Current concepts in pediatric bone disease

Overview of Traditional and Environmental Factors Related to Bone Health

Bone mass in adulthood depends on growth and mineralization acquired during childhood and adolescence. It is well known that these stages of life are crucial for bone development, where genetic, nutritional, hormonal, and lifestyle factors play a significant role. Bone loss is normally a natural and slow process that begins years later after the peak bone mass is achieved and continues throughout the lifespan. Lifestyle choices in childhood and adolescence such as minimal physical activity, excessive caffeine or carbonated beverages intake, malnutrition, cigarette use, or high alcohol consumption and other factors like environmental pollutants can also negatively affect bone health and accelerate the bone loss process. The aim of this work is an overview of risk factors associated with inadequate bone health in early life.

Bone Health in Pediatric Patients with IBD: What Is New?

PURPOSE OF THE REVIEW

Patients with inflammatory bowel disease (IBD) have increased bone fragility, demonstrated by increased fracture risk, and often have low bone density and altered bone geometry, but the underlying pathophysiology remains poorly understood.

RECENT FINDINGS

Children and adolescents with IBD appear to have decreased bone formation, at diagnosis, which frequently improves with treatment of their underlying IBD. There is a growing body of evidence regarding how the immune system interacts with bone metabolism. There are likely multi-factorial etiologies that contribute to suboptimal bone accrual and subsequent lack of peak bone mass attainment in growing patients with IBD. There appears to be differential effects dependent upon IBD sub-type and bone compartment. Pediatric patients with IBD require recognition of several risk factors that may adversely impact their bone accrual. Future studies are necessary to further delineate the effects of IBD on pediatric bone health.

Dual-energy X-ray absorptiometry bone densitometry in pediatrics: a practical review and update

The assessment of pediatric bone mineral content and density is an evolving field. In this manuscript we provide a practical review and update on the interpretation of dual-energy X-ray absorptiometry (DXA) in pediatrics including historical perspectives as well as a discussion of the recently published 2019 Official Position Statements of the International Society of Clinical Densitometry (ISCD) that apply to children.

Exercise Capacity in Pediatric Patients with End-Stage Renal Disease

Objective

To evaluate the correlation between exercise capacity and hemoglobin in pediatric patients with end-stage renal disease (ESRD) treated with automated peritoneal dialysis (APD) and hemodialysis.

Design

Prospective case-control study and retrospective review.

Setting

Dialysis summer camp and Children's Mercy Hospital exercise laboratory.

Participants

Prospective evaluation conducted with 14 patients (9 males, mean age 14.5 ± 2.5 years) who received either home APD (5 patients) or in-center hemodialysis (9 patients), and 8 healthy age-matched controls. Retrospective data derived from 10 children (7 males, mean age 12.3 ± 3.3 years), all of whom received APD.

Intervention

Maximal treadmill evaluation conducted with each patient and control. The hemoglobin value of each patient was also assessed.

Main Outcome Measures

Comparison of the following data generated during treadmill protocol: peak heart rate, blood pressure, oxygen saturation, treadmill time, oxygen consumption (VO2), ventilation (Ve), oxygen consumption at anaerobic threshold (VO2 AT), and respiratory exchange ratio.

Results

The hemoglobin value of the current patient group (12.8 ± 1.6 g/dL) was significantly greater than the previously studied patients (10.5 ± 1.1 g/dL) ( p = 0.001). Treadmill time, VO2, and VO2 AT were significantly lower in both groups of dialysis patients compared to the control subjects ( p < 0.05). No differences were noted in any of these variables when comparing these two groups of dialysis patients only.

Conclusion

The exercise capacity of pediatric dialysis patients is significantly poorer than that of healthy children, an outcome apparently related to factors other than normalization of the hemoglobin value.

Bone mineral density and vitamin D status in children with remission phase of steroid-sensitive nephrotic syndrome

Children with idiopathic nephrotic syndrome are primarily treated with glucocorticoids (GCs), but long-term GC use can lead to undesired side effects. We investigated the bone mineral density (BMD) and 25-hydroxyvitamin D (25-OH D) levels in children with the remission phase of steroid-sensitive nephrotic syndrome (SSNS). This study included 32 patients with SSNS who had not received GC treatment in the last 6 months and a control group of 20 healthy children. Serum levels of calcium, phosphate, alkaline phosphatase, 25-(OH)D, and parathyroid hormone (PTH) were measured. BMD was determined in the lumbar spinal region using dual-energy X-ray absorptiometry (DEXA). Serum 25-(OH)D levels were lower in the SSNS patients than in the healthy children (P <0.05), with 22 patients (68.8%) having Z-scores <-1. The Z-scores were positively correlated with 25-(OH)D levels (r = 0.424, P <0.05). PTH levels were higher in patients with osteoporosis than in patients with Z-scores ≥-1 (P <0.05). Bone mineral content and BMD were positively correlated with the age of diagnosis (P <0.01). Receiver-operating characteristic curve analysis showed that the cutoff value of 25-(OH)D levels for predicting low BMD was 14.67 ng/mL with a sensitivity of 90% and a specificity of 64%. The area under the curve (AUC ± standard error) was 0.868 ± 0.064 (95% confidence interval: 0.742-0.994, P = 0.001). Decreased 25-(OH)D levels and the negative effects of long-term GC treatment on BMD persist in SSNS remission phase. Levels of 25-(OH)D <14.67 ng/mL could predict abnormal DEXA scans in children with SSNS remission phase.

Grip strength cutpoints for youth based on a clinically relevant bone health outcome

The National Academy of Medicine recommends the handgrip for school-based surveillance of muscle strength for bone health. We established grip strength cutpoints that are linked to bone health in both US and European youth. These cutpoints could serve as a potential set of standards for surveillance and clinical applications.

PURPOSE

The U.S. National Academy of Medicine and experts in Europe recommend the use of grip strength as a valuable and accessible musculoskeletal fitness measure due to its association with bone health. This is the first study to facilitate this recommendation by developing bone health-related grip strength cutpoints for youth based on empirical associations with the well accepted marker of bone development, i.e., height-adjusted total body less head bone mineral content (TBLH_BMC).

METHODS

A purposive sample of healthy youth from Midwest USA (n = 433 youth; 14.1 ± 2.3 years; 1998-2004) and a random sample of healthy adolescents from Zaragoza, Spain (n = 355 youth; 14.9 ± 1.2 years; 2006-2007) were used to develop and test cut-points. Participants' grip strength was measured using a hand-held dynamometer while height-adjusted TBLH_BMC was determined using dual-energy x-ray absorptiometry. Grip strength scores were linked to TBLH_BMC using receiver operator characteristic curves, and grip strength cutpoints were tested based on the area under the curve (AUC), sensitivity (Se), specificity (Sp), and predictive odds ratios. All analyses were conducted in 2016.

RESULTS

The AUC approximated or exceeded 0.80 for grip strength cutpoints, and the associated Se and Sp indices ranged from 53.6 to 92.5%. Sensitivity and Sp remained similar in the validation sample and those not meeting the grip strength cutpoints were five to eight times more likely to have insufficient TBLH_BMC, depending on their sex and cutpoint being considered.

CONCLUSIONS

Grip strength is strongly related to TBLH_BMC, and the proposed cutpoints demonstrated acceptable classification accuracy for screening healthy youth and tracking healthy bone development in community settings. The utility of the cutpoints should be further examined in more diverse populations of youth.

Clinical and biochemical characteristics and bone mineral density of homozygous, compound heterozygous and heterozygous carriers of three novel IGFALS mutations

OBJECTIVE

Acid-labile subunit (ALS) deficiency (ACLSD), caused by homozygous or compound heterozygous IGFALS mutations, is associated with moderate short stature, delayed puberty, low serum IGF-I and ALS and extremely low serum IGFBP-3. Its effect on birth weight, head circumference, bone mineral density (BMD), serum IGF-II and IGFBP-2 is uncertain, as well as the phenotype of heterozygous carriers of IGFALS mutations (partial ACLSD).

