Identification of novel genes including NAV2 associated with isolated tall stature

Very tall people attract much attention and represent a clinically and genetically heterogenous group of individuals. Identifying the genetic etiology can provide important insights into the molecular mechanisms regulating linear growth. We studied a three-generation pedigree with five isolated (non-syndromic) tall members and one individual with normal stature by whole exome sequencing; the tallest man had a height of 211 cm. Six heterozygous gene variants predicted as damaging were shared among the four genetically related tall individuals and not present in a family member with normal height. To gain insight into the putative role of these candidate genes in bone growth, we assessed the transcriptome of murine growth plate by microarray and RNA Seq. Two (Ift140, Nav2) of the six genes were well-expressed in the growth plate. Nav2 (p-value 1.91E-62) as well as Ift140 (p-value of 2.98E-06) showed significant downregulation of gene expression between the proliferative and hypertrophic zone, suggesting that these genes may be involved in the regulation of chondrocyte proliferation and/or hypertrophic differentiation. IFT140, NAV2 and SCAF11 have also significantly associated with height in GWAS studies. Pathway and network analysis indicated functional connections between IFT140, NAV2 and SCAF11 and previously associated (tall) stature genes. Knockout of the all-trans retinoic acid responsive gene, neuron navigator 2 NAV2, in Xenopus supports its functional role as a growth promotor. Collectively, our data expand the spectrum of genes with a putative role in tall stature phenotypes and, among other genes, highlight NAV2 as an interesting gene to this phenotype.

A Novel Pathogenic IGSF1 Variant in a Patient with GH and TSH Deficiency Diagnosed by High IGF-I Values at Transition to Adult Care

IGSF1 deficiency is a rare X-linked condition characterized by central hypothyroidism and a wide variety of other clinical features with variable prevalence, including a delayed pubertal testosterone rise and growth spurt in the context of normal or accelerated testicular growth, and adult macroorchidism with relatively low serum testosterone concentrations. Other features include increased waist circumference, attention deficit, prolactin deficiency and transient partial growth hormone (GH) deficiency in childhood, contrasting with an increased GH secretion in adulthood. Patients with this disorder are not detected shortly after birth if neonatal screening programs are based on thyroid-stimulating hormone (TSH) concentrations. A 13.2-year-old male patient was referred to pediatric endocrinology for evaluation of short stature. He was born large for gestational age into a nonconsanguineous family. During work-up for short stature, deficiencies of TSH, prolactin and GH were detected, leading to treatment with levothyroxine and GH. At 16.9 years, GH treatment was stopped and during transition to adult care, his insulin-like growth factor 1 level was above the normal range. This prompted an analysis of IGSF1, in which a novel hemizygous variant causing a stop codon at c.3559C>T (p.Q1187*) was found, confirming the diagnosis of IGSF1 deficiency syndrome. In this report, we describe his clinical and hormonal characteristics at presentation and during long-term follow-up.

Assessment of Nutritional Status in the Diagnostic Evaluation of the Child with Growth Failure

Current clinical guidelines provide information about the diagnostic workup of children with growth failure. This mini-review focuses on the nutritional assessment, which has received relatively little attention in such guidelines. The past medical history, in particular a low birth size and early feeding problems, can provide information that can increase the likelihood of nutritional deficits or several genetic causes. The current medical history should include a dietary history and can thereby reveal a poorly planned or severely restricted diet, which can be associated with nutritional deficiencies. Children on a vegan diet should receive various nutritional supplements, but insufficient compliance has been reported in one-third of cases. While proper use of nutritional supplements in children consuming a vegan diet appears to be associated with normal growth and development, insufficient intake of supplements may impede growth and bone formation. Physical examination and analysis of height and weight over time can help differentiating between endocrine causes, gastrointestinal disorders, psychosocial problems, or underlying genetic conditions that prevent adequate nutritional intake. Laboratory screening should be part of the workup in every child with short stature, and further laboratory tests can be indicated if warranted by the dietary history, especially in children on a poorly planned vegan diet.

Growth charts for Marfan syndrome in the Netherlands and analysis of genotype-phenotype relationships

To optimize care for children with Marfan syndrome (MFS) in the Netherlands, Dutch MFS growth charts were constructed. Additionally, we aimed to investigate the effect of FBN1 variant type (haploinsufficiency [HI]/dominant negative [DN]) on growth, and compare MFS-related height increase across populations. Height and weight data of individuals with MFS aged 0-21 years were retrospectively collected. Generalized Additive Models for Location, Scale and Shape (GAMLSS) was used for growth chart modeling. To investigate genotype-phenotype relationships, FBN1 variant type was included as an independent variable in height-for-age and BMI-for-age models. MFS-related height increase was compared with that of previous MFS growth studies from the United States, Korea, and France. Height and weight data of 389 individuals with MFS were included (210 males). Height-for-age, BMI-for-age, and weight-for-height charts reflected the tall and slender MFS habitus throughout childhood. Mean increase in height of individuals with MFS compared with the general Dutch population was significantly lower than in the other three MFS populations compared to their reference populations. FBN1-HI variants were associated with taller height in both sexes, and decreased BMI in females (p-values <0.05). This Dutch MFS growth study broadens the notion that genetic background and MFS variant type (HI/DN) influence tall and slender stature in MFS.

Long-acting PEGylated growth hormone in children with idiopathic short stature: time to reconsider our diagnostic and treatment policy?

Idiopathic short stature (ISS) is a diagnosis of exclusion, and therefore each child with short stature or slow growth referred to a paediatrician deserves a full medical history and physical examination, as well as radiological and laboratory screening tests. In patients with an increased likelihood of a genetic cause, genetic testing is indicated. Idiopathic short stature is an approved indication for recombinant human growth hormone (rhGH) in the USA but not in most other parts of the world. In a recent article published in this journal, Luo et al reported on the 1-year's results of a multicentre randomized controlled trial (n = 360) on the efficacy and safety of two dosages of long-acting PEGylated rhGH (PEG-rhGH, Jintrolong®) (0.1 or 0.2 mg/kg body weight per week, respectively) in children with ISS compared with an untreated control group. The growth response to the higher dosage was similar to reported data on daily rhGH. In this commentary, we discuss whether the recent data on genetic causes of short stature in children who initially were labelled ISS, and data on the long-term safety of daily rhGH, may influence the balance between risks and benefits of rhGH treatment in children with ISS. We further discuss the pharmacokinetic and -dynamic profile of PEG-rhGH and its potential consequences for long-term safety.

Atypical STAT5B deficiency, severe short stature and mild immunodeficiency associated with a novel homozygous STAT5B Variant

STAT5B deficiency, a rare autosomal recessive disorder characterized by severe growth hormone insensitivity (GHI) and immunodeficiency, can manifest as fatal pulmonary complications. We describe atypical STAT5B deficiency associated with a novel homozygous frame-shift STAT5B variant [c.1453delG, p.(Asp485Thrfs*29)] identified in a young 17.6 yr old female subject who had severe postnatal growth impairment, biochemistries typical of GHI, an immune profile notable for hypergammaglobulinaemia and elevated B lymphocytes, and lack of pulmonary disease. Marked elevation of serum prolactin and pathologically diagnosed eczema were evident. In reconstitution studies, the STAT5B p.(Asp485Thrfs*29) was expressed although expression was reduced compared to wild-type STAT5B and a previously identified STAT5B p.(Gln368Profs*9) variant. Both truncated STAT5B peptides could not be activated by GH, nor mobilize to the nucleus. We conclude that an intact, functional, STAT5B is essential for normal GH-mediated growth, while expressed loss-of-function STAT5B variants may alleviate severe immune and pulmonary issues normally associated with STAT5B deficiency.

