moreover, optimal stimulation of periosteal growth is only obtained in the presence of both AR and ER activation.

Androgens↗
PubMed2006

Addressing and meeting the needs of osteoporotic patients with strontium ranelate: a review.

Patients with osteoporosis need a safe and effective treatment that reduces the risk of vertebral and non-vertebral fractures, leading to clinical benefits such as reduced back pain and height loss. Strontium ranelate corrects bone turnover, producing a more physiological state. Double-blind, placebo-controlled studies in postmenopausal osteoporosis show it to be effective in reducing vertebral and non-vertebral fracture risks. Treatment efficacy has been documented across a wide range of patient profiles, and appears to be independent of all the major determinants of fracture risk, including the severity of the disease at baseline, the number of prevalent fractures, and the age of the patient. This antifracture efficacy translates into clinical benefits, such as a 20% reduction in the rate of height loss and a 29% increase in the number of patients free of back pain. The effect of treatment with strontium ranelate on well-being has been assessed using the Quality-of-Life Questionnaire in Osteoporosis, which is a supplement to the 36-question Short-Form Health Survey. Treatment with strontium ranelate had a significant beneficial effect on the emotional, physical, and global Quality-of-Life Questionnaire in Osteoporosis scores compared with placebo. The rates of compliance with treatment were over 80% in phase III studies, reflecting the tolerability and safety profile and the ease of administration of this agent. Together with the antifracture data, the clinical benefits and quality of life data endorse the treatment of postmenopausal osteoporosis with strontium ranelate.

Bone Density↗
PubMed2006

Safety and efficacy of teriparatide in elderly women with established osteoporosis: bone anabolic therapy from a geriatric perspective.

OBJECTIVES: To assess the safety and efficacy of teriparatide in patients aged 75 and older and compare these findings with those of women younger than 75 using data from the Fracture Prevention Trial (FPT). DESIGN: The FPT was a randomized, multicenter, double-blind, placebo-controlled study. SETTING: The FPT multicenter international study. PARTICIPANTS: Postmenopausal women aged 42 to 86 were randomized to placebo (N=544) or teriparatide 20 mug (N=541) by daily self-injection for a median of 19 months. Patients received daily oral supplements of 1,000 mg calcium and 400 to 1,200 IU vitamin D. For this analysis, subgroups were defined according to patient age younger than 75 (N=841) and 75 and older (N=244). MEASUREMENTS: The effects of teriparatide on bone mineral density (BMD) of the lumbar spine and femoral neck; the incidence of new vertebral and new nonvertebral fragility fractures; bone turnover markers, including bone-specific alkaline phosphatase; and urinary deoxypyridinoline corrected for creatinine clearance, as well as the safety of teriparatide, were investigated. RESULTS: There were no significant treatment-by-age interactions for the bone turnover markers, femoral neck BMD, vertebral fractures, nonvertebral fragility fractures, height loss, hyperuricemia, or hypercalcemia. A significant treatment-by-age interaction for lumbar spine BMD (P=.08) was due to an increase in BMD observed in the placebo group aged 75 and older. There were no treatment-by-age interactions for important treatment-emergent adverse events (TEAEs), including back pain, nausea, leg cramps, and dizziness. The most important TEAEs in women aged 80 and older (23 patients from the placebo group and 25 patients from the teriparatide group) were also reviewed; no unexpected TEAEs were found in the patients treated with teriparatide. These results indicate that the clinical effects of teriparatide were consistent in the older and younger women. CONCLUSION: Age does not affect the safety and efficacy of teriparatide in postmenopausal women with osteoporosis.

Age Factors↗
PubMed2006

Strontium ranelate reduces the risk of vertebral and nonvertebral fractures in women eighty years of age and older.

