Similar effects of long-term exogenous growth hormone (GH) on bone and muscle parameters: a pQCT study of GH-deficient and small-for-gestational-age (SGA) children

Inadequate linear catch-up growth in children born small for gestational age: Influencing factors and underlying mechanisms

A minority of children born small for gestational age (SGA) may experience catch-up growth failure and remain short in adulthood. However, the underlying causes and mechanisms of this phenomenon are not yet fully comprehended. We reviewed the present state of research concerning the growth hormone-insulin-like growth factor axis and growth plate in SGA children who fail to achieve catch-up growth. Additionally, we explored the factors influencing catch-up growth in SGA children and potential molecular mechanisms involved. Furthermore, we considered the potential benefits of supplementary nutrition, specific dietary patterns, probiotics and drug therapy in facilitating catch-up growth.

Longitudinal assessment of bone health index as a measure of bone health in short-statured children before and during treatment with recombinant growth hormone

OBJECTIVES

The aim of our study was the longitudinal assessment of bone health index (BHI) in short-statured children during growth hormone (GH) treatment to estimate changes in their bone health.

METHODS

256 short-statured children (isolated GH deficiency (IGHD) n=121, multiple pituitary hormone deficiency (MPHD) n=49, intrauterine growth retardation (small for gestational age (SGA)) n=52, SHOX (short stature homeobox gene) deficiency n=9, Ullrich Turner syndrome (UTS) n=25) who started with GH between 2010 and 2018 were included. Annual bone ages (Greulich and Pyle, GP) and BHI were, retrospectively, analysed in consecutive radiographs of the left hand (BoneXpert software) from GH therapy start (T0) up to 10 years (T10) thereafter, with T max indicating the individual time point of the last available radiograph. The results are presented as the median (25 %/75 % interquartile ranges, IQR) and statistical analyses were performed using non-parametric tests as appropriate.

RESULTS

The BHI standard deviation scores (SDS) were reduced (-0.97, -1.8/-0.3) as bone ages were retarded (-1.6 years, -2.31/-0.97) in all patients before start of GH and were significantly lower in patients with growth hormone deficiency (GHD) (-1.04, -1.85/-0.56; n=170) compared to non-GHD patients (-0.79, -1.56/-0.01; n=86; p=0.022). BHI SDS increased to -0.17 (-1/0.58) after 1 year of GH (T1, 0.5-1.49, p<0.001) and to -0.20 (-1/-0.50, p<0.001) after 5.3 years (T max, 3.45/7.25).

CONCLUSIONS

BHI SDS are reduced in treatment-naive short-statured children regardless of their GH status, increase initially with GH treatment while plateauing thereafter, suggesting sustained improved bone health.

Increase of jump performance during GH treatment in short children born SGA

Background

Short children born small for gestational age (SGA) often have low muscle mass. Studies on maximal isometric grip-force (MIGF) observed lower muscle strength in these children. In contrast to MIGF, jumping is an everyday muscle activity for children. Our hypothesis was that GH treatment would cause an increase in jumping strength. So, we aimed to study jumping by mechanography in short SGA children before and during GH treatment.

Methods

Monocentric prospective longitudinal study in a tertiary pediatric endocrinology center. We studied 50 prepubertal short children (23 females) born SGA (mean age 7.2 y, height -3.24 SDS) during GH treatment (mean dose 45 µg/kg/d). Main outcome measures were Peak jump force (PJF) and peak jump power (PJP) measured by Leonardo^® ground reaction force plate at baseline and after 12 months of GH treatment. Mechanography data were compared to sex, age and height related references (SD-Score). Fitness was estimated as PJP/kg body weight by use of the Esslinger-Fitness-Index (EFI).

Results

At start of GH treatment PJP/body weight was low at -1.52 SDS and increased significantly to -0.95 SDS during 12 months of treatment (p<0.001). PJF was low-normal compared to height dependent references and remained unchanged. PJP was normal compared to height dependent references and increased only slightly from -0.34 to -0.19 SDS_HT.

Conclusions

Jumping performance (EFI) measured by mechanography increased during one year of GH treatment in short children born SGA.

Association Between the Growth Hormone/Insulin-Like Growth Factor-1 Axis and Muscle Density in Children and Adolescents of Short Stature

OBJECTIVE

To evaluate the association between the growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis and muscle density in children and adolescents of short stature.

METHODS

Participants were children and adolescents of short stature hospitalized in the Affiliated Hospital of Jining Medical University between January 2020 and June 2021. All participants had CT scan images available. We performed an analysis of the images to calculate the muscle density or skeletal muscle attenuation (SMA), skeletal muscle index (SMI), and fat mass index (FMI). Bioelectrical impedance analysis (BIA) was used to ensure that chest CT is a credible way of evaluating body composition.