A Novel Method for Adult Height Prediction in Children with Idiopathic Short Stature Derived from a German-Dutch Cohort

Context

Prediction of adult height (AH) is important in clinical management of short children. The conventional methods of Bayley-Pinneau (BP) or Roche-Wainer-Thissen (RWT) have limitations.

Objective

We aimed to develop a set of algorithms for AH prediction in patients with idiopathic short stature (ISS) which are specific for combinations of predicting variables.

Methods

Demographic and auxologic data were collected in childhood (1980s) and at AH (1990s). Data were collected by Dutch and German referral centers for pediatric endocrinology. A total of 292 subjects with ISS (219 male, 73 female) were enrolled. The population was randomly split into modeling (n = 235) and validation (n = 57) cohorts. Linear multi-regression analysis was performed with predicted AH (PAH) as response variable and combinations of chronological age (CA), baseline height, parental heights, relative bone age (BA/CA), birth weight, and sex as exploratory variables.

Results

Ten models including different exploratory variables were selected with adjusted R² ranging from 0.84 to 0.78 and prediction errors from 3.16 to 3.68 cm. Applied to the validation cohort, mean residuals (PAH minus observed AH) ranged from −0.29 to −0.82 cm, while the conventional methods showed some overprediction (BP: +0.53 cm; RWT: +1.33 cm; projected AH: +3.81 cm). There was no significant trend of residuals with PAH or any exploratory variables, in contrast to BP and projected AH.

Conclusion

This set of 10 multi-regression algorithms, developed specifically for children with ISS, provides a flexible tool for AH prediction with better accuracy than the conventional methods.

Primary Ovarian Failure in Addition to Classical Clinical Features of Coats Plus Syndrome in a Female Carrying 2 Truncating Variants of CTC1

Coats plus syndrome is an autosomal recessive multisystemic and pleiotropic disorder affecting the eyes, brain, bone, and gastrointestinal tract, usually caused by compound heterozygous variants of the conserved telomere maintenance component 1 gene (CTC1), involved in telomere homeostasis and replication. So far, most reported patients are compound heterozygous for a truncating mutation and a missense variant. The phenotype is believed to result from telomere dysfunction, with accumulation of DNA damage, cellular senescence, and stem cell depletion. Here, we report a 23-year-old female with prenatal and postnatal growth retardation, microcephaly, osteopenia, recurrent fractures, intracranial calcification, leukodystrophy, parenchymal brain cysts, bicuspid aortic valve, and primary ovarian failure. She carries a previously reported maternally inherited pathogenic variant in exon 5 (c.724_727del, p.(Lys242Leufs*41)) and a novel, paternally inherited splice site variant (c.1617+5G>T; p.(Lys480Asnfs*17)) in intron 9. CTC1 transcript analysis showed that the latter resulted in skipping of exon 9. A trace of transcripts was normally spliced resulting in the presence of a low level of wild-type CTC1 transcripts. We speculate that ovarian failure is caused by telomere shortening or chromosome cohesion failure in oocytes and granulosa cells, with early decrease in follicular reserve. This is the first patient carrying 2 truncating CTC1 variants and the first presenting primary ovarian failure.

Biallelic POC1A variants cause syndromic severe insulin resistance with muscle cramps

OBJECTIVE

To describe clinical, laboratory, and genetic characteristics of three unrelated cases from Chile, Portugal, and Saudi Arabia with severe insulin resistance, SOFT syndrome, and biallelic pathogenic POC1A variants.

DESIGN

Observational study.

METHODS

Probands' phenotypes, including short stature, dysmorphism, and insulin resistance, were compared with previous reports.

RESULTS

Cases 1 (female) and 3 (male) were homozygous for known pathogenic POC1A variants: c.649C>T, p.(Arg217Trp) and c.241C>T, p.(Arg81*), respectively. Case 2 (male) was compound heterozygous for p.(Arg217Trp) variant and the rare missense variant c.370G>A, p.(Asp124Asn). All three cases exhibited severe insulin resistance, acanthosis nigricans, elevated serum triglycerides and decreased HDL, and fatty liver, resembling three previously reported cases. All three also reported severe muscle cramps. Aggregate analysis of the six known cases with biallelic POC1A variants and insulin resistance showed decreased birth weight and length mean (s.d.): -2.8 (0.9) and -3.7 (0.9) SDS, respectively), severe short stature mean (s.d.) height: -4.9 (1.7) SDS) and moderate microcephaly (mean occipitofrontal circumference -3.0 (range: -4.7 to -1.2)). These findings were similar to those reported for patients with SOFT syndrome without insulin resistance. Muscle biopsy in Case 3 showed features of muscle involvement secondary to a neuropathic process.

CONCLUSIONS

Patients with SOFT syndrome can develop severe dyslipidaemic insulin resistance, independent of the exonic position of the POC1A variant. They also can develop severe muscle cramps. After diagnosis, patients should be regularly screened for insulin resistance and muscle complaints.

Differential Diagnosis of the Short IGF-I-Deficient Child with Apparently Normal Growth Hormone Secretion

The current differential diagnosis for a short child with low insulin-like growth factor I (IGF-I) and a normal growth hormone (GH) peak in a GH stimulation test (GHST), after exclusion of acquired causes, includes the following disorders: (1) a decreased spontaneous GH secretion in contrast to a normal stimulated GH peak ("GH neurosecretory dysfunction," GHND) and (2) genetic conditions with a normal GH sensitivity (e.g., pathogenic variants of GH1 or GHSR) and (3) GH insensitivity (GHI). We present a critical appraisal of the concept of GHND and the role of 12- or 24-h GH profiles in the selection of children for GH treatment. The mean 24-h GH concentration in healthy children overlaps with that in those with GH deficiency, indicating that the previously proposed cutoff limit (3.0-3.2 μg/L) is too high. The main advantage of performing a GH profile is that it prevents about 20% of false-positive test results of the GHST, while it also detects a low spontaneous GH secretion in children who would be considered GH sufficient based on a stimulation test. However, due to a considerable burden for patients and the health budget, GH profiles are only used in few centres. Regarding genetic causes, there is good evidence of the existence of Kowarski syndrome (due to GH1 variants) but less on the role of GHSR variants. Several genetic causes of (partial) GHI are known (GHR, STAT5B, STAT3, IGF1, IGFALS defects, and Noonan and 3M syndromes), some responding positively to GH therapy. In the final section, we speculate on hypothetical causes.

