Pubertal timing and body mass index gain from birth to maturity in relation with femoral neck BMD and distal tibia microstructure in healthy female subjects

Exploring developmental changes in femoral midneck cross-sectional properties

This research delves deeper into previous works on femoral cross-sectional properties during ontogeny by focusing for the first time on the human femoral midneck. The ontogenetic pattern of cross-sectional properties at femoral midneck is established and compared with those at three different femoral locations: the proximal femur, the midshaft, and the distal femur. The study sample includes 99 femora (70 non-adults and 29 adults) belonging to archaeological specimens. Cross-sectional properties were extracted from computed tomographic scans and analyzed with the MomentMacro plugin of ImageJ. Ontogenetic trends of these variables were assessed using locally estimated scatterplot smoothing and segmented regressions, along with Wilcoxon post hoc tests for all possible age group pairings. Our results show that the femoral midneck exhibits a unique growth pattern. Area variables showed rapid growth until adolescence, followed by a more gradual increase leading into adulthood. Nonetheless, the relative cortical area does not demonstrate any significant drops or rise during growth. The morphology of the midneck section of the femur remains stable during ontogeny, with early adolescence and the onset of adulthood marking two periods of significant change. In contrast to the femoral diaphysis, the acquisition of a mature bipedal gait does not appear to constitute a period of significant morphological change at the femoral midneck cross section.

Acquisition of peak bone mass

Peak bone mass (PBM) is a key determinant of bone mass and fragility fractures later in life. The increase in bone mass during childhood and adolescence is mainly related to an increase in bone size rather to changes in volumetric bone density. Race, gender, and genetic factors are the main determinants of PBM achievement. Nevertheless, environmental factors such as physical activity, calcium and protein intakes, weight and age at menarche, are also playing an important role in bone mass accrual during growth. Therefore, optimization of calcium and protein intakes and weight-bearing physical activity during growth is an important strategy for optimal acquisition of PBM and bone strength and for contributing to prevent fractures later in life.

Association between age at menarche and body mass index, waist circumference, waist to hip ratio, and waist to height ratio in adult women

OBJECTIVES

The aim of the present study was to examine associations between age at menarche and body mass index (BMI), waist circumference (WC), waist-to-height ratio (WHtR), and waist-to-hip ratio (WHR) in young adult women.

METHODS

Anthropometric data and age at menarche information were collected in two cross-sectional surveys conducted in the years 2004-2006 (Cohort 1) and 2016-2018 (Cohort 2). A total of 2419 women, aged 19-24 years., were included.

RESULTS

Statistically significant relationships between age at menarche and BMI, WHtR, and WC were observed. The values of the anthropometric parameters decreased with increasing age at menarche. The onset of menstruation before the age of 12 years. was linked to a heightened risk of overweight and obesity (BMI ≥ 25) and abdominal obesity defined as WC > 80 cm and/or WHtR ≥ 0.5. First menstruation after the age of 14 y. was associated with a lower risk of overweight and obesity (BMI ≥ 25, WC > 80 cm and/or WHtR ≥ 0.5), as well as a higher risk of being underweight (BMI < 18.5 and/or WHtR < 0.4). Associations between anthropometry and menarcheal timing were stronger in Cohort 1.

CONCLUSION

Both early and late onset of menarche are associated with abnormal body composition: Early menarche is associated with overweight, while later maturing girls have a heightened risk of underweight.

Osteoporosis in Premenopausal Women: A Clinical Narrative Review by the ECTS and the IOF

CONTEXT

Consensus regarding diagnosis and management of osteoporosis in premenopausal women (PW) is still lacking due to few studies carried out in this population.

DESIGN

The European Calcified Tissue Society and the International Osteoporosis Foundation convened a working group to produce an updated review of literature published after 2017 on this topic.

RESULTS

Fragility fractures in PW are rare and mostly due to secondary osteoporosis (ie, in presence of an underlying disease such as hormonal, inflammatory, or digestive disorders). In absence of another disorder, low bone mineral density (BMD) together with fragility fractures qualifies as idiopathic osteoporosis. In contrast, low BMD alone does not necessarily represent osteoporosis in absence of bone microarchitectural abnormalities. BMD increases in PW with osteoporosis when the underlying disease is treated. For example, in celiac disease, an increase of 9% in radius trabecular volumetric density was achieved after 1 year of gluten-free diet, while anti-tumor necrosis factor alpha improved BMD in PW with inflammatory bowel diseases. In amenorrhea, including anorexia nervosa, appropriately delivered estrogen replacement therapy can also improve BMD. Alternatively, antiresorptive or anabolic therapy has been shown to improve BMD in a variety of conditions, the range of improvement (3%-16%) depending on skeletal site and the nature of the secondary cause. No studies were powered to demonstrate fracture reduction. The effects of bisphosphonates in childbearing women have been scantly studied and caution is needed.