RESULTS

A total of 297 subjects were included with the mean age of 10.00 ± 3.42 years, mean height standard deviation score (SDS) of -2.51 ± 0.53, and mean IGF-1 SDS of -0.60 ± 1.07. The areas of muscle and fat tissues at the fourth thoracic vertebra level in the CT images showed strong correlation with the total weights of the participants (R²  = 0.884 and 0.897, respectively). The peak of GH was negatively associated with FMI (r = - 0.323, P <.01) and IGF-1 SDS was positively associated with SMI (r = 0.303, P <.01). Both the peak GH and IGF-1 SDS were positively associated with SMA (r = 0.244, P <.01 and r = 0.165, P <.05, respectively). Multiple stepwise linear regression analysis demonstrated that the GH peak was the predictor of FMI (β = - 0.210, P < .01), the IGF-1 SDS was the predictor of SMI (β = 0.224, P < .01), and both the peak GH and IGF-1 SDS were predictors of SMA (β = 0.180, P < .01 and β = 0.222, P < .01).

CONCLUSIONS

A chest CT scan is a credible method of evaluating body composition in children and adolescents of short stature. In these patients, peak GH and IGF-1 SDS are independent predictors of muscle density and the GF/IGF-1 axis may regulate body composition through complex mechanisms.

Short stature and the effect of human growth hormone: Guidelines for the care of people with spina bifida

It is estimated that a significant percentage of individuals with spina bifida (SB) are shorter than their age-matched typical peers. Parents of children with spina bifida may ask if human growth hormone is appropriate for their child. This article discusses short stature and the use of human growth hormone among children with SB. This guideline was developed for SB Healthcare Guidelines from the 2018 Spina Bifida Association's Fourth Edition of the Guidelines for the Care of People with Spina Bifida.

Stable bone density in adolescents with severe growth hormone deficiency after six months off rhGH

OBJECTIVE

Severe growth hormone deficiency causes lean body mass loss in male adolescents and increased fat mass in both sexes. The changes appear after a 6 month GH pause.

AIM

The aim was to examine bone density and structure changes in adolescents with severe GHD during a 6-month rhGH treatment interruption.

PATIENTS AND METHODS

In total, 113 adolescents (20 females) paused rhGH treatment for 6 months at near-final height, and they were retested with arginine-GHRH challenge and basal IGF-1. Severe GHD was diagnosed in 19 individuals (5 females, GH peak <16 ng/ml and IGF-1 < -1.9 SDS) and excluded in 94 (15 females). Bone density and structure were measured by pQCT of the forearm and DXA of the total body at cessation of rhGH and 6 months later.

RESULTS

In severe adolescent GHD (sGHD) patients, trabecular density (mg/cm³) decreased from 214 to 202 (p < 0.01); changes in the adolescents with normal test results (tGHD) were from 221 to 214 (p < 0.05). Cortical density (mg/cm³) increased from 1077 to 1099 (p < 0.01) in sGHD patients and from 1060 to 1082 in tGHD patients (p < 0.001). The strength strain index (mm³) showed no significant changes in sGHD patients (306 to 307) but changed from 302 to 315 in tGHD patients (p < 0.05). Total bone area (mm²) shifted from 145.1 to 145.2 in sGHD patients and from 153 to 156 in tGHD patients. Total body aBMD (g/cm²) increased in both groups: from 1.10 to 1.12 in sGHD patients and from 1.11 to 1.14 in tGHD patients (p < 0.01). All bone measurements remained within the reference ranges, and there were no differences between sGHD and tGHD patients.

CONCLUSION

During a 6-month pause of rhGH treatment, the bone structure and density of adolescents with sGHD did not show changes implying harm. Routine retesting of adolescents, including 6 months without GH, is unlikely to be detrimental to the bone.