The IGSF1 Deficiency Syndrome May Present with Normal Free T4 Levels, Severe Obesity, or Premature Testicular Growth

Our objective was to further expand the spectrum of clinical characteristics of the IGSF1 deficiency syndrome in affected males. These characteristic include almost universal congenital central hypothyroidism (CeH) with disharmonious pubertal development (normally timed testicular growth, but delayed rise of serum testosterone), macroorchidism, increased body mass index (BMI), and decreased attentional control. In addition, a subset of patients show prolactin deficiency, transient partial growth hormone deficiency in childhood and increased growth hormone secretion in adulthood. We present a family in which the proband was diagnosed with CeH and low serum prolactin. Severe weight gain started at two years old, with a BMI of 42.3 at 13.9 years. Testicular enlargement (5-6 mL, 3.8-4.3 standard deviation score) started aged three years. A pathogenic variant was found in the IGSF1 gene: c.3411_3412del, p.(Tyr1137*). His brother was referred for short stature at age 13 years and was diagnosed with CeH, normal serum prolactin and IGF-1, and disharmonious puberty. In four male relatives (the proband’s brother and three cousins) with the variant (one adult), free thyroxine (fT4) was below the lower limit of the reference range in two, and just above this limit in the other two. Three were overweight or obese, adolescents had disharmonious pubertal development and the adult had profound macroorchidism. In conclusion, male hemizygous carriers of a pathogenic IGSF1 variant can present with fT4 concentration above the lower limit of the reference range while severe early onset obesity or premature testicular growth are part of the phenotypic spectrum.

Arm Span and Its Relation to Height in a 2- to 17-Year-Old Reference Population and Heterozygous Carriers of ACAN Variants

BACKGROUND/OBJECTIVES

In the clinical assessment of a short or tall child, estimating body disproportion is useful to assess the likelihood of a primary growth disorder, e.g., skeletal dysplasia. Our objectives were (1) to use data from the Maastricht study on healthy children (2-17 years) to calculate relative arm span (AS) for height (H) to serve as age references for clinical purposes; (2) to assess its age and sex dependency; and (3) to investigate relative AS adjustment for age and sex in individuals with ACAN haploinsufficiency.

METHODS

The Maastricht study data (2,595 Caucasian children, 52% boys, 48% girls) were re-analysed to produce reference tables and graphs for age and sex of AS - H and AS/H. Published information on AS/H in Europeans was used as reference data for adults. Relative AS from 33 patients with ACAN haploinsufficiency were plotted against reference data and expressed as standard deviation score (SDS) for age and sex.

RESULTS

Mean AS - H from 2 to 17 years increased from -1.2 to +1.5 cm in boys and from -4.8 to +1.6 cm in girls. Mean AS/H increased from 0.9848 to 1.0155 in boys and from 0.9468 to 1.0028 in girls. Mean AS/H in patients with ACAN haploinsufficiency was approximately 1.0, 1.5 and 0.5 SDS in young children, adolescents and 20- to 50-year-olds, respectively, and normal thereafter.

CONCLUSIONS

These reference charts can be used for 2- to 17-year-old children/adolescents. Carriers of ACAN haploinsufficiency have an elevated mean AS/H in childhood and adolescence and a slightly elevated ratio till 50 years.

Important Tools for Use by Pediatric Endocrinologists in the Assessment of Short Stature

Assessment and management of children with growth failure has improved greatly over recent years. However, there remains a strong potential for further improvements by using novel digital techniques. A panel of experts discussed developments in digitalization of a number of important tools used by pediatric endocrinologists at the third 360° European Meeting on Growth and Endocrine Disorders, funded by Merck KGaA, Germany, and this review is based on those discussions. It was reported that electronic monitoring and new algorithms have been devised that are providing more sensitive referral for short stature. In addition, computer programs have improved ways in which diagnoses are coded for use by various groups including healthcare providers and government health systems. Innovative cranial imaging techniques have been devised that are considered safer than using gadolinium contrast agents and are also more sensitive and accurate. Deep-learning neural networks are changing the way that bone age and bone health are assessed, which are more objective than standard methodologies. Models for prediction of growth response to growth hormone (GH) treatment are being improved by applying novel artificial intelligence methods that can identify non-linear and linear factors that relate to response, providing more accurate predictions. Determination and interpretation of insulin-like growth factor-1 (IGF-1) levels are becoming more standardized and consistent, for evaluation across different patient groups, and computer-learning models indicate that baseline IGF-1 standard deviation score is among the most important indicators of GH therapy response. While physicians involved in child growth and treatment of disorders resulting in growth failure need to be aware of, and keep abreast of, these latest developments, treatment decisions and management should continue to be based on clinical decisions. New digital technologies and advancements in the field should be aimed at improving clinical decisions, making greater standardization of assessment and facilitating patient-centered approaches.

Anthropometric, biochemical and hormonal profiles of the partially admixed pygmoid group in Rampasasa (Flores, Indonesia)

OBJECTIVES

We performed a cross-sectional study on anthropometric and laboratory characteristics of inhabitants of Rampasasa (Flores, Indonesia). Adults were categorised according to ancestry into three groups: pygmoid (P/P, offspring of pygmoid parents, n=8), mixed pygmoid (P/N, offspring of pygmoid and non-pygmoid parents, n=12) and non-pygmoid (N/N, n=10). Children (n=28) were P/N.

METHODS

Measurements included height, weight, sitting height, arm span, head circumference, haematological analysis and serum albumin, calcium, vitamin D, insulin-like growth factor-I (IGF-I) and IGF binding protein 3 (IGFBP-3). Pubertal stage and bone age was assessed in children. Anthropometric data were expressed as standard deviation score (SDS) for age. IGF-I, IGFBP-3 and IGF-I/IGFBP-3 ratio were expressed as SDS for age, bone age and pubertal stage.

RESULTS

Mean height SDS showed a gradient from P/P (-4.0) via P/N (-3.2) to N/N (-2.3) (-3.4, -3.1 and -2.2 adjusted for age-associated shrinking). Sitting height and head circumference showed similar gradients. Serum IGF-I SDS was similar among groups (approximately -1 SDS). IGFBP-3 SDS tended toward a gradient from P/P (-1.9) via P/N (-1.5) to N/N (-1.1), but IGF-I/IGFBP-3 ratio was normal in all groups. In P/P and P/N, mean head circumference SDS was >2 SD greater than mean height SDS. Children showed a progressive growth failure and bone age delay, delayed female pubertal onset and an initial low serum IGF-I, normal IGFBP-3 and low IGF-I/IGFBP-3 ratio.

CONCLUSIONS

P/P showed proportionate short stature with relative macrocephaly and relatively low IGFBP-3; P/N presented an intermediate pattern. P/N children were progressively short, showed delayed skeletal maturation, delayed puberty in girls and low IGF-I and IGF-I/IGFBP-3.

Guideline for referring short or tall children in preventive child health care

AIM

To develop a guideline for preventive child healthcare professionals in order to improve early detection of pathological disorders associated with short stature (or growth faltering) or tall stature (or accelerated growth).

METHODS

We updated the previous Dutch guideline for short stature in children aged 0-9 years and extended it to adolescents (10-17 years), and added a guideline for tall stature, based on literature and input from an expert committee. Specificities were calculated in a cohort of healthy Dutch children aged 0-9 years (n = 970). We investigated the impact of a late onset of puberty on height standard deviation score based on the Dutch growth charts.

RESULTS

Growth parameters of the guideline include height, the distance between height and target height and change of height over time. Other parameters include diagnostic clues from medical history and physical examination, for example behavioural problems, precocious or delayed puberty, body disproportion and dysmorphic features.

CONCLUSION

Preventive child healthcare professionals now have an updated guideline for referring short or tall children to specialist care. Further research is needed on the diagnostic yield after referral and specificity at field level.