CONCLUSION

The majority of PW with osteoporosis have an underlying disease. Specific therapy of these diseases, as well as antiresorptive and anabolic drugs, improve BMD, but without evidence of fracture reduction.

Bone Health in Children and Youth with Cystic Fibrosis: A Systematic Review and Meta-Analysis of Matched Cohort Studies

OBJECTIVE

To assess the evidence regarding the differences in areal bone mineral density (aBMD) between children and adolescents with cystic fibrosis (CF) compared with their healthy peers, based on data from longitudinal studies.

STUDY DESIGN

We searched MEDLINE, SPORTDiscus, the Cochrane Library, PEDro (Physiotherapy Evidence Database), and Embase databases. Observational studies addressing the change of aBMD in children with CF and healthy children and adolescents were eligible. The DerSimonian and Laird method was used to compute pooled estimates of effect sizes (ES) and 95% CIs for the change of whole body (WB), lumbar spine (LS), and femoral neck (FN) aBMD.

RESULTS

Six studies with participants with CF and 26 studies with healthy participants were included in the systematic review and meta-analysis. For the analysis in children with CF, the pooled ES for the change of WB aBMD was 0.29 (95% CI -0.15 to 0.74), for the change of LS aBMD was 0.13 (95% CI -0.16 to 0.41), and for the change of FN aBMD was 0.09 (95% CI -0.39 to 0.57). For the analysis in healthy children, the pooled ES for the change of WB aBMD was 0.37 (95% CI 0.26-0.49), for the change of LS aBMD was 0.13 (95% CI -0.16 to 0.41), and for the change of FN aBMD was 0.52 (95% CI 0.19-0.85).

CONCLUSIONS

aBMD development might not differ between children and adolescents with CF receiving medical care compared with their healthy peers. Further longitudinal studies in a CF population during growth and development are required to confirm our findings.

Long-term childhood body mass index and adult bone mass are linked through concurrent body mass index and body composition

Body mass plays a crucial role in the bone growth and development, but few studies have examined the association of long-term cumulative impact and trajectory patterns of childhood body mass index (BMI) with adult bone mass, and the mediation effect of adult BMI and body composition on these associations. A total of 397 Chinese adults (54.4%) who had been examined for BMI 4-8 times during childhood (6-19 years) and bone mass in adulthood (29-37 years), were included for analysis. Adult bone mineral content (BMC), areal bone mineral density (aBMD) and body composition were assessed via dual-energy x-ray absorptiometry. Childhood BMI growth curves were constructed using a random-effects mixed model. The area under the curve (AUC) was calculated to represent the long-term impact of childhood BMI. At baseline, 24.4%, 66.2%, 7.6% and 1.8% of the participants were underweight, normal weight, overweight and obese, respectively. Quadratic curve parameters of childhood BMI differed significantly between groups of adult whole body (WB) BMC, lumbar spine (LS) aBMD and femoral neck (FN) aBMD, with low BMC/aBMD groups having lower childhood BMI than the normal groups. AUC of childhood BMI was significantly and positively related to adult WB BMC and aBMD at each site, irrespective of sex. Significant mediation effects of adult BMI were shown on the association of childhood BMI AUC with adult WB BMC in males (52.0%) and FN aBMD in both sexes (males: 65.4%; females: 64.3%). Additionally, mediation effect of fat mass index was only noted on the association of childhood BMI AUC with adult WB BMC (41.3%), with a positive total indirect effect estimated at 0.118. The adult lean mass index, by contrast, mediated the childhood BMI-adult BMC/aBMD association positively at all sites in males (71.5%~89.2%) and at WB BMC in females (45.0%). These findings suggest that the impact of body weight on adult bones originates from childhood, which is mediated by concurrent BMI and body composition.

Clinical Considerations Regarding the Use of Obesity Pharmacotherapy in Adolescents with Obesity

A growing number of youth suffer from obesity and in particular severe obesity for which intensive lifestyle intervention does not adequately reduce excess adiposity. A treatment gap exists wherein effective treatment options for an adolescent with severe obesity include intensive lifestyle modification or metabolic and bariatric surgery while the application of obesity pharmacotherapy remains largely underutilized. These youth often present with numerous obesity-related comorbid diseases, including hypertension, dyslipidemia, prediabetes/type 2 diabetes, obstructive sleep apnea, nonalcoholic fatty liver disease, musculoskeletal problems, and psychosocial issues such as depression, anxiety, and social stigmatization. Current pediatric obesity treatment algorithms for pediatric primary care providers focus primarily on intensive lifestyle intervention with escalation of treatment intensity through four stages of intervention. Although a recent surge in the number of Food and Drug Administration-approved medications for obesity treatment has emerged in adults, pharmacotherapy options for youth remain limited. Recognizing treatment and knowledge gaps related to pharmacological agents and the urgent need for more effective treatment strategies in this population, discussed here are the efficacy, safety, and clinical application of obesity pharmacotherapy in youth with obesity based on current literature. Legal ramifications, informed consent regulations, and appropriate off-label use of these medications in pediatrics are included, focusing on prescribing practices and prescriber limits.

