It's not about the height: Prader–Willi Syndrome. Effects of Growth Hormone Treatment

Persistent short stature, other potential outcomes, and the effect of growth hormone treatment in children who are born small for gestational age.

Premature mortality and hypopituitarism

To study the effect of growth hormone (GH) treatment (2-4 months) on insulin action in adipocytes isolated from children with Prader-Willi syndrome (PWS), in whom GH deficiency appears to be a primary defect. We investigated the complex effects of GH on carbohydrate metabolism, as part of a current clinical trial of GH treatment in children with PWS. Biopsies of subcutaneous abdominal adipose tissue were obtained from 12 children with PWS before and after 2-4 months of GH treatment. Lipogenesis was determined by the incorporation of radiolabelled glucose into lipids in isolated adipocytes, and glycerol release to the incubation medium was used as an index of lipolysis. GLUT4 RNA was measured by solution hybridization. With low glucose concentrations, at which glucose transport is rate-limiting, maximal insulin-induced lipogenesis was increased by 120% after GH treatment (P < 0.05), but the sensitivity to insulin (half-maximum effective hormone concentration) was unchanged. This was not accompanied by a significant change in the RNA expression of GLUT4. Neither responsiveness (maximum effect) nor sensitivity of insulin-induced inhibition of lipolysis was affected by GH treatment. GH treatment of children with PWS results in an upregulation of insulin-induced lipogenesis in isolated adipocytes, with no effect on insulin-induced inhibition of lipolysis. The data suggest that the site of the effect of GH on lipogenesis is distal to the insulin hormone-receptor interaction, but does not involve altered GLUT4 expression.

Sleep disordered breathing and growth hormone therapy in children with Prader Willi syndrome

A controlled, randomized study was conducted to assess the effect of growth hormone (GH) treatment on growth, body composition and behaviour in prepubertal children (3-12 years of age) with Prader-Willi syndrome. GH treatment was given to one group of 15 patients (group A) at a dose of 0.1 IU/kg/day for 2 years. The second group (group B; n = 12) was not treated for the first year and was then given GH at a dose of 0.2 IU/kg/day for the second year. All patients had low 24-hour levels of GH and insulin-like growth factor I before GH treatment. Height velocity SDS increased from -1.9 +/- 2.0 to 6.0 +/- 3.2 during the first year of GH treatment in group A, and from -1.4 +/- 1.2 to 10.1 +/- 3.9 in the second year of the study in group B. When GH treatment was stopped, height velocity declined dramatically. Height SDS followed a similar pattern. GH treatment reduced the percentage body fat and increased the muscle area of the thigh. Isometric muscle strength was also increased. In addition, GH treatment appeared to have psychological and behavioural benefits, which were reversed after cessation of treatment. It was concluded that GH treatment improves growth, body composition and behaviour in children with Prader-Willi syndrome.

This chapter proposes a new concept of foot growth regulation in addition to known endocrine and genetic factors. The Prader–Willi syndrome (PWS) is a genetically defined complex neurodevelopmental disorder characterized by short stature with small hands and feet, severe hypoactivity, progressive obesity, and endocrine disorders such as growth hormone deficiency. In PWS children as opposed to height, foot catch-up growth on growth hormone therapy is delayed and incomplete, contrasting to symmetric and complete catch-up growth observed in children with growth hormone deficiency, growth hormone insensitivity, and born small for gestational age. In hemiplegic and paraplegic children inactive legs are shorter than active legs. We therefore explored the hypothesis that in PWS children the relative reduction in foot length (FL) compared to height may be caused by reduced musculoskeletal loading reflecting severely reduced physical activity. In 37 PWS children we correlated foot length before and after 6 years of growth hormone therapy with parental and sibling’s FL, height and factors reflecting musculoskeletal loading such as weight for height (WfH), lean body mass (LBM), physical activity, and walk age. Because of the typically biphasic evolution of body mass and the late walk age in PWS, children were divided into age groups younger and older than 2.5 years. PWS children normalized height but not FL after 6 years of GHT. Parental FL correlation with PWS’s FL was lower than with sibling’s FL. In children older than 2.5 years FL positively correlated with WfH, LBM, and physical activity. In children younger than 2.5 years FL negatively correlated with age at onset of free walking. Foot catch-up growth on growth hormone therapy was slower in the younger compared to older children. We conclude that in PWS FL is positively associated with musculoskeletal loading. Small feet in PWS children before and during long-term growth hormone therapy may be more than just another dysmorphic feature, but possibly reflect decreased musculoskeletal loading influencing foot growth together with genetic and endocrine factors. Comparable to the “muscle-bone unit” explaining interdependency between bone remodeling and muscle strength, musculoskeletal loading impacts on foot growth, explaining about 25–50% of total variance of age-corrected FL. If our findings in PWS can be expanded to healthy children, the progressive reduction of physical activity observed over the last decades in healthy children may have consequences for FL of future generations.