Growth failure: 'idiopathic' only after a detailed diagnostic evaluation

The terms 'idiopathic short stature' (ISS) and 'small for gestational age' (SGA) were first used in the 1970s and 1980s. ISS described non-syndromic short children with undefined aetiology who did not have growth hormone (GH) deficiency, chromosomal defects, chronic illness, dysmorphic features or low birth weight. Despite originating in the pre-molecular era, ISS is still used as a diagnostic label today. The term 'SGA' was adopted by paediatric endocrinologists to describe children born with low birth weight and/or length, some of whom may experience lack of catch-up growth and present with short stature. GH treatment was approved by the FDA for short children born SGA in 2001, and by the EMA in 2003, and for the treatment of ISS in the US, but not Europe, in 2003. These approvals strengthened the terms 'SGA' and 'ISS' as clinical entities. While clinical and hormonal diagnostic techniques remain important, it is the emergence of genetic investigations that have led to numerous molecular discoveries in both ISS and SGA subjects. The primary message of this article is that the labels ISS and SGA are not definitive diagnoses. We propose that the three disciplines of clinical evaluation, hormonal investigation and genetic sequencing should have equal status in the hierarchy of short stature assessments and should complement each other to identify the true pathogenesis in poorly growing patients.

Catch-up Growth in Prepubertal Children Treated for Juvenile Hypothyroidism and Growth Hormone Deficiency can be Modelled with a Monomolecular Function

OBJECTIVE

We hypothesized that modelling catch-up growth (CUG) as developed for coeliac disease (CD), might also fit CUG in adequately treated children with juvenile hypothyroidism (JHT) or growth hormone deficiency (GHD).

METHODS

We used a monomolecular function for all available prepubertal data on height standard deviation score (HSDS) minus target height SDS (adjHSDS) in children with JHT (n=20) and GHD (n=18) on a conventional (CoD) or high GH dose (HD), based either on a national height reference with an age cut-off of 10 (girls) and 12 (boys) years (model 1) or prepubertal height reference values, if age (0) was ≥3, with no upper age limit (model 2).

RESULTS

The models could be fitted in 83-90% of cases; in other cases the HSDS decreased after several measurements, which violated the assumption of an irreversible growth process. In JHT, the rate constant (k) and adjHSDS (0) were lower than in CD (p=0.02), but adjHSDS (end) was similar. In GHD (model 1), k was lower than for CD (p=0.004) but similar to JHT, while adjHSDS (0) and adjHSDS (end) were similar to CD and JHT. Thus, the shape of CUG is similar for children with JHT and GHD, while children with CD had less growth deficit at start and a faster CUG. The differences in CUG parameters between GH dose subgroups did not reach statistical significance.

CONCLUSION

Modelling CUG of prepubertal children with JHT and GHD can be used for assessing the adequacy of CUG and the influence of clinical treatment modalities on its speed and magnitude.

IGSF1 Does Not Regulate Spermatogenesis or Modify FSH Synthesis in Response to Inhibins or Activins

Loss-of-function mutations in the X-linked immunoglobulin superfamily, member 1 (IGSF1) gene result in central hypothyroidism, often associated with macroorchidism. Testicular enlargement in these patients might be caused by increases in follicle-stimulating hormone (FSH) levels, as IGSF1 has been proposed to function as an inhibin B receptor or as an inhibitor of activin type I receptor (ALK4) activity in pituitary gonadotrope cells. If true, loss of IGSF1 should lead to reduced inhibin B action or disinhibition of activin signaling, thereby increasing FSH synthesis. Here, we show that FSH levels and sperm counts are normal in male Igsf1 knockout mice, although testis size is mildly increased. Sperm parameters are also normal in men with IGSF1 deficiency, although their FSH levels may trend higher and their testes are enlarged. Inhibin B retains the ability to suppress FSH synthesis in pituitaries of Igsf1-knockout mice and IGSF1 does not interact with ALK4 or alter activin A/ALK4 stimulation of FSHβ (Fshb/FSHB) subunit transcription or expression. In light of these results, it is unlikely that macroorchidism in IGSF1 deficiency derives from alterations in spermatogenesis or inhibin/activin regulation of FSH.

SCUBE3 loss-of-function causes a recognizable recessive developmental disorder due to defective bone morphogenetic protein signaling

Signal peptide-CUB-EGF domain-containing protein 3 (SCUBE3) is a member of a small family of multifunctional cell surface-anchored glycoproteins functioning as co-receptors for a variety of growth factors. Here we report that bi-allelic inactivating variants in SCUBE3 have pleiotropic consequences on development and cause a previously unrecognized syndromic disorder. Eighteen affected individuals from nine unrelated families showed a consistent phenotype characterized by reduced growth, skeletal features, distinctive craniofacial appearance, and dental anomalies. In vitro functional validation studies demonstrated a variable impact of disease-causing variants on transcript processing, protein secretion and function, and their dysregulating effect on bone morphogenetic protein (BMP) signaling. We show that SCUBE3 acts as a BMP2/BMP4 co-receptor, recruits the BMP receptor complexes into raft microdomains, and positively modulates signaling possibly by augmenting the specific interactions between BMPs and BMP type I receptors. Scube3-/- mice showed craniofacial and dental defects, reduced body size, and defective endochondral bone growth due to impaired BMP-mediated chondrogenesis and osteogenesis, recapitulating the human disorder. Our findings identify a human disease caused by defective function of a member of the SCUBE family, and link SCUBE3 to processes controlling growth, morphogenesis, and bone and teeth development through modulation of BMP signaling.

Should Skeletal Maturation Be Manipulated for Extra Height Gain?

Skeletal maturation can be delayed by reducing the exposure to estrogens, either by halting pubertal development through administering a GnRH analogue (GnRHa), or by blocking the conversion of androgens to estrogens through an aromatase inhibitor (AI). These agents have been investigated in children with growth disorders (off-label), either alone or in combination with recombinant human growth hormone (rhGH). GnRHa is effective in attaining a normal adult height (AH) in the treatment of children with central precocious puberty, but its effect in short children with normal timing of puberty is equivocal. If rhGH-treated children with growth hormone deficiency or those who were born small-for-gestational age are still short at pubertal onset, co-treatment with a GnRHa for 2-3 years increases AH. A similar effect was seen by adding rhGH to GnRHa treatment of children with central precocious puberty with a poor AH prediction and by adding rhGH plus GnRHa to children with congenital adrenal hyperplasia with a poor predicted adult height on conventional treatment with gluco- and mineralocorticoids. In girls with idiopathic short stature and relatively early puberty, rhGH plus GnRHa increases AH. Administration of letrozole to boys with constitutional delay of growth puberty may increase AH, and rhGH plus anastrozole may increase AH in boys with growth hormone deficiency or idiopathic short stature, but the lack of data on attained AH and potential selective loss-of-follow-up in several studies precludes firm conclusions. GnRHas appear to have a good overall safety profile, while for aromatase inhibitors conflicting data have been reported.

Evidence That Non-Syndromic Familial Tall Stature Has an Oligogenic Origin Including Ciliary Genes

Human growth is a complex trait. A considerable number of gene defects have been shown to cause short stature, but there are only few examples of genetic causes of non-syndromic tall stature. Besides rare variants with large effects and common risk alleles with small effect size, oligogenic effects may contribute to this phenotype. Exome sequencing was carried out in a tall male (height 3.5 SDS) and his parents. Filtered damaging variants with high CADD scores were validated by Sanger sequencing in the trio and three other affected and one unaffected family members. Network analysis was carried out to assess links between the candidate genes, and the transcriptome of murine growth plate was analyzed by microarray as well as RNA Seq. Heterozygous gene variants in CEP104, CROCC, NEK1, TOM1L2, and TSTD2 predicted as damaging were found to be shared between the four tall family members. Three of the five genes (CEP104, CROCC, and NEK1) belong to the ciliary gene family. All genes are expressed in mouse growth plate. Pathway and network analyses indicated close functional connections. Together, these data expand the spectrum of genes with a role in linear growth and tall stature phenotypes.

