Bone mineral density and effects of growth hormone treatment in prepubertal children with Prader-Willi syndrome: a randomized controlled trial

Endocrine features of Prader-Willi syndrome: a narrative review focusing on genotype-phenotype correlation

Prader-Willi syndrome (PWS) is a complex genetic disorder caused by three different types of molecular genetic abnormalities. The most common defect is a deletion on the paternal 15q11-q13 chromosome, which is seen in about 60% of individuals. The next most common abnormality is maternal disomy 15, found in around 35% of cases, and a defect in the imprinting center that controls the activity of certain genes on chromosome 15, seen in 1-3% of cases. Individuals with PWS typically experience issues with the hypothalamic-pituitary axis, leading to excessive hunger (hyperphagia), severe obesity, various endocrine disorders, and intellectual disability. Differences in physical and behavioral characteristics between patients with PWS due to deletion versus those with maternal disomy are discussed in literature. Patients with maternal disomy tend to have more frequent neurodevelopmental problems, such as autistic traits and behavioral issues, and generally have higher IQ levels compared to those with deletion of the critical PWS region. This has led us to review the pertinent literature to investigate the possibility of establishing connections between the genetic abnormalities and the endocrine disorders experienced by PWS patients, in order to develop more targeted diagnostic and treatment protocols. In this review, we will review the current state of clinical studies focusing on endocrine disorders in individuals with PWS patients, with a specific focus on the various genetic causes. We will look at topics such as neonatal anthropometry, thyroid issues, adrenal problems, hypogonadism, bone metabolism abnormalities, metabolic syndrome resulting from severe obesity caused by hyperphagia, deficiencies in the GH/IGF-1 axis, and the corresponding responses to treatment.

Subcutaneous adipose tissue is a positive predictor for bone mineral density in prepubertal children with Prader-Willi syndrome independent of lean mass

OBJECTIVES

Emerging evidence suggests a fat depot-specific relationship with bone mineral density (BMD) in children, particularly in those who are overweight/obese. However, this has not yet been investigated in detail in children with Prader-Willi syndrome (PWS), a genetic syndrome characterized by a decreased lean mass (LM) and increased fat mass (FM). The objective of this study is to investigate the relationships of LM and FM, particularly fat distribution, with bone mineral parameters.

METHODS

This is a retrospective and cross-sectional study. Forty-seven prepubertal Japanese children with PWS (22 males, mean age: 6.86 years) were included. No subjects had type 2 diabetes mellitus or osteoporotic medications. LM, FM, and BMD and bone mineral content in the total body less head and the lumbar spine were measured using dual-energy x-ray absorptiometry, in addition to subcutaneous/visceral adipose tissue (SAT/VAT), and the ratio of VAT to SAT (V/S) by computed tomography at the umbilical level. Bone mineral apparent density was calculated to correct for bone size.

RESULTS

LM positively correlated with bone mineral parameters after controlling for age, sex, growth hormone (GH) treatment, and FM. Although FM did not correlate with bone mineral parameters, compartment-specific analysis revealed that SAT positively and V/S negatively correlated with bone mineral parameters after controlling for age, sex, GH treatment and LM.

CONCLUSIONS

A compartment-specific effect of FM on bone mineral parameters was noted such that SAT was a positive predictor for BMD independent of LM in prepubertal children with PWS.

Irisin and Secondary Osteoporosis in Humans

Irisin is a peptide secreted by skeletal muscle following exercise that plays an important role in bone metabolism. Numerous experiments in vitro and in mouse models have shown that the administration of recombinant irisin promotes osteogenesis, protects osteocytes from dexamethasone-induced apoptosis, prevents disuse-induced loss of bone and muscle mass, and accelerates fracture healing. Although some aspects still need to be elucidated, such as the dose- and frequency-dependent effects of irisin in cell cultures and mouse models, ample clinical evidence is emerging to support its physiological relevance on bone in humans. A reduction in serum irisin levels, associated with an increased risk of osteoporosis and bone fractures, was observed in postmenopausal women and in both men and women during aging, Recently, cohort studies of subjects with secondary osteoporosis showed that these patients have lower circulating levels of irisin, suggesting that this myokine could be a novel marker to monitor bone quality in this disease. Although there are still few studies, this review discusses the emerging data that are highlighting the involvement of irisin in some diseases that cause secondary osteoporosis.

The genetic background and vitamin D supplementation can affect irisin levels in Prader-Willi syndrome

BACKGROUND

Prader-Willi syndrome (PWS) is associated to distinctive clinical symptoms, including obesity, cognitive and behavioral disorders, and bone impairment. Irisin is a myokine that acts on several target organs including brain adipose tissue and bone. The present study was finalized to explore circulating levels of irisin in children and adult PWS patients.