Management of primary and secondary osteoporosis in children

Osteoporosis in children differs from adults in terms of definition, diagnosis, monitoring and treatment options. Primary osteoporosis comprises primarily of osteogenesis imperfecta (OI), but there are significant other causes of bone fragility in children that require treatment. Secondary osteoporosis can be a result of muscle disuse, iatrogenic causes, such as steroids, chronic inflammation, delayed or arrested puberty and thalassaemia major. Investigations involve bone biochemistry, dual-energy X-ray absorptiometry scan for bone densitometry and vertebral fracture assessment, radiographic assessment of the spine and, in some cases, quantitative computed tomography (QCT) or peripheral QCT. It is important that bone mineral density (BMD) results are adjusted based on age, gender and height, in order to reflect size corrections in children. Genetics are being used increasingly for the diagnosis and classification of various cases of primary osteoporosis. Bone turnover markers are used less frequently in children, but can be helpful in monitoring treatment and transiliac bone biopsy can assist in the diagnosis of atypical cases of osteoporosis. The management of children with osteoporosis requires a multidisciplinary team of health professionals with expertise in paediatric bone disease. The prevention and treatment of fragility fractures and improvement of the quality of life of patients are important aims of a specialised service. The drugs used most commonly in children are bisphosphonates, that, with timely treatment, can give good results in improving BMD and reshaping vertebral fractures. The data regarding their effect on reducing long bone fractures are equivocal. Denosumab is being used increasingly for various conditions with mixed results. There are more drugs trialled in adults, but these are not yet licenced for children. Increasing awareness of risk factors for paediatric osteoporosis, screening and referral to a specialist team for appropriate management can lead to early detection and treatment of asymptomatic fractures and prevention of further bone damage.

What is the evidence for beneficial effects of growth hormone treatment beyond height in short children born small for gestational age? A review of published literature

Background An increasing body of evidence supports the view that both an adverse intrauterine milieu and rapid postnatal weight gain in children born small for gestational age (SGA) contribute towards the risk for the development of chronic diseases in adult life. Content The aim of this review was to identify and summarize the published evidence on metabolic and cardiovascular risk, as well as risk of impaired cardiac function, intellectual capacity, quality of life, pubertal development and bone strength among children born SGA. The review will then address whether growth hormone (GH) therapy, commonly prescribed to reduce the height deficit in children born SGA who do not catch up in height, increases or decreases these risks over time. Summary Overall, there are limited data in support of a modest beneficial effect of GH therapy on the adverse metabolic and cardiovascular risk observed in short children born SGA. Evidence to support a positive effect of GH on bone strength and psychosocial outcomes is less convincing. Outlook Further evaluation into the clinical relevance of any potential long-term benefits of GH therapy on metabolic and cardiovascular endpoints is warranted.

Fetuin-A in Infants Born Small- or Large-for-Gestational-Age

Fetuin-A is a multifunctional glycoprotein that has been implicated in insulin resistance and bone metabolism. We assessed whether fetuin-A is associated with poor or excessive fetal growth. In the Shanghai Birth Cohort, we conducted a nested case-control study of 60 trios of small-for-gestational-age (SGA, birth weight <10th percentile), optimal-for-gestational-age (OGA, 25-75th, the reference) and large-for-gestational-age (LGA, >90th percentile) infants matched by sex and gestational age. Cord plasma concentrations of fetuin-A and fetal growth factors [insulin, proinsulin, insulin-like growth factor (IGF)-I and IGF-II] were measured. Cord plasma fetuin-A concentrations were higher in SGA (809.4 ± 306.9 μg/ml, P = 0.026) and LGA (924.2 ± 375.9 μg/ml, P < 0.001) relative to OGA (680.7 ± 262.1 μg/ml) newborns, and were not correlated to insulin, proinsulin, IGF-I and IGF-II (all P > 0.2). Higher fetuin-A concentrations were associated with increased risks of SGA [OR = 1.67 (1.08-2.58) per SD increment, P = 0.024] and LGA [OR = 2.36 (1.53-3.66), P < 0.001]. Adjusting for maternal and neonatal characteristics and fetal growth factors, the elevated risk changed little for LGA [adjusted OR = 2.28 (1.29-4.01), P = 0.005], but became non-significant for SGA (P = 0.202). Our study is the first to demonstrate that fetuin-A may be involved in excessive fetal growth. This association is independent of fetal growth factors.

Childhood-onset growth hormone deficiency and the transition to adulthood: current perspective

Childhood-onset growth hormone deficiency (CO-GHD) is an endocrine condition associated with a broad range of health issues from childhood through to adulthood, which requires particular attention during the transition period from adolescence to young adulthood. There is uncertainty in the clinical practice of the management of CO-GHD during transition regarding the clinical assessment and management of individual patients during and after transition to obtain optimal follow-up and improved health outcomes. Despite the availability of clinical guidelines providing the framework for transition of young adults with CO-GHD, there remains substantial variation in approaching transitional care among pediatric and adult services. A well-structured and coordinated transitional plan with clear communication and direct collaboration between pediatric and adult health care to ensure optimal management of adolescents with CO-GHD during transition is needed.

Anabolic Therapy for the Treatment of Osteoporosis in Childhood

PURPOSE OF REVIEW

Numerous forms of osteoporosis in childhood are characterized by low bone turnover (for example, osteoporosis due to neuromuscular disorders and glucocorticoid exposure). Anti-resorptive therapy, traditionally used to treat osteoporosis in the young, is associated with further reductions in bone turnover, raising concerns about the long-term safety and efficacy of such therapy. These observations have led to increasing interest in the role of anabolic therapy to treat pediatric osteoporosis.