DESIGN

From all available members of five Turkish families, carrying three mutations in exon 2 of IGFALS (c.1462G > A, p.Asp488Asn (families A, B, E); c.251A > G, p.Asn84Ser (families C and E) and c.1477del, p.Arg493fs (family D)), clinical, laboratory and BMD data were collected.

METHODS

Auxological and biochemical findings were expressed as SDS for age and gender. Ternary complex formation in serum was investigated by size-exclusion chromatography. BMD using DXA bone densitometry was adjusted for height and age (Ha-BMD z-score).

RESULTS

In ACLSD (n = 24), mean ± s.d. height SDS (-2.7 ± 1.2), head circumference SDS (-2.3 ± 0.5) and body mass index (BMI) (-0.6 ± 1.0 SDS) were lower than those in partial ACLSD (n = 26, P ≤ 0.01) and birth weight SDS (n = 7) tended to be lower (-2.2 ± 1.1 vs -0.6 ± 0.3 in partial ACLSD (P = 0.07)). Serum IGF-I was -3.7 ± 1.4 vs -1.0 ± 1.0, IGF-II: -5.6 ± 0.7 vs -1.3 ± 0.7, ALS: <-4.4 ± 1.2 vs -2.1 ± 0.9 and IGFBP-3: -9.0 ± 1.9 vs -1.6 ± 0.8 SDS respectively (P < 0.001). Ha-BMD z-score was similar and normal in both groups.

CONCLUSIONS

To the known phenotype of ACLSD (i.e. short stature, reduced serum levels of IGF-I and ALS, extremely low serum IGFBP-3 and disturbed ternary complex formation), we add reduced birth weight, head circumference and serum IGF-II.

Genetics of pediatric bone strength

Osteoporosis is one of the most common chronic forms of disability in postmenopausal women and represents a major health burden around the world. Bone fragility is affected by bone mineral density (BMD), and, one of the most important factors in preventing osteoporosis is optimizing peak bone mass, which is achieved during growth in childhood and adolescence. BMD is a complex trait resulting from environmental and genetic factors. Genome-wide association studies have discovered robust genetic signals influencing BMD in adults, and similar studies have also been conducted to investigate the genetics of BMD in the pediatric setting. These latter studies have revealed that many adult osteoporosis-related loci also regulate BMD during growth. These investigations have the potential to profoundly impact public health and will allow for the eventual development of effective interventions for the prevention of osteoporosis.

Vitamin D in incident nephrotic syndrome: a Midwest Pediatric Nephrology Consortium study

BACKGROUND

Cross-sectional studies of children with prevalent nephrotic syndrome (NS) have shown 25-vitamin D (25(OH)D) deficiency rates of 20-100 %. Information on 25(OH)D status in incident patients or following remission is limited. This study aimed to assess 25(OH)D status of incident idiopathic NS children at presentation and longitudinally with short-term observation.

METHODS

Multicenter longitudinal study of children (2-18 years old) from 14 centers across the Midwest Pediatric Nephrology Consortium with incident idiopathic NS. 25(OH)D levels were assessed at diagnosis and 3 months later.

RESULTS

Sixty-one children, median age 5 (3, 11) years, completed baseline visit and 51 completed second visit labs. All 61 (100 %) had 25(OH)D < 20 ng/ml at diagnosis. Twenty-seven (53 %) had 25(OH)D < 20 ng/ml at follow-up. Fourteen (28 %) children were steroid resistant. Univariate analysis showed that children prescribed vitamin D supplements were less likely to have 25(OH)D deficiency at follow-up (OR 0.2, 95 % CI 0.04, 0.6). Steroid response, age, and season did not predict 25(OH)D deficiency. Multivariable linear regression modeling showed higher 25(OH)D levels at follow-up by 13.2 ng/ml (SE 4.6, p < 0.01) in children supplemented with vitamin D.

CONCLUSIONS

In this incident idiopathic NS cohort, all children at diagnosis had 25(OH)D deficiency and the majority continued to have a deficiency at 2-4 months. Supplemental vitamin D decreased the odds of 25(OH)D deficiency at follow-up, supporting a role for supplementation in incident NS.

Effect of glucocorticoids on growth and bone mineral density in children with nephrotic syndrome

Glucocorticosteroids (GCs) are the first-line treatment for idiopathic nephrotic syndrome (NS), but prolonged administration interferes with growth and bone mineralization. We conducted a retrospective study to analyze the long-term impact of prednisone on growth and bone mineral density (BMD) in children with NS. Data from children with NS followed during almost 10 years were analyzed. Height and spine BMD values were converted to Z-scores (standard deviation [SD]). The mean cumulative dose of GCs received was calculated and correlated to patient's growth and spine BMD using linear regression and subgroup analysis. We included 30 patients diagnosed at 3.7 years old (interquartile range (IQR) 2.6-4.8) and followed over 9.8 years (IQR 6.6-11.7). The one half of NS patients was steroid sensitive and one half dependent or resistant. The median cumulative dose of GCs received was 0.27 mg/kg/day (IQR 0.18-0.35). Growth and spine BMD were both negatively associated with the cumulative dose of GCs (P=0.001 and P=0.037, respectively). Final height Z-scores were significantly lower in patients receiving >0.2 mg/kg/day GCs (P=0.001). No difference was observed in spine BMD between subgroups.

CONCLUSION

Increasing doses of GCs were significantly associated with lower height and BMD Z-scores. A significant effect on growth was observed with cutoff doses above 0.2 mg/kg/day.

Low-dose combined oral contraceptive use is associated with lower bone mineral content variation in adolescents over a 1-year period

BACKGROUND

Low-dose combined oral contraceptives (COCs) can interfere with bone mass acquisition during adolescence. This study aimed to evaluate bone mineral density (BMD) and bone mineral content (BMC) in female adolescents taking a standard low-dose COC (ethinylestradiol 20 μg/desogestrel 150 μg) over a 1-year period and to compare their data with those of healthy adolescents from the same age group not taking COCs.

METHODS

This was a non-randomized parallel-control study with a 1-year follow-up. Sixty-seven adolescents aged from 12 to 19 years, divided into COC users (n = 41) taking 20 μg ethinylestradiol/150 μg desogestrel and COC non-user controls (n = 26), were evaluated by bone densitometry examinations at baseline and after 12 months. Comparisons between the groups at the study onset were performed using the Mann-Whitney test with the significance level fixed at 5% or p < 0.05. Comparisons between the groups at the study onset and after 12 months were based on variations in the median percentages for bone mass variables.

RESULTS

The COC users presented with low bone mass acquisition in the lumbar spine, and had BMD and BMC median variations of 2.07% and +1.57%, respectively, between the measurements at baseline and 12 months. The control group had median variations of +12.16% and +16.84% for BMD and BMC, respectively, over the same period. The total body BMD and BMC showed similar evolutions during the study in both groups. Statistical significance (p < 0.05) was seen for the BMC percentage variation between COC users and non-users.

CONCLUSIONS

Use of a low-dose COC (ethinylestradiol 20 μg/desogestrel 150 μg) was associated with lower bone mass acquisition in adolescents during the study period.

TRIAL REGISTRATION

Registry Number, RBR-5h9b3c.

Endocrinopathies in children infected with human immunodeficiency virus

Endocrine changes (including adrenal insufficiency, disorders of growth and puberty, thyroid dysfunction, metabolic abnormalities and osteopenia) accompany human immunodeficiency virus (HIV) infection in pediatric patients. The cause of these changes is multifactorial and includes direct viral effects of HIV, and effects of antiretroviral therapy. These effects may be of particular importance in childhood given the critical developmental processes that occur during this time period and the likelihood of prolonged exposure to the virus and medications.