METHODS

Seventy-eight subjects with PWS, 26 children (15 females, mean age 9.48 ± 3.6 years) and 52 adults (30 females, mean age 30.6 ± 10.7) were enrolled. Irisin serum levels were measured in patients and controls. Its levels were related with anthropometric and metabolic parameters, cognitive performance and bone mineral density either in pediatric or adult PWS. Multiple regression analysis was also performed.

RESULTS

Irisin serum levels in PWS patients did not show different compared with controls. A more in-depth analysis showed that both pediatric and adult PWS with DEL15 displayed significantly reduced irisin levels compared to controls. Otherwise, no differences in irisin concentration were found in UPD15 patients with respect to controls. Our study revealed that in pediatric PWS the 25(OH) vitamin-D levels affected irisin serum concentration. Indeed, patients who were not supplemented with vitamin D showed lower irisin levels than controls and patients performing the supplementation. Multiple regression analysis showed that irisin levels in pediatric and adult PWS were predicted by the genetic background and 25(OH)-vitamin D levels, whereas in a group of 29 adult PWS also by intelligent quotient.

CONCLUSION

We demonstrated the possible role of genetic background and vitamin-D supplementation on irisin serum levels in PWS patients.

Growth hormone treatment and bone mineral density in pediatric patients with Prader-Willi syndrome

OBJECTIVES

Previous reports indicate that growth hormone (GH) treatment for Prader-Willi syndrome (PWS) improves bone mineral density (BMD) only when initiated at a young age and not when initiated in adulthood. However, there are no data on BMD during long-term GH treatment of Japanese children and adolescents with PWS. Thus, this study aimed to investigate BMD changes among patients with PWS, who were undergoing GH treatment from childhood to adolescence.

METHODS

Sixty-seven pediatric patients with PWS who had GH treatment initiated during childhood between January 2003 and June 2020 were evaluated. To avoid underestimation, we used total body BMD, which was evaluated using dual-X-ray absorptiometry adjusted for the BMD z-score using patient height, sex, and age.

RESULTS

In both sexes, age was negatively correlated with the BMD-standard deviation score (SDS) (male: r=-0.156 [p=0.042]; female: r=-0.197 [p=0.043]), which started to decrease in childhood.

CONCLUSIONS

The BMD-SDS of patients with PWS decreases gradually despite GH treatment. As there are no clear recommendations about monitoring of bone health in patients with PWS, further studies are needed to improve the guidelines for screening of BMD and treatment of patients with PWS.

Growth Hormone Treatment for Adults With Prader-Willi Syndrome: A Meta-Analysis

CONTEXT

Features of Prader-Willi syndrome (PWS) overlap with features of growth hormone (GH) deficiency, like small hands and feet, short stature, increased body fat, and low muscle mass and strength. In children with PWS, GH treatment (GHt) improves physical health and cognition. GHt has become the standard of care in PWS children, but in adults this is not yet the case.

OBJECTIVE

This work aims to provide an overview of the current knowledge on GHt in PWS adults.

METHODS

Medline, Embase, and the Cochrane Central Register of Controlled Trials databases were searched. Study selection included randomized clinical trials (RCTs) and nonrandomized (un)controlled trials (NRCTs) that reported data for adults with PWS, who received GHt for at least 6 months. Data on body composition, body mass index (BMI), cardiovascular end points, bone, cognitive function, quality of life, and safety were extracted.

RESULTS

Nine RCTs and 20 NRCTs were included. Body composition improved during 12 months of GHt with an increase in mean (95% CI) lean body mass of 1.95 kg (0.04 to 3.87 kg) and a reduction of mean (95% CI) fat mass of -2.23% (-4.10% to -0.36%). BMI, low-density lipoprotein cholesterol levels, fasting glucose levels, and bone mineral density did not change during GHt. There were no major safety issues.

CONCLUSION

GHt appears to be safe and improves body composition in adults with PWS. Because poor body composition is closely linked to the observed high incidence of cardiovascular morbidity in adults with PWS, improving body composition might reduce cardiovascular complications in this vulnerable patient group.

