Limited additional value of karyotyping cultured amniotic fluid cell colonies in addition to microarray on uncultured cells for confirmation of abnormal non-invasive prenatal testing results.

OBJECTIVES: Non-invasive prenatal testing (NIPT) allows the detection of placental chromosome aberrations. To verify whether the fetus also has the chromosome aberration, diagnostic follow-up testing is required. The aim of this retrospective study was to assess the added value of analyzing amniotic fluid (AF) cell cultures in addition to uncultured AF cells for the detection of fetal mosaicism. METHOD: NIPT was performed as part of the Dutch TRIDENT study. Cytogenetic studies in uncultured AF were performed using single nucleotide polymorphism (SNP)-array. Cultured AF cell colonies (in situ method) were investigated with fluorescent in situ hybridization and/or karyotyping. Clinical outcome data were collected in cases with discordant results. RESULTS: Between April 2014 and December 2021, 368 amniocenteses were performed after a chromosomal aberration was detected with NIPT. Excluding 134 cases of common aneuploidies (confirmed by quantitative fluorescence polymerase chain reaction), 29 cases with investigation of uncultured cells only and 1 case without informed consent, 204 cases were eligible for this study. In 196 (96%) cases, the results in uncultured and cultured cells were concordant normal, abnormal or mosaic. Five cases (2%) showed mosaicism in cultured AF cells, whereas uncultured AF cells were normal. Two (1%) of these, one mosaic trisomy 13 and one mosaic trisomy 16, were considered true fetal mosaics. CONCLUSION: The added value of investigating AF cell cultures in addition to uncultured cells is limited to two of 204 (1%) cases in which true fetal mosaicsm would otherwise be missed. The clinical relevance of one (trisomy 13) remained unknown and the other case also showed ultrasound anomalies, which determined pregnancy management. This seems to justify limiting prenatal cytogenetic confirmatory testing to SNP arrays on uncultured AF cells, considerably shortening the reporting time.

Free Insulin-like Growth Factor (IGF)-I in Children with PWS.

In children with Prader−Willi syndrome (PWS), the standard growth hormone (GH) dose often results in high immunoreactive IGF-I levels. These high immunoreactive IGF-I levels lead to concern because their long-term effects are unknown. As a result, clinicians have to lower the GH dose, which worsens body composition and quality of life. As clinical features do not seem to correspond to immunoreactive IGF-I values, it is questionable whether immunoreactive IGF-I is a suitable marker for GH dosing, or whether another parameter better reflects IGF-I bioavailability and bioactivity. We, therefore, investigate serum immunoreactive IGF-I, free IGF-I and IGFBP-3 levels in 70 GH-treated children with PWS. Our study showed that, although immunoreactive IGF-I levels were high (>2 SDS) in the vast majority of prepubertal and pubertal children, free IGF-I SDS levels were <0 SDS in most and <1 SDS in all. Free IGF-I correlated with the immunoreactive IGF-I, IGFBP-3 and IGF-I/IGFBP-3 ratio. We conclude that there is a major discrepancy between immunoreactive and free IGF-I levels. While in the majority of GH-treated children with PWS, immunoreactive IGF-I levels were high, free IGF-I levels were <0 SDS in most. Our data appear to be very reassuring and suggest that free IGF-I levels should also be taken into consideration when the immunoreactive IGF-I levels are >2 SDS in GH-treated children with PWS.

Complementing the phenotypical spectrum of TUBA1A tubulinopathy and its role in early-onset epilepsies.

TUBA1A tubulinopathy is a rare neurodevelopmental disorder associated with brain malformations as well as early-onset and intractable epilepsy. As pathomechanisms and genotype-phenotype correlations are not completely understood, we aimed to provide further insights into the phenotypic and genetic spectrum. We here present a multicenter case series of ten unrelated individuals from four European countries using systematic MRI re-evaluation, protein structure analysis, and prediction score modeling. In two cases, pregnancy was terminated due to brain malformations. Amongst the eight living individuals, the phenotypic range showed various severity. Global developmental delay and severe motor impairment with tetraparesis was present in 63% and 50% of the subjects, respectively. Epilepsy was observed in 75% of the cases, which showed infantile onset in 83% and a refractory course in 50%. One individual presented a novel TUBA1A-associated electroclinical phenotype with evolvement from early myoclonic encephalopathy to continuous spike-and-wave during sleep. Neuroradiological features comprised a heterogeneous spectrum of cortical and extracortical malformations including rare findings such as cobblestone lissencephaly and subcortical band heterotopia. Two individuals developed hydrocephalus with subsequent posterior infarction. We report four novel and five previously published TUBA1A missense variants whose resulting amino acid substitutions likely affect longitudinal, lateral, and motor protein interactions as well as GTP binding. Assessment of pathogenic and benign variant distributions in synopsis with prediction scores revealed sections of variant enrichment and intolerance to missense variation. We here extend the clinical, neuroradiological, and genetic spectrum of TUBA1A tubulinopathy and provide insights into residue-specific pathomechanisms and genotype-phenotype correlations.