Treatment of osteoporosis in children with glucocorticoid-treated diseases

Glucocorticoid induced osteoporosis (GIO) is the most frequent form of drug induced osteoporosis. Glucocorticoids affect osteoblastogenesis, osteoclastogenesis and promote the apoptosis of osteoblasts and osteocytes. A decrease of bone mineral density has been described in several pediatric diseases that require glucocorticoids, both as long-term replacement therapy, such as Congenital Adrenal Hyperplasia, and as treatment of acute phase or relapses, such as asthma, juvenile rheumatoid arthritis, inflammatory bowel diseases, systemic lupus erythematosus, organ transplantation and Steroid Sensitive Nephrotic Syndrome. The increasing number of children with GIO and at risk of fractures reflects the complex nature of this condition, and the need of development of anti-osteoporotic drugs. In this review, we focus on the mechanisms of GIO in some pediatric diseases and on treatment of osteoporosis. We also report data on new signaling pathways as potential targets for future anti-osteoporotic drugs.

Calcium and vitamin D for osteoprotection in children with new-onset nephrotic syndrome treated with steroids: a prospective, randomized, controlled, interventional study

BACKGROUND

There are no robust guidelines on strategies to prevent the adverse skeletal effects of glucocorticoids in children.

OBJECTIVES

To evaluate the role of prophylactic calcium and vitamin D on bone health in children with new-onset nephrotic syndrome (NS) treated with short-term (12 weeks), high-dose glucocorticoids.

METHODS

Prospective, randomized, controlled, single blind, interventional study conducted on 41 steroid-naïve pre-pubertal children (29 boys, 12 girls). All children received prednisolone for 12 weeks (60 mg/m(2)/day daily for 6 weeks, followed by 40 mg/m(2)/day alternate days for 6 weeks). Recruited children were randomized into the intervention group (IG; vitamin D 1,000 IU/day and elemental calcium 500 mg/day) and the control group (CG). Bone mineral content (BMC) and bone mineral density (BMD) at the lumbar spine (L1-L4) were estimated at baseline and at 12 weeks. Mean percentage changes in BMC and BMD in IG and CG were compared.

RESULTS

Children in the IG showed an increase of 11.2 % in BMC versus the CG, who showed an 8.9 % fall (p < 0.0001). Net intervention-attributable difference in BMC was 20.1 %. BMD increased in both groups (IG 2.8 % vs CG 0.74 %), but the difference was not statistically significant (p = 0.27).

CONCLUSIONS

Short-term, high-dose glucocorticoid therapy decreases the BMC of the lumbar spine in steroid-naïve children with NS. Vitamin D and calcium co-administration not only prevents this decline, but also enhances BMC of the lumbar spine.

Evaluation of bone mineral status in adolescent idiopathic scoliosis

Background

Several reports have suggested low bone mineral density (BMD) in patients with adolescent idiopathic scoliosis (AIS). We determined bone mineral status in patients with AIS to evaluate the effect of brace treatment on BMD.

Methods

BMD was measured in 46 patients (mean age, 17.8 ± 4.9 years) with AIS (17 with brace and 29 without brace) by dual-energy X-ray absorptiometry scan and compared the results to an age-matched (mean age, 16.6 ± 3.9 years) control group (n = 54).

Results

The AIS group had significantly lower bone mass at the lumbar spine (Z-score, -1.500 vs. -0.832) and hip (Z-score, -1.221 vs. -0.754) except at the femoral neck. No difference in BMD was found between patients with AIS who used a brace and those who did not.

Conclusions

The results confirmed that BMD was low in AIS patients and it was not affected by brace treatment.

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.

Diagnostic evaluation of bone densitometric size adjustment techniques in children with and without low trauma fractures

Several established methods are used to size adjust dual-energy X-ray absorptiometry (DXA) measurements in children. However, there is no consensus as to which method is most diagnostically accurate. All size-adjusted bone mineral density (BMD) values were more diagnostically accurate than non-size-adjusted values. The greatest odds ratio was estimated volumetric BMD for vertebral fracture.

INTRODUCTION

The size dependence of areal bone density (BMDa) complicates the use of DXA in children with abnormal stature. Despite several size adjustment techniques being proposed, there is no consensus as to the most appropriate size adjustment technique for estimating fracture risk in children. The aim of this study was to establish whether size adjustment techniques improve the diagnostic ability of DXA in a cohort of children with chronic diseases.

METHODS

DXA measurements were performed on 450 children, 181 of whom had sustained at least one low trauma fracture. Lumbar spine (L2-L4) and total body less head (TBLH) Z-scores were calculated using different size adjustment techniques, namely BMDa and volumetric BMD for age (bone mineral apparent density (BMAD)); bone mineral content (BMC) and bone area for height; BMC for bone area; BMC for lean mass (adjusted for height); and BMC for bone and body size.

RESULTS

Unadjusted L2-L4 and TBLH BMDa were most sensitive but least specific at distinguishing children with fracture. All size adjustments reduced sensitivity but increased post-test probabilities, from a pre-test probability of 40 % to between 58 and 77 %. The greatest odds ratio for fracture was L2-L4 BMAD for a vertebral fracture and TBLH for lean body mass (LBM) (adjusted for height) for a long bone fracture with diagnostic odds ratios of 9.3 (5.8-14.9) and 6.5 (4.1-10.2), respectively.

CONCLUSION

All size adjustment techniques improved the predictive ability of DXA. The most accurate method for assessing vertebral fracture was BMAD for age. The most accurate method for assessing long bone fracture was TBLH for LBM adjusted for height.

Bone mineral density estimated by osteorisk in patients with adolescent idiopathic scoliosis

OBJECTIVE:

The prevalence of osteoporosis in patients with Adolescent Idiopathic Scoliosis (AIS) is believed to be higher than in the general adolescent population. An alternative to radiology for the characterization of bone mineral density may be through correlative indexes like the Osteorisk index, which is easy to access and low in cost, and which helps the doctor in the request for Bone Densitometry. Our belief that osteoporosis can affect the evolution and treatment of AIS was what motivated us to conduct this study. Our objective was to subjectively evaluate bone mineral density by the Osteorisk index in patients with AIS.

METHODS:

Healthy patients (control group, n=30) and patients with AIS (n = 30) were evaluated, documenting age, weight and height, and establishing the Osteorisk. The unpaired Student t test was performed, with a level of significance of p <0.05.

RESULTS:

The mean Osteorisk found for the patients with AIS was 6.38 ± 2.2 while in the control group, it was 8.27 ± 2.14, which represents a low risk of developing osteoporosis in both groups. Comparing these means between the groups, a lower Osteorisk was observed in the AIS group.

CONCLUSION:

Our study showed that there is low risk of developing osteoporosis in patients with AIS. Level of Evidence I, Prospective study.

Human biology at the interface of paediatrics: measuring bone mineral accretion during childhood

BACKGROUND

Professor Tanner established a paradigm for the study of growth and development that demands precise growth measurements, description of normal variability through development to adulthood, consideration of the effects of tempo and the study of factors that influence growth outcomes. The relatively new field of paediatric bone health assessment fits this paradigm and reflects the collaboration of human biologists and paediatricians in understanding the growth of the human skeleton.

REVIEW

This review describes the reasons for clinical assessment of bone density in children, the technological developments in bone health assessment in children, the development of reference curves and the effects of growth, body composition, pubertal timing, genetics and lifestyle on bone health outcomes.

Quantitative computed tomography and computed tomography in children

Quantitative computed tomography (QCT) methodologies have been instrumental in deepening our understanding of bone acquisition and strength during childhood. Important publications in the last year have drawn attention to the functional muscle-bone unit, showing that factors such as population ancestry, bone size, and muscle composition are additional dimensions of bone strength that affect muscle-bone relationships. The role of adiposity in pediatric bone health is complex and may vary by sex, puberty stage, and degree of obesity. Several new studies have demonstrated the association of peripheral QCT (pQCT) outcomes with fracture, although pQCT outcomes are not superior to dual-energy x-ray absorptiometry measures in this regard. New high-resolution pQCT studies document transient weakness in mid-puberty that coincides developmentally with the period of peak fracture incidence. These new studies will ultimately help us understand the development of sex differences in bone strength that emerge in adolescence.