Effects of Childhood Multidisciplinary Care and Growth Hormone Treatment on Health Problems in Adults with Prader-Willi Syndrome

Prader-Willi syndrome (PWS) is a complex hypothalamic disorder. Features of PWS include hyperphagia, hypotonia, intellectual disability, and pituitary hormone deficiencies. The combination of growth hormone treatment and multidisciplinary care (GHMDc) has greatly improved the health of children with PWS. Little is known about the effects of childhood GHMDc on health outcomes in adulthood. We retrospectively collected clinical data of 109 adults with PWS. Thirty-nine had received GHMDc during childhood and adolescence (GHMDc+ group) and sixty-three had never received growth hormone treatment (GHt) nor multidisciplinary care (GHMDc− group). Our systematic screening revealed fewer undetected health problems in the GHMDc+ group (10%) than in the GHMDc− group (84%). All health problems revealed in the GHMDc+ group had developed between the last visit to the paediatric and the first visit to the adult clinic and/or did not require treatment. Mean BMI and the prevalence of diabetes mellitus type 2 were significantly lower in the GHMDc+ group compared to the GHMDc− group. As all patients who received GHt were treated in a multidisciplinary setting, it is unknown which effects are the result of GHt and which are the result of multidisciplinary care. However, our data clearly show that the combination of both has beneficial effects. Therefore, we recommend continuing GHMDc after patients with PWS have reached adult age.

Magel2 Modulates Bone Remodeling and Mass in Prader-Willi Syndrome by Affecting Oleoyl Serine Levels and Activity

Among a multitude of hormonal and metabolic complications, individuals with Prader-Willi syndrome (PWS) exhibit significant bone abnormalities, including decreased BMD, osteoporosis, and subsequent increased fracture risk. Here we show in mice that loss of Magel2, a maternally imprinted gene in the PWS critical region, results in reduced bone mass, density, and strength, corresponding to that observed in humans with PWS, as well as in individuals suffering from Schaaf-Yang syndrome (SYS), a genetic disorder caused by a disruption of the MAGEL2 gene. The low bone mass phenotype in Magel2^-/- mice was attributed to reduced bone formation rate, increased osteoclastogenesis and osteoclast activity, and enhanced trans-differentiation of osteoblasts to adipocytes. The absence of Magel2 in humans and mice resulted in reduction in the fatty acid amide bone homeostasis regulator, N-oleoyl serine (OS), whose levels were positively linked with BMD in humans and mice as well as osteoblast activity. Attenuating the skeletal abnormalities in Magel2^-/- mice was achieved with chronic administration of a novel synthetic derivative of OS. Taken together, Magel2 plays a key role in modulating bone remodeling and mass in PWS by affecting OS levels and activity. The use of potent synthetic analogs of OS should be further tested clinically as bone therapeutics for treating bone loss. © 2018 American Society for Bone and Mineral Research.

Visceral adipose tissue increases shortly after the cessation of GH therapy in adults with Prader-Willi syndrome

GH therapy in pediatric patients with Prader-Willi syndrome (PWS) improves body composition, but discontinuation of GH after achieving adult height has been implicated in its deterioration. Although there is evidence for the deleterious effects of visceral adipose tissue (VAT) rather than subcutaneous adipose tissue (SAT) on the development of obesity-related complications, the effects of GH discontinuation on fat distribution in adults with PWS has not been fully investigated. Therefore, we utilized dual-energy X-ray absorptiometry (DEXA) and abdominal computed tomography (CT) to compare the fat distribution between before and 6 months or 12 months after the cessation of GH therapy in 7 adult PWS patients. GH therapy was initiated at a mean age of 4.1 ± 1.4 years and discontinued at a mean age of 18.9 ± 1.8 years. Serum IGF-1 levels were decreased by discontinuation of GH therapy. Fat mass was significantly increased 6 and 12 months after GH cessation, whereas muscle mass and bone mineral density were unchanged during both study periods. Abdominal CT analysis revealed that elevations in fat mass were due to increases in VAT rather than SAT. Circulating low-density lipoprotein (LDL) cholesterol levels were significantly elevated 6 months after GH cessation. In conclusion, discontinuation of GH therapy caused rapid increases in visceral adipose tissue and LDL cholesterol levels. These findings indicate that continuation of GH therapy may be a therapeutic option to maintain body composition; however, further studies regarding the long-term benefits and adverse effects of GH therapy in adults with PWS are required.