Update on bone density measurements and their interpretation in children and adolescents

Following the increased awareness about the central role of the pediatric age in building bone for life, clinicians face more than ever the necessity of assessing bone health in pediatric subjects at risk for early bone mass derangements or in healthy children, in order to optimize their bone mass accrual and prevent osteoporosis. Although the diagnosis of osteoporosis is not made solely upon bone mineral density measurements during growth, such determination can be very useful in the follow-up of pediatric patients with primary and secondary osteoporosis. The ideal instrument would give information on the mineral content and density of the bone, and on its architecture. It should be able to perform the measurements on the skeletal sites where fractures are more frequent, and it should be minimally invasive, accurate, precise and rapid. Unfortunately, none of the techniques currently utilized fulfills all requirements. In the present review, we focus on the pediatric use of dual-energy X-ray absorptiometry (DXA), quantitative computed tomography (QCT), peripheral QCT (pQCT), and magnetic resonance imaging (MRI), highlighting advantages and limits for their use and providing indications for bone densitometry interpretation and of vertebral fractures diagnosis in pediatric subjects.

Effects of Gymnastics Activities on Bone Accrual during Growth: A Systematic Review

The amount of bone gained during childhood and adolescence impacts greatly on lifetime skeletal health. The purpose of this review is to summarize current evidence of the effects of gymnastics activities on bone mineral accrual during growth and to describe possible factors that influence bone mineral gains. The PubMed and SportDiscus databases were searched, and a total of 24 articles met the selection criteria and were included in this review. Artistic and rhythmic gymnasts presented higher bone mineral density and content values compared to untrained controls, despite possible negative effects associated with hormonal levels, dietary restrictions and body fat. The results suggest that gymnasts had similar bone turnover values compared to untrained controls. High-intensity mechanical loading of gymnastics activity appears to increase bone development and counterbalance negative effects, such as later pubertal development, lower body fat mass and lower hormone levels. In conclusion, gymnasts present higher bone mineral values in comparison with untrained controls. The osteogenic effect of gymnastics athletic activity has a positive influence on bone mineral accrual and overcomes the possible negative influence of high athletic activity that may cause negative energy balance and low body fat mass which are associated with lower bone accrual.

Sexual Dimorphism and the Origins of Human Spinal Health

Recent observations indicate that the cross-sectional area (CSA) of vertebral bodies is on average 10% smaller in healthy newborn girls than in newborn boys, a striking difference that increases during infancy and puberty and is greatest by the time of sexual and skeletal maturity. The smaller CSA of female vertebrae is associated with greater spinal flexibility and could represent the human adaptation to fetal load in bipedal posture. Unfortunately, it also imparts a mechanical disadvantage that increases stress within the vertebrae for all physical activities. This review summarizes the potential endocrine, genetic, and environmental determinants of vertebral cross-sectional growth and current knowledge of the association between the small female vertebrae and greater risk for a broad array of spinal conditions across the lifespan.

Structural Strength Benefits Observed at the Hip of Premenarcheal Gymnasts Are Maintained Into Young Adulthood 10 Years After Retirement From the Sport

PURPOSE

Premenarcheal female gymnasts have been consistently found to have greater bone mass and structural advantages. However, little is known about whether these structural advantages are maintained after the loading stimulus is removed. Therefore, the purpose of this study was to investigate the structural properties at the hip after long-term retirement from gymnastics.

METHODS

Structural properties were derived from dual-energy X-ray absorptiometry scans using the hip structural analysis program for the same 24 gymnasts and 21 nongymnasts both in adolescence (8-15 y) and adulthood (22-30 y). Structural measures were obtained at the narrow neck, intertrochanter, and femoral shaft and included cross-sectional area, section modulus, and buckling ratio. Multivariate analysis of covariance was used to assess differences between groups in bone measures while controlling for size, age, maturity, and physical activity.

RESULTS

Gymnasts were found to have structural advantages at the narrow neck in adolescence (16% greater cross-sectional area, 17% greater section modulus, and 25% lower buckling ratio) and 14 years later (13% greater cross-sectional area and 26% lower buckling ratio). Benefits were also found at the intertrochanter and femoral shaft sites in adolescence and adulthood.