Effects of 8 years of growth hormone treatment on scoliosis in children with Prader-Willi syndrome.

OBJECTIVE: Scoliosis is frequently seen in children with Prader-Willi syndrome (PWS). There is still concern that growth hormone (GH) treatment might increase the risk of onset or progression of scoliosis. Short-term data suggested no adverse effects of GH on scoliosis, but long-term effects of GH treatment on development of scoliosis in PWS are unknown. This study investigated the effects of 8 years of GH treatment on scoliosis in children with PWS. DESIGN: Open-label, prospective cohort study in 103 children with PWS receiving GH for 8 years was analyzed. Prevalence and severity of scoliosis were compared to a group of 23 age-matched GH-untreated children with PWS. METHODS: Spine X-rays and DEXA-scans were performed, and Cobb angel was measured by two independent observers. RESULTS: After 8 years of GH treatment, at median age of 10.8 years, prevalence of scoliosis was 77.7%. No difference in prevalence or severity of scoliosis was found between GH-treated and age-matched untreated children with PWS (P = 0.409 and P = 0.709, respectively). Height SDS and trunkLBM were significantly higher in GH-treated children. Higher bone mineral density of the lumbar spine was found in children without scoliosis after 8 years of GH. Bone mineral apparent density of lumbar spine (BMADLS) SDS was associated with lower Cobb angle (r = -0.270, P = 0.008). CONCLUSIONS: Eight years of GH treatment has no adverse effects on the prevalence and severity of scoliosis in children with PWS until 11 years of age. As BMADLS SDS is inversely associated with Cobb angle, it is pivotal to optimize the BMD status in children with PWS.

Bone mineral density during 3 years of growth hormone in previously GH-treated young adults with PWS.

OBJECTIVE: In children with Prader-Willi syndrome (PWS), growth hormone (GH) treatment has positive effects on bone mineral density (BMD). Two 1-year studies did not show a difference between GH or placebo on BMD in young adults with PWS. However, there are no studies investigating BMD during longer-term GH treatment in young adults with PWS. DESIGN: Open-label, a prospective study in 43 young adults with PWS. METHODS: BMD of the total body (BMDTBSDS) and lumbar spine (BMADLSSDS) measured by DXA. RESULTS: In the total group, estimated mean (95% CI) of BMDTB remained similar during 3 years of GH, being -0.76 (-1.11 to -0.41) SDS at start and -0.90 (-1.27 to -0.54) SDS after 3 years (P = 0.11), as did BMADLS, being -0.36 (-0.72 to 0.01) SDS and -0.46 (-0.77 to -0.16) SDS, respectively (P = 0.16). In men, there was a significant decrease in BMDTBSDS during 3 years of GH, while BMADLSSDS remained similar. In women, both BMDTBSDS and BMADLSSDS remained similar. BMDTBSDS was associated with female sex, lean body mass and age. The majority of patients received sex steroid replacement therapy (SSRT). CONCLUSIONS: During 3 years of combined GH and SSRT treatment, BMD remained stable in the normal range in young adults with PWS. However, men showed a decline in BMDTBSDS, probably due to insufficient SSRT. We recommended to continue GH treatment in young adults with PWS and to start SSRT during adolescence unless puberty progresses normally.

Oxytocin in young children with Prader-Willi syndrome: Results of a randomized, double-blind, placebo-controlled, crossover trial investigating 3 months of oxytocin.

