Adrenarche in Prader-Willi syndrome appears not related to insulin sensitivity and serum adiponectin

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.

Premature adrenarche in Prader-Willi syndrome is associated with accelerated pre-pubertal growth and advanced bone age

OBJECTIVES

Prader-Willi syndrome (PWS) is characterized by obesity, growth hormone deficiency, hypogonadism, and a high prevalence of premature adrenarche despite reported hypothalamic-pituitary-adrenal axis dysfunction. While idiopathic premature adrenarche is associated with accelerated pre-pubertal growth and advanced bone age, the consequences of elevated adrenal androgens on growth and bone maturation in PWS remain unknown. This study therefore sought to describe age-related changes in dehydroepiandrosterone sulfate (DHEAS) and their effects on growth and bone maturation in PWS.

METHODS

This retrospective observational study included 62 children with PWS. Simple and multiple regression models were constructed to relate age and BMI-SDS with DHEAS levels. Height velocity was compared to age and sex-based norms with t-tests and two-way ANOVA. Patterns in bone age Z-score were examined with two-way ANOVA, and the contributions of age, BMI-SDS, and DHEAS to bone age Z-score were analyzed with multiple regression.

RESULTS

DHEAS levels rose earlier and were less strongly correlated with age in males and females with PWS (R²=0.12 and 0.30) compared to healthy controls (R²=0.89 and 0.88) in a pattern unrelated to BMI-SDS (adjusted R²=0.076, p=0.10 for age, and 0.29 for BMI-SDS). Mid-childhood height velocity was increased in males and preserved in females with PWS before declining at the age of expected puberty (p<0.0001). Peri-adrenarchal bone age was advanced in a manner associated with DHEAS but not BMI-SDS (p<0.0001; adjusted R²=0.48, p=0.0014 for DHEAS, and 0.78 for BMI-SDS).

CONCLUSIONS

An obesity-independent increase in adrenal androgens is associated with accelerated mid-childhood growth and bone maturation in PWS.

Central adrenal insufficiency screening with morning plasma cortisol and ACTH levels in Prader-Willi syndrome

OBJECTIVES

Prader-Willi syndrome (PWS) is a complex genetic disorder with severe hypotonia, failure to thrive, childhood obesity, hypogonadism/hypogenitalism and learning/behavioral problems with endocrine-related growth and other hormone deficiencies. The prevalence of central adrenal insufficiency (CAI) using dynamic testing ranges from rare to 60%. We compared routine morning plasma cortisol (MPC) and ACTH levels in large cohorts of PWS and control children to address CAI.

METHODS

Retrospective analysis of MPC and ACTH levels was undertaken in 128 PWS growth hormone (GH)-treated children under medical care before considering dynamic testing for CAI and 128 non-syndromic control children with short stature evaluated for GH deficiency.

RESULTS

The average MPC level in PWS was 9.7 ± 3.7 μg/dL with no difference in age, gender or PWS genetic subtype and 13.4 ± 5.7 μg/dL in the control group. MPC levels were significantly lower (p < 0.05) in PWS but in the normal range. The morning plasma ACTH level in the PWS group was 22.1 ± 8.0 pg/mL with one individual having an initial low plasma ACTH level (8 pg/mL), but normal upon repeat.

CONCLUSIONS

MPC levels in PWS are normal and comparable with control children, without evidence or increased risk of CAI. Lower but normal MPC levels were seen in PWS and suggestive of reduced local regeneration of cortisol from cortisone in adipose tissue by the GH-IGF-I system. Hence, MPC measures alone or in combination with ACTH should be considered for initial screening for CAI in PWS but prior to dynamic testing.

Effects of Recombinant Human Growth Hormone Treatment, Depending on the Therapy Start in Different Nutritional Phases in Paediatric Patients with Prader-Willi Syndrome: A Polish Multicentre Study

Recombinant human growth hormone (rhGH) treatment is an established management in patients with Prader-Willi syndrome (PWS), with growth promotion and improvement in body composition and possibly the metabolic state. We compared anthropometric characteristics, insulin-like growth factor 1 (IGF1) levels, metabolic parameters and the bone age/chronological age index (BA/CA) in 147 children with PWS, divided according to age of rhGH start into four groups, corresponding to nutritional phases in PWS. We analysed four time points: baseline, rhGH1 (1.21 ± 0.81 years), rhGH2 (3.77 ± 2.17 years) and rhGH3 (6.50 ± 2.92 years). There were no major differences regarding height SDS between the groups, with a higher growth velocity (GV) (p = 0.00) and lower body mass index (BMI) SDS (p < 0.05) between the first and older groups during almost the whole follow-up. IGF1 SDS values were lower in group 1 vs. other groups at rhGH1 and vs. groups 2 and 3 at rhGH2 (p < 0.05). Glucose metabolism parameters were favourable in groups 1 and 2, and the lipid profile was comparable in all groups. BA/CA was similar between the older groups. rhGH therapy was most effective in the youngest patients, before the nutritional phase of increased appetite. We did not observe worsening of metabolic parameters or BA/CA advancement in older patients during a comparable time of rhGH therapy.