RECENT FINDINGS

While growth hormone and androgens appears to be relatively weak anabolic modulators of bone mass, emerging therapies targeting bone formation pathways (anti-transforming growth factor beta antibody and anti-sclerostin antibody) hold considerable promise. Teriparatide remains an attractive option that merits formal study for patients post-epiphyseal fusion, although it must be considered that adult studies have shown its effect is blunted when administered following bisphosphonate therapy. Mechanical stimulation of bone through whole body vibration therapy appears to be much less effective than bisphosphonate therapy for treating osteoporosis in children. New anabolic therapies which target important pathways in skeletal metabolism merit further study in children, including their effects on fracture risk reduction and after treatment discontinuation.

Astragalus Extract Mixture HT042 Improves Bone Growth, Mass, and Microarchitecture in Prepubertal Female Rats: A Microcomputed Tomographic Study

Astragalus extract mixture HT042 is a standardized multiherbal mixture comprising Astragalus membranaceus, Eleutherococcus senticosus, and Phlomis umbrosa, which has proven to promote children's height growth. The aim of this study was to investigate the effects of HT042 on longitudinal bone growth, bone mass, and bone microstructure in growing rats using a high-resolution microcomputed tomography system. Four-week-old female rats were fed an HT042-containing diet for 2 weeks. Tibial length was measured at baseline and weekly in vivo. At the end of the study, volumetric bone mineral density (vBMD) and microarchitectural parameters were estimated in the trabecular and cortical bone of the tibia. Tibial length gain was significantly increased by HT042 compared to that reported with the control diet. In the proximal tibial metaphysis, HT042-treated rats had significantly higher trabecular vBMD, bone volume fraction, and trabecular number and lower trabecular separation, trabecular pattern factor, and structure model index values than control rats did. Total cross-sectional area and bone area of the cortical bone in the tibial diaphysis also increased. These findings suggest that HT042 increases longitudinal bone growth rate, improves trabecular bone mass, and enhances the microarchitecture of trabecular and cortical bone during growth.

Muscle and skeletal health in children and adolescents with GH deficiency

In addition to promoting linear growth, GH plays a key role in the regulation of bone and muscle development and metabolism. Although GH deficiency is frequently listed among the causes of secondary osteoporosis in children, its impact on bone and muscle health and on fracture risk is still not completely established. Current data suggest that childhood-onset GH deficiency can affect bone and muscle mass and strength, with GH replacement therapy exerting beneficial effects. Moreover, GH withdrawal at final height can result in reduced peak bone and muscle mass, potentially leading to increased fracture risk in adulthood. Thus, the muscle-bone unit in GH deficient subjects should be monitored during childhood and adolescence in order to prevent osteoporosis and increased fracture risk and GH replacement should be tailored to ensure an optimal bone and muscle health.

Peripheral quantitative computed tomography (pQCT) for the assessment of bone strength in most of bone affecting conditions in developmental age: a review

Peripheral quantitative computed tomography provides an automatical scan analysis of trabecular and cortical bone compartments, calculating not only their bone mineral density (BMD), but also bone geometrical parameters, such as marrow and cortical Cross-Sectional Area (CSA), Cortical Thickness (CoTh), both periosteal and endosteal circumference, as well as biomechanical parameters like Cross-Sectional Moment of Inertia (CSMI), a measure of bending, polar moment of inertia, indicating bone strength in torsion, and Strength Strain Index (SSI). Also CSA of muscle and fat can be extracted. Muscles, which are thought to stimulate bones to adapt their geometry and mineral content, are determinant to preserve or increase bone strength; thus, pQCT provides an evaluation of the functional 'muscle-bone unit', defined as BMC/muscle CSA ratio. This functional approach to bone densitometry can establish if bone strength is normally adapted to the muscle force, and if muscle force is adequate for body size, providing more detailed insights to targeted strategies for the prevention and treatment of bone fragility. The present paper offers an extensive review of technical features of pQCT and its possible clinical application in the diagnostic of bone status as well as in the monitoring of the skeleton's health follow-up.