CONTEXT: Prader-Willi syndrome (PWS) is characterized by hypothalamic dysfunction, hyperphagia and a typical behavioural phenotype, with characteristics of autism spectrum disorder (ASD) like stubbornness, temper tantrums and compulsivity. It has been suggested that the oxytocin system in patients with PWS is dysfunctional. In ASD, intranasal oxytocin treatment has favourable effects on behaviour. OBJECTIVE: To evaluate the effects of 3 months of twice daily intranasal oxytocin (dose range 16-40 IU/day), compared to placebo, on behaviour and hyperphagia in children with PWS. DESIGN: Randomized, double-blind, placebo-controlled, crossover study in the Dutch PWS Reference Center. PATIENTS: Twenty-six children with PWS aged 3-11 years. MAIN OUTCOME MEASURES: (Change in) behaviour and hyperphagia measured by Oxytocin Questionnaire and Dykens hyperphagia questionnaire. RESULTS: In the total group, no significant effects of oxytocin on social behaviour or hyperphagia were found. However, in boys, the Oxytocin Questionnaire scores improved significantly during oxytocin treatment, compared to a deterioration during placebo (4.5 (-0.8 to 15.3) vs. -4.0 (-11.3 to 0.8), P = .025). The Dykens hyperphagia questionnaire scores remained similar during oxytocin treatment, while there was a deterioration during placebo (0.0 (-0.8 to 4.3) vs. -3.5 (-6.0 to 0.0), P = .046). Patients with a deletion had significant improvements in both questionnaire scores during oxytocin treatment, but deteriorations during placebo. Oxytocin treatment was well tolerated, and there were no serious adverse events. CONCLUSIONS: Intranasal oxytocin treatment has positive effects on social and eating behaviour in 3-11 years aged boys with PWS and in children with a deletion without safety concerns. Intranasal oxytocin in children with PWS might be considered, but individual effects should be carefully evaluated and treatment discontinued if no effects are found.

Three years of growth hormone treatment in young adults with Prader-Willi Syndrome previously treated with growth hormone in childhood: Effects on glucose homeostasis and metabolic syndrome.

CONTEXT: Growth hormone (GH) has been approved for children with Prader-Willi syndrome (PWS) and significantly improves body composition in adults with PWS. Adults with PWS are predisposed to develop impaired glucose tolerance (IGT) and diabetes mellitus type 2 (DMT2). Continuation of GH maintains body composition, but GH is known to induce insulin resistance, which might affect glucose homeostasis. Studies on long-term effects of GH treatment in adults are very limited. OBJECTIVE: To investigate effects of 3 years of GH treatment on glucose homeostasis and prevalence of metabolic syndrome (MS) in adults with PWS. DESIGN: Open-label, prospective study. PATIENTS: 43 young adults with PWS. SETTING: Dutch PWS Reference Center. MAIN OUTCOME MEASURES: Glucose and insulin during oral glucose tolerance test. RESULTS: Estimated mean (95% CI) fasting glucose and insulin levels remained stable during 3 years of GH treatment. Glucose being 4.6 (4.4-4.8) mmol/l at start and 4.7 (4.6-4.9) mmol/l after 3 years (P = .07); insulin being 59.5 (45.2-75.8) pmol/l and 56.7 (45.2-69.6) pmol/l resp. (P = .72). Sex, ethnicity and fat mass percentage were significantly associated with fasting glucose levels, while IGF-I or GH-dose were not. Blood pressure, lipids and prevalence of MS remained stable during 3 years of GH. IGT prevalence was variable over time, six patients had IGT at start and eleven after 3 years of GH. One patient developed DMT2. However, prevalence of IGT or DMT2 was not significantly higher after 3 years than at study start. CONCLUSIONS: Three years of GH treatment in adults with PWS does not impair glucose homeostasis and does not lead to an increased prevalence of DMT2.

Three years of growth hormone treatment in young adults with Prader-Willi syndrome: sustained positive effects on body composition.

BACKGROUND: In children with Prader-Willi syndrome (PWS), the benefits of growth hormone treatment are well established. Several one-year studies have shown that growth hormone is also beneficial for adults with PWS, improving body composition. However, little is known about the longer-term effects. This study investigated the effects on body composition in adult patients with PWS during 3 years of growth hormone therapy in a dose of 0.33 mg/m2/day. METHODS: Open-label, prospective study in 43 young adults with PWS with a median (IQR) age of 19.0 (17.5 to 20.7) years. Fat mass percentage SDS and lean body mass SDS were measured annually by DXA. RESULTS: Estimated mean (95% CI) fat mass percentage SDS decreased during the three-year study from 2.1 (1.9 to 2.3) SDS at start to 1.9 (1.8 to 2.1) SDS, p = 0.012, while lean body mass SDS remained stable at - 2.1 (- 2.4 to - 1.8) SDS at start to - 1.9 (- 2.3 to - 1.6) after 3 years, p = 0.15. Fasting glucose and insulin remained similar during the three-year study, glucose being 4.6 (4.4 to 4.8) mmol/l at start and 4.6 (4.5 to 4.7) mmol/l after 3 years of growth hormone, p = 0.93 and insulin being 59.5 (42.2 to 81.5) pmol/l and 55.0 (42.4 to 69.2) pmol/l, resp., p = 0.54. There were no growth hormone-related adverse events during the study. CONCLUSIONS: Three years of growth hormone treatment in young adults with PWS maintains the positive effects on body composition attained during childhood. Thus, adults with PWS benefit from longer-term growth hormone treatment. TRIAL REGISTRATION: EudraCT, EudraCT number 2011-001313-14. Registered 17 October 2012.