Mechanism of osteoporosis in adolescent idiopathic scoliosis: experimental scoliosis in pinealectomized chickens

To clarify the mechanism of osteoporosis in adolescent idiopathic scoliosis (AIS), we investigated radiological and histological changes in the cervical vertebrae of a chicken thoracic scoliosis model. Forty newly hatched broiler chicks were randomly divided into four equal groups: sham-operated chickens serving as control (CON), pinealectomized chickens (PNX), sham-operated (CON + MLT) and pinealectomized chickens (PNX + MLT) that received intraperitoneal administration of melatonin. Pinealectomy was performed at the age of 3 days, and the chickens were killed at 2 months of age. Postmortem X-rays were examined for the presence of scoliosis, and micro-computed tomography (micro-CT) images were taken to evaluate the microstructure of the cervical vertebrae. Histological specimens of the scanned cervical vertebra were prepared, and a midsagittal section was stained with hematoxylin and eosin and tartrate-resistant acid phosphatase to evaluate the numbers of osteoblasts and osteoclasts, respectively. Scoliosis developed at the thoracic spine in all chickens of the PNX and in two of the PNX + MLT group. Micro-CT data revealed that chickens in the PNX group had a greater degree of generalized osteoporosis compared with the other birds. The number of osteoblasts was significantly decreased in the PNX group, while no significant difference was observed among chickens in the numbers of osteoclasts. Our results suggest that melatonin deficiency reduces osteoblast proliferation and leads to the development of scoliosis and osteoporosis. The restoration of melatonin prevented the development of scoliosis and osteoporosis, indicating that melatonin levels may be crucial to the development of deformity and osteoporosis in AIS.

Obstacles in the optimization of bone health outcomes in the female athlete triad

Maintaining low body weight for the sake of performance and aesthetic purposes is a common feature among young girls and women who exercise on a regular basis, including elite, college and high-school athletes, members of fitness centres, and recreational exercisers. High energy expenditure without adequate compensation in energy intake leads to an energy deficiency, which may ultimately affect reproductive function and bone health. The combination of low energy availability, menstrual disturbances and low bone mineral density is referred to as the 'female athlete triad'. Not all athletes seek medical assistance in response to the absence of menstruation for 3 or more months as some believe that long-term amenorrhoea is not harmful. Indeed, many women may not seek medical attention until they sustain a stress fracture. This review investigates current issues, controversies and strategies in the clinical management of bone health concerns related to the female athlete triad. Current recommendations focus on either increasing energy intake or decreasing energy expenditure, as this approach remains the most efficient strategy to prevent further bone health complications. However, convincing the athlete to increase energy availability can be extremely challenging. Oral contraceptive therapy seems to be a common strategy chosen by many physicians to address bone health issues in young women with amenorrhoea, although there is little evidence that this strategy improves bone mineral density in this population. Assessment of bone health itself is difficult due to the limitations of dual-energy X-ray absorptiometry (DXA) to estimate bone strength. Understanding how bone strength is affected by low energy availability, weight gain and resumption of menses requires further investigations using 3-dimensional bone imaging techniques in order to improve the clinical management of the female athlete triad.

Revised reference curves for bone mineral content and areal bone mineral density according to age and sex for black and non-black children: results of the bone mineral density in childhood study

CONTEXT

Deficits in bone acquisition during growth may increase fracture risk. Assessment of bone health during childhood requires appropriate reference values relative to age, sex, and population ancestry to identify bone deficits.

OBJECTIVE

The objective of this study was to provide revised and extended reference curves for bone mineral content (BMC) and areal bone mineral density (aBMD) in children.

DESIGN

The Bone Mineral Density in Childhood Study was a multicenter longitudinal study with annual assessments for up to 7 yr.

SETTING

The study was conducted at five clinical centers in the United States.

PARTICIPANTS

Two thousand fourteen healthy children (992 males, 22% African-Americans) aged 5-23 yr participated in the study.

INTERVENTION

There were no interventions.

MAIN OUTCOME MEASURES

Reference percentiles for BMC and aBMD of the total body, lumbar spine, hip, and forearm were obtained using dual-energy x-ray absorptiometry for Black and non-Black children. Adjustment factors for height status were also calculated.

RESULTS

Extended reference curves for BMC and aBMD of the total body, total body less head, lumbar spine, total hip, femoral neck, and forearm for ages 5-20 yr were constructed relative to sex and age for Black and non-Black children. Curves are similar to those previously published for 7-17 year olds. BMC and aBMD values were greater for Black vs. non-Black children at all measurement sites.

CONCLUSIONS

We provide here dual-energy x-ray absorptiometry reference data on a well-characterized cohort of 2012 children and adolescents. These reference curves provide the most robust reference values for the assessment and monitoring of bone health in children and adolescents in the literature to date.

Height adjustment in assessing dual energy x-ray absorptiometry measurements of bone mass and density in children

CONTEXT

In children, bone mineral content (BMC) and bone mineral density (BMD) measurements by dual-energy x-ray absorptiometry (DXA) are affected by height status. No consensus exists on how to adjust BMC or BMD (BMC/BMD) measurements for short or tall stature.

OBJECTIVE

The aim of this study was to compare various methods to adjust BMC/BMD for height in healthy children.

DESIGN

Data from the Bone Mineral Density in Childhood Study (BMDCS) were used to develop adjustment methods that were validated using an independent cross-sectional sample of healthy children from the Reference Data Project (RDP).

SETTING

We conducted the study in five clinical centers in the United States.

PARTICIPANTS

We included 1546 BMDCS and 650 RDP participants (7 to 17 yr of age, 50% female).

INTERVENTION

No interventions were used.

MAIN OUTCOME MEASURES

We measured spine and whole body (WB) BMC and BMD Z-scores for age (BMC/BMD(age)), height age (BMC/BMD(height age)), height (BMC(height)), bone mineral apparent density (BMAD(age)), and height-for-age Z-score (HAZ) (BMC/BMD(haz)).

RESULTS

Spine and WB BMC/BMD(age)Z and BMAD(age)Z were positively (P < 0.005; r = 0.11 to 0.64) associated with HAZ. Spine BMD(haz) and BMC(haz)Z were not associated with HAZ; WB BMC(haz)Z was modestly associated with HAZ (r = 0.14; P = 0.0003). All other adjustment methods were negatively associated with HAZ (P < 0.005; r = -0.20 to -0.34). The deviation between adjusted and BMC/BMD(age) Z-scores was associated with age for most measures (P < 0.005) except for BMC/BMD(haz).

CONCLUSIONS

Most methods to adjust BMC/BMD Z-scores for height were biased by age and/or HAZ. Adjustments using HAZ were least biased relative to HAZ and age and can be used to evaluate the effect of short or tall stature on BMC/BMD Z-scores.

Serum RANKL, osteoprotegerin (OPG), and RANKL/OPG ratio in nephrotic children

Receptor activator of NF-kB ligand (RANKL) and osteoprotegerin (OPG) play key roles in the pathogenesis of glucocorticoid-induced osteoporosis (GIO). The aim of our study was to determine whether the cumulative glucocorticoid dose (CGCS) in children with idiopathic nephrotic syndrome (INS) has any effect on the concentration of serum RANKL and OPG and the RANKL/OPG ratio. The study population consisted of 90 children with INS, aged 3-20 years, who were treated with GCS. These children were divided into two groups according to the CGCS: low (L)<1 g/kg body weight (BW) and high (H)>or=1 g/kg BW, respectively. The control group (C) consisted of 70 healthy children. RANKL concentration was observed to be significantly higher and OPG significantly lower in INS children than in the reference group: 0.21 (range 0.01-1.36) versus 0.15 (0-1.42) pmol/l (p<0.05), respectively, and 3.76 (1.01-7.25) versus 3.92 (2.39-10.23) pmol/l (p<0.05), respectively. The RANKL/OPG ratio was significantly higher in INS children (p<0.01). The concentration of RANKL, similar to the RANKL/OPG ratio, was significantly higher in Group H children than in Group L children: 0.46 (0.02-1.36 ) versus 0.19 (0.01-1.25) (p<0.01) and 0.14 (0.01-0.71) versus 0.05 (0.002-0.37) (p<0.01), respectively. The concentration of OPG was similar in both groups. There was a positive correlation between CGCS and the concentration of sRANKL as well as the RANKL/OPG ratio (in both cases r=0.33, p<0.05). Based on these results, we suggest that long-term exposure to GCS results in a dose-dependent increase in serum RANKL concentration and the RANKL/OPG ratio, but not in the level of serum OPG.