Disorders of IGFs and IGF-1R signaling pathways

The insulin-like growth factor (IGF) system comprises two ligands, IGF-I and IGF-II, that regulate multiple physiological processes, including mammalian development, metabolism and growth, through the type 1 IGF receptor (IGF-1R). The growth hormone (GH)-IGF-I axis is the major regulator of longitudinal growth. IGF-II is expressed in many tissues, notably the placenta, to regulate human pre- and post-natal growth and development. This review provides a brief introduction to the IGF system and summarizes findings from reports arising from recent larger genomic sequencing studies of human genetic mutations in IGF1 and IGF2 and genes of proteins regulating IGF action, namely the IGF-1R, IGF-1R signaling pathway components and the IGF binding proteins (IGFBPs). A perspective on the effect of homozygous mutations on structure and function of the IGFs and IGF-1R is also given and this is related to the effects on growth.

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.

Identification of novel genetic variants associated with short stature in a Baka Pygmies population

Human growth is a complex trait determined by genetic factors in combination with external stimuli, including environment, nutrition and hormonal status. In the past, several genome-wide association studies (GWAS) have collectively identified hundreds of genetic variants having a putative effect on determining adult height in different worldwide populations. Theoretically, a valuable approach to better understand the mechanisms of complex traits as adult height is to study a population exhibiting extreme stature phenotypes, such as African Baka Pygmies. After phenotypic characterization, we sequenced the whole exomes of a cohort of Baka Pygmies and their non-Pygmies Bantu neighbors to highlight genetic variants associated with the reduced stature. Whole exome data analysis revealed 29 single nucleotide polymorphisms (SNPs) significantly associated with the reduced height in the Baka group. Among these variants, we focused on SNP rs7629425, located in the 5′-UTR of the Hyaluronidase-2 (HYAL2) gene. The frequency of the alternative allele was significantly increased compared to African and non-African populations. In vitro luciferase assay showed significant differences in transcription modulation by rs7629425 C/T alleles. In conclusion, our results suggested that the HYAL2 gene variants may play a role in the etiology of short stature in Baka Pygmies population.

A Proposal for the Interpretation of Serum IGF-I Concentration as Part of Laboratory Screening in Children with Growth Failure

The serum insulin-like growth factor-I (IGF-I) concentration is commonly used as a screening tool for growth hormone deficiency (GHD), but there is no consensus on the cut-off limit of IGF-I standard deviation score (SDS) to perform GH stimulation tests for confirmation or exclusion of GHD. We argue that the cut-off limit is dependent on the clinical pre-test likelihood of GHD and propose a diagnostic strategy in which the cut-off limit varies between zero to -2 SDS.

IGSF1 Deficiency Results in Human and Murine Somatotrope Neurosecretory Hyperfunction

CONTEXT

The X-linked immunoglobulin superfamily, member 1 (IGSF1), gene is highly expressed in the hypothalamus and in pituitary cells of the POU1F1 lineage. Human loss-of-function mutations in IGSF1 cause central hypothyroidism, hypoprolactinemia, and macroorchidism. Additionally, most affected adults exhibit higher than average IGF-1 levels and anecdotal reports describe acromegaloid features in older subjects. However, somatotrope function has not yet been formally evaluated in this condition.

OBJECTIVE

We aimed to evaluate the role of IGSF1 in human and murine somatotrope function.

PATIENTS, DESIGN, AND SETTING

We evaluated 21 adult males harboring hemizygous IGSF1 loss-of-function mutations for features of GH excess, in an academic clinical setting.

MAIN OUTCOME MEASURES

We compared biochemical and tissue markers of GH excess in patients and controls, including 24-hour GH profile studies in 7 patients. Parallel studies were undertaken in male Igsf1-deficient mice and wild-type littermates.

RESULTS

IGSF1-deficient adult male patients demonstrated acromegaloid facial features with increased head circumference as well as increased finger soft-tissue thickness. Median serum IGF-1 concentrations were elevated, and 24-hour GH profile studies confirmed 2- to 3-fold increased median basal, pulsatile, and total GH secretion. Male Igsf1-deficient mice also demonstrated features of GH excess with increased lean mass, organ size, and skeletal dimensions and elevated mean circulating IGF-1 and pituitary GH levels.

CONCLUSIONS

We demonstrate somatotrope neurosecretory hyperfunction in IGSF1-deficient humans and mice. These observations define a hitherto uncharacterized role for IGSF1 in somatotropes and indicate that patients with IGSF1 mutations should be evaluated for long-term consequences of increased GH exposure.

Towards a Rational and Efficient Diagnostic Approach in Children Referred for Tall Stature and/or Accelerated Growth to the General Paediatrician

Tall stature and/or accelerated growth (TS/AG) in a child can be the result of a primary or secondary growth disorder, but more frequently no cause can be found (idiopathic TS). The conditions with the most important therapeutic implications are Klinefelter syndrome, Marfan syndrome and secondary growth disorders such as precocious puberty, hyperthyroidism and growth hormone excess. We propose a diagnostic flow chart offering a systematic approach to evaluate children referred for TS/AG to the general paediatrician. Based on the incidence, prevalence and clinical features of medical conditions associated with TS/AG, we identified relevant clues for primary and secondary growth disorders that may be obtained from the medical history, physical evaluation, growth analysis and additional laboratory and genetic testing. In addition to obtaining a diagnosis, a further goal is to predict adult height based on growth pattern, pubertal development and skeletal maturation. We speculate that an improved diagnostic approach in addition to expanding use of genetic testing may increase the diagnostic yield and lower the age at diagnosis of children with a pathologic cause of TS/AG.

Towards a Rational and Efficient Diagnostic Approach in Children Referred for Growth Failure to the General Paediatrician

Based on a recent Dutch national guideline, we propose a structured stepwise diagnostic approach for children with growth failure (short stature and/or growth faltering), aiming at high sensitivity for pathologic causes at acceptable specificity. The first step is a detailed clinical assessment, aiming at obtaining relevant clinical clues from the medical history (including family history), physical examination (emphasising head circumference, body proportions and dysmorphic features) and assessment of the growth curve. The second step consists of screening: a radiograph of the hand and wrist (for bone age and assessment of anatomical abnormalities suggestive for a skeletal dysplasia) and laboratory tests aiming at detecting disorders that can present as isolated short stature (anaemia, growth hormone deficiency, hypothyroidism, coeliac disease, renal failure, metabolic bone diseases, renal tubular acidosis, inflammatory bowel disease, Turner syndrome [TS]). We advise molecular array analysis rather than conventional karyotyping for short girls because this detects not only TS but also copy number variants and uniparental isodisomy, increasing diagnostic yield at a lower cost. Third, in case of diagnostic clues for primary growth disorders, further specific testing for candidate genes or a hypothesis-free approach is indicated; suspicion of a secondary growth disorder warrants adequate further targeted testing.