Evidence for Accelerated Biological Aging in Young Adults with Prader-Willi Syndrome.

OBJECTIVE: Adults with Prader-Willi syndrome (PWS) are at increased risk of developing age-associated diseases early in life and, like in premature aging syndromes, aging might be accelerated. We investigated leukocyte telomere length (LTL), a marker of biological age, in young adults with PWS and compared LTL to healthy young adults of similar age. As all young adults with PWS were treated with growth hormone (GH), we also compared LTL in PWS subjects to GH-treated young adults born short for gestational age (SGA). DESIGN: Cross-sectional study in age-matched young adults; 47 with PWS, 135 healthy, and 75 born SGA. MEASUREMENTS: LTL measured by quantitative polymerase chain reaction, expressed as telomere/single copy gene ratio. RESULTS: Median (interquartile range) LTL was 2.6 (2.4-2.8) at a median (interquartile range) age of 19.2 (17.7-21.3) years in PWS, 3.1 (2.9-3.5) in healthy young adults and 3.1 (2.8-3.4) in the SGA group. Median LTL in PWS was significantly lower compared to both control groups (P < .01). In PWS, a lower LTL tended to be associated with a lower total IQ (r = 0.35, P = .08). There was no association between LTL and duration of GH treatment, cumulative GH dose, or several risk factors for type 2 diabetes mellitus or cardiovascular disease. CONCLUSIONS: Young adults with PWS have significantly shorter median LTL compared to age-matched healthy young adults and GH-treated young adults born SGA. The shorter telomeres might play a role in the premature aging in PWS, independent of GH. Longitudinal research is needed to determine the influence of LTL on aging in PWS.

Prevalence of growth hormone (GH) deficiency in previously GH-treated young adults with Prader-Willi syndrome.

OBJECTIVE: Some features of subjects with Prader-Willi syndrome (PWS) resemble those seen in growth hormone deficiency (GHD). Children with PWS are treated with growth hormone (GH), which has substantially changed their phenotype. Currently, young adults with PWS must discontinue GH after attainment of adult height when they do not fulfil the criteria of adult GHD. Limited information is available about the prevalence of GHD in adults with PWS. This study aimed to investigate the GH/insulin-like growth factor (IGF-I) axis and the prevalence of GHD in previously GH-treated young adults with PWS. DESIGN: Cross-sectional study in 60 young adults with PWS. MEASUREMENTS: Serum IGF-I and IGFBP-3 levels, GH peak during combined growth hormone-releasing hormone (GHRH)-arginine stimulation test. RESULTS: Serum IGF-I was <-2 standard deviation scores (SDS) in 2 (3%) patients, and IGFBP-3 was within the normal range in all but one patient. Median (IQR) GH peak was 17.8 µg/L (12.2; 29.7) [~53.4 mU/L] and below 9 µg/L in 9 (15%) patients. Not one patient fulfilled the criteria for adult GHD (GH peak < 9 µg/L and IGF-I < -2 SDS), also when BMI-dependent criteria were used. A higher BMI and a higher fat mass percentage were significantly associated with a lower GH peak. There was no significant difference in GH peak between patients with a deletion or a maternal uniparental disomy (mUPD). CONCLUSIONS: In a large group of previously GH-treated young adults with PWS, approximately 1 in 7 exhibited a GH peak <9 µg/L during a GHRH-arginine test. However, none of the patients fulfilled the consensus criteria for adult GHD.

Sleep-Related Breathing Disorders in Young Adults With Prader-Willi Syndrome: A Placebo-Controlled, Crossover GH Trial.