UNLABELLED: Strontium ranelate produces an early and sustained reduction of both vertebral and nonvertebral fractures in patients > or = 80 years of age. INTRODUCTION: About 25-30% of the population burden of all fragility fractures in the community arise from women > or = 80 years of age, because this population is at high risk for all types of fracture, particularly nonvertebral fractures. Despite this, evidence that therapies reduce the risk of both vertebral and nonvertebral fractures in this group is lacking. The aim of this study was to determine whether strontium ranelate, an agent that reduces the risk of vertebral and nonvertebral fractures in postmenopausal women >50 years of age, also reduces fractures in the elderly. MATERIALS AND METHODS: An analysis based on preplanned pooling of data from two international, phase III, randomized, placebo-controlled, double-blind studies (the Spinal Osteoporosis Therapeutic Intervention [SOTI] and TReatment Of Peripheral OSteoporosis [TROPOS]) included 1488 women between 80 and 100 years of age followed for 3 years. Yearly spinal X-rays were performed in 895 patients. Only radiographically confirmed nonvertebral fractures were included. RESULTS: Baseline characteristics did not differ in placebo and treatment arms. In the intent-to-treat analysis, the risk of vertebral, nonvertebral, and clinical (symptomatic vertebral and nonvertebral) fractures was reduced within 1 year by 59% (p = 0.002), 41% (p = 0.027), and 37% (p = 0.012), respectively. At the end of 3 years, vertebral, nonvertebral, and clinical fracture risks were reduced by 32% (p = 0.013), 31% (p = 0.011), and 22% (p = 0.040), respectively. The medication was well tolerated, and the safety profile was similar to that in younger patients. CONCLUSIONS: Treatment with strontium ranelate safely reduces the risk of vertebral and nonvertebral fractures in women with osteoporosis > or = 80 years of age. Even in the oldest old, it is not too late to reduce fracture risk.

Age Factors↗
PubMed2006

Optimizing the benefits of bisphosphonates in osteoporosis : the importance of appropriate calcium intake.

Osteoporosis is a major cause of morbidity, mortality, and healthcare costs. The socioeconomic burden of osteoporosis is likely to increase dramatically if improvements in prevention are not made. Calcium supplementation effectively reduces the rate of bone loss in postmenopausal women, yet most women do not achieve an adequate calcium intake. In fact, use of calcium supplementation appears to have declined as the more effective antiresorptive therapies, such as bisphosphonates, have become available. Among patients prescribed bisphosphonates, calcium intake is often insufficient, despite the fact that adequate calcium intake may be necessary to gain the maximum benefits from antiresorptive therapy. In addition, because calcium interferes with bisphosphonate absorption, incorrect use of calcium may limit the efficacy of bisphosphonate therapy. This underscores the need for new initiatives to reduce the confusion surrounding appropriate calcium use during antiresorptive therapy. Co-packaging of bisphosphonates with calcium supplements is one strategy to help ensure that patients taking bisphosphonates not only achieve adequate calcium intake but also gain the maximum benefit from bisphosphonate therapy.

Calcium, Dietary↗
PubMed2005

Clinical Review: Sex steroids and the periosteum--reconsidering the roles of androgens and estrogens in periosteal expansion.

CONTEXT: Traditionally, differences in periosteal bone formation between men and women have been assumed to reflect two diverging endocrine effects: stimulatory effects of androgens in men and inhibitory effects of estrogens in women. In line with this concept, it is tempting to speculate that men experience more periosteal bone expansion than women because they are exposed to more endogenous androgens and less estradiol. However, recent data challenge this traditional concept. EVIDENCE ACQUISITION: A PubMed search was conducted for relevant most recent findings in both humans and animals in the context of an intriguing observation of ongoing periosteal expansion after estrogen treatment in an aromatase-deficient boy. EVIDENCE SYNTHESIS: Human experiments of nature have provided evidence that androgens and estrogens are both required for the process of pubertal periosteal bone expansion typically associated with the male bone phenotype. Androgens alone appear insufficient to drive male periosteal bone formation. In both sexes, androgens may stimulate periosteal bone formation, but low levels of estrogen may increase the mechanical sensitivity of the periosteum. Higher concentrations of endogenous estrogen, however, inhibit periosteal bone apposition and/or its interaction with mechanical loading. This biphasic action of estrogen on the periosteum may result from a direct effect on its receptor, either alpha or beta, but may also depend on changes in serum IGF-I. CONCLUSIONS: Simple concepts of the roles of sex steroids in periosteal apposition have to be reconsidered in the context of these recent findings.

Androgens↗
PubMed2005

Evidence-based guidelines for the prevention and treatment of glucocorticoid-induced osteoporosis: a consensus document of the Belgian Bone Club.