Analysis of Circulating Mediators of Bone Remodeling in Prader-Willi Syndrome

We tested the hypothesis that the levels of bone remodeling mediators may be altered in Prader-Willi syndrome (PWS). We assessed RANKL, OPG, sclerostin, DKK-1 serum levels, and bone metabolism markers in 12 PWS children (7.8 ± 4.3 years), 14 PWS adults (29.5 ± 7.2 years), and 31 healthy controls matched for sex and age. Instrumental parameters of bone mineral density (BMD) were also evaluated. Lumbar spine BMD Z-scores were reduced in PWS children (P < 0.01), reaching osteopenic levels in PWS adults. PWS patients showed lower 25(OH)-vitamin D serum levels than controls (P < 0.001). Osteocalcin was increased in PWS children but reduced in adults respect to controls (P < 0.005 and P < 0.01, respectively). RANKL levels were higher in both pediatric and PWS adults than controls (P < 0.004), while OPG levels were significantly reduced (P < 0.004 and P < 0.006, respectively). Sclerostin levels were increased in children (P < 0.04) but reduced in adults compared to controls (P < 0.01). DKK-1 levels did not show significant difference between patients and controls. In PWS patients, RANKL, OPG, and sclerostin significantly correlated with metabolic and bone instrumental parameters. Consistently, with adjustment for age, multiple linear regression analysis showed that BMD and osteocalcin were the most important predictors for RANKL, OPG, and sclerostin in children, and GH and sex steroid replacement treatment in PWS adults. We demonstrated the involvement of RANKL, OPG, and sclerostin in the altered bone turnover of PWS subjects suggesting these molecules as markers of bone disease and new potential pharmacological targets to improve bone health in PWS.

Hormonal, metabolic and skeletal phenotype of Schaaf-Yang syndrome: a comparison to Prader-Willi syndrome

Background

Nonsense and frameshift mutations in the maternally imprinted, paternally expressed gene MAGEL2, located in the Prader-Willi critical region 15q11-15q13, have been reported to cause Schaaf-Yang syndrome (SYS), a genetic disorder that manifests as developmental delay/intellectual disability, hypotonia, feeding difficulties and autism spectrum disorder. Prader-Willi syndrome (PWS) is a genetic disorder characterised by severe infantile hypotonia, hypogonadotrophic hypogonadism, early childhood onset obesity/hyperphagia, developmental delay/intellectual disability and short stature. Scoliosis and growth hormone insufficiency are also prevalent in PWS.

There is extensive documentation of the endocrine and metabolic phenotypes for PWS, but not for SYS. This study served to investigate the hormonal, metabolic and body composition phenotype of SYS and its potential overlap with PWS.

Methods

In nine individuals with SYS (5 female/4 male; aged 5–17 years), we measured serum ghrelin, glucose, insulin-like growth factor 1 (IGF-1), insulin-like growth factor binding protein 3, follicle-stimulating hormone, luteinising hormone, thyroid-stimulating hormone, free T4, uric acid and testosterone, and performed a comprehensive lipid panel. Patients also underwent X-ray and dual-energy X-ray absorptiometry analyses to assess for scoliosis and bone mineral density.

Results

Low IGF-1 levels despite normal weight/adequate nutrition were observed in six patients, suggesting growth hormone deficiency similar to PWS. Fasting ghrelin levels were elevated, as seen in individuals with PWS. X-rays revealed scoliosis >10° in three patients, and abnormal bone mineral density in six patients, indicated by Z-scores of below −2 SDs.

Conclusion

This is the first analysis of the hormonal, metabolic and body composition phenotype of SYS. Our findings suggest that there is marked, but not complete overlap between PWS and SYS.

Review of Prader-Willi syndrome: the endocrine approach

Prader-Willi syndrome (PWS) is a complex genetic disorder with implications on the endocrine and neurologic systems, metabolism, and behavior. Early in life, PWS is characterized by hypotonia and failure to thrive, followed by obesity and hyperphagia. Patients with PWS develop hypothalamic dysfunction which may lead growth hormone deficiency (GHD), hypogonadism, hypothyroidism, adrenal insufficiency, and poor bone mineral density (BMD). In addition to hypothalamic dysfunction, individuals with PWS have increased risk for obesity which may be complicated by metabolic syndrome and type 2 diabetes mellitus (T2DM). In this paper, we will review the current literature pertaining to the endocrine concerns of PWS and current recommendations for screening and management of these conditions.

Diagnosis and treatment of GH deficiency in Prader-Willi syndrome

Prader-Willi syndrome (PWS) results from under-expression of the paternally-derived chromosomal region 15q11-13. Growth failure is a recognized feature of PWS, and both quantitative and qualitative defects of the GH/IGF-I axis revealing GH deficiency (GHD) have been demonstrated in most children with PWS. In PWS adults, criteria for GHD are biochemically fulfilled in 8-38% of the studied cohorts. Published data support benefits of early institution of GH therapy (GHT) in PWS children, with positive effects on statural growth, body composition, metabolic homeostasis, and neurocognitive function. Like in pediatric PWS, GHT also yields beneficial effects on lean and body fat, exercise capacity, and quality of life of PWS adults. Although GHT has been generally administered safely in PWS children and adults, careful surveillance of risks is mandatory during prolonged GH replacement for all PWS individuals.