CONTEXT: Sleep-related breathing disorders (SRBD) are common in people with Prader-Willi syndrome (PWS). Young adults with PWS benefit from GH continuation after attaining adult height by maintaining the improved body composition obtained during childhood. There are, no studies about the effects of GH on SRBD in young adults with PWS who were treated with GH during childhood. OBJECTIVE: Investigate the effects of GH vs placebo on SRBD in young adults with PWS who were treated with GH during childhood and had attained adult height. DESIGN: Two-year, randomized, double-blind, placebo-controlled, crossover study in 27 young adults with PWS, stratified for sex and body mass index. SETTING: Dutch PWS Reference Center. INTERVENTION: Crossover intervention with GH (0.67 mg/m2/d) and placebo, both over one year. MAIN OUTCOME MEASURES: Apnea hypopnea index (AHI), obstructive apnea index (OAI), central apnea index (CAI), measured by polysomnography. RESULTS: Compared with placebo, GH did not increase AHI, CAI, or OAI (P > 0.35). The effect of GH vs placebo was neither different between men and women, nor between patients with a deletion or maternal uniparental disomy/imprinting center defect. After two years, there was no difference in AHI, CAI, or OAI compared with baseline (P > 0.18). Two patients (7%) fulfilled the criteria of obstructive sleep apnea regardless of GH or placebo. CONCLUSIONS: GH compared with placebo does not cause a substantial increase in AHI, CAI, or OAI in adults with PWS who were treated with GH during childhood and have attained adult height. Our findings are reassuring and prove that GH can be administered safely.

Novel Clinical Criteria Allow Detection of Short Stature Homeobox-Containing Gene Haploinsufficiency Caused by Either Gene or Enhancer Region Defects.

INTRODUCTION: Short stature homeobox-containing gene (SHOX) haploinsufficiency is associated with short stature, Madelung deformity and mesomelia. Current clinical screening tools are based on patients with intragenic variants or deletions. However, recent discoveries showed that deletions of the enhancer elements are quite common. The majority of these patients show less body disproportion and respond better to recombinant human growth hormone treatment. We redefined clinical criteria for genetic analysis to facilitate detection of the full spectrum of SHOX haploinsufficiency. METHODS: We analyzed 51 children with SHOX variants or deletions and 25 children with a deletion in its enhancer region. Data were compared to 277 children referred for suspicion of growth failure without endocrine or genetic pathology. RESULTS: Only half of the patients with an enhancer region deletion fulfilled any of the current screening criteria. We propose new clinical criteria based on sitting height to height ratio >1 SDS or arm span ≥3 cm below height, with a sensitivity of 99%. When these criteria are combined with obligatory short stature, the sensitivity to detect SHOX haploinsufficiency is 68.1%, the specificity 80.6%, and the number needed to screen 21 patients. CONCLUSION: Novel clinical criteria for screening for SHOX haploinsufficiency allow the detection of patients within the full genetic spectrum, that is, intragenic variants and enhancer region deletions.

Improved Mental and Motor Development During 3 Years of GH Treatment in Very Young Children With Prader-Willi Syndrome.

Context: Infants and toddlers with Prader-Willi syndrome (PWS) have mental and motor developmental delay. Short-term data suggest a positive effect of GH on mental and motor development in infants and children with PWS. There are, however, no longer-term results about the effects of GH treatment on mental and motor development. Objective: To investigate the longer-term effects of GH on psychomotor development in infants and toddlers with PWS and the effect of age at start of GH treatment on psychomotor development. Design: Prospective cohort study during 3 years of GH treatment. Setting: The PWS Reference Center in the Netherlands. Intervention: All children were treated with GH 1 mg/m2/d (≈0.035 mg/kg/d). Main Outcome Measures: Mental and motor developmental age assessed with Bayleys Scales of Infant Development II and expressed as percentage of the expected development (100%). Results: During 3 years of GH, mean (SEM) mental development increased from 58.1% (2.8) at baseline to 79.6% (3.7), and motor development increased from 41.9% (2.9) to 78.2% (3.9; both P < 0.01). A lower baseline psychomotor development and a younger age at start of GH treatment were associated with a higher increase in mental and motor development (P < 0.01). Conclusions: Mental and motor development increased significantly during 3 years of GH treatment, reducing the gap between infants with PWS and healthy peers. A younger age at start of GH treatment leads to greater improvement in psychomotor development.

A Transcriptomic Signature of the Hypothalamic Response to Fasting and BDNF Deficiency in Prader-Willi Syndrome.