SGA children: auxological and metabolic outcomes - the role of GH treatment

The definition Small for Gestational Age (SGA) describes those newborns weighing and/or measuring in length <-2 SD than expected for their gestational age. These subjects are at higher risk of short stature, neonatal complications, alterations of glucose, lipid metabolism, body composition, bone metabolism and puberty, neurocognitive vulnerabilities and alterations of the GH-IGF-I axis. With regards to growth, in 85-90% of the cases children born SGA experience a period of catch up growth that allows them to achieve an adult stature within normal range. In a 10-15% of the cases, the catch up growth period does not take place and this entails short stature in adulthood. In the latter group, GH treatment may be considered to achieve adult height in the range of genetical target stature. With reference to glucose and lipid metabolism, young adults born SGA and particularly those with early catch up growth are at higher risk of developing insulin resistance, type 2 diabetes mellitus, arterial hypertension, dyslipidemia, overweight, obesity and metabolic syndrome. Subjects born SGA are in need of a correct diagnostic and eventually therapeutic approach.

Isolated growth hormone deficiency (GHD) in childhood and adolescence: recent advances

The diagnosis of GH deficiency (GHD) in childhood is a multistep process involving clinical history, examination with detailed auxology, biochemical testing, and pituitary imaging, with an increasing contribution from genetics in patients with congenital GHD. Our increasing understanding of the factors involved in the development of somatotropes and the dynamic function of the somatotrope network may explain, at least in part, the development and progression of childhood GHD in different age groups. With respect to the genetic etiology of isolated GHD (IGHD), mutations in known genes such as those encoding GH (GH1), GHRH receptor (GHRHR), or transcription factors involved in pituitary development, are identified in a relatively small percentage of patients suggesting the involvement of other, yet unidentified, factors. Genome-wide association studies point toward an increasing number of genes involved in the control of growth, but their role in the etiology of IGHD remains unknown. Despite the many years of research in the area of GHD, there are still controversies on the etiology, diagnosis, and management of IGHD in children. Recent data suggest that childhood IGHD may have a wider impact on the health and neurodevelopment of children, but it is yet unknown to what extent treatment with recombinant human GH can reverse this effect. Finally, the safety of recombinant human GH is currently the subject of much debate and research, and it is clear that long-term controlled studies are needed to clarify the consequences of childhood IGHD and the long-term safety of its 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.

Impact of the growth hormone replacement on bone status in growth hormone deficient adults

INTRODUCTION

Growth hormone deficiency (GHD) is associated with reduced bone mineral density (BMD). GH replacement has positive effect on BMD but the magnitude of this effect and its mechanism are debated.

OBJECTIVES

The objectives of this study was first, to assess the effect of GH replacement on BMD, and second, to evaluate the effect of GH treatment on bone turnover and microarchitecture and to assess the factors influencing the effect of the therapy on BMD.

PATIENTS AND METHODS

Adult GHD (AO-GHD) and childhood onset GHD (CO-GHD) patients treated with GH using IGF-I normalization GH replacement regimen were prospectively followed during 2 years. Lumbar spine (L1-L4) and total femur BMD by Hologic discovery, in the subset of patients also bone turnover markers; osteocalcin and carboxy-terminal collagen crosslinks (CTx) were assessed at baseline and at months 3, 6, 12 and 24, respectively. The trabecular bone score (TBS) derived from lumbar spine DXA by the iNsight® software was assessed in a subset of study population at baseline and months 12 and 24.

RESULTS

In total, 147 GHD patients (age 35.1 years, 84 males/63 females, 43 of childhood onset GHD/104 AO-GHD) were included. BMD of lumbar spine and femur increased significantly during the treatment (14% and 7% increase at 2 years, respectively; p<0.0001). Bone markers increased during the first 12 months of treatment with subsequent decrease of CTx. At month 24, significant increase in TBS was observed (4%, p=0.02). BMD increase was significantly higher in males (15% increase in males vs. 10% in females, p=0.037) and childhood onset GHD (CO-GHD) patients (13% increase in CO-GHD, p=0.004).

CONCLUSION

GH supplementation leads to an increase of BMD with corresponding changes in bone turnover markers and changes in microarchitecture as assessed by trabecular bone score. Positive effect of GH on bone status is more pronounced in males and CO-GHD adults.

Growth hormone treatment in boys with Duchenne muscular dystrophy and glucocorticoid-induced growth failure

This study evaluated efficacy and safety of growth hormone treatment in Duchenne muscular dystrophy boys with glucocorticoid-induced growth failure. We reviewed 39 consecutive boys (average age 11.5 years; 32 ambulatory) treated with growth hormone for 1 year during a four-year period. Boys were on long-term daily deflazacort or prednisone (mean duration 5 ± 2.2 years; dosing regimen prednisone 0.75 mg/kg/day equivalent). Primary outcomes were growth velocity and height-for-age z-scores (height SD) at 1 year. Height velocity increased from 1.3 ± 0.2 to 5.2 ± 0.4 cm/year on growth hormone (p<0.0001). Pre-growth hormone decline in height SD (-0.5 ± 0.2SD/year) stabilized at height SD -2.9 ± 0.2 on growth hormone (p<0.0001). The rate of weight gain was unchanged, at 2.8 ± 0.6 kg/year pre-growth hormone and 2.6 ± 0.7 kg/year at 1 year. Motor function decline was similar pre-growth hormone and at 1 year. Cardiopulmonary function was unchanged. Three experienced side effects. In this first comprehensive report of growth hormone in Duchenne muscular dystrophy, growth hormone improved growth at 1 year, without detrimental effects observed on neuromuscular and cardiopulmonary function.