CONCLUSION

Ten years after retirement from gymnastics, former gymnasts' maintained significantly better hip bone structure than females who did not participate in gymnastics during growth.

Vertebral cross-sectional area: an orphan phenotype with potential implications for female spinal health

A high priority in imaging-based research is the identification of the structural basis that confers greater risk for spinal disorders. New evidence indicates that factors related to sex influence the fetal development of the axial skeleton. Girls are born with smaller vertebral cross-sectional area compared to boys-a sexual dimorphism that is present throughout life and independent of body size. The smaller female vertebra is associated with greater flexibility of the spine that could represent the human adaptation to fetal load. It also likely contributes to the higher prevalence of spinal deformities, such as exaggerated lordosis and progressive scoliosis in adolescent girls when compared to boys, and to the greater susceptibility for spinal osteoporosis and vertebral fractures in elderly women than men.

Estrogens and Androgens in Skeletal Physiology and Pathophysiology

Estrogens and androgens influence the growth and maintenance of the mammalian skeleton and are responsible for its sexual dimorphism. Estrogen deficiency at menopause or loss of both estrogens and androgens in elderly men contribute to the development of osteoporosis, one of the most common and impactful metabolic diseases of old age. In the last 20 years, basic and clinical research advances, genetic insights from humans and rodents, and newer imaging technologies have changed considerably the landscape of our understanding of bone biology as well as the relationship between sex steroids and the physiology and pathophysiology of bone metabolism. Together with the appreciation of the side effects of estrogen-related therapies on breast cancer and cardiovascular diseases, these advances have also drastically altered the treatment of osteoporosis. In this article, we provide a comprehensive review of the molecular and cellular mechanisms of action of estrogens and androgens on bone, their influences on skeletal homeostasis during growth and adulthood, the pathogenetic mechanisms of the adverse effects of their deficiency on the female and male skeleton, as well as the role of natural and synthetic estrogenic or androgenic compounds in the pharmacotherapy of osteoporosis. We highlight latest advances on the crosstalk between hormonal and mechanical signals, the relevance of the antioxidant properties of estrogens and androgens, the difference of their cellular targets in different bone envelopes, the role of estrogen deficiency in male osteoporosis, and the contribution of estrogen or androgen deficiency to the monomorphic effects of aging on skeletal involution.

Estrogens and Androgens in Skeletal Physiology and Pathophysiology

Estrogens and androgens influence the growth and maintenance of the mammalian skeleton and are responsible for its sexual dimorphism. Estrogen deficiency at menopause or loss of both estrogens and androgens in elderly men contribute to the development of osteoporosis, one of the most common and impactful metabolic diseases of old age. In the last 20 years, basic and clinical research advances, genetic insights from humans and rodents, and newer imaging technologies have changed considerably the landscape of our understanding of bone biology as well as the relationship between sex steroids and the physiology and pathophysiology of bone metabolism. Together with the appreciation of the side effects of estrogen-related therapies on breast cancer and cardiovascular diseases, these advances have also drastically altered the treatment of osteoporosis. In this article, we provide a comprehensive review of the molecular and cellular mechanisms of action of estrogens and androgens on bone, their influences on skeletal homeostasis during growth and adulthood, the pathogenetic mechanisms of the adverse effects of their deficiency on the female and male skeleton, as well as the role of natural and synthetic estrogenic or androgenic compounds in the pharmacotherapy of osteoporosis. We highlight latest advances on the crosstalk between hormonal and mechanical signals, the relevance of the antioxidant properties of estrogens and androgens, the difference of their cellular targets in different bone envelopes, the role of estrogen deficiency in male osteoporosis, and the contribution of estrogen or androgen deficiency to the monomorphic effects of aging on skeletal involution.

Pubertal timing and bone phenotype in early old age: findings from a British birth cohort study

Objectives: To investigate the effect of pubertal timing, assessed in adolescence, on bone size, strength and density in men and women in early old age.

Design: A British birth cohort study with prospective indicators of pubertal timing based on age at menarche, clinical assessment of pubertal stage, and growth tempo from serial height measures, and bone measures derived from peripheral quantitative computed tomography (pQCT) and dual-energy X-ray absorptiometry (DXA) at 60-64 years of age among 866 women and 792 men.

Methods: A first set of regression models investigated the relationships between pubertal timing and bone size, strength and density, adjusting for current height and weight, smoking and adult socioeconomic position. To make an equivalent comparison between men and women, the percentage difference in bone outcomes was calculated for a 5-year difference in age at menarche, and in men a comparison between those who were fully mature or pre-adolescent at 14.5 years. A second set of models investigated the percentage difference in bone outcomes for a 5-year difference in timing of peak height velocity (height tempo) derived from longitudinal growth modelling (Superimposition by Translation and Rotation model; SITAR).