Transcriptional analysis of brain tissue from people with molecularly defined causes of obesity may highlight disease mechanisms and therapeutic targets. We performed RNA sequencing of hypothalamus from individuals with Prader-Willi syndrome (PWS), a genetic obesity syndrome characterized by severe hyperphagia. We found that upregulated genes overlap with the transcriptome of mouse Agrp neurons that signal hunger, while downregulated genes overlap with the expression profile of Pomc neurons activated by feeding. Downregulated genes are expressed mainly in neuronal cells and contribute to neurogenesis, neurotransmitter release, and synaptic plasticity, while upregulated, predominantly microglial genes are involved in inflammatory responses. This transcriptional signature may be mediated by reduced brain-derived neurotrophic factor expression. Additionally, we implicate disruption of alternative splicing as a potential molecular mechanism underlying neuronal dysfunction in PWS. Transcriptomic analysis of the human hypothalamus may identify neural mechanisms involved in energy homeostasis and potential therapeutic targets for weight loss.

Bone mineral density in young adults with Prader-Willi syndrome: A randomized, placebo-controlled, crossover GH trial.

CONTEXT: The prevalence of osteoporosis is increased in adults with Prader-Willi syndrome (PWS). In children with PWS, growth hormone (GH) treatment has beneficial effects on bone mineral density (BMD). BMD might deteriorate after cessation of GH at adult height (AH), while continuing GH might maintain BMD. OBJECTIVE: To investigate the effects of GH vs placebo, and furthermore the effects of sex steroid replacement therapy (SSRT), on BMD in GH-treated young adults with PWS who had attained AH. DESIGN: Two-year, randomized, double-blind, placebo-controlled, crossover GH study. PATIENTS: Twenty-seven young adults with PWS were stratified for gender and BMI and then randomly and blindly assigned to receive GH (0.67 mg/m2 /day) or placebo for 1 year, after which they crossed over to the alternative treatment for another year. MEASUREMENTS: Bone mineral density of the total body (BMDTB ) and lumbar spine (BMDLS ) SDS were measured by dual-energy x-ray absorptiometry. RESULTS: At AH, BMDTB SDS was significantly lower compared to healthy peers (P < .01), while BMADLS SDS was similar. Both BMDTB SDS and BMADLS SDS were similar during 1 year of GH vs 1 year of placebo. In hypogonadal young adults without SSRT, BMDTB SDS and BMADLS SDS decreased during the 2-year study (P = .11 and P = .01), regardless of GH or placebo, while BMDTB SDS increased in those with SSRT (P < .01). CONCLUSIONS: Compared to GH treatment, 1 year of placebo after attainment of AH does not deteriorate BMD SDS in young adults with PWS. In addition, our data suggest that GH is not able to prevent the decline in BMD SDS in hypogonadal young adults with PWS, unless it is combined with SSRT.

Beneficial Effects of GH in Young Adults With Prader-Willi Syndrome: A 2-Year Crossover Trial.

CONTEXT: Patients with Prader-Willi syndrome (PWS) are severely at risk to develop morbid obesity, diabetes mellitus type 2, and cardiovascular disease, leading to high mortality. They have an increased fat mass (FM) and decreased lean body mass (LBM). During childhood, GH treatment counteracts the natural course of increasing obesity. Discontinuation of GH treatment at attainment of adult height (AH) might deteriorate their improved clinical condition, whereas continuation might benefit them. OBJECTIVE: To investigate the effects of GH versus placebo on body composition in young adults with PWS who were GH treated for many years during childhood and had attained AH. DESIGN: Two-year, randomized, double-blind, placebo-controlled crossover study with stratification for gender and body mass index in 27 young adults with PWS. SETTING: PWS Reference Center in The Netherlands. INTERVENTION: Crossover intervention with GH (0.67 mg/m2 · d) and placebo, both during 1 year. MAIN OUTCOME MEASURES: Body composition, measured by dual-energy x-ray absorptiometry. RESULTS: During placebo, FM increased (relative change +21.5%; P < .001). Compared with placebo, GH treatment resulted in lower FM (-2.9 kg; P = .004) and higher LBM (+1.5 kg; P = .005), representing relative changes of -17.3% FM and +3.5% LBM. Both limb and trunk FM percentage were lower during GH versus placebo (relative change +17.3% and +15.6%; P < .001 and P = .007, respectively). No GH-related adverse events occurred. CONCLUSIONS: GH-treated young adults with PWS who have attained AH benefit from continuation of GH treatment. FM increases during placebo, whereas GH versus placebo results in lower FM and higher LBM. Thus, GH treatment maintains the improved body composition without safety concerns.