The effect of growth hormone deficiency on size-corrected bone mineral measures in pre-pubertal children

Growth hormone deficiency (GHD) in children has been frequently perceived to be a cause of low bone mass accrual. The confounding effects of poor growth limit the interpretation of prior studies of bone health in GHD. We studied size-corrected bone mineral measures in 30 pre-pubertal GHD children and 75 healthy controls. Our study shows that size-corrected whole-body bone mineral content of GHD children were comparable with controls.

INTRODUCTION

The purpose of this study is to evaluate the effects of GHD on size-corrected bone measures at the lumbar spine (LS) and the whole body (WB).

METHODS

LS bone area (BA), LS bone mineral content (BMC), WB BA, WB BMC, and lean body mass (LBM) were measured in 30 pre-pubertal GHD children and 75 controls by dual-energy X-ray absorptiometry. Multiple linear regressions were used to calculate size-corrected (Sc) LS BA(Sc), LS BMC(Sc), WB BA(Sc), and WB BMC(Sc) from control subjects using height and age as independent variables. Furthermore, the relationship between muscle and bone was studied by first assessing LBM for height (LBM(Ht)) and then determining WB BMC for LBM (WB BMC(LBM)). All values were converted to Z-scores and compared with the control.

RESULTS

At diagnosis, WB BMC(Sc) Z-score of GHD children was not significantly different from controls. However, mean Z-scores of LS BA(Sc) (-0.89 ± 0.84, p < 0.0001), LS BMC(Sc) (-0.70 ± 1.1, p < 0.001), WB BA(Sc) (-0.65 ± 1.0, p < 0.006), and LBM(Ht) (-0.66 ± 1.7, p < 0.01) were significantly reduced, and WB BMC(Lbm) (0.78 ± 1.5, p < 0.003) was significantly higher in GHD children than controls.

CONCLUSION

Size-corrected WB BMC of GHD children were comparable with controls, and bones were normally adapted for muscle mass. Determinants of bone strength which may primarily be affected by GHD are muscle mass, bone size, and geometry rather than bone mass.

Muscle-bone characteristics in children with Prader-Willi syndrome

BACKGROUND

A decrease in muscle mass, low motor performance, and normal lumbar spine bone mineral density (BMD) have been reported in children with Prader-Willi syndrome (PWS). However, these data are limited by the fact that PWS children (who have short stature) were compared to age-matched healthy or obese individuals of normal height.

OBJECTIVE

The goal of the present study was to compare bone and muscle characteristics in PWS children to sex- and age- or height-matched healthy subjects.

MATERIALS AND METHODS

The study population included 17 PWS children (ages 6.2 to 17.5 yr; nine girls) who were not treated with GH. The axial skeleton was analyzed at the lumbar spine using dual-energy x-ray absorptiometry, and the appendicular skeleton (radius and tibia) was evaluated using peripheral quantitative computed tomography. Muscle parameters (mass, size, and functional parameters) were measured by dual-energy x-ray absorptiometry, peripheral quantitative computed tomography, and jumping mechanography, respectively.

RESULTS

Compared to height-matched controls, PWS patients had normal axial and appendicular BMD, as well as normal muscle size. Compared to age- or height-matched controls of normal weight, PWS patients had lower maximal muscle force and power relative to body mass during jumping. PWS patients had similar absolute maximal muscle force but lower absolute maximal power compared to age- or height-matched controls. Relationships between bone mass and muscle size and force were similar in PWS patients and in healthy subjects.

CONCLUSION

Relative to their height, PWS patients not treated with GH had normal axial and appendicular BMD, muscle size, and muscle-bone relationships.