Diagnosis, Genetics, and Therapy of Short Stature in Children: A Growth Hormone Research Society International Perspective

The Growth Hormone Research Society (GRS) convened a Workshop in March 2019 to evaluate the diagnosis and therapy of short stature in children. Forty-six international experts participated at the invitation of GRS including clinicians, basic scientists, and representatives from regulatory agencies and the pharmaceutical industry. Following plenary presentations addressing the current diagnosis and therapy of short stature in children, breakout groups discussed questions produced in advance by the planning committee and reconvened to share the group reports. A writing team assembled one document that was subsequently discussed and revised by participants. Participants from regulatory agencies and pharmaceutical companies were not part of the writing process. Short stature is the most common reason for referral to the pediatric endocrinologist. History, physical examination, and auxology remain the most important methods for understanding the reasons for the short stature. While some long-standing topics of controversy continue to generate debate, including in whom, and how, to perform and interpret growth hormone stimulation tests, new research areas are changing the clinical landscape, such as the genetics of short stature, selection of patients for genetic testing, and interpretation of genetic tests in the clinical setting. What dose of growth hormone to start, how to adjust the dose, and how to identify and manage a suboptimal response are still topics to debate. Additional areas that are expected to transform the growth field include the development of long-acting growth hormone preparations and other new therapeutics and diagnostics that may increase adult height or aid in the diagnosis of growth hormone deficiency.

Isolated Growth Hormone Deficiency Type 2 due to a novel GH1 Mutation: A Case Report

Isolated growth hormone (GH) deficiency (IGHD) type 2 is a rare autosomal dominant disorder characterized by severe short stature with low GH level. Timely diagnosis is important for optimal results of recombinant human GH (rhGH) treatment and detection of additional pituitary deficiencies in affected relatives. A male child presented at the age of one year with severe, proportionate short stature [-4.9 standard deviation score (SDS)] and with a normal body mass index (-1.1 SDS). Physical examination revealed frontal bossing, midfacial hypoplasia, normal external genitalia and no dysmorphic features. Paternal and maternal heights were -6.1 and -1.9 SDS. Serum insulin-like growth factor-1 (IGF-1) and IGF-binding protein-3 were undetectable and the peak GH concentration by clonidine stimulation test was extremely low (0.18 ng/mL). Brain magnetic resonance imaging showed anterior pituitary hypoplasia. Genetic analysis identified a novel heterozygous mutation (c.291+2T>G) expected to lead to splicing out exon 3 of GH1. rhGH from age 2.4 years led to appropriate catch-up. In conclusion, we identified a novel GH1 gene mutation in an infant with classical IGHD type 2 presentation.

Achieving Optimal Short- and Long-term Responses to Paediatric Growth Hormone Therapy

It is over sixty years since the first administration of human growth hormone (GH) to children with GH deficiency, and over thirty years since recombinant human GH has been available for treatment of GH deficiency and a wider range of non-GH deficiency disorders. From a diagnostic perspective, genetic analysis, using single gene or Sanger sequencing and more recently next generation or whole exome sequencing, has brought advances in the diagnosis of specific causes of short stature, which has enabled therapy to be targeted more accurately. Genetic discoveries have ranged from defects of pituitary development and GH action to abnormalities in intracellular mechanisms, paracrine regulation and cartilage matrix formation. The strategy of GH therapy using standard doses has evolved to individualised GH dosing, depending on diagnosis and predictors of growth response. Evidence of efficacy of GH in GH deficiency, Turner syndrome and short children born small for gestational age is reviewed. The importance of critical assessment of growth response is discussed, together with the recognition and management of a poor or unsatisfactory growth response and the organisational issues related to prevention, detection and intervention regarding suboptimal adherence to GH therapy.

Intrauterine Twin Discordancy and Partial Postnatal Catch-up Growth in a Girl with a Pathogenic IGF1R Mutation

OBJECTIVE

Insulin like growth factors-1 (IGF-1) is essential for normal in utero and postnatal human growth. It mediates its effects through the IGF-1 receptor (IGF1R), a widely expressed cell surface tyrosine kinase receptor. The aim of the study was to analyze pre- and post-natal growth, clinical features and laboratory findings in a small for gestational age (SGA) girl in whom discordant postnatal growth persisted and her appropriate for gestational age (AGA) brother.

METHODS

A girl born with a low weight and length [-2.3 and -2.4 standard deviation (SD) score (SDS), respectively] but borderline low head circumference (-1.6 SD) presented with a height of -1.7 SDS, in contrast to a normal height twin brother (0.0 SDS). IGF-1 resistance was suspected because of elevated serum IGF-1 levels.

RESULTS

Sequencing revealed the presence of a previously described pathogenic heterozygous mutation (p.Glu1050Lys) in the SGA girl which was not present in the parents nor in the AGA twin brother.

CONCLUSION

The pathogenic IGF1R mutation in this girl led to intrauterine growth retardation followed by partial postnatal catch-up growth. Height in mid-childhood was in the lower half of the reference range, but still 1.7 SD shorter than her twin brother.

Phenotypic Features and Response to GH Treatment of Patients With a Molecular Defect of the IGF-1 Receptor

CONTEXT

The phenotype and response to GH treatment of children with an IGF1R defect is insufficiently known.

OBJECTIVE

To develop a clinical score for selecting children with short stature for genetic testing and evaluate the efficacy of treatment.

DESIGN AND SETTING

Case series with an IGF1R defect identified in a university genetic laboratory.

PATIENTS AND INTERVENTIONS

Of all patients with sufficient clinical data, 18 had (likely) pathogenic mutations (group 1) and 7 had 15q deletions including IGF1R (group 2); 19 patients were treated with GH.

MAIN OUTCOME MEASURES

Phenotype and response to GH treatment.

RESULTS

In groups 1 and 2, mean (range) birth weight, length, and head circumference (HC) SD scores (SDSs) were -2.1 (-3.7 to -0.4), -2.7 (-5.0 to -1.0), and -1.6 (-3.0 to 0.0), respectively. At presentation, height, HC, and serum IGF-1 SDSs were -3.0 (-5.5 to -1.7), -2.5 (-4.2 to -0.5), and +1.2 (-1.3 to 3.2), respectively. Feeding problems were reported in 15 of 19 patients. A clinical score with 76% sensitivity is proposed. After 3 years of GH treatment [1.1 (0.2) mg/m2/d] height gain in groups 1 (n = 12) and 2 (n = 7) was 0.9 SDS and 1.3 SDS (at a mean IGF-1 of 3.5 SDS), less than reported for small for gestational age (1.8 SDS).

CONCLUSION

A clinical score encompassing birth weight and/or length, short stature, microcephaly, and IGF-1 is useful for selecting patients for IGF1R analysis. Feeding problems are common and the growth response to GH treatment is moderate.

Children Born Small for Gestational Age: Differential Diagnosis, Molecular Genetic Evaluation, and Implications

Children born small for gestational age (SGA), defined as a birth weight and/or length below -2 SD score (SDS), comprise a heterogeneous group. The causes of SGA are multifactorial and include maternal lifestyle and obstetric factors, placental dysfunction, and numerous fetal (epi)genetic abnormalities. Short-term consequences of SGA include increased risks of hypothermia, polycythemia, and hypoglycemia. Although most SGA infants show catch-up growth by 2 years of age, ∼10% remain short. Short children born SGA are amenable to GH treatment, which increases their adult height by on average 1.25 SD. Add-on treatment with a gonadotropin-releasing hormone agonist may be considered in early pubertal children with an expected adult height below -2.5 SDS. A small birth size increases the risk of later neurodevelopmental problems and cardiometabolic diseases. GH treatment does not pose an additional risk.