Anthropometric adjustments are helpful in the interpretation of BMD and BMC Z-scores of pediatric patients with Prader-Willi syndrome

Anthropometric adjustments of bone measurements are necessary in Prader-Willi syndrome patients to correctly assess the bone status of these patients. This enables physicians to get a more accurate diagnosis of normal versus abnormal bone, allow for early and effective intervention, and achieve better therapeutic results.

INTRODUCTION

Bone mineral density (BMD) is decreased in patients with Prader-Willi syndrome (PWS). Because of largely abnormal body height and weight, traditional BMD Z-scores may not provide accurate information in this patient group. The goal of the study was to assess a cohort of individuals with PWS and characterize the development of low bone density based on two adjustment models applied to a dataset of BMD and bone mineral content (BMC) from dual-energy X-ray absorptiometry (DXA) measurements.

METHODS

Fifty-four individuals, aged 5-20 years with genetically confirmed PWS, underwent DXA scans of spine and hip. Thirty-one of them also underwent total body scans. Standard Z-scores were calculated for BMD and BMC of spine and total hip based on race, sex, and age for all patients, as well as of whole body and whole-body less head for those patients with total-body scans. Additional Z-scores were generated based on anthropometric adjustments using weight, height, and percentage body fat and a second model using only weight and height in addition to race, sex, and age.

RESULTS

As many PWS patients have abnormal anthropometrics, addition of explanatory variables weight, height, and fat resulted in different bone classifications for many patients. Thus, 25-70 % of overweight patients, previously diagnosed as normal, were subsequently diagnosed as below normal, and 40-60 % of patients with below-normal body height changed from below normal to normal depending on bone parameter.

CONCLUSIONS

This is the first study to include anthropometric adjustments into the interpretation of BMD and BMC in children and adolescents with PWS. This enables physicians to get a more accurate diagnosis of normal versus abnormal BMD and BMC and allows for early and effective intervention.

Association between physical activity and bone in children with Prader-Willi syndrome

BACKGROUND

The aim of the study was to determine if physical activity (PA) is associated with bone health in children with Prader-Willi syndrome (PWS).

METHODS

Participants included 23 children with PWS (age: 11.0±2.0 years). PA, measured by accelerometry, was categorized into light, moderate, vigorous and moderate plus vigorous intensities. Hip, total body minus the head (body), bone mineral content (BMC), bone mineral density (BMD) and BMD z-score (BMDz) were measured by dual X-ray absorptiometry. Separate hierarchical regression models were completed for all bone parameters, PA intensity and select covariates.

RESULTS

Moderate PA and select covariates explained the most variance in hip BMC (84.0%), BMD (61.3%) and BMDz (34.9%; p<0.05 for all). Likewise, for each body parameter, moderate PA and select covariates explained the most variance in body BMC (75.8%), BMD (74.4%) and BMDz (31.8%; p<0.05 for all).

CONCLUSIONS

PA of at least moderate intensity appears important for BMC and BMD in children with PWS.

Growth hormone therapy for Prader-willi syndrome: challenges and solutions

Prader-Willi syndrome (PWS) is characterized by a dysregulation of growth hormone (GH)/insulin-like growth factor I axis, as the consequence of a complex hypothalamic involvement. PWS' clinical picture seems to resemble the classic non-PWS GH deficiency (GHD), including short stature, excessive body fat, decreased muscle mass, and impaired quality of life. GH therapy is able to ameliorate the phenotypic appearance of the syndrome, as well as to improve body composition, physical strength, and cognitive level. In this regard, however, some pathophysiologic and clinical questions still remain, representing a challenge to give the most appropriate care to PWS patients. Data about the prevalence of GHD in PWS children are not unequivocal, ranging from 40% to 100%. In this context, to establish whether the presence (or not) of GHD may have a different effect on clinical course during GH therapy may be helpful. In addition, the comparison of GH effects in PWS children diagnosed as small for gestational age with those obtained in subjects born appropriate for gestational age is of potential interest for future trials. Emerging information seems to demonstrate the maintenance of beneficial effects of GH therapy in PWS subjects after adolescent years. Thus, GH retesting after achievement of final height should be taken into consideration for all PWS patients. However, it is noteworthy that GH administration exerts positive effects both in PWS adults with and without GHD. Another critical issue is to clarify whether the genotype-phenotype correlations may be relevant to specific outcome measures related to GH therapy. Moreover, progress of our understanding of the role of GH replacement and concomitant therapies on bone characteristics of PWS is required. Finally, a long-term surveillance of benefits and risks of GH therapy is strongly recommended for PWS population, since most of the current studies are uncontrolled and of short duration.