Glucocorticoids (GCs) are frequently prescribed for various inflammatory and/or life-threatening conditions concerning many systems in the body. However, they can provoke many aftereffects, of which osteoporosis (OP) is one of the most crippling complications, with its host of fractures. The dramatic increase in bone fragility is mainly attributable to the GC-induced rapid bone loss in all skeletal compartments. We have reviewed the meta-analyses and randomized controlled studies reporting medical therapeutic interventions currently registered in Belgium for the management of GC-OP comparatively with a placebo. Based on this research, an expert meeting developed a consensus on the prevention and therapy of GC-OP. The pathophysiology of GC-OP is complex. Several factors, acting separately or synergistically, have been described. Their great number could help to understand the rapidity of bone loss and of bone fragility occurrence, indicating that a rapid therapeutic intervention should be implemented to avoid complications. All patients on GCs are threatened with OP, so the prevention and/or therapy of GC-OP should be considered not only for postmenopausal females, but also for osteopenic premenopausal females and for males put on a daily dose of at least 7.5 mg equivalent prednisolone that is expected to last at least 3 months. Non-pharmacological interventions, such as exercise and avoidance of tobacco and alcohol, should be recommended, even if their role is not definitely settled in GC-OP prevention. Supplemental calcium and vitamin D should be considered as the first-line therapy because of the decrease in intestinal calcium absorption provoked by GCs. They also could be considered either as isolated therapy in patients taking less than 7.5 mg prednisolone daily and/or for a predicted period shorter than 3 months or as adjuvant therapy to other more potent drugs. Hormone replacement therapy could be considered in young postmenopausal females on GC, such as in postmenopausal OP, or in men with low androgen levels. Calcitonin appears to have a protective effect on trabecular bone in GC-OP, just as in postmenopausal OP. There is an increasing body of evidence supporting the antifracture efficacy of bisphosphonates, notably alendronate and risedronate. Preventative and curative therapy of GC-OP should be maintained as long as the patient is on GC treatment and could be stopped after weaning from GC, because there is more than circumstantial evidence of some recovery of BMD when GCs are stopped. There is no indication in GC-OP for any combination of two antiresorptive agents (except for calcium and vitamin D) or for an antiresorptive and an anabolic agent. There is indeed no proof that the increased costs of combined treatments will translate into increased therapeutic efficacy.

Bone Density↗
PubMed2005

Safety and efficacy of risedronate in patients with age-related reduced renal function as estimated by the Cockcroft and Gault method: a pooled analysis of nine clinical trials.

UNLABELLED: The incidences of osteoporosis and renal insufficiency increase with age. We studied the influence of renal function on the safety and efficacy of risedronate 5 mg daily in osteoporotic women. Risedronate was safe and effective in osteoporotic women with mild, moderate, or severe age-related renal impairment. INTRODUCTION: The incidences of both osteoporosis and renal insufficiency increase with age; thus, the effect of renal impairment on the safety and efficacy of osteoporosis treatments is a clinical concern. Risedronate is a pyridinyl bisphosphonate well established as safe and effective in the treatment and prevention of osteoporosis. Currently, there is little available information about the effect of bisphosphonate treatment in patients with renal insufficiency. This retrospective analysis was conducted to study the influence of renal function on the safety and efficacy of risedronate in a population of osteoporotic women. MATERIALS AND METHODS: Combined data from nine randomized, double-blind, placebo-controlled phase III risedronate trials were analyzed. The patients in these studies had no markedly abnormal laboratory parameters that were considered clinically significant and no evidence of significant disease. This analysis included patients who received placebo (n = 4,500) or risedronate 5 mg (n = 4,496) for up to 3 years (average duration of exposure, 2 years) and who had renal impairment (creatinine clearance [CrCl] < 80 ml/min). CrCl was estimated by the Cockcroft and Gault method, based on age, weight, and serum creatinine. Patients were categorized as having mild (CrCl >or=50 to <80 ml/min), moderate (CrCl >or=30 to <50 ml/min), or severe (CrCl < 30 ml/min) renal impairment. RESULTS: Of the patients studied, renal impairment at baseline was mild in 48% (mean [range] serum creatinine, 0.9 [0.4-1.6] mg/dl), moderate in 45% (1.1 [0.6-1.9] mg/dl), and severe in 7% (1.3 [0.7-2.7] mg/dl). In both the placebo and risedronate treatment groups, the patients with the most severe renal impairment were older and had more severe osteoporosis. The incidences of overall adverse events and of renal function-related adverse events were similar in the placebo and risedronate 5 mg groups regardless of renal function. Furthermore, evaluation of changes from baseline in serum creatinine revealed no difference in renal function between the placebo and risedronate 5 mg groups in any of the renal impairment subgroups at any time-point. In all three subgroups, risedronate effectively preserved BMD and reduced the incidence of vertebral fractures. CONCLUSIONS: These findings show that risedronate is safe and effective in osteoporotic women with age-related mild, moderate, or severe renal impairment.