Bone mineral density in children with steroid-sensitive nephrotic syndrome

OBJECTIVE

To observe the influence of prednisolone treatment on bone mineral density (BMD) in children with idiopathic nephrotic syndrome.

METHODS

Duel-energy X-ray absorptiometry of lumbar spine (L1-L4) was performed on 40 patients (18 first episode and 22 relapsers) of steroid sensitive idiopathic nephrotic syndrome.

RESULTS

Patients of first episode and relapsers had comparable values of mean age, weight, height, body mass index, serum calcium, phosphate, spine area, bone mineral content (BMC) and BMD. Relapsing nephrotic syndrome patients received significantly higher mean total cumulative dose of prednisolone in comparison to first episode (p<0.001). The BMD Z-scores were normal in 39 of 40 (97.5%) patients. On regression analysis, it was found that both BMC and BMD did not correlate with cumulative dose of prednisolone, when other co-variants such as age, weight, height and spine area were adjusted.

CONCLUSION

Bone mineral density in steroid sensitive nephrotic syndrome is unaffected by cumulative dose of prednisolone therapy both in first episode as well as relapser group of patients.

The recognition and treatment of growth disorders - a 50-year retrospective

The past 50 years have seen great progress in the understanding and treatment of classic growth disorders. Advances such as the recognition of hormone receptor defects, the development of recombinant growth hormone, and the expanding awareness of epigenetic phenomena affecting growth are among these great achievements. Yet growth failure remains a pervasive problem among children with complex health conditions, such as survivors of childhood cancers, premature infants, organ transplant recipients, and children with cystic fibrosis. The significant increases in life expectancy among these groups underscores the potential consequences of poor growth, whether due to the underlying conditions or medical treatments, as they may have long-lasting effects into adulthood. The ongoing contributions of human biologists to the study of human growth remain essential in the recognition and treatment of growth disorders, by defining normal patterns of growth and body composition, the interplay of growth and maturation, the role of environmental, behavioral and genetic factors, and the long-term consequences of growth patterns. Examples will be given based on two common genetic disorders, cystic fibrosis and sickle-cell anemia, to highlight the relationships between growth failure, survival, and malnutrition. Also, a study of bone mineral accretion in children with cystic fibrosis will illustrate the importance of understanding patterns of growth in healthy children, and their application in the diagnosis and management of children with chronic disease. These examples accentuate the need for continued participation of human biologists in the study of growth and development and the care of children.

Bone health in a nonjaundiced population of children with biliary atresia

Objectives. To assess bone health in a cohort of nonjaundiced children with biliary atresia (BA) and the effect of growth and development on bone outcomes. Methods. Children ages one to eighteen years receiving care from Children's Hospital of Philadelphia were recruited. Each child was seen once and assessed for growth, pubertal development, concurrent medications, bilirubin, ALT, albumin, vitamin D status, bone mineral density (BMD), and bone mineral content (BMC) of the lumbar spine and whole body. Results. BMD declined significantly with age, and upon further analysis with a well-phenotyped control cohort, it was found that BMC was significantly decreased for both lumbar spine and whole body, even after adjustment for confounding variables. An age interaction was identified, with older subjects having a significantly greater impairment in BMC. Conclusions. These preliminary results demonstrate that children with BA, including those without jaundice, are likely to have compromised bone health even when accounting for height and puberty, which are common confounding factors in chronic disease. Further investigation is needed to identify the determinants of poor bone mineral status and to develop strategies to prevent osteoporosis later in life.

Revised pediatric reference data for the lateral distal femur measured by Hologic Discovery/Delphi dual-energy X-ray absorptiometry

Lateral distal femur (LDF) scans by dual-energy X-ray absorptiometry (DXA) are often feasible in children for whom other sites are not measurable. Pediatric reference data for LDF are not available for more recent DXA technology. The objective of this study was to assess older pediatric LDF reference data, construct new reference curves for LDF bone mineral density (BMD), and demonstrate the comparability of LDF BMD to other measures of BMD and strength assessed by DXA and by peripheral quantitative computed tomography (pQCT). LDF, spine and whole body scans of 821 healthy children, 5-18 yr of age, recruited at a single center were obtained using a Hologic Discovery/Delphi system (Hologic, Inc., Bedford, MA). Tibia trabecular and total BMD (3% site), cortical geometry (38% site) (cortical thickness, section modulus, and strain-strength index) were assessed by pQCT. Sex- and race-specific reference curves were generated using LMS Chartmaker (LMS Chartmaker Pro, version 2.3. Tim Cole and Huiqi Pan. Copyright 1997-2006, Medical Research Council, UK) and Z-scores calculated and compared by correlation analysis. Z-scores for LDF BMD based on published findings demonstrated overestimation or underestimation of the prevalence of low BMD-for-age depending on the region of interest considered. Revised LDF reference curves were generated. The new LDF Z-scores were strongly and significantly associated with weight, body mass index, spine and whole body BMD Z-scores, and all pQCT Z-scores. These findings demonstrate the comparability of LDF measurements to other clinical and research bone density assessment modes, and enable assessment of BMD in children with disabilities, who are particularly prone to low trauma fractures of long bones, and for whom traditional DXA measurement sites are not feasible.

Effect of puberty on body composition

PURPOSE OF REVIEW

Here we examine the effect of puberty on components of human body composition, including adiposity (total body fat, percentage body fat and fat distribution), lean body mass and bone mineral content and density. New methods and longitudinal studies have expended our knowledge of these remarkable changes.

RECENT FINDINGS

Human differences in adiposity, fat free mass and bone mass reflect differences in endocrine status (particularly with respect to estrogens, androgens, growth hormone and IGF-1), genetic factors, ethnicity and the environment. During puberty, males gain greater amounts of fat free mass and skeletal mass, whereas females acquire significantly more fat mass. Both genders reach peak bone accretion during the pubertal years, though males develop a greater skeletal mass. Body proportions and fat distribution change during the pubertal years as well, with males assuming a more android body shape and females assuming a more gynecoid shape. Pubertal body composition may predict adult body composition and affects both pubertal timing and future health.

SUMMARY

Sexual dimorphism exists to a small degree at birth, but striking differences develop during the pubertal years. The development of this dimorphism in body composition is largely regulated by endocrine factors, with critical roles played by growth hormone and gonadal steroids. It is important for clinicians and researchers to know the normal changes in order to address pathologic findings in disease states.

Bone mineral content deficits of the spine and whole body in children at time of diagnosis with celiac disease

BACKGROUND

The aim of this study was to determine whether children with celiac disease (CD) have deficits in spine (SP) and whole body (WB) bone mineral content (BMC) at time of diagnosis, and whether the deficits are related to altered growth and body composition. The secondary aim was to examine the effect of histological grade on BMC.

PATIENTS AND METHODS

A retrospective study of children who had undergone a dual energy x-ray absorptiometry scan at the time of diagnosis with CD between October 1, 2003, and June 15, 2006, were compared with a healthy reference sample of similar age and race from the same geographic region in the United States. SP and WB BMC were expressed as sex-specific z scores relative to age and relative to height to assess differences in the CD group versus controls. Pearson correlation, t tests, and analysis of variance were performed to determine predictors of BMC.

RESULTS

Forty-four children (mean age 10.6 +/- 3.4 years; 77% female, 96% white) with CD were evaluated and compared with 338 healthy children. Children with CD were shorter than children of similar age and sex. SP and WB BMC for age z scores were significantly lower in the CD group compared with controls. When adjusted for height, significant deficits in WB BMC persisted in patients with CD. Low SP and WB BMC correlated with advanced histological grade in CD. Low body mass index correlated with low WB BMC in CD.