Microscopic structure of dental hard tissues in primary and permanent teeth from individuals with Prader-Willi syndrome

OBJECTIVE

severe tooth wear, in terms of both erosive wear and attrition, is a significant problem in individuals with Prader-Willi syndrome (PWS). The purpose of the present study was to describe the structure of enamel and dentine in primary and permanent teeth from individuals with PWS.

DESIGN

thirty-two primary and 10 permanent teeth representing 16 individuals with PWS were investigated in the study. The enamel surface was studied using scanning electron microscopy (SEM). The microscopic structure of enamel and dentine was studied using SEM, microradiography and light microscopy.

RESULTS

the microscopic structure of enamel and dentine was found to be normal with the exception of a slight increase of interglobular dentine (IGD). Severe erosive defects were observed in primary teeth and also in permanent teeth with long exposure to the oral environment.

CONCLUSION

the erosive enamel defects in individuals with PWS seem more related to the factors in the oral environment than to enamel structure which appeared normal. The occurrence of IGD indicate deficient mineralization but is probably of minor clinical significance. Gastro-oesophageal reflux is worthy of further investigation in individuals with Prader-Willi syndrome.

Prader-Willi Critical Region, a Non-Translated, Imprinted Central Regulator of Bone Mass: Possible Role in Skeletal Abnormalities in Prader-Willi Syndrome

Prader-Willi Syndrome (PWS), a maternally imprinted disorder and leading cause of obesity, is characterised by insatiable appetite, poor muscle development, cognitive impairment, endocrine disturbance, short stature and osteoporosis. A number of causative loci have been located within the imprinted Prader-Willi Critical Region (PWCR), including a set of small non-translated nucleolar RNA's (snoRNA). Recently, micro-deletions in humans identified the snoRNA Snord116 as a critical contributor to the development of PWS exhibiting many of the classical symptoms of PWS. Here we show that loss of the PWCR which includes Snord116 in mice leads to a reduced bone mass phenotype, similar to that observed in humans. Consistent with reduced stature in PWS, PWCR KO mice showed delayed skeletal development, with shorter femurs and vertebrae, reduced bone size and mass in both sexes. The reduction in bone mass in PWCR KO mice was associated with deficiencies in cortical bone volume and cortical mineral apposition rate, with no change in cancellous bone. Importantly, while the length difference was corrected in aged mice, consistent with continued growth in rodents, reduced cortical bone formation was still evident, indicating continued osteoblastic suppression by loss of PWCR expression in skeletally mature mice. Interestingly, deletion of this region included deletion of the exclusively brain expressed Snord116 cluster and resulted in an upregulation in expression of both NPY and POMC mRNA in the arcuate nucleus. Importantly, the selective deletion of the PWCR only in NPY expressing neurons replicated the bone phenotype of PWCR KO mice. Taken together, PWCR deletion in mice, and specifically in NPY neurons, recapitulates the short stature and low BMD and aspects of the hormonal imbalance of PWS individuals. Moreover, it demonstrates for the first time, that a region encoding non-translated RNAs, expressed solely within the brain, can regulate bone mass in health and disease.

Bone status in genetic syndromes: a review

More and more data seem to indicate the presence of an increasing number of syndromes and genetic diseases characterized by impaired bone mass and quality. Meanwhile, the improvement of etiopathogenetic knowledge and the employment of more adequate treatments have generated a significant increase in survival related to these syndromes and diseases. It is thus important to identify and treat bone impairment in these patients in order to assure a better quality of life. This review provides an updated overview of bone pathophysiology and characteristics in patients with Down, Turner, Klinefelter, Marfan, Williams, Prader-Willi, Noonan, and 22q11 deletions syndrome. In addition, some options for the treatment of the bone status impairment in these patients will be briefly discussed.

Growth hormone treatment for osteoporosis in patients with scoliosis of Prader-Willi syndrome

BACKGROUND

Patients with Prader-Willi syndrome (PWS) have fragile bones. Osteoporosis is a major concern in scoliosis surgery. Our aim was to investigate bone mineral density (BMD) in PWS patients and to verify the efficacy of and scoliosis deterioration with growth hormone (GH) administration for osteoporosis.

METHODS

We followed 148 PWS patients who underwent lumbar spine (L2-4) BMD testing. Sixty-four patients had scoliosis, and 84 were non-scoliosis patients. Patients were treated with GH (0.245 mg/kg/week) until they reached a skeletal age of 17 years for males and 15 years for females. We also evaluated the effect of GH treatment on BMD in 101 patients (60 males, 41 females) undergoing BMD testing more than twice. The mean patient age was 5.4 years. The mean duration of GH administration was 54 months.