Short stature, obesity, decreased lean mass, cryptorchidism, and hypogonadism are characteristic features of PWS. The growth pattern in PWS suggest an abnormality in GH secretion or action. Body composition changes in PWS including increased adipose and decreased muscle mass are similar to those children with IGHD. In GH deficiency, GH secretion is negligible and IGF levels are low, leading to decreased linear growth. In exogenous obesity the GH are low but the IGF levels however are normal or high. Contrary to exogenous obesity PWS children have decreased growth velocity, sexual development, muscle mass, and IGF levels. Other investigators and ourselves have shown blunted GH secretion in both obese and non-obese PWS children and the benefits of GH therapy (J of Ped End & Metab. 9,943-400, 1996.). We now compare the growth velocity in 96 PWS children and 6965 children with IGHD from the National Cooperative Growth Study (NCGS) after 4 years of GH therapy. The linear growth was similar in both groups. Although is unlikely that GHD is the only cause of short stature, decreased growth velocity and increased adiposity in PWS children, suggest that GHD is a common feature and significant contributory factor in expression of PWS phenotype. Figure

Prader-Willi syndrome (PWS) is a genetic disorder characterized by mild mental retardation, short stature, abnormal body composition, muscular hypotonia and distinctive behavioural features. Excessive eating causes progressive obesity with increased cardiovascular morbidity and mortality. In the PWS genotype loss of one or more normally active paternal genes in region q11-13 on chromosome 15 is seen. It is supposed that the genetic alteration leads to dysfunction of several hypothalamic centres and growth hormone (GH) deficiency (GHD) is common. PWS is well described in children, in whom GH treatment improves body composition, linear growth, physical strength and agility. Few studies have focused on adults. We examined a cohort of 19 young adults with clinical PWS (13 with positive genotype) and mean BMI of 35 kg/m2. At baseline the activity of the GH-insulin-like growth factor-I (IGF-I) system was impaired with low GH values, low total IGF-I and in relation to the obesity low levels of free IGF-I and non-suppressed IGF-binding-protein-1 (IGFBP-1). 2/3 were hypogonadal. Bone mineral density (BMD) was low. Four patients had impaired glucose tolerance and nine patients high homeostasis model assessment (HOMA) index, indicating insulin resistance. Seven patients had a moderate dyslipidemia. The 13 patients with the PWS genotype were shorter and had significantly lower IGF-I. Seventeen (9 men and 8 women), subsequently completed a 12 months GH treatment trial, and GH had beneficial effects on body composition without significant adverse effects. The effects were more pronounced in the patients with the PWS genotype. Analysis of peptides involved in appetite regulation showed that leptin levels were high reflecting obesity and as a consequence NPY levels were low. In relation to the patients obesity circulating oxytocin levels were abnormally low and ghrelin levels abnormally high. Thus, oxytocin and ghrelin might be involved in the hyperphagia. NPY, leptin and ghrelin did not change during GH treatment. In conclusion this pilot study showed that adults with PWS have a partial GH deficiency, and GH treatment has beneficial effects on body composition in adult PWS without significant side-effects. Larger and longer term studies on the effect of GH replacement in adult PWS are encouraged.

Prader-Willi syndrome (PWS) is a multisystem genetic disorder characterized by short stature, muscular hypotonia, hyperphagia, obesity, maladaptive behaviour, hypogonadism and partial growth hormone (GH) deficiency (GHD). Severe GHD of other aetiologies has been shown to affect mood and quality of life negatively, and there are reports of improvements with GH replacement. We have studied cognitive, emotional, physical and social parameters in PWS adults at baseline, during and after GH treatment. Nineteen patients, 9 females and 10 males, median age 25 years, mean BMI 35 kg/m2 participated in this study. Approximately half of the group had GHD. All patients fulfilled the clinical criteria for PWS and 13 had a positive genotype. The patients were randomized to 6 months of treatment with either GH [1.6 IU/day (0.53 mg/day)] or placebo, followed by 12 months of active GH treatment. Treatment was then stopped, and the patients were followed for an additional period of 6 months. A test battery for general cognitive evaluation and a computer-based measurement of reaction time, motor speed and fluency were employed at baseline, after 6 months and at the end of GH treatment. At the same time intervals, a self-evaluation questionnaire was answered at the end of each test session. Other questionnaires reflecting the patients' cognitive, emotional, physical and social status were answered by relatives/caretakers at baseline and at 3 and 6 months following cessation of GH treatment. Baseline cognitive level was estimated to be moderately to mildly impaired; IQ range was 40-90. The results from some of the cognitive and the motor performance tests improved significantly after 6 and 18 months of GH treatment. According to the questionnaires, both the patients and the relatives/caretakers evaluated physical status rather negatively at baseline, but still, impairments in both physical and social status and overall functioning were observed when GH treatment was discontinued. The self-evaluation did not change in any aspect during GH treatment. In this pilot study of an adult PWS cohort, we were able to document beneficial effects in mental speed and flexibility and in motor performance during GH treatment. Impairment was seen in physical and social status as well as overall functioning, when GH treatment stopped. Studies of larger cohorts are needed to further elucidate the role of GH treatment in this group of patients.