Age Factors↗
PubMed2005

Growth without growth hormone receptor: estradiol is a major growth hormone-independent regulator of hepatic IGF-I synthesis.

UNLABELLED: The role of estrogens in the regulation of pubertal growth independently of GH and its receptor was studied in male mice with disrupted GHRKO. E(2) rescued skeletal growth rates in GHRKO associated with an increase in hepatic and serum IGF-I. These data show that E(2) rescues pubertal growth during GH resistance through a novel mechanism of GHR-independent stimulation of hepatic IGF-I production. INTRODUCTION: Growth hormone (GH) and estrogen play a pivotal role in pubertal growth and bone mineral acquisition. Estrogens can affect GH secretion and thereby provide a GH-dependent mechanism for their effects on skeletal growth. It is presently unclear if or to what extent estrogens are able to regulate pubertal growth and bone mineral accrual independently of GH and its receptor. MATERIALS AND METHODS: Estradiol (E(2); 0.03 mug/day by subcutaneous silastic implants) was administered to orchidectomized (ORX) male mice with disrupted GHR (GHRKO) and corresponding WTs during late puberty (6-10 weeks). Longitudinal and radial bone growth, IGF-I in serum and its expression in liver, muscle, and bone, and liver gene expression were studied by histomorphometry, RIA, RT-PCR, microarrays, and Western blotting, respectively. RESULTS: E(2) stimulated not only longitudinal (femur length and growth plate thickness) and radial growth (cortical thickness and periosteal perimeter), but also rescued longitudinal and periosteal growth rates in ORX GHRKO, whereas no significant changes occurred in WT. E(2) thereby upregulated serum IGF-I and liver IGF-I synthesis (+21% and +52%, respectively) in ORX GHRKO, whereas IGF-I synthesis in femur or muscle was unaffected. Study of the underlying mechanism of the stimulation of hepatic IGF-I expression showed that E(2) restored downregulated receptor signaling systems, such as the estrogen receptor alpha and the prolactin receptor. E(2) thereby recovered the Janus kinase (JAK)/signal transducers and activators of transcription (STAT) pathway as evidenced by a significantly increased activation of the transcription factor STAT5 in ORX GHRKO. CONCLUSIONS: Our data show a stimulation of skeletal growth through upregulation of hepatic IGF-I by a hormone other than GH. E(2) rescues pubertal skeletal growth during GH resistance through a novel mechanism of GHR-independent stimulation of IGF-I synthesis in the liver.

Animals↗
PubMed2005

Effect of osteoporosis treatments on risk of non-vertebral fractures: review and meta-analysis of intention-to-treat studies.