Microarchitecture, but not bone mechanical properties, is rescued with growth hormone treatment in a mouse model of growth hormone deficiency

Growth hormone (GH) deficiency is related to an increased fracture risk although it is not clear if this is due to compromised bone quality or a small bone size. We investigated the relationship between bone macrostructure, microarchitecture and mechanical properties in a GH-deficient (GHD) mouse model undergoing GH treatment commencing at an early (prepubertal) or late (postpubertal) time point. Microcomputed tomography images of the femur and L4 vertebra were obtained to quantify macrostructure and vertebral trabecular microarchitecture, and mechanical properties were determined using finite element analyses. In the GHD animals, bone macrostructure was 25 to 43% smaller as compared to the GH-sufficient (GHS) controls (P < 0.001). GHD animals had 20% and 19% reductions in bone volume ratio (BV/TV) and trabecular thickness (Tb.Th), respectively. Whole bone mechanical properties of the GHD mice were lower at the femur and vertebra (67% and 45% resp.) than the GHS controls (P < 0.001). Both early and late GH treatment partially recovered the bone macrostructure (15 to 32 % smaller than GHS controls) and the whole bone mechanical properties (24 to 43% larger than GHD animals) although there remained a sustained 27-52% net deficit compared to normal mice (P < 0.05). Importantly, early treatment with GH led to a recovery of BV/TV and Tb.Th with a concomitant improvement of trabecular mechanical properties. Therefore, the results suggest that GH treatment should start early, and that measurements of microarchitecture should be considered in the management of GHD.

The benefits of growth hormone therapy in patients with Turner syndrome, Noonan syndrome and children born small for gestational age

This review will summarize the effects of growth hormone (GH) on height, body composition, bone and psychosocial parameters in children with Turner syndrome or Noonan syndrome and those born small for gestational age. The safety of GH treatment in children with these diagnoses is also reported. Despite the reported efficacy and safety of GH in these indications, however, not all children achieve their target height potential, due in some part to poor adherence to GH therapy regimens; indeed up to 50% of children are less than fully compliant with treatment. With this in mind the present and future administration of GH therapy is discussed with respect to advances being made in the presentation of GH for injection and advances in GH injection devices. It is hoped that such progress, aimed at making the administration of GH easier and less painful for the patient will improve treatment adherence and outcome benefits.

Timing of growth hormone treatment affects trabecular bone microarchitecture and mineralization in growth hormone deficient mice

Growth hormone (GH) is essential in the development of bone mass, and a growth hormone deficiency (GHD) in childhood is frequently treated with daily injections of GH. It is not clear what effect GHD and its treatment has on bone. It was hypothesized that GHD would result in impaired microarchitecture, and an early onset of treatment would result in a better recovery than late onset. Growth hormone deficient homozygous (lit/lit) mice of both sexes were divided into two treatment groups receiving daily injections of GH, starting at an early (21 days of age) or a late time point (35 days of age, corresponding to the end of puberty). A group of heterozygous mice with normal levels of growth hormone served as controls. In vivo micro-computed tomography scans of the fourth lumbar vertebra were obtained at five time points between 21 and 60 days of age, and trabecular morphology and volumetric BMD were analyzed to determine the effects of GH on bone microarchitecture. Early GH treatment led to significant improvements in bone volume ratio (p=0.006), tissue mineral density (p=0.005), and structure model index (p=0.004) by the study endpoint (day 60), with no detected change in trabecular thickness. Trabecular number increased and trabecular separation decreased in GHD mice regardless of treatment compared to heterozygous mice. This suggests fundamental differences in the structure of trabecular bone in GHD and GH treated mice, reflected by an increased number of thinner trabeculae in these mice compared to heterozygous controls. There were no significant differences between the late treatment group and GHD mice except for connectivity density. Taken together, these results indicate that bone responds to GH treatment initiated before puberty but not to treatment commencing post-puberty, and that GH treatment does not rescue the structure of trabecular bone to that of heterozygous controls.

Growth hormone: health considerations beyond height gain

The therapeutic benefit of growth hormone (GH) therapy in improving height in short children is widely recognized; however, GH therapy is associated with other metabolic actions that may be of benefit in these children. Beneficial effects of GH on body composition have been documented in several different patient populations as well as improvements in lipid profile. Marked augmentation of bone mineral density also seems evident in many pediatric populations. Some of these benefits may require continued therapy past the acquisition of adult height. With long-term therapy of any kind, the adverse consequences of treatment should also be considered. Fortunately, long-term GH treatment seems to be safe and well-tolerated. This review describes the long-term metabolic effects of GH treatment in the pediatric population and considers how these may benefit children who are treated with GH.

Growth patterns and the use of growth hormone in the mucopolysaccharidoses

Short stature is characteristic of patients with mucopolysaccharidosis (MPS) diseases. For children with skeletal dysplasias, such as MPS, it is important to know the natural history of growth. An understanding of the natural growth pattern in each MPS disease provides a measurement to which treatments can be compared, as well as data which can help families and providers make individualized decisions about growth promoting treatments. Multiple advancements have been made in the treatment of MPS with both hematopoietic cell transplantation (HCT) and enzyme replacement therapy (ERT). The long term benefit of these treatments on growth is unknown. This article will review the published data on growth in children with MPS, and describe preliminary data on the use of human growth hormone (hGH) in children with MPS.