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Recombinant human growth hormone has revolutionised the management of children with growth hormone deficiency, chronic renal insufficiency, Turner syndrome, Prader-Willi syndrome, small-for-gestational-age status, idiopathic short stature and other growth disorders...

Prader-Willi syndrome (PWS) is a rare genetic disorder characterized by various clinical features linked to hypothalamic/pituitary gland abnormalities. Growth hormone deficiency is a prominent feature of PWS that results in poor linear growth and delayed development. This review discusses the evaluation and effects of growth hormone therapy (GHT) in PWS. Heterogeneity in growth hormone secretion patterns based on genotype and the potential for personalized GHT were explored. The benefits of GHT, including improvements in motor and cognitive development, growth, and body composition, are discussed in detail. Safety considerations for GHT initiation and response to GHT in adults with PWS are discussed, along with ongoing debates regarding the efficacy and safety. Although controversies persist, an evolving understanding of the long-term effects and safety of GHT underscores the need for comprehensive research in this field.

Children with Prader-Willi syndrome (PWS) are routinely treated with GH and have a response comparable with that observed in children with GH deficiency (GHD). The objective of the study was to compare changes in serum IGF-I, IGF binding protein 3 (IGFBP-3), IGF-I to IGFBP-3 molar ratio, and growth velocity during the first 2 yr of GH therapy in PWS and GHD children. Thirty-three children with PWS (14 boys, 4.9 ± 3.8 yr) and 591 with GHD (351 boys, 9.6 ± 3.6 yr), all naive to GH treatment, were included in this study. Serum IGF-I and IGFBP-3 were measured at 0, 6, 12, and 24 months of GH therapy. The mean initial dose of GH was 0.9 and 1 mg/m(2) · d in the PWS and GHD groups, respectively. Mean ± SD IGF-I sdscore (SDS) and IGFBP-3 SDS were significantly higher in PWS compared with GHD. The IGF-I to IGFBP-3 molar ratio was significantly lower at baseline and subsequently not different. Despite significantly lower GH doses in PWS children at 6, 12, and 24 months (P = 0.021, P = 0.021, P = 0.001), IGF-I reached 2.8 ± 1.2 SDS at 24 months (72% of values > 2 SDS), and remained at 0.7 ± 1.6 SDS in GHD children (17% of values > 2 SDS). IGFBP-3 did not exceed 2 SDS in either group. There was no significant change in the IGF-I to IGFBP-3 molar ratio. IGF-I SDS increases to a greater extent in PWS than GHD. Bioavailable IGF-I is apparently not different, suggesting that any possible safety issues related to elevated IGF-I are similar in both groups.

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.

Obesity, short stature, decreased growth rate and delayed skeletal maturation are common features of children with Prader-Willi syndrome (PWS). In contrast to PWS, children with simple exogenous obesity have normal or increased growth rate and normal or advanced skeletal maturation. Decreased growth hormone (GH) secretion evaluated by pharmacological or physiological testing associated with increased plasma insulin-like growth factor (IGF-I) and GH-binding protein (GH-BP) levels are also characteristic of simple obesity. In order to understand whether the suboptimal GH secretion in PWS is an artifact of the obesity, we studied 33 obese and 11 non-obese PWS children, aged 2-16 years.GH secretion was evaluated with three pharmacological stimuli (insulin, clonidine and L-dopa) and by spontaneous 24-hour GH secretion. Skeletal maturation was delayed in 70% whereas plasma IGF-I and GH-BP were either low or normal. Forty subjects, including ten non-obese children, had GH deficiency by standard testing (failure to respond to two pharmacological stimuli), and all but one had blunted spontaneous 24-h GH secretion. No significant correlation between body mass index (wt/ht2) and spontaneous 24-h GH secretion (r = 0.145), p > 0.06) or GH-BP levels (r = 0.19, p > 0.07) was found. Thirty documented GH deficient children have completed at least two years of GH therapy. With treatment the overall mean height SD and weight SD changed from -2.2 to -0.8 and from 3.5 to 2.4 respectively (p < 0.0001). No patient has developed diabetes mellitus. In conclusion, growth velocity, skeletal maturation, GH secretion and GH dependent proteins in PWS resemble GH deficiency more than simple obesity. Our ongoing study suggests that GH deficiency in PWS is not an artifact of obesity. Although it is unlikely that GH deficiency is the only cause of decreased growth velocity and increased adiposity in PWS, it is a common feature and significant contributory factor. Long term observation will be required until achievement of adult height to determine whether GH therapy actually improves final height.