Results: After adjustment for current height and weight, a 5-year increase in age at menarche was associated with an 8% [95% confidence interval (CI) -17%, 0.5%, P = 0.07) lower trabecular volumetric bone mineral density (vBMD); men who were pre-adolescent at 14.5 years had a 9%, (95% CI -14%, -4%; P = 0.001) lower trabecular vBMD compared with those who had been fully mature. Other confounders did not attenuate these estimates further. Patterns of association were similar but somewhat weaker for lumbar spine and total hip areal BMD. Age at peak height velocity was associated with even larger differences in BMD in men and women, and was negatively associated with bone size and strength.

Conclusions: The association between later puberty and lower BMD persists into early old age. The 9-10% lower trabecular vBMD in later compared with earlier maturers could be clinically important given a rate of bone loss from midlife of 1-2% a year and the negative association between BMD and fracture.

The Relationship Between Greater Prepubertal Adiposity, Subsequent Age of Maturation, and Bone Strength During Adolescence

This longitudinal study investigated whether greater prepubertal adiposity was associated with subsequent timing of maturation and bone strength during adolescence in 135 girls and 123 boys participating in the Iowa Bone Development Study. Greater adiposity was defined using body mass index (BMI) data at age 8 years to classify participants as overweight (OW, ≥85th percentile for age and sex) or healthy weight (HW). Maturation was defined as the estimated age of peak height velocity (PHV) based on a series of cross-sectional estimates. Measurements were taken at ages 11, 13, 15, and 17 years for estimates of body composition by dual-energy X-ray absorptiometry (DXA), bone compression (bone strength index), and torsion strength (polar strength-strain index) at the radius and tibia by pQCT, and femoral neck bending strength (section modulus) by hip structural analysis. Bone strength in OW versus HW were evaluated by fitting sex-specific linear mixed models that included centered age (visit age - grand mean age of cohort) as the time variable and adjusted for change in fat mass, and limb length in model 1. Analyses were repeated using biological age (visit age - age PHV) as the time variable for model 1 with additional adjustment for lean mass in model 2. BMI was negatively associated with age of maturation (p < 0.05). OW versus HW girls had significantly greater bone strength (p < 0.001) in model 1, whereas OW versus HW boys had significantly greater bone strength (p < 0.001) at the tibia and femoral neck but not radius (p > 0.05). Analyses were repeated using biological age, which yielded reduced parameter estimates for girls but similar results for boys (model 1.) Differences were no longer present after adjustment for lean mass (model 2) in girls (p > 0.05) whereas differences at the tibia were sustained in boys (p < 0.05). These findings demonstrate sex- and site-specific differences in the associations between adiposity, maturation, and bone strength. © 2016 American Society for Bone and Mineral Research.

Osteoporosis: Modern Paradigms for Last Century's Bones

The skeleton is a metabolically active organ undergoing continuously remodelling. With ageing and menopause the balance shifts to increased resorption, leading to a reduction in bone mineral density and disruption of bone microarchitecture. Bone mass accretion and bone metabolism are influenced by systemic hormones as well as genetic and lifestyle factors. The classic paradigm has described osteoporosis as being a “brittle bone” disease that occurs in post-menopausal, thin, Caucasian women with low calcium intakes and/or vitamin D insufficiency. However, a study of black women in Africa demonstrated that higher proportions of body fat did not protect bone health. Isoflavone interventions in Asian postmenopausal women have produced inconsistent bone health benefits, due in part to population heterogeneity in enteric bacterial metabolism of daidzein. A comparison of women and men in several Asian countries identified significant differences between countries in the rate of bone health decline, and a high incidence rate of osteoporosis in both sexes. These studies have revealed significant differences in genetic phenotypes, debunking long-held beliefs and leading to new paradigms in study design. Current studies are now being specifically designed to assess genotype differences between Caucasian, Asian, African, and other phenotypes, and exploring alternative methodology to measure bone architecture.

Endocrine disorders in adolescent and young female athletes: impact on growth, menstrual cycles, and bone mass acquisition

CONTEXT

Puberty is a crucial period of dramatic hormonal changes, accelerated growth, attainment of reproductive capacity, and acquisition of peak bone mass. Participation in recreational physical activity is widely acknowledged to provide significant health benefits in this period. Conversely, intense training imposes several constraints, such as training stress and maintenance of very low body fat to maximize performance. Adolescent female athletes are therefore at risk of overtraining and/or poor dietary intake, which may have several consequences for endocrine function. The "adaptive" changes in the hypothalamic-pituitary-gonadal, -adrenal, and somatotropic axes and the secretory role of the adipose tissue are reviewed, as are their effects on growth, menstrual cycles, and bone mass acquisition.