Influence of molecular classes and growth hormone treatment on growth and dysmorphology in Prader-Willi syndrome: A multicenter study

Prader-Willi syndrome (PWS) is a complex genetic disorder with three molecular classes but clinical ascertainment is based on distinctive features. The prevalence of dysmorphic features was studied in 355 PWS participants (61% deletion, 36% maternal disomy [UPD], and 3% imprinting defects) from the National Institute of Health PWS Rare Diseases Clinical Research Network. The effect of growth hormone (GH) treatment on growth and dysmorphic features was compared. Among participants, upslanting palpebral fissures were seen in 23%; strabismus in 42%; abnormal dentition in 32%; small hands in 63% and small feet in 70%; hypopigmentation in 30%; striae in 32% and skin picking in 26%. Compared to those with UPD, participants with deletions were found to be heavier (p = 0.002), had smaller head circumference (HC) (p = 0.009), higher incidence of a flat occiput (p = 0.005); low-anterior hairline (p = 0.04); abnormal dentition (p = 0.009); abdominal striae (p = 0.045), nail abnormalities (p = 0.050), and fair-haired (p < 0.001). Participants in both genetic groups receiving GH were taller (p = 0.005), had larger HCs (p = 0.005), and longer hands (p = 0.049). This study suggested that PWS genetic subtypes and GH treatment can influence growth and dysmorphic features that may impact clinical diagnosis of PWS, such as stature, head shape and appearance of the eyes, nose, and genitalia.

Hypogonadism in Patients with Prader Willi Syndrome: A Narrative Review

Prader-Willi syndrome (PWS) is a multisystemic complex genetic disorder related to the lack of a functional paternal copy of chromosome 15q11-q13. Several clinical manifestations are reported, such as short stature, cognitive and behavioral disability, temperature instability, hypotonia, hypersomnia, hyperphagia, and multiple endocrine abnormalities, including growth hormone deficiency and hypogonadism. The hypogonadism in PWS is due to central and peripheral mechanisms involving the hypothalamus-pituitary-gonadal axis. The early diagnosis and management of hypogonadism in PWS are both important for physicians in order to reach a better quality of life for these patients. The aim of this study is to summarize and investigate causes and possible therapies for hypogonadism in PWS. Additional studies are further needed to clarify the role of different genes related to hypogonadism and to establish a common and evidence-based therapy.

Premature Adrenarche in Children with Prader-Willi Syndrome Treated with Recombinant Human Growth Hormone Seems to Not Influence the Course of Central Puberty and the Efficacy and Safety of the Therapy

Puberty in children with Prader-Willi syndrome (PWS) is usually delayed and/or incomplete but in some patients premature/early adrenarche is observed. We assessed the premature adrenarche (PA) in PWS patients during the recombinant human growth hormone (rhGH) therapy and influence of PA on the course of central puberty (CP), rhGH efficacy and safety, and patients’ metabolic state. Forty-nine PWS patients were treated with rhGH, 11 presented with PA (group 1) and 14 had normal course of adrenarche (group 2). PA was observed in 22.5% of the PWS children treated with rhGH. The mean time between the rhGH start and the adrenarche, the rhGH dose, the growth velocity and the insulin-like growth factor 1 SD (IGF1 SD) during the treatment, as well as the time of CP, final height SD and BMI SD were similar in both groups. There were also no significant differences in the metabolic assessment—the oral glucose tolerance test (OGTT) and lipid profile results. PA may be a part of the clinical picture of PWS, apart from hypogonadotrophic hypogonadism and it seems to have no influence on CP in PWS patients. The rhGH efficacy and safety were comparable in the patients with PA and the normal course of adrenarche.

Adipokines: A gear shift in puberty

In this review, we discuss the role of adipokines in the onset of puberty in children with obesity during adrenarche and gonadarche and provide a clear and detailed overview of the biological processes of two major players, leptin and adiponectin. Adipokines, especially leptin and adiponectin, seem to induce an early onset of puberty in girls and boys with obesity by affecting the hypothalamic-pituitary-gonadal (HPG) axis. Moreover, adipokines and their receptors are expressed in the gonads, suggesting a role in sexual maturation and reproduction. All in all, adipokines may be a clue in understanding mechanisms underlying the onset of puberty in childhood obesity and puberty onset variability.