RESULTS

Mean lumbar BMD was 0.567 g/cm(2). Fifty patients (33.8%) had osteoporosis and 41 (27.7%) had osteopenia. There was no significant difference in mean BMD between patients with scoliosis (0.598 g/cm(2)) and without scoliosis (0.548 g/cm(2)). GH treatment caused a significant increase in Z score (pre-GH: mean -2.28 vs. post-GH: mean -1.53, P < 0.001). There was no statistical difference in the prevalence of scoliosis between the GH treatment group (45/112, 40.1%) and non-treatment group (19/36, 52.8%).

CONCLUSIONS

Among patients with PWS, 61.5% had low BMDs. GH administration significantly improved the lumbar BMD (Z score). There were no statistically significant differences in the prevalence of scoliosis among patients who received GH treatment compared to patients who did not.

Prader-Willi syndrome and growth hormone deficiency

Prader-Willi syndrome (PWS) is a rare multisystem genetic disorder demonstrating great variability with changing clinical features during patient's life. It is characterized by severe hypotonia with poor sucking and feeding difficulties in early infancy, followed by excessive eating and gradual development of morbid obesity in later infancy or early childhood. The phenotype is most probably due to hypothalamic dysfunction which is also responsible for growth hormone (GH) and thyroid-stimulating hormone (TSH) deficiencies, central adrenal insufficiency and hypogonadism. The multidimensional problems of patients with PWS can be managed with multidisciplinary approach. Reduced GH secretion, low peak GH response to stimulation, decreased spontaneous GH secretion and low serum IGF-1 levels in PWS patients have been documented in many studies. GH therapy has multiple beneficial effects on growth and body composition, motor and mental development in PWS patients. The recommended dosage for GH is 0.5-1 mg/m2/day. GH therapy should not be started in the presence of obstructive sleep apnea syndrome, adenotonsillar hypertrophy, severe obesity and diabetes mellitus. GH treatment should be considered for patients with genetically confirmed PWS in conjunction with dietary, environmental and life-style measures.

Effect of genetic subtypes and growth hormone treatment on bone mineral density in Prader-Willi syndrome

Abstract Background: Currently, there is limited information on the effects of growth hormone and of the different genetic subtypes on bone mineral density (BMD) in Prader-Willi syndrome (PWS).

METHODS

We evaluated BMD in 79 individuals with the common subtypes of PWS (48 with deletion and 27 with UPD) and the effect of growth hormone treatment (n=46) vs. no growth hormone treatment.

RESULTS

Forty-four percent of the individuals studied had whole body, hip, or spine BMD <-1 standard deviation (SD) and 10% had a BMD <-2 SD. BMD Z-scores and total BMD (g/cm2) of the spine were significantly higher in the growth hormone group. With each year of growth hormone treatment, these values increased by a factor of 0.207 and 0.011 (p=0.006 and 0.032), respectively. Individuals with uniparental disomy revealed higher spine BMD compared with deletion subclass; however, the differences were not significant.

CONCLUSION

This study emphasizes the importance of evaluating bone mineralization in individuals with PWS and the beneficial effects of prolonged treatment with growth hormone. There was a trend for a higher BMD in individuals with uniparental disomy.

Update on body composition and bone density in children with Prader-Willi syndrome

AIM

To compare body composition in children with Prader-Willi syndrome (PWS) not naïve to growth hormone (GH) with obese and lean controls.

METHODS

Participants included 12 children with PWS, 12 children with obesity (body fat percentage >95th percentile for age and sex) and 12 lean children (body fat percentage <85th percentile for age and sex) matched by age and height. Fat mass, lean mass, bone mineral content (BMC), bone mineral density (BMD) and BMD z-score for total body, hips and lumbar spine were obtained through dual X-ray absorptiometry.

RESULTS

PWS had higher fat percentage in the legs (p = 0.04) but similar leg fat mass (p = 1.00) compared to obese. PWS exhibited lower lean mass in the body (p = 0.04) and legs (p = 0.02) than obese, but similar to lean (p = 1.00 and p = 0.89, respectively). PWS had lower hip BMC (p < 0.01), BMD (p < 0.01) and BMD z-score (p < 0.01) compared to obese but similar to lean. No other differences were found between PWS and obese (p > 0.05 for all).

CONCLUSIONS

Children with PWS not naïve to GH present differences in fat and lean mass distribution compared to obese controls. BMC and BMD appear unaffected by PWS, except at the hips.