DESIGN

A systematic search on Medline between 1990 and 2013 was conducted using the following terms: "intense training," "physical activity," or "exercise" combined with "hormone," "endocrine," and "girls," "women," or "elite female athletes." All articles reporting on the endocrine changes related to intense training and their potential implications for growth, menstrual cycles, and bone mass acquisition were considered.

RESULTS AND CONCLUSION

Young female athletes present a high prevalence of menstrual disorders, including delayed menarche, oligomenorrhea, and amenorrhea, characterized by a high degree of variability according to the type of sport. Exercise-related reproductive dysfunction may have consequences for growth velocity and peak bone mass acquisition. Recent findings highlight the endocrine role of adipose tissue and energy balance in the regulation of homeostasis and reproductive function. A better understanding of the mechanisms whereby intense training affects the endocrine system may orient research to develop innovative strategies (ie, based on nutritional or pharmacological approaches and individualized modalities of training and competition) to improve the medical care of these adolescents and protect their reproductive function.

Pubertal timing, bone acquisition, and risk of fracture throughout life

Pubertal maturation plays a fundamental role in bone acquisition. In retrospective epidemiological surveys in pre- and postmenopausal women, relatively later menarcheal age was associated with low bone mineral mass and increased risk of osteoporotic fracture. This association was usually ascribed to shorter time exposure to estrogen from the onset of pubertal maturation to peak bone mass attainment. Recent prospective studies in healthy children and adolescents do not corroborate the limited estrogen exposure hypothesis. In prepubertal girls who will experience later menarche, a reduced bone mineral density was observed before the onset of pubertal maturation, with no further accumulated deficit until peak bone mass attainment. In young adulthood, later menarche is associated with impaired microstructural bone components and reduced mechanical resistance. This intrinsic bone deficit can explain the fact that later menarche increases fracture risk during childhood and adolescence. In healthy individuals, both pubertal timing and bone development share several similar characteristics including wide physiological variability and strong effect of heritable factors but moderate influence of environmental determinants such as nutrition and physical activity. Several conditions modify pubertal timing and bone acquisition, a certain number of them acting in concert on both traits. Taken together, these facts should prompt the search for common genetic regulators of pubertal timing and bone acquisition. It should also open epigenetic investigation avenues to pinpoint which environmental exposure in fetal and infancy life, such as vitamin D, calcium, and/or protein supplies, influences both pubertal timing and bone acquisition.

Compromised peak bone mass in patients with inflammatory bowel disease--a prospective study

OBJECTIVE

To evaluate peak bone mass attainment in children and adolescents with inflammatory bowel disease and to identify risk factors for suboptimal bone mass attainment.

STUDY DESIGN

We conducted a prospective follow-up study of 47 children and adolescents (24 males) with ulcerative colitis (n = 30) or Crohn's disease (n = 17). They were assessed for lumbar spine areal bone mineral density (aBMD) and for height-adjusted whole body less head bone mineral content (BMC); the values were corrected for bone age.

RESULTS

Altogether, 73% of the patients had completed pubertal development after the median follow-up time of over 5 years. Despite clinical inactivity of the disease in 70% of the patients at the follow-up visit, BMD or BMC Z-scores improved in none of the measurement sites. Lumbar spine aBMD Z-scores (mean difference [95% CI], -0.47 [-0.92 to -0.03]; P = .04) and whole body less head BMC height- and bone age-adjusted Z-scores (-0.52 [-1.01 to -0.02]; P = .04) decreased in patients who were pubertal at baseline and completed their pubertal development during the follow-up. Postpubertal patients had lower aBMD and BMC Z-scores in comparison with prepubertal and pubertal patients. Low lumbar spine aBMD (Z-score < -1.0) was associated with completed pubertal development, underweight, and greater lifetime cumulative weight-adjusted prednisolone dose. Vertebral fractures were detected in 3 patients (6%). One-fourth of the patients had insufficient serum 25-hydroxyvitamin D concentrations (<50 nmol/L).

CONCLUSIONS

The longitudinal follow-up over the pubertal years shows that inflammatory bowel disease poses a significant threat for bone health. The suboptimal peak bone mass attainment may have life-long consequences.