Adrenarche in nonhuman primates: the evidence for it and the need to redefine it

Adrenarche is most commonly defined as a prepubertal increase in circulating adrenal androgens, dehydroepiandrosterone (DHEA) and its sulfo-conjugate (DHEAS). This event is thought to have evolved in humans and some great apes but not in Old World monkeys, perhaps to promote brain development. Whether adrenarche represents a shared, derived developmental event in humans and our closest relatives, adrenal androgen secretion (and its regulation) is of considerable clinical interest. Specifically, adrenal androgens play a significant role in the pathophysiology of polycystic ovarian disease and breast and prostate cancers. Understanding the development of androgen secretion by the human adrenal cortex and identifying a suitable model for its study are therefore of central importance for clinical and evolutionary concerns. This review will examine the evidence for adrenarche in nonhuman primates (NHP) and suggest that a broader definition of this developmental event is needed, including morphological, biochemical, and endocrine criteria. Using such a definition, evidence from recent studies suggests that adrenarche evolved in Old World primates but spans a relatively brief period early in development compared with humans and some great apes. This emphasizes the need for frequent longitudinal sampling in evaluating developmental changes in adrenal androgen secretion as well as the tenuous nature of existing evidence of adrenarche in some species among the great apes. Central to an understanding of the regulation of adrenal androgen production in humans is the recognition of the complex nature of adrenarche and the need for more carefully conducted comparative studies and a broader definition in order to promote investigation among NHP in particular.

Endocrine problems in children with Prader-Willi syndrome: special review on associated genetic aspects and early growth hormone treatment

Prader-Willi syndrome (PWS) is a complex multisystem genetic disorder characterized by hypothalamic-pituitary dysfunction. The main clinical features include neonatal hypotonia, distinctive facial features, overall developmental delay, and poor growth in infancy, followed by overeating with severe obesity, short stature, and hypogonadism later in development. This paper reviews recent updates regarding the genetic aspects of this disorder. Three mechanisms (paternal deletion, maternal disomy, and deficient imprinting) are recognized. Maternal disomy can arise because of 4 possible mechanisms: trisomy rescue (TR), gamete complementation (GC), monosomy rescue (MR), and postfertilization mitotic nondisjunction (Mit). Recently, TR/GC caused by nondisjunction at maternal meiosis 1 has been identified increasingly, as a result of advanced maternal childbearing age in Korea. We verified that the d3 allele increases the responsiveness of the growth hormone (GH) receptor to endogenous GH. This paper also provides an overview of endocrine dysfunctions in children with PWS, including GH deficiency, obesity, sexual development, hypothyroidism, and adrenal insufficiency, as well as the effects of GH treatment. GH treatment coupled with a strictly controlled diet during early childhood may help to reduce obesity, improve neurodevelopment, and increase muscle mass. A more active approach to correct these hormone deficiencies would benefit patients with PWS.

Pubarche and serum dehydroepiandrosterone sulphate levels in children with Prader-Willi syndrome

CONTEXT

Premature pubarche (PP) is reported in children with Prader-Willi Syndrome (PWS). Pubarche is preceded by adrenarche - an increase in serum levels of adrenal androgens, most specifically dehydroepiandrosterone sulphate (DHEAS).

OBJECTIVES

To assess DHEAS levels, the age at and progression of pubarche and the prevalence of PP in children with PWS.

DESIGN/PATIENTS

In the Dutch PWS Cohort Study, 120 children (6 months-17 years) are prospectively followed. Their age at onset of pubarche and various pubic hair stages and prevalence of PP were determined. Serum DHEAS levels were assessed in 97 children.

RESULTS

Median serum DHEAS levels were significantly higher in children with PWS than in healthy age-matched controls at ages 3-6 years (girls: P = 0·004 and boys: P = 0·010) and 6-10 years (girls: P = 0·045 and boys: P = 0·001). Age and gender significantly influenced DHEAS levels in children with PWS. The median [P10-P90] age at onset of pubarche in children with PWS was significantly younger than in healthy peers, 9·04[6·75-11·84] years in PWS girls (P < 0·0001) and 10·31 [8·65-12·29] years in PWS boys (P = 0·003). The prevalence of PP in children with PWS was 30·0% in girls and 16·1% in boys.

CONCLUSIONS

Compared to healthy children, children with PWS have significantly higher DHEAS levels from 3 to 10 years of age. They are younger at onset of pubarche and have a higher prevalence of premature pubarche. DHEAS levels in PWS are influenced by age and gender. Our findings indicate earlier maturation of the zona reticularis of the adrenal glands in children with PWS.