CONCLUSIONS

Newly diagnosed children with CD may benefit from screening for low bone mineral content. Patients with low body mass index and those with advanced histological damage (Marsh grade IIIc) particularly may be at risk for osteopenia.

Low bone mineral status in adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is a pathological entity of unknown etiology. The causes of osteoporosis or osteopenia in AIS remain undetermined. Whether poor bone quality is an etiologic factor remains controversial. To determine the correlation between low bone mineral status and AIS, a review of literature was performed. After a literature search from 1966 to June 2007 (using Medline, EMBASE, Cochrane DSR, ACP Journal Club, DARE, CCTR, CINAHL and hand searches of references) for studies regarding low bone mineral status and AIS, 20 studies meeting the inclusion criteria were reviewed in terms of the appropriateness of valuation technique, the validity of descriptive system, the number and type of respondents, and overall quality of the studies. Nearly all investigations demonstrated that low bone mineral density (BMD) was a generalized phenomenon and a systematic disorder in AIS. The prevalence of AIS with osteoporosis is approximately 20-38%. The follow-up studies indicated that osteopenia in patients with AIS may be a persistent phenomenon. BMD could be affected by the mechanical loading and lower bone mineral mass is always associated with lower bone strength. The spinal architecture associated with the osteopenia may aggravate the spinal deformity. However, with regard to the concave and convex femoral neck BMD values, and the correlation of BMD to scoliosis parameters, the results remain inconsistent. Bracing may not result in permanent loss of bone mineral mass. The effect of the eccentric tension-compression environments on BMD, the correlation of BMD with scoliosis parameters and the effect of bracing on BMD should be investigated further in prospective, randomized and longitudinal follow-up studies.

Risk factors for low bone mineral density in children and adolescents with inflammatory bowel disease

OBJECTIVE

To evaluate bone mineral density of the lumbar spine in children and adolescents with inflammatory bowel disease, and to identify the clinical risk factors associated with low bone mineral density.

METHODS

Bone mineral density of the lumbar spine was evaluated using dual-energy X-ray absorptiometry (DXA) in 40 patients with inflammatory bowel disease. Patients were 11.8 (SD = 4.1) years old and most of them were male (52.5%). Multiple linear regression analysis was performed to identify potential associations between bone mineral density Z-score and age, height-for-age Z-score, BMI Z-score, cumulative corticosteroid dose in milligrams and in milligrams per kilogram, disease duration, number of relapses, and calcium intake according to the dietary reference intake.

RESULTS

Low bone mineral density (Z-score bellow -2) was observed in 25% of patients. Patients with Crohn's disease and ulcerative colitis had equivalent prevalence of low bone mineral density. Multiple linear regression models demonstrated that height-for-age Z-score, BMI Z-score, and cumulative corticosteroid dose in mg had independent effects on BMD, respectively, beta = 0.492 (P = 0.000), beta = 0.460 (P = 0.001), beta = - 0.014 (P = 0.000), and these effects remained significant after adjustments for disease duration, respectively, beta = 0.489 (P = 0.013), beta = 0.467 (P = 0.001), and beta = - 0.005 (P = 0.015). The model accounted for 54.6% of the variability of the BMD Z-score (adjusted R2 = 0.546).

CONCLUSIONS

The prevalence of low bone mineral density in children and adolescents with inflammatory bowel disease is considerably high and independent risk factors associated with bone mineral density are corticosteroid cumulative dose in milligrams, height-for-age Z-score, and BMI Z-score.

Peripheral quantitative computed tomography in children and adolescents: the 2007 ISCD Pediatric Official Positions

Peripheral quantitative computed tomography (pQCT) has mainly been used as a research tool in children. To evaluate the clinical utility of pQCT and formulate recommendations for its use in children, the International Society of Clinical Densitometry (ISCD) convened a task force to review the literature and propose areas of consensus and future research. The types of pQCT technology available, the clinical application of pQCT for bone health assessment in children, the important elements to be included in a pQCT report, and quality control monitoring techniques were evaluated. The review revealed a lack of standardization of pQCT techniques, and a paucity of data regarding differences between pQCT manufacturers, models and software versions and their impact in pediatric assessment. Measurement sites varied across studies. Adequate reference data, a critical element for interpretation of pQCT results, were entirely lacking, although some comparative data on healthy children were available. The elements of the pQCT clinical report and quality control procedures are similar to those recommended for dual-energy X-ray absorptiometry. Future research is needed to establish evidence-based criteria for the selection of the measurement site, scan acquisition and analysis parameters, and outcome measures. Reference data that sufficiently characterize the normal range of variability in the population also need to be established.

The effect of fluoride on enamel and dentin formation in the uremic rat incisor

Renal impairment in children is associated with tooth defects that include enamel pitting and hypoplasia. However, the specific effects of uremia on tooth formation are not known. In this study, we used rat mandibular incisors, which continuously erupt and contain all stages of tooth formation, to characterize the effects of uremia on tooth formation. We also tested the hypothesis that uremia aggravates the fluoride (F)-induced changes in developing teeth. Rats were subjected to a two-stage 5/6 nephrectomy or sham operation and then exposed to 0 (control) or 50 ppm NaF in drinking water for 14 days. The effects of these treatments on food intake, body growth rate, and biochemical serum parameters for renal function and calcium metabolism were monitored. Nephrectomy reduced food intake and weight gain. Intake of F by nephrectomized rats increased plasma F levels twofold and further decreased food intake and body weight gain. Uremia affected formation of dentin and enamel and was more extensive than the effect of F alone. Uremia also significantly increased predentin width and induced deposition of large amounts of osteodentin-like matrix-containing cells in the pulp chamber. In enamel formation, the cells most sensitive to uremia were the transitional-stage ameloblasts. These data demonstrate that intake of F by rats with reduced renal function impairs F clearance from the plasma and aggravates the already negative effects of uremia on incisor tooth development.

Observational study of bone accretion during successful weight loss in obese adolescents

OBJECTIVE

To assess bone mineral content (BMC) among obese adolescents who lose weight during a critical period for bone accretion.

METHODS AND PROCEDURES

Whole body, lumbar spine, lower, and upper limb BMC were measured in 62 obese adolescents who completed an intensive 12-month weight loss trial. BMC was adjusted for height (z -scores) using data from a reference group of 66 adolescents (who were 18% overweight).

RESULTS

At baseline, the BMC of the obese group was higher than the reference group. During the 12-month weight loss program, unadjusted BMC increased among the obese adolescents, despite successful weight loss. After adjustment for height, whole body BMC did not change significantly from baseline to 12 months (mean +/- s.d.: 1.08 +/- 0.67 to 1.06 +/- 0.67, P = 0.7). Region-specific BMC-for-height however decreased for the lower (1.07 +/- 0.57 to 0.95 +/- 0.59, P < 0.001) and upper (1.29 +/- 0.56 to 1.18 +/- 0.57, P = 0.01) limbs, but lumbar spine BMC-for-height increased (0.14 +/- 1.06 to 0.40 +/- 0.94, P < 0.001). These changes were largely and independently explained by changes in lean and fat mass.

DISCUSSION

This study confirms that obese adolescents have high BMC for height and suggests that, unlike adults, their BMC continues to increase during weight loss and remains higher than the BMC of a reference group. After adjustment for growth-related changes, lower and upper limb BMC appears to decrease, while lumbar spine BMC appears to increase. These results suggest that to optimize the health benefits of weight loss among obese adolescents, their bone health should be better understood and addressed.