Most osteoporosis treatments have proven efficacy in reducing the risk of vertebral fractures, whereas evidence is less straightforward for prevention of non-vertebral fractures. Conclusions as to the efficacy of a treatment should be based primarily on analyses of the intention to treat (ITT) population rather than on exploratory subgroup analyses; however, non-vertebral anti-fracture efficacy has been largely derived by post-hoc subgroup analyses. This review and meta-analysis was performed to assess non-vertebral anti-fracture efficacy of several osteoporosis therapies, including a more stringent assessment of the ITT populations. Data on non-vertebral anti-fracture efficacy, a defined endpoint of the ITT analyses and confirmed by radiographs, were obtained from randomized, placebo-controlled, phase III clinical trials of at least 3-year duration. Meta-analyses were performed for the two bisphosphonates, alendronate and risedronate. Relative risks (RR), 95% confidence intervals (CI) and statistical significance for active treatment compared with placebo were calculated. Eleven clinical trials met the criteria for review, three of which showed statistically significant ( P < or =0.05) non-vertebral anti-fracture efficacy in the ITT population: two trials with risedronate and one trial with strontium. A meta-analysis showed significant reductions in the relative risk of non-vertebral fracture for both alendronate (RR=0.86; 95% CI: 0.76-0.97, P =0.012) and risedronate (RR=0.81; 95% CI: 0.71-0.92, P =0.001). Risedronate and strontium ranelate were the only treatments to show non-vertebral anti-fracture efficacy in this robust assessment of anti-fracture efficacy of osteoporosis therapy using ITT populations in trials of 3 years or more in duration. Risedronate was the only agent shown to demonstrate efficacy in more than one trial. Meta-analysis showed that both alendronate and risedronate provide non-vertebral anti-fracture efficacy.

Aged↗
PubMed2005

Vertebral fracture risk reduction with risedronate in post-menopausal women with osteoporosis: a meta-analysis of individual patient data.

BACKGROUND AND AIMS: The effect of risedronate, a potent pyridinyl bisphosphonate, on vertebral fractures in post-menopausal women was evaluated in randomized, placebo-controlled clinical trials. These trials included two large vertebral fracture studies that used time-to-event methods to evaluate the effects of treatment on fracture risk, thereby allowing both the occurrence and the timing of fractures to be considered. METHODS: We used individual patient data (IPD) and time-to-event methods to perform a meta-analysis of the anti-fracture efficacy of risedronate (2.5 or 5 mg daily) in osteoporotic women enrolled in five double-blind, placebo-controlled clinical trials. Women were included in the analysis if, at baseline, they had either at least one prevalent vertebral fracture or a femoral neck bone mineral density (BMD) T-score of less than -2.5, were at least 1 year post-menopausal, and had had vertebral fracture assessments (N = 3331). RESULTS: Risedronate 5 mg daily reduced the risk of radiographically defined vertebral fracture by 64% (95% CI, 46 to 76%, p < 0.001) in the first year of treatment and 45% (95% CI, 31 to 57%, p < 0.001) in 3 years. The numbers of patients who needed to be treated with risedronate 5 mg to prevent one new vertebral fracture over 1 and 3 years were 21 and 13, respectively. Comparable findings were observed in sub-populations defined on the basis of either prevalent vertebral fracture without regard to femoral neck BMD, or femoral neck BMD without regard to vertebral fracture status. Risedronate significantly reduced the incidence of clinical (symptomatic) vertebral fractures in the first 6 months of treatment (p < 0.001). CONCLUSIONS: This meta-analysis, based upon five trials and using IPD and time-to-event statistical methods, provides a more precise estimate of the effect of risedronate in reducing vertebral fracture risk in postmenopausal osteoporotic women than a meta-analysis using summary statistics from the literature.

Bone Density↗
PubMed2005

Bone and muscle protective potential of the prostate-sparing synthetic androgen 7alpha-methyl-19-nortestosterone: evidence from the aged orchidectomized male rat model.

This study reports the preclinical evaluation of the bone and muscle protective potential of the synthetic androgen 7alpha-methyl-19-nortestosterone (MENTtrade mark), as assessed in the aged orchidectomized rat model. Aged (13-month-old) orchidectomized Wistar rats were treated with different doses of MENT (4, 12 or 36 microg/day) subcutaneously for 16 weeks via mini-osmotic pumps. Analysis of the effects of androgen deficiency versus MENT replacement was performed using quantitative computed tomography (pQCT), dual energy X-ray absorptiometry (DEXA) and biochemical markers of bone turnover. At the end of the study period, prostate weight in orchidectomized rats treated with low- (4 microg/day) or mid-dose (12 mug/day) MENT remained significantly lower compared to the sham-operated animals (-47% and -25%, respectively). High-dose MENT (36 microg/day), on the other hand, induced prostate hypertrophy (+21% versus sham). Low-, mid- and high-dose MENT were found to be effective in suppressing the acceleration of bone remodeling following orchidectomy, as assessed by osteocalcin and deoxypyridinoline. In addition, low-, mid- and high-dose were able to prevent the orchidectomy-induced bone loss, as evaluated by DEXA at the femur and total-body and by pQCT at the femur. Compared to sham-operated animals, the low- and mid-dose MENT groups showed no decline in lean body mass and no muscle atrophy (as measured by m. quadriceps weight) at 16 weeks, whereas high-dose MENT was associated with a significant decline in lean body mass (-8.5% versus sham) and quadriceps weight (-10.6%). We conclude that, in the aged orchidectomized rat model, low- and mid-doses of the synthetic androgen MENT have bone and muscle protective effects and do not induce prostate hypertrophy. The bone protective action of high-dose MENT, however, occurs at the expense of muscle wasting and prostate hypertrophy. Our findings support the need for human studies to explore the potential of MENT as an option for androgen replacement in aging men.