Quantitative computer tomography in children and adolescents: the 2013 ISCD Pediatric Official Positions

In 2007, International Society of Clinical Densitometry Pediatric Positions Task Forces reviewed the evidence for the clinical application of peripheral quantitative computed tomography (pQCT) in children and adolescents. At that time, numerous limitations regarding the clinical application of pQCT were identified, although its use as a research modality for investigation of bone strength was highlighted. The present report provides an updated review of evidence for the clinical application of pQCT, as well as additional reviews of whole body QCT scans of the central and peripheral skeletons, and high-resolution pQCT in children. Although these techniques remain in the domain of research, this report summarizes the recent literature and evidence of the clinical applicability and offers general recommendations regarding the use of these modalities in pediatric bone health assessment.

Specific bone mass acquisition in elite female athletes

CONTEXT

Cross-sectional studies have demonstrated that physical activity can improve bone mass acquisition. However, this design is not adequate to describe the specific kinetics of bone mass gain during pubertal development.

OBJECTIVE

To compare the kinetics of bone mass acquisition in female adolescent athletes of sports that impose different mechanical loads and untrained controls throughout puberty.

STUDY PARTICIPANTS

A total of 72 girls with ages ranging from 10.8 to 18.0 years were recruited: 24 rhythmic gymnasts (RG, impact activity group), 24 swimmers (SW, no-impact activity), and 24 age-matched controls (CON).

MAIN OUTCOME MEASURES

Areal bone mineral density (aBMD) was determined using dual-energy x-ray absorptiometry and bone turnover markers were analyzed. All the investigations were performed at baseline and after 1 year.

RESULTS

At baseline and after 1 year of follow-up, RG presented significantly greater aBMD adjusted for age, fat-free soft tissue, and fat mass compared with CON and SW, only at the femoral region. When aBMD variation throughout the pubertal period was modeled for each group from individual values, the aBMD at the femoral region was significantly higher in RG compared with the other 2 groups from 12.5 to 14 years, and this difference lasted up to 18 years. Moreover, the mean annual aBMD gain tended to be higher in RG compared with SW and CON only at the femoral region and this gain lasted longer in RG. Bone remodeling markers decreased similarly with age in the 3 groups.

CONCLUSIONS

This study, which was based on linear mixed models for longitudinal data, demonstrated that the osteogenic effect of gymnastics is characterized by greater bone mass gain localized at mechanically loaded bone (ie, the proximal femur) principally around the menarcheal period. Moreover, the bone mass gain lasts longer in gymnasts, which may be explained by the delay in sexual maturation.

Alterations of bone microstructure and strength in end-stage renal failure

End-stage renal disease (ESRD) patients have a high risk of fractures. We evaluated bone microstructure and finite-element analysis-estimated strength and stiffness in patients with ESRD by high-resolution peripheral computed tomography. We observed an alteration of cortical and trabecular bone microstructure and of bone strength and stiffness in ESRD patients.

INTRODUCTION

Fragility fractures are common in ESRD patients on dialysis. Alterations of bone microstructure contribute to skeletal fragility, independently of areal bone mineral density.

METHODS

We compared microstructure and finite-element analysis estimates of strength and stiffness by high-resolution peripheral quantitative computed tomography (HR-pQCT) in 33 ESRD patients on dialysis (17 females and 16 males; mean age, 47.0 ± 12.6 years) and 33 age-matched healthy controls.

RESULTS

Dialyzed women had lower radius and tibia cortical density with higher radius cortical porosity and lower tibia cortical thickness, compared to controls. Radius trabecular number was lower with higher heterogeneity of the trabecular network. Male patients displayed only a lower radius cortical density. Radius and tibia cortical thickness correlated negatively with bone-specific alkaline phosphatase (BALP). Microstructure did not correlate with parathyroid hormone (PTH) levels. Cortical porosity correlated positively with "Kidney Disease: Improving Global Outcomes" working group PTH level categories (r = 0.36, p < 0.04). BMI correlated positively with trabecular number (r = 0.4, p < 0.02) and negatively with trabecular spacing (r = -0.37, p < 0.03) and trabecular network heterogeneity (r = -0.4, p < 0.02). Biomechanics positively correlated with BMI and negatively with BALP.

CONCLUSION

Cortical and trabecular bone microstructure and calculated bone strength are altered in ESRD patients, predominantly in women. Bone microstructure and biomechanical assessment by HR-pQCT may be of major clinical relevance in the evaluation of bone fragility in ESRD patients.