Assessment of material, structural, and functional properties of the human skeleton by pQCT systems

Peripheral quantitative computed tomography (pQCT) systems measure bone parameters noninvasively using low radiation doses. This limits image resolution but is practical for the diagnosis and quantitative monitoring of the properties of the peripheral human skeleton. pQCT determines volumetric bone mineral density separately in trabecular and cortical bone. It may combine densitometry determinations with geometric estimates and use strain-stress indexes, and it may be used to analyze muscle variables in some areas, allowing the study of regional fragility. Experimental and clinical ex vivo studies show that pQCT variables correlate with biomechanical predictors of fragility and/or fractures. Since pQCT was approved by the US Food and Drug Administration in 1997, new skeletal regions (human femur and mandible) have been considered in the development of the system. Basically, pQCT explores intraindividual and interindividual variations in greater detail and compares the impact of skeletal diseases, risk factors, and anabolic and catabolic treatments within a given bone cross section.

Skeletal muscle and mortality results from the InCHIANTI Study

BACKGROUND

Sarcopenia, the age-related loss of muscle mass, may not be an isolated process but is associated with an increase in fat mass. The aim of this study was to estimate the mortality risk of sarcopenia in the presence or absence of obesity.

METHODS

Data are from 934 participants aged 65 years or older, enrolled in the "Invecchiare in Chianti" study, and followed for 6 years. At baseline, a peripheral quantitative computerized tomography (pQCT) scan was performed on all participants to evaluate the muscle density, and the muscular and fat cross-sectional areas of the calf. Walking speed was measured on a 7-m track. Cox proportional hazard models were performed to estimate the association of pQCT measures (per 1 standard deviation increase) with mortality.

RESULTS

Unadjusted analyses showed significant associations of muscle density (hazard ratio [HR] 0.78, 95% confidence interval [CI] 0.69-0.88), muscle area (HR 0.75, 95% CI 0.66-0.86), and fat area (HR 0.82, 95% CI 0.73-0.92) with mortality. After adjustment for potential confounders, no body composition parameter was significantly associated with mortality. Walking speed (used as a reference measure to verify whether the negative results were due to peculiarities of the study sample) confirmed its well-established association with mortality risk (HR 0.73, 95% CI 0.60-0.88). These results did not change after the analyses were stratified according to sarcopenia and body mass index groups, and restricted to participants with frailty or a high inflammatory profile.

CONCLUSIONS

Calf skeletal muscle and fat mass are not significant risk factors for mortality in community-dwelling older adults. Walking speed confirmed to be a powerful predictor of health-related events.

Muscle function improves during growth hormone therapy in short children born small for gestational age: results of a peripheral quantitative computed tomography study on body composition

BACKGROUND

Short small for gestational age (SGA) children can be affected by a lack of muscle mass rather than fat mass. They also face a high risk of the metabolic syndrome developing after childhood. It is not known whether low muscle mass influences muscle function.

AIM

Our aim was to investigate muscle-fat distribution and muscle function before and during GH treatment in short SGA children.

PATIENTS

A total of 34 prepubertal short SGA children (11 females, seven with Silver-Russell syndrome) were included in the study. Mean values were: age at GH start 7.3 yr; height sd score (SDS) -3.3; and birth weight SDS -2.7.

METHODS

Investigations over 24 months on GH treatment (57 microg/kg.d) were performed. Body composition, including fat area and muscle area (MA), was assessed through peripheral quantitative computed tomography (XCT 2000; Stratec, Inc., Pforzheim, Germany). Maximal isometric grip force was performed with a Jamar dynamometer (Preston, Jackson, MI). Comparison with height-dependent reference values (SDS(Height)) was calculated.

RESULTS

MA SDS(Height) at GH start was -1.8 and increased to -0.8 (P < 0.001) and -0.8, and fat area SDS(Height) decreased from -0.6 to -2.0 (P < 0.001) and -1.5 after 12 and 24 months on GH. Maximal isometric grip force SDS(Height) increased from -0.9 to 0.3 (P < 0.001) and 0.5. MA at start correlated negatively with height velocity (R = -0.54; P < 0.001) and MA SDS at start and Delta-height SDS during the first year of GH treatment (R = -0.40; P < 0.001).

CONCLUSIONS

Short stature in SGA children is associated with low muscle mass and function. Supraphysiological GH doses led to a concomitant increment in height, muscle mass, and function, whereas fat mass decreased. Furthermore, body composition at GH start gives insight into GH responsiveness and the individual risk of metabolic syndrome.