Endocrine manifestations and management of Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a complex genetic disorder, caused by lack of expression of genes on the paternally inherited chromosome 15q11.2-q13. In infancy it is characterized by hypotonia with poor suck resulting in failure to thrive. As the child ages, other manifestations such as developmental delay, cognitive disability, and behavior problems become evident. Hypothalamic dysfunction has been implicated in many manifestations of this syndrome including hyperphagia, temperature instability, high pain threshold, sleep disordered breathing, and multiple endocrine abnormalities. These include growth hormone deficiency, central adrenal insufficiency, hypogonadism, hypothyroidism, and complications of obesity such as type 2 diabetes mellitus. This review summarizes the recent literature investigating optimal screening and treatment of endocrine abnormalities associated with PWS, and provides an update on nutrition and food-related behavioral intervention. The standard of care regarding growth hormone therapy and surveillance for potential side effects, the potential for central adrenal insufficiency, evaluation for and treatment of hypogonadism in males and females, and the prevalence and screening recommendations for hypothyroidism and diabetes are covered in detail. PWS is a genetic syndrome in which early diagnosis and careful attention to detail regarding all the potential endocrine and behavioral manifestations can lead to a significant improvement in health and developmental outcomes. Thus, the important role of the provider caring for the child with PWS cannot be overstated.

GrowthHormone Research Society workshop summary: consensus guidelines for recombinant human growth hormone therapy in Prader-Willi syndrome

CONTEXT

Recombinant human GH (rhGH) therapy in Prader-Willi syndrome (PWS) has been used by the medical community and advocated by parental support groups since its approval in the United States in 2000 and in Europe in 2001. Its use in PWS represents a unique therapeutic challenge that includes treating individuals with cognitive disability, varied therapeutic goals that are not focused exclusively on increased height, and concerns about potential life-threatening adverse events.

OBJECTIVE

The aim of the study was to formulate recommendations for the use of rhGH in children and adult patients with PWS.

EVIDENCE

We performed a systematic review of the clinical evidence in the pediatric population, including randomized controlled trials, comparative observational studies, and long-term studies (>3.5 y). Adult studies included randomized controlled trials of rhGH treatment for ≥ 6 months and uncontrolled trials. Safety data were obtained from case reports, clinical trials, and pharmaceutical registries.

METHODOLOGY

Forty-three international experts and stakeholders followed clinical practice guideline development recommendations outlined by the AGREE Collaboration (www.agreetrust.org). Evidence was synthesized and graded using a comprehensive multicriteria methodology (EVIDEM) (http://bit.ly.PWGHIN).

CONCLUSIONS

Following a multidisciplinary evaluation, preferably by experts, rhGH treatment should be considered for patients with genetically confirmed PWS in conjunction with dietary, environmental, and lifestyle interventions. Cognitive impairment should not be a barrier to treatment, and informed consent/assent should include benefit/risk information. Exclusion criteria should include severe obesity, uncontrolled diabetes mellitus, untreated severe obstructive sleep apnea, active cancer, or psychosis. Clinical outcome priorities should vary depending upon age and the presence of physical, mental, and social disability, and treatment should be continued for as long as demonstrated benefits outweigh the risks.

Two years of growth hormone treatment in adults with Prader-Willi syndrome do not improve the low BMD

BACKGROUND

Bone mineral density (BMD) in adult patients with Prader-Willi syndrome (PWS) might be low due to high bone turnover.

OBJECTIVES

The objective of the study was to investigate bone mass in a group of adult PWS subjects and study the effects of GH treatment on BMD and markers of bone turnover.

DESIGN

Forty-six adults with genetically verified PWS were randomized to GH or placebo for 12 months, followed by open prospective GH for 24 additional months. BMD at the lumbar spine (LS) L1-4, the total hip, and the total body was assessed by dual-energy x-ray absorptiometry at baseline and every 12th month thereafter. Markers of bone turnover were measured at baseline and at the end of the controlled study.

RESULTS

In this cohort of adult subjects with PWS, baseline BMD was reduced in all compartments compared with the reference (Z-scores). Men had lower Z-scores BMD than women in LS and total body (P < .05). With 12 months of GH, LS-BMD was significantly reduced compared with placebo. No changes in BMD were observed with continuous GH treatment for 24 months. The bone formation markers increased with GH therapy compared with placebo, whereas the resorption marker did not change.

CONCLUSIONS

Adult PWS subjects, especially the men, have low bone mass that was not improved with GH treatment for 2 years. Because PWS subjects are short, BMD might be underestimated and should be adjusted for. Further studies, with adequate GH and sex hormone replacement throughout puberty and early adult life, are needed to better characterize PWS.

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.