Physical activity, calcium intake and bone health in children and adolescents

Osteoporosis is a serious and potentially debilitating disease, which can lead to a variety of health complications and a diminished quality of life. Consequently, the development of bone mineral density (BMD) and content (BMC) during childhood and adolescence is of great importance, as it may attenuate the effects and incidence of osteoporosis later in life. Identifying the mechanisms by which bones are strengthened early in life is crucial. This review highlights research examining factors that influence BMD and BMC in children and adolescents. While a sizeable amount of variation in BMD and BMC in children and adolescents can be attributed to genetic factors and body size, studies have also shown the positive influence of physical activity and calcium intake on bone development. Research supporting the role of these modifiable factors varies according to age, sex and the bone site studied. During the pubertal years, large gains in BMD and BMC are evident. However, physical activity and calcium intake are also important to the development of BMD and BMC during the prepubertal years. Thus, actions taken throughout childhood may exert a great impact on BMD and BMC, and overall bone health as an adult.

Bone Mineral Density in Children with Non-Cystic Fibrosis Bronchiectasis

BACKGROUND

Bronchiectasis presents as a common sequela of several chronic pulmonary diseases. Bone mineral density (BMD) is generally decreased in children with cystic fibrosis (CF). Although children with non-CF bronchiectasis have similar risk factors for osteopenia/osteoporosis, data on BMD in this group of patients are lacking.

OBJECTIVE

To evaluate BMD in children with non-CF bronchiectasis.

METHODS

In this study, we evaluated BMD of the radius and tibia in 32 children (17 girls) with non-CF bronchiectasis and in 23 healthy controls matched for age, sex and pubertal stage by quantitative ultrasound (speed of sound). Daily calcium intake and pulmonary function tests and data about steroid use were noted.

RESULTS

Mean age was 12.5 +/- 4.6 years. Six children (18%) had moderate-to-severe lung disease (FEV(1) <60% predicted). All except 2 children (94%) were receiving inhaled steroids. There was no significant difference in BMD (expressed as z-score) of the radius and tibia between the patient and control groups (tibia z-scores: -0.1 +/- 0.9 vs. -0.8 +/- 0.8 and radius z-scores -1.3 +/- 1.4 vs. -1.0 +/- 0.9 in bronchiectasis patients and controls, respectively, p > 0.05). However, more children with non-CF bronchiectasis had osteopenia (z-scores between -1 and -2 SD) and osteoporosis (z-score <or=2 SD) compared to the control group (62 vs. 30%, p = 0.019). There was a significant correlation between age and radius z-scores (r = -0.365, p = 0.04). There was no correlation between BMD and severity of lung illness, calcium intake or cumulative steroid doses.

CONCLUSION

Osteopenia is more common in children with non-CF bronchiectasis compared to controls and the risk of osteoporosis and osteopenia increases with age.

Glucocorticoid-induced osteoporosis in children: impact of the underlying disease

Glucocorticoids inhibit osteoblasts through multiple mechanisms, which results in significant reductions in bone formation. The growing skeleton may be especially vulnerable to adverse glucocorticoid effects on bone formation, which could possibly compromise trabecular and cortical bone accretion. Although decreased bone mineral density has been described in various pediatric disorders that require glucocorticoids, and a population-based study reported increased fracture risk in children who require >4 courses of glucocorticoids, some of the detrimental bone effects attributed to glucocorticoids may be caused by the underlying inflammatory disease. For example, inflammatory cytokines that are elevated in chronic disease, such as tumor necrosis factor alpha, suppress bone formation and promote bone resorption through mechanisms similar to glucocorticoid-induced osteoporosis. Summarized in this review are changes in bone density and dimensions during growth, the effects of glucocorticoids and cytokines on bone cells, the potential confounding effects of the underlying inflammatory-disease process, and the challenges in interpreting dual-energy x-ray absorptiometry results in children with altered growth and development in the setting of glucocorticoid therapy. Two recent studies of children treated with chronic glucocorticoids highlight the differences in the effect of underlying disease, as well as the importance of associated alterations in growth and development.

Glucocorticoid-Induced Osteoporosis: Mechanisms and Therapeutic Approach

GCs constitute a therapeutic class largely used in clinical medicine for the curative or supportive treatment of various conditions involving the intervention of numerous medical specialties. Beyond their favorable therapeutic effects, GCs almost invariably provoke bone loss and a rapid increase in bone fragility, with its host of fractures. Men and postmenopausal women constitute a preferential target for the bone complications of GCs. The premenopausal status is not, however, a shelter; bone loss also happens in young women who are on GCs. Exposure to GCs yields a fracture risk exceeding the risk conferred by a low BMD per se. Therefore, some reason exists to settle the BMD threshold for therapeutic intervention not at -2.5 T-scores but at -1.0 or -1.5 T-scores, even if no prospective randomized trial so far endorses that opinion. Nowadays, bisphosphonate therapy should be proposed to every patient at risk for fragility fracture, along with calcium and vitamin D supplementation. Studies of other therapeutic modalities (eg, promoters of bone formation) are in progress.

Bone mineral density decrements and children diagnosed with cancer

This integrative literature review is focused on (1) the prevalence of bone mineral density (BMD) decrements in children treated for acute lymphoblastic leukemia (ALL), and when these decrements are observed; (2) the risk factors associated with the development of decreased BMD and resultant complications in children treated for ALL; (3) the role, if any, that corticosteroids play in decreasing BMD in children treated for ALL; (4) interventions that can potentially manage bone loss in people treated for ALL during childhood or adolescence. The results showed that people who have been diagnosed with ALL can have decrements in BMD. The etiology of BMD decrements can be attributed to multiple factors including genetic endowment, lifestyle behaviors, the leukemia disease process, and treatment exposures especially to corticosteroids and cranial radiotherapy. Male gender, age greater than 10 years, and physical inactivity are associated with BMD decrements in ALL survivors. The role of pediatric oncology nurses in the management of bone disease in children with cancer across the illness trajectory is discussed.

Osteoporosis in children and adolescents: etiology and management

Bone mass increases progressively during childhood, but mainly during adolescence when approximately 40% of total bone mass is accumulated. Peak bone mass is reached in late adolescence, and is a well recognised risk factor for osteoporosis later in life. Thus, increasing peak bone mass can prevent osteoporosis. The critical interpretation of bone mass measurements is a crucial factor for the diagnosis of osteopenia/osteoporosis in children and adolescents. To date, there are insufficient data to formally define osteopenia/osteoporosis in this patient group, and the guidelines used for adult patients are not applicable. In males and females aged <20 years the terminology 'low bone density for chronologic age' may be used if the Z-score is less than -2. For children and adolescents, this terminology is more appropriate than osteopenia/osteoporosis. Moreover, the T-score should not be used in children and adolescents. Many disorders, by various mechanisms, may affect the acquisition of bone mass during childhood and adolescence. Indeed, the number of disorders that have been identified as affecting bone mass in this age group is increasing as a consequence of the wide use of bone mass measurements. The increased survival of children and adolescents with chronic diseases or malignancies, as well as the use of some treatment regimens has resulted in an increase in the incidence of reduced bone mass in this age group. Experience in treating the various disorders associated with osteoporosis in childhood is limited at present. The first approach to osteoporosis management in children and adolescents should be aimed at treating the underlying disease. The use of bisphosphonates in children and adolescents with osteoporosis is increasing and their positive effect in improving bone mineral density is encouraging. Osteoporosis prevention is a key factor and it should begin in childhood. Pediatricians should have a fundamental role in the prevention of osteoporosis, suggesting strategies to achieve an optimal peak bone mass.