Bi-allelic Loss-of-Function Mutations in the NPR-C Receptor Result in Enhanced Growth and Connective Tissue Abnormalities

The natriuretic peptide signaling pathway has been implicated in many cellular processes, including endochondral ossification and bone growth. More precisely, different mutations in the NPR-B receptor and the CNP ligand have been identified in individuals with either short or tall stature. In this study we show that the NPR-C receptor (encoded by NPR3) is also important for the regulation of linear bone growth. We report four individuals, originating from three different families, with a phenotype characterized by tall stature, long digits, and extra epiphyses in the hands and feet. In addition, aortic dilatation was observed in two of these families. In each affected individual, we identified a bi-allelic loss-of-function mutation in NPR3. The missense mutations (c.442T>C [p.Ser148Pro] and c.1088A>T [p.Asp363Val]) resulted in intracellular retention of the NPR-C receptor and absent localization on the plasma membrane, whereas the nonsense mutation (c.1524delC [p.Tyr508^∗]) resulted in nonsense-mediated mRNA decay. Biochemical analysis of plasma from two affected and unrelated individuals revealed a reduced NTproNP/NP ratio for all ligands and also high cGMP levels. These data strongly suggest a reduced clearance of natriuretic peptides by the defective NPR-C receptor and consequently increased activity of the NPR-A/B receptors. In conclusion, this study demonstrates that loss-of-function mutations in NPR3 result in increased NPR-A/B signaling activity and cause a phenotype marked by enhanced bone growth and cardiovascular abnormalities.

Characterization of an activating R1353H insulin-like growth factor 1 receptor variant in a male with extreme tall height

OBJECTIVE

The insulin-like growth factor1 receptor (IGF1R) is important in growth and development, and inactivating IGF1R mutations cause short stature and relatively high levels of serum IGF-I. We identified an unclassified IGF1R^R1353H variant in a male with extreme tall height, very low levels of serum IGF-I and delayed and prolonged growth spurt. The index case's mother and three sons all carried the variant, but so far only the eldest son (age 18 years) presented with tall height. We hypothesized that the variant could constitute an activating mutation.

DESIGN

The IGF1R^R1353H variant was investigated in Igf1r^-/- mouse embryonic fibroblasts (R-cells) by cell cycle, colony formation and transcriptome analyses.

RESULTS

The IGF1R^R1353H (R-1353) exhibited significantly increased cell proliferation, G1-S progression and colony formation in soft agar. RNA sequencing identified 195 differentially expressed genes between R-WT and R-1353 (adjusted P < 1E-100). Most genes were upregulated in R-1353, including the gene encoding the androgen receptor (AR). Gene expression profiling showed the most significant enrichment in extracellular matrix organization (P = 2.76E-7), collagen biosynthesis (P = 1.21E-5) and cell adhesion (P = 7.38E-5). Retrospective biochemical analysis of the index case revealed decreased testosterone and sex hormone-binding globulin levels, whereas LH and FSH were within normal ranges. This profile suggests an increased sensitivity to androgen, which is compatible with the enhanced expression of Ar in R-1353 cells.

CONCLUSIONS

Our findings suggest that R1353H constitutes an activating IGF1R variant. The possible deregulation of collagen turnover and increased androgen sensitivity implicates an association to tall phenotype in male carriers.

How Much Nutrition for How Much Growth?

BACKGROUND/AIMS

Increasing agreement exists about the use of length-for-age as the indicator of choice in monitoring the long-term impact of chronic nutritional deficiency. Yet, already shortly after World War I, a causal link between nutrition and growth was questioned. Also, modern meta-analyses of controlled nutrition intervention studies show that the net effect of nutrition on body height is small. Broad evidence obtained from historic observations on human starvation made since the 19th century questions an obligatory association between nutrition and growth. Many additional explanations for the apparent shortness of people from developing countries have been published since, focusing on genetic factors, environment, economy, epigenetics, and, recently, psychosocial factors, such as strategic growth adjustments suggesting stature to be a social signal.

CONCLUSION

The marked variability in average population height of up to 20 cm within a few generations complicates the use of normative growth charts, even though they have been widely propagated. We support the concept of local growth references, for example using the "Synthetic Growth References" methodology. These references combine local growth information obtained from a given population of interest and common features of human population growth, with LMS values for height, weight, and BMI from birth to maturity.
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Growth hormone - past, present and future

Growth hormone (GH) research and its clinical application for the treatment of growth disorders span more than a century. During the first half of the 20th century, clinical observations and anatomical and biochemical studies formed the basis of the understanding of the structure of GH and its various metabolic effects in animals. The following period (1958-1985), during which pituitary-derived human GH was used, generated a wealth of information on the regulation and physiological role of GH - in conjunction with insulin-like growth factors (IGFs) - and its use in children with GH deficiency (GHD). The following era (1985 to present) of molecular genetics, recombinant technology and the generation of genetically modified biological systems has expanded our understanding of the regulation and role of the GH-IGF axis. Today, recombinant human GH is used for the treatment of GHD and various conditions of non-GHD short stature and catabolic states; however, safety concerns still accompany this therapeutic approach. In the future, new therapeutics based on various components of the GH-IGF axis might be developed to further improve the treatment of such disorders. In this Review, we describe the history of GH research and clinical use with a particular focus on disorders in childhood.

Long-term BMI and growth profiles in offspring of women with gestational diabetes

AIMS/HYPOTHESIS

Gestational diabetes mellitus (GDM) is reported to be associated with childhood obesity, however the magnitude of this association and relation to intrauterine growth is uncertain. We, therefore, aimed to assess whether the growth trajectories of large for gestational age (LGA) and non-LGA offspring of mothers with GDM (OGDM) are different until early adolescence. We also aimed to explore whether growth trajectories of OGDM differ from those of offspring of mothers with type 1 or 2 diabetes (ODM1, ODM2).

METHODS

We studied height and BMI standard deviation score (SDS) of the OGDM group, up to the age of 14 years, with subgroup analysis comparing LGA with non-LGA at birth as a reflection of the intrauterine environment. All mothers with GDM who delivered at the University Medical Center Utrecht between 1990 and 2006 were contacted to participate; informed consent was received for 104 OGDM of 93 mothers. Offspring data were collected through Dutch infant welfare centres. Recorded height and weight were converted to BMI and age- and sex-specific SDS values for Dutch children. Additionally, we compared the OGDM group with ODM1 and ODM2 groups in order to identify those offspring with the highest risk of becoming overweight. Growth trajectories were compared between non-LGA and LGA OGDM and between OGDM, ODM1 and ODM2, using a random-effects model. In the longitudinal follow-up a mean of 7.4 ± 2 measurements per infant were available.

RESULTS

Mothers had a prepregnancy BMI of 25.8 kg/m² and 24% of their infants were LGA at birth. Heights of OGDM were no different from those of the Dutch Growth Study. Non-LGA OGDM showed a BMI SDS comparable with that of the reference population, with a slight increase in early adolescence. LGA OGDM had a higher BMI SDS trajectory than non-LGA OGDM and the reference population, which plateaued at around 10 years of age. Comparison of growth trajectories of OGDM, ODM1 and ODM2 showed ODM2 to have the highest trajectory followed by ODM1 and OGDM, with the LGA counterparts of all three offspring groups in the highest BMI SDS ranges.