The evolutionary biology of child health

I apply evolutionary perspectives and conceptual tools to analyse central issues underlying child health, with emphases on the roles of human-specific adaptations and genomic conflicts in physical growth and development. Evidence from comparative primatology, anthropology, physiology and human disorders indicates that child health risks have evolved in the context of evolutionary changes, along the human lineage, affecting the timing, growth-differentiation phenotypes and adaptive significance of prenatal stages, infancy, childhood, juvenility and adolescence. The most striking evolutionary changes in humans are earlier weaning and prolonged subsequent pre-adult stages, which have structured and potentiated maladaptations related to growth and development. Data from human genetic and epigenetic studies, and mouse models, indicate that growth, development and behaviour during pre-adult stages are mediated to a notable degree by effects from genomic conflicts and imprinted genes. The incidence of cancer, the primary cause of non-infectious childhood mortality, mirrors child growth rates from birth to adolescence, with paediatric cancer development impacted by imprinted genes that control aspects of growth. Understanding the adaptive significance of child growth and development phenotypes, in the context of human-evolutionary changes and genomic conflicts, provides novel insights into the causes of disease in childhood.

Systematic review of the clinical and genetic aspects of Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a complex multisystem genetic disorder that is caused by the lack of expression of paternally inherited imprinted genes on chromosome 15q11-q13. This syndrome has a characteristic phenotype including severe neonatal hypotonia, early-onset hyperphagia, development of morbid obesity, short stature, hypogonadism, learning disabilities, behavioral problems, and psychiatric problems. PWS is an example of a genetic condition caused by genomic imprinting. It can occur via 3 main mechanisms that lead to the absence of expression of paternally inherited genes in the 15q11.2-q13 region: paternal microdeletion, maternal uniparental disomy, and an imprinting defect. Over 99% of PWS cases can be diagnosed using DNA methylation analysis. Early diagnosis of PWS is important for effective long-term management. Growth hormone (GH) treatment improves the growth, physical phenotype, and body composition of patients with PWS. In recent years, GH treatment in infants has been shown to have beneficial effects on the growth and neurological development of patients diagnosed during infancy. There is a clear need for an integrated multidisciplinary approach to facilitate early diagnosis and optimize management to improve quality of life, prevent complications, and prolong life expectancy in patients with PWS.

Colloquium papers: Transfers and transitions: parent-offspring conflict, genomic imprinting, and the evolution of human life history

Human offspring are weaned earlier than the offspring of other great apes but take longer to reach nutritional independence. An analysis of human disorders of imprinted genes suggests genes of paternal origin, expressed in infants, have been selected to favor more intense suckling than genes of maternal origin. The same analysis suggests that genes of maternal origin may favor slower childhood growth but earlier sexual maturation. These observations are consistent with a hypothesis in which slow maturation was an adaptation of offspring that reduced maternal fitness, whereas early weaning was an adaptation of mothers that reduced the fitness of individual offspring.

Altered distribution of adiponectin isoforms in children with Prader-Willi syndrome (PWS): association with insulin sensitivity and circulating satiety peptide hormones

OBJECTIVE

Prader-Willi syndrome (PWS) is a genetic syndrome characterized by relative hypoinsulinaemia and normal or increased insulin sensitivity despite profound obesity. We hypothesized that this increased insulin sensitivity is mediated by increased levels of total and high molecular weight adiponectin and associated with changes in levels of satiety hormones.

DESIGN, PATIENTS AND MEASUREMENTS

We measured total adiponectin and its isoforms [high molecular weight (HMW), middle molecular weight (MMW) and low molecular weight (LMW) adiponectin] and satiety hormones in 14 children with PWS [median age 11.35 years, body mass index (BMI) Z-score 2.15] and 14 BMI-matched controls (median age 11.97 years, BMI Z-score 2.34).

RESULTS

Despite comparable BMI Z-scores and leptin levels, the PWS children exhibited lower fasting insulin and HOMA-IR (homeostasis model assessment of insulin resistance) scores compared to obese controls. For any given BMI Z-score, the PWS children showed higher concentrations of fasting total and HMW adiponectin and higher HMW/total adiponectin ratios. The HMW/total adioponectin ratio was preserved in children with PWS at high degrees of obesity. In PWS children, fasting plasma total adiponectin, HMW adiponectin and HMW/total adiponectin ratio correlated negatively with age (P < 0.05), HOMA-IR (P < 0.01), BMI Z-score (P < 0.05), insulin (P < 0.01) and leptin (P < 0.05). In addition to higher fasting ghrelin concentrations, the PWS children showed significantly higher fasting levels of total peptide YY (PYY) and gastric inhibitory polypeptide (GIP) compared to obese controls.

CONCLUSIONS

Relative to controls of similar age and BMI Z-score, the PWS children had significantly higher levels of total and HMW adiponectin, and increased ratios of HMW/total adiponectin. These findings may explain in part the heightened insulin sensitivity of PWS children relative to BMI-matched controls.