Absorptiometry, Photon↗
PubMed2005

The bone quality framework: determinants of bone strength and their interrelationships, and implications for osteoporosis management.

BACKGROUND: Bone mineral density (BMD) measurements are the standard tool in the diagnosis of osteoporosis. However, recent developments in bone research show that a BMD measurement, while still important in a clinical setting, is in itself insufficient to accurately predict fracture risk or measure treatment effects of an antiosteoporosis drug. Clinical experience with patient follow-up strongly suggests that bone quality must also be taken into account. OBJECTIVES: The objectives of this paper are. (1) to describe the determinants of bone strength (structural and material properties of bone, both of which are affected by bone turnover) and their interrelationships, and (2) to provide a schematic explanation of these determinants of bone strength, which in this paper is referred to as the Bone Quality Framework. METHODS: Relevant information from the primary literature and review articles published in the English language were identified through a MEDLINE search of the medical literature, from 1990 to October 2004, in the fields of bone density, bone strength, bone quality, fracture risk, and fracture risk reduction. Additional publications were identified from the reference lists of the resulting articles. Identified publications relevant to the objectives of this review paper were selected. CONCLUSIONS: The Bone Quality Framework is presented in this paper as a means of summarizing and explaining the determinants of bone strength. In this framework, bone quality can be understood as an umbrella term that describes the set of characteristics that influence bone strength and explains the interrelationships of these characteristics. Bone strength depends on the structural and material properties of bone, both of which are influenced by the rate of bone turnover. Not all determinants of bone strength are well represented by a BMD measurement. The Bone Quality Framework presents an opportunity to examine all the determinants of bone strength. Greater understanding of the concept of bone quality will ultimately help improve the assessment of fracture risk and monitoring of patients receiving treatment for osteoporosis.

Aging↗
PubMed2005

Reversing sex steroid deficiency and optimizing skeletal development in the adolescent with gonadal failure.

During puberty, the acquisition of skeletal mass and areal bone mineral density (BMD) mainly reflects an increase in bone size (length and perimeters) and not true volumetric BMD. Sexual dimorphism in bone mass and areal BMD is also explained by differences in bone size (longer and wider bones in males) and not by differences in volumetric BMD. Androgens stimulate skeletal growth by activation of the androgen receptor, whereas estrogens (following aromatization of androgens and stimulation of estrogen receptors) have a biphasic effect on skeletal growth during puberty. Recent evidence from clinical cases has shown that many of the growth-promoting effects of the sex steroids are mediated through estrogens rather than androgens. In addition, skeletal maturation and epiphyseal fusion are also estrogen-dependent in both sexes. Nevertheless, independent actions of androgens in these processes also occur. Both sex steroids maintain volumetric BMD during puberty. Androgens interact with the growth hormone (GH)-insulin-like growth factor-I (IGF-I) axis neonatally, resulting in a sexual dimorphic GH pattern during puberty, whereas estrogens stimulate GH and hereby IGF-I in both sexes. Hypogonadism in adolescents impairs not only bone size but also maintenance of volumetric BMD, hereby severely reducing peak areal BMD. Delayed puberty in boys and Turner's syndrome in women impair both bone length and size, reducing areal BMD. Whether volumetric BMD is also reduced and whether fracture risk is increased in these conditions remains controversial. Replacing sex steroids according to a biphasic pattern (starting at low doses and ending at high-normal doses) seems the safest approach to reach targeted height and to optimize bone development.

Adolescent↗