Bone status in an animal model of chronic sub-optimal nutrition: a morphometric, densitometric and mechanical study

In children, inappropriate eating habits can induce a disease known as nutritional dwarfing (ND). Due to the link between nutritional condition and bone growth, the effects induced by a 20 % reduction of food intake on bone competence were assessed in an animal model of ND. Bone status during catch-up growth was also analysed. Male Wistar rats were divided into control (C) and ND groups. C rats were fed ad libitum. ND received 80 % of the diet consumed by C for 4 weeks (T4); thereafter, they were fed ad libitum for 8 weeks. Results, expressed as mean (SEM) for ND v. C, were as follows. At T4, body weight (g) and length (cm) and femur weight (g) and length (mm) were 97.35 (SEM 5.89) v. 199.07 (SEM 9.24), 16.91 (SEM 0.41) v. 20.26 (SEM 0.31), 0.30 (SEM 0.01) v. 0.46 (SEM 0.01) and 23.09 (SEM 0.29) v. 26.98 (SEM 0.26), respectively (P<0.001); bone mineral content (g) and density (g/cm(2)) were 0.014 (SEM 0.002) v. 0.030 (SEM 0.002) and 0.061 (SEM 0.004) v. 0.080 (SEM 0.003), respectively (P<0.001); load-bearing capacity (N), yielding load (N) and elastic stiffness (N/mm) were 25.06 (SEM 1.24) v. 50.34 (SEM 2.94), 23.72 (SEM 1.02) v. 46.97 (SEM 1.75) and 65.98 (SEM 4.42) v. 115.07 (SEM 3.85), respectively (P<0.001); cross-sectional area (mm(2)) and moment of inertia (mm(4)) were 2.86 (SEM 0.19) v. 4.54 (SEM 0.17) and 1.27 (SEM 0.08) v. 3.03 (SEM 0.16), respectively (P<0.001). Significant effects were not evident in material properties. Parameters assessed normalized during re-feeding. These results suggest that the impaired mechanical femur competence in ND rats could be due to an altered bone mass and architectural distribution rather than to intrinsic quality. Re-feeding caused a reversal of the effects of food restriction on growth and bone parameters in ND rats.

Poor nutrition in prepubertal Japanese children at the end of World War II suppressed bone development

OBJECTIVE

To assess the extent to which malnutrition in childhood affects bone mineral density (BMD) decades later.

METHODS

BMDs were compared in healthy women (35-59 years old) who visited our hospital for annual examinations between 1992 and 1993 (group 1) and between 1999 and 2002 (group 2).

RESULTS

The BMDs of 50- to 54-year-old women in group 1 averaged 0.86+/-0.15 g/cm2, which was significantly (p<0.001) lower than age-matched women in group 2 (1.02+/-0.16 g/cm2).

CONCLUSION

At the end of World War II (1945) undernutrition was rampant throughout Japan, and there were unprecedented numbers of cases of malnutrition. BMD was lower in women who experienced those conditions while they were 5 years old in average, a time when rapid skeletal growth was beginning. Thus, nutrition in childhood is a particularly crucial determinant of lifelong bone health.

Large variations occur in bone density measurements of children when using different software

BACKGROUND

Paediatric dual X-ray absorptiometry (DXA) studies present a number of technical problems. One of these is that the edge detection algorithms designed for the adult skeleton may fail for paediatric studies. Hologic provide alternative algorithms for low bone density studies.

AIM

To assess low-density software for the analysis of paediatric DXA studies and to compare with the adult protocol.

METHODS

Our centre has scanned 450 normal children as part of a normal range study. A subgroup of 103 children was selected using a random number generator. The group was distributed evenly between males and females and across the age range 5-17 years. Each individual underwent both a lumbar spine and a whole-body scan on a Hologic QDR-4500W DXA scanner. Both scans were analysed using the standard adult protocol and then re-analysed using the Hologic experimental paediatric protocol for whole body and the Hologic low-density protocol for lumbar spine.

RESULTS

Both lumbar spine protocols showed an increase in bone mineral density with age; however, the low-density protocol always produced a lower bone mineral density result than the adult protocol. Bland-Altman analysis showed limits of agreement of 0.031-0.093 g x cm(-2) (male, 0.032-0.089 g x cm(-2); female, 0.031-0.096 g x cm(-2)). This represents a mean difference of 9%. Five results showed differences greater than the upper limit of agreement. All these cases were children under 11 years of age who had large areas of spine not identified as bone by the adult protocol. These children were all below the 30th percentile for the body mass index. The whole-body protocols showed similar increases in bone mineral density with age; however, the experimental paediatric protocol always produced a lower bone mineral density result than the adult protocol. Paired results showed limits of agreement of 0.0668-0.130 g x cm(-2) (male, 0.063-0.124 g x cm(-2); female, 0.073-0.134 g x cm(-2)). This represents a mean difference of 11%. Five results showed differences greater than the upper limit of agreement.

CONCLUSIONS

For anteroposterior (AP) lumbar spine scans, the use of the paediatric algorithm in children under 11 years of age would prevent the largest failures in analysis. For whole-body scanning, the adult algorithm showed no major failures in children of 11 years or older. It is hoped that forthcoming improvements in whole-body density analysis will improve the results for those under 11 years of age. Normal range data should be generated for any new algorithm to allow proper interpretation of clinical studies.

Randomized trial comparing two methods of increasing dietary calcium intake in children with inflammatory bowel disease

OBJECTIVE

To examine the efficacy of behavioral intervention compared with enhanced standard of care nutrition intervention on increasing dietary calcium intake of children with inflammatory bowel disease.

METHOD

Children aged 5 to 12 years old (N = 32) were randomly assigned to the behavioral intervention or enhanced standard of care conditions. Three-day food diaries collected on all participants at baseline and post-treatment were analyzed for dietary calcium intake.

RESULTS

Children in the behavioral intervention group achieved a significantly greater mean increase in dietary calcium intake (M= 984 mg) than children in the enhanced standard of care group (M = 274 mg) (P < 0.05). In the behavioral intervention group 81% of children achieved the daily calcium intake goal of 1500 mg/day compared with only 19% of children in the enhanced standard of care group, (P < 0.05).

CONCLUSIONS

Behavioral modification appears to be significantly more effective than nutrition education alone in modifying calcium intake in children with inflammatory bowel disease.

Radiographic vertebral morphology: a diagnostic tool in pediatric osteoporosis

OBJECTIVE

To assess the value of spinal radiographs in determining the significance of reductions in bone mass or density in chronically ill children.

STUDY DESIGN

A pediatric scoring method for assessment of osteoporotic vertebral changes, developed on the basis of radiographs of 70 healthy controls and established adult scoring methods, was subsequently used to assess 32 pediatric patients with suspected secondary osteoporosis. Radiographic findings were correlated with bone mineral density (BMD), clinical data, and biochemistry.

RESULTS

Thirty-two patients (median age 14.1 years) were included. Assessment of spinal radiographs with the developed scoring method found previously undiagnosed spinal compression deformities in 11 patients (34%) of whom 9 were asymptomatic and 8 had lumbar spine (size-corrected) BMD measurements within +/-2.0 SD of the age- and sex-specific norms. Fracture history and cumulative glucocorticoid (GC) dose did not differ between those with and without compression deformities.

CONCLUSIONS

Vertebral compression fractures can be documented in a significant number of chronically ill children and are poorly predicted by single BMD measurements and clinical history. Assessment of vertebral morphology is recommended as an additional tool in the diagnostic workup of pediatric osteoporosis.

Prevention of Osteoporosis: A Randomized Clinical Trial to Increase Calcium Intake in Children with Juvenile Rheumatoid Arthritis

OBJECTIVE

To test the efficacy of a behavioral intervention (BI) compared to an enhanced standard of care (ESC) dietary counseling on increasing dietary calcium (Ca) intake in children with juvenile rheumatoid arthritis (JRA).

METHODS

Three-day food diaries collected at baseline and posttreatment were analyzed for Ca intake in 49 children with JRA randomly assigned to either BI or an ESC treatment.

RESULTS

Children in the BI (N = 25) demonstrated a significantly greater increase in average dietary Ca intake (M = 839) than children in the ESC (N = 24; M = 420) (F = 14.39; p < .001). Post hoc analysis revealed that children in both groups demonstrated significant gains in dietary Ca intake baseline to posttreatment. A significantly greater percentage of children in the BI (92%) attained the goal of 1500 mg/Ca at posttreatment compared to the ESC (17%), X2= 28.09; p < .001.

CONCLUSIONS

Behavioral intervention can have a positive impact on increasing dietary Ca intake. Future research will need to evaluate the maintenance of gains in dietary Ca intake following treatment cessation and the impact of increased Ca intake on bone mineral density.