CONCLUSIONS/INTERPRETATION

Until early adolescence, OGDM have a BMI that is 0.5 SDS higher than that of the Dutch background population. LGA OGDM appear to be at particularly higher risk of being overweight in adolescence compared with non-LGA OGDM, putting them also at a higher lifetime risk of being overweight and developing obesity. ODM2 showed the highest BMI SDS values and had an average BMI SDS of +1.6 until the age of 14, when it became +2 SD. These results emphasize the importance of adequate recognition and timely treatment of maternal gestational diabetes to prevent fetal macrosomia in obstetrics.

Genetic Analyses in Small-for-Gestational-Age Newborns

CONTEXT

Small for gestational age (SGA) can be the result of fetal growth restriction, which is associated with perinatal morbidity and mortality. Mechanisms that control prenatal growth are poorly understood.

OBJECTIVE

The aim of the current study was to gain more insight into prenatal growth failure and determine an effective diagnostic approach in SGA newborns. We hypothesized that one or more copy number variations (CNVs) and disturbed methylation and sequence variants may be present in genes associated with fetal growth.

DESIGN

A prospective cohort study of subjects with a low birth weight for gestational age.

SETTING

The study was conducted at an academic pediatric research institute.

PATIENTS

A total of 21 SGA newborns with a mean birth weight below the first centile and a control cohort of 24 appropriate-for-gestational-age newborns were studied.

INTERVENTIONS

Array comparative genomic hybridization, genome-wide methylation studies, and exome sequencing were performed.

MAIN OUTCOME MEASURES

The numbers of CNVs, methylation disturbances, and sequence variants.

RESULTS

The genetic analyses demonstrated three CNVs, one systematically disturbed methylation pattern, and one sequence variant explaining SGA. Additional methylation disturbances and sequence variants were present in 20 patients. In 19 patients, multiple abnormalities were found.

CONCLUSION

Our results confirm the influence of a large number of mechanisms explaining dysregulation of fetal growth. We concluded that CNVs, methylation disturbances, and sequence variants all contribute to prenatal growth failure. These genetic workups can be an effective diagnostic approach in SGA newborns.

From Consternation to Revelation: Discovery of a Role for IGSF1 in Pituitary Control of Thyroid Function

Immunoglobulin superfamily, member 1 (IGSF1) is a transmembrane glycoprotein highly expressed in the mammalian pituitary gland. Shortly after its discovery in 1998, the protein was proposed to function as a coreceptor for inhibins (and was even temporarily renamed inhibin binding protein). However, subsequent investigations, both in vitro and in vivo, failed to support a role for IGSF1 in inhibin action. Research on IGSF1 nearly ground to a halt until 2011, when next-generation sequencing identified mutations in the X-linked IGSF1 gene in boys and men with congenital central hypothyroidism. IGSF1 was localized to thyrotrope cells, implicating the protein in pituitary control of the thyroid. Investigations in two Igsf1 knockout mouse models converged to show that IGSF1 deficiency leads to reduced expression of the receptor for thyrotropin-releasing hormone (TRH) and impaired TRH stimulation of thyrotropin secretion, providing a candidate mechanism for the central hypothyroidism observed in patients. Nevertheless, the normal functions of IGSF1 in thyrotropes and other cells remain unresolved. Moreover, IGSF1 mutations are also commonly associated with other clinical phenotypes, including prolactin and growth hormone dysregulation, and macroorchidism. How the loss of IGSF1 produces these characteristics is unknown. Although early studies of IGSF1 ran into roadblocks and blind alleys, armed with the results of detailed clinical investigations, powerful mouse models, and new reagents, the field is now poised to discover IGSF1’s function in endocrine tissues, including the pituitary and testes.

Screening for potential child maltreatment in parents of a newborn baby: The predictive validity of an Instrument for early identification of Parents At Risk for child Abuse and Neglect (IPARAN)

For preventive purposes it is important to be able to identify families with a high risk of child maltreatment at an early stage. Therefore we developed an actuarial instrument for screening families with a newborn baby, the Instrument for identification of Parents At Risk for child Abuse and Neglect (IPARAN). The aim of this study was to assess the predictive validity of the IPARAN and to examine whether combining actuarial and clinical methods leads to an improvement of the predictive validity. We examined the predictive validity by calculating several performance indicators (i.e., sensitivity, specificity and the Area Under the receiver operating characteristic Curve [AUC]) in a sample of 4692 Dutch families with newborns. The outcome measure was a report of child maltreatment at Child Protection Services during a follow-up of 3 years. For 17 children (.4%) a report of maltreatment was registered. The predictive validity of the IPARAN was significantly better than chance (AUC=.700, 95% CI [.567-.832]), in contrast to a low value for clinical judgement of nurses of the Youth Health Care Centers (AUC=.591, 95% CI [.422-.759]). The combination of the IPARAN and clinical judgement resulted in the highest predictive validity (AUC=.720, 95% CI [.593-.847]), however, the difference between the methods did not reach statistical significance. The good predictive validity of the IPARAN in combination with clinical judgment of the nurse enables professionals to assess risks at an early stage and to make referrals to early intervention programs.

Practical Application of Linear Growth Measurements in Clinical Research in Low- and Middle-Income Countries

BACKGROUND/AIMS

Childhood stunting is a prevalent problem in low- and middle-income countries and is associated with long-term adverse neurodevelopment and health outcomes. In this review, we define indicators of growth, discuss key challenges in their analysis and application, and offer suggestions for indicator selection in clinical research contexts.

METHODS

Critical review of the literature.

RESULTS

Linear growth is commonly expressed as length-for-age or height-for-age z-score (HAZ) in comparison to normative growth standards. Conditional HAZ corrects for regression to the mean where growth changes relate to previous status. In longitudinal studies, growth can be expressed as ΔHAZ at 2 time points. Multilevel modeling is preferable when more measurements per individual child are available over time. Height velocity z-score reference standards are available for children under the age of 2 years. Adjusting for covariates or confounders (e.g., birth weight, gestational age, sex, parental height, maternal education, socioeconomic status) is recommended in growth analyses.

CONCLUSION

The most suitable indicator(s) for linear growth can be selected based on the number of available measurements per child and the child's age. By following a step-by-step algorithm, growth analyses can be precisely and accurately performed to allow for improved comparability within and between studies.

Determinants of Advanced Bone Age in Childhood Obesity

BACKGROUND

Childhood obesity is associated with advanced bone age (BA). Previous studies suggest that androgens, oestrogens, sex hormone-binding globulin, and insulin are responsible for this phenomenon, but results are contradictory and might be biased by confounders. We aim to elucidate this matter by applying a multivariate approach.

METHOD

We performed a correlation analysis of BA standard deviation score (SDS) with age- and sex-specific SDS for androgens, oestrogens, and with indicators of insulin secretion derived from oral glucose tolerance testing, in a group of obese children. A multivariate analysis was performed to investigate which parameters were independently predictive of BA SDS.

RESULTS

In this cohort (n = 101; mean age 10.9 years; mean BA 11.8 years; mean BMI SDS 3.3), BMI SDS was significantly correlated to BA SDS (r = 0.55, p < 0.001). In a regression analysis in the total cohort (B = 0.27, p < 0.001) as well as in females (B = 0.34, p = 0.042), males (B = 0.31, p = 0.006), and pubertal children (B = 0.32, p = 0.046), dehydroepiandrosterone sulphate (DHEAS) showed a positive, independent association with BA SDS. No association with indicators of insulin secretion was found.

CONCLUSION

BMI SDS is highly correlated to BA SDS in obese children. Increased DHEAS has a central role in advanced BA in obese children.
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