Three-dimensional microarchitecture of adolescent cancellous bone

This study investigated microarchitectural, mechanical, collagen and mineral properties of normal adolescent cancellous bone, and compared them with adult and aging cancellous bone, to obtain more insight into the subchondral bone adaptations during development and growth. Twenty-three human proximal tibiae were harvested and divided into 3 groups according to their ages: adolescence (9 to 17 years, n=6), young adult (18 to 24 years, n=9), and adult (25 to 30 years, n=8). Twelve cubic cancellous bone samples with dimensions of 8×8×8 mm(3) were produced from each tibia, 6 from each medial and lateral condyle. These samples were micro-CT scanned (vivaCT 40, Scanco Medical AG, Switzerland) resulting in cubic voxel sizes of 10.5*10.5*10.5 μm(3). Microarchitectural properties were calculated. The samples were then tested in compression followed by collagen and mineral determination. Interestingly, the adolescent cancellous bone had similar bone volume fraction (BV/TV), structure type (plate, rod or mixtures), and connectivity (3-D trabecular networks) as the adult cancellous bone. The adolescent cancellous bone had significantly lower bone surface density (bone surface per total volume of specimen) but higher collagen concentration (collagen weight per dry weight of specimen) than the adult cancellous bone; and significant greater trabecular separation (mean distance between trabeculae), significant lower trabecular number (number of trabeculae per volume), tissue density (dry weight per volume of bone matrix excluding marrow space) and mineral concentration (ash weight per dry weight of specimen) than the young adult and adult cancellous bones. Despite these differences, ultimate stress and failure energy were not significantly different among the three groups, only the Young's modulus in anterior-posterior direction was significantly lower in adolescence. Apparent density appears to be the single best predictor of mechanical properties. In conclusion, adolescent cancellous bone has similar bone volume fraction, structure type, and connectivity as the young adult and adult cancellous bones, and significant lower tissue density, bone surface density and mineral concentration but higher collagen concentration than in the young adult and adult bone. Despite these differences, the mechanical properties did not show significant difference among the three groups except less stiffness in anterior-posterior direction in the adolescents.

Cortical consolidation of the radius and tibia in young men and women

CONTEXT

Bone size, geometry, density, and microarchitecture are important determinants of bone strength. By understanding how these properties change during skeletal development, we can better understand bone fragility.

OBJECTIVES

The aim of the study was to compare the geometry, microarchitecture, and strength of the radius and tibia in men and women at the end of adolescence and in young adulthood and to relate these properties to biochemical bone turnover markers and bone regulatory hormones.

DESIGN

We conducted a cross-sectional study of 116 healthy men and women ages 16-18 (n = 56) and 30-32 (n = 60) yr.

OUTCOME MEASURES

We used high-resolution peripheral quantitative computed tomography to measure bone size, geometry, and microarchitecture at the distal radius and tibia and micro-finite element modeling to estimate bone strength. We measured bone turnover markers (β C-terminal telopeptide of type I collagen and amino-terminal propeptide of type I procollagen) and hormones known to affect bone metabolism (estradiol, testosterone, IGF-I, and PTH).

RESULTS

Bone strength was greater in men than in women, and at the radius it was greater in men ages 30-32 yr than ages 16-18 yr. The gender difference was due to greater cortical perimeter, trabecular area, and trabecular density in men. The age difference was due to greater cortical thickness and cortical tissue mineral density and lower cortical porosity. IGF-I was related to two of these five key properties at the radius (cortical perimeter and cortical thickness). None of the hormones were predictors of density or structure at the tibia.

CONCLUSIONS

Cortical modeling of long bones continues beyond the end of adolescence. IGF-I may be a determinant of this process at the radius.

Heterogeneous glycation of cancellous bone and its association with bone quality and fragility

Non-enzymatic glycation (NEG) and enzymatic biochemical processes create crosslinks that modify the extracellular matrix (ECM) and affect the turnover of bone tissue. Because NEG affects turnover and turnover at the local level affects microarchitecture and formation and removal of microdamage, we hypothesized that NEG in cancellous bone is heterogeneous and accounts partly for the contribution of microarchitecture and microdamage on bone fragility. Human trabecular bone cores from 23 donors were subjected to compression tests. Mechanically tested cores as well as an additional 19 cores were stained with lead-uranyl acetate and imaged to determine microarchitecture and measure microdamage. Post-yield mechanical properties were measured and damaged trabeculae were extracted from a subset of specimens and characterized for the morphology of induced microdamage. Tested specimens and extracted trabeculae were quantified for enzymatic and non-enzymatic crosslink content using a colorimetric assay and Ultra-high Performance Liquid Chromatography (UPLC). Results show that an increase in enzymatic crosslinks was beneficial for bone where they were associated with increased toughness and decreased microdamage. Conversely, bone with increased NEG required less strain to reach failure and were less tough. NEG heterogeneously modified trabecular microarchitecture where high amounts of NEG crosslinks were found in trabecular rods and with the mechanically deleterious form of microdamage (linear microcracks). The extent of NEG in tibial cancellous bone was the dominant predictor of bone fragility and was associated with changes in microarchitecture and microdamage.