Growth hormone is effective in treatment of short stature associated with short stature homeobox-containing gene deficiency: Two-year results of a randomized, controlled, multicenter trial

The Treatment of Growth Disorders in Childhood and Adolescence

BACKGROUND

3% of all children are unusually short, and 3% are unusually tall. New approaches have broadened the range of therapeutic options in treating growth disorders.

METHODS

This review is based on publications retrieved by a selective review of the literature and on the authors' clinical experience.

RESULTS

Pituitary growth hormone deficiency is treated with recombinant growth hormone. Long-acting preparations of this type became available recently, but their long-term safety and efficacy are still unknown. Vosoritide, a CNP analogue, has also been approved for the treatment of achondroplasia, and severe primary deficiency of insulin-like growth factor 1 (IGF-1) can be treated with recombinant IGF-1. In the treatment of excessively tall stature, new information on the safety of growth-attenuating treatment and an altered perception of above-average height in society have led to a change in management.

CONCLUSION

There are new options for the treatment of rare causes of short stature, while new information on the safety of treatment strategies for excessive tallness have led to a reconsideration of surgical intervention. There is insufficient evidence on the benefits and risks of supraphysiological GH therapy and of newer treatment options for which there are as yet no robust data on adult height. Therefore, before any treatment is provided, physicians should give patients and their families detailed information and discuss their expectations from treatment and the goals that treatment can be expected to achieve.

Efficacy and safety of GH treatment in Japanese children with short stature due to SHOX deficiency: a randomized phase 3 study

We conducted a randomized phase 3 study to investigate the efficacy and safety of GH treatment in prepubertal Japanese patients with short stature due to SHOX deficiency. The patients were randomly allocated to the GH-GH group (n = 10), in which the patients were treated with GH (0.35 mg/kg/wk) subcutaneously once daily for 24 mo, or the no-treatment (NT)-GH group (n = 9), in which the patients were untreated for the first 12 mo and then administered the same dosage of GH for the next 12 mo. At month 12, the ∆height standard deviation score (SDS) for chronological age (CA) and serum IGF-1 level were significantly higher in the GH-GH group than those in the NT-GH group. In contrast, bone age (BA) and ΔBA/ΔCA were numerically higher in the GH-GH group but were not statistically significant. At month 24, these parameters were comparable between the two groups. The height velocity was significantly larger in the GH-GH group during the first year and in the NT-GH group during the second year. No serious adverse drug reactions were observed; however, one patient in the GH-GH group exhibited increased insulin resistance at month 24. These results indicated that GH is a promising treatment option for short stature in patients with SHOX deficiency.

Identification of a second genetic alteration in patients with SHOX deficiency individuals: a potential explanation for phenotype variability

OBJECTIVE

Our study aimed to assess the impact of genetic modifiers on the significant variation in phenotype that is observed in individuals with SHOX deficiency, which is the most prevalent monogenic cause of short stature.

DESIGN AND METHODS

We performed a genetic analysis in 98 individuals from 48 families with SHOX deficiency with a target panel designed to capture the entire SHOX genomic region and 114 other genes that modulate growth and/or SHOX action. We prioritized rare potentially deleterious variants.

RESULTS

We did not identify potential deleterious variants in the promoter or intronic regions of the SHOX genomic locus. In contrast, we found eight heterozygous variants in 11 individuals from nine families in genes with a potential role as genetic modifiers. In addition to a previously described likely pathogenic (LP) variant in CYP26C1 observed in two families, we identified LP variants in PTHLH and ACAN, and variants of uncertain significance in NPR2, RUNX2, and TP53 in more affected individuals from families with SHOX deficiency. Families with a SHOX alteration restricted to the regulatory region had a higher prevalence of a second likely pathogenic variant (27%) than families with an alteration compromising the SHOX coding region (2.9%, P = .04).

CONCLUSION

In conclusion, variants in genes related to the growth plate have a potential role as genetic modifiers of the phenotype in individuals with SHOX deficiency. In individuals with SHOX alterations restricted to the regulatory region, a second alteration could be critical to determine the penetrance and expression of the phenotype.

Leri-Weill Dyschondrosteosis Caused by a Leaky Homozygous SHOX Splice-Site Variant

SHOX deficiency is a common genetic cause of short stature of variable degree. SHOX haploinsufficiency causes Leri-Weill dyschondrosteosis (LWD) as well as nonspecific short stature. SHOX haploinsufficiency is known to result from heterozygous loss-of-function variants with pseudo-autosomal dominant inheritance, while biallelic SHOX loss-of-function variants cause the more severe skeletal dysplasia, Langer mesomelic dyschondrosteosis (LMD). Here we report for the first time the pseudo-autosomal recessive inheritance of LWD in two siblings caused by a novel homozygous non-canonical, leaky splice-site variant in intron 3 of SHOX: c.544+5G>C. Transcript analyses in patient-derived fibroblasts showed homozygous patients to produce approximately equal amounts of normally spliced mRNA and mRNA with the abnormal retention of intron 3 and containing a premature stop codon (p.Val183Glyfs*31). The aberrant transcript was shown to undergo nonsense-mediated mRNA decay, and thus resulting in SHOX haploinsufficiency in the homozygous patient. Six healthy relatives who are of normal height are heterozygous for this variant and fibroblasts from a heterozygote for the c.544+5G>C variant produced wild-type transcript amounts comparable to healthy control. The unique situation reported here highlights the fact that the dosage of SHOX determines the clinical phenotype rather than the Mendelian inheritance pattern of SHOX variants. This study extends the molecular and inheritance spectrum of SHOX deficiency disorder and highlights the importance of functional testing of SHOX variants of unknown significance in order to allow appropriate counseling and precision medicine for each family individual.

Genetic Analysis and Sonography Characteristics in Fetus with SHOX Haploinsufficiency

OBJECTIVE

SHOX haploinsufficiency have been commonly found in isolated short stature (ISS) and Léri-Weill dyschondrosteosis (LWD) patients. However, few publications have described the genetic analysis and clinical characteristics of fetuses with SHOX haploinsufficiency.

METHODS

Chromosomal microarray (CMA) were applied in 14,051 fetuses and sequentially whole exome sequence (WES) in 1340 fetuses who underwent prenatal diagnosis during 2016-2021. The analysis and summary of molecular genetics, sonographic characteristics, and follow-up results were performed in fetuses with SHOX haploinsufficiency without other genetic etiologies. A comparison was made between three groups according to prenatal diagnostic indications.

RESULTS

8 (0.06%) fetuses of SHOX haploinsufficiency were all detected by CMA, of which 5 (62.5%) were detected with short long bones by ultrasound scan, and 4 were inherited from their previously undiagnosed parents. No pathogenic SHOX variants were found by WES. The detection rate of SHOX haploinsufficiency was obviously higher in the short long bone group (2.6%, 5/191) than the other abnormality group (0.03%, 1/3919) or no ultrasound abnormality group (0.02%, 2/9941). Three of the fetuses were liveborn with normal growth up to the age of four and four were terminated.

CONCLUSION

The phenotype of fetuses with SHOX haploinsufficiency is highly varied. Over 1/3 of the cases exhibited no phenotype and nearly 2/3 with short long bones, in the absence of Madelung deformity during fetal development. SHOX haploinsufficiency should be considered in all antenatal presentations, especially in the case of isolated short long bones. CMA can provide effective detection.

Increased testicular insulin-like growth factor 1 is associated with gonadal activation by recombinant growth hormone in immature rats

BACKGROUND

In children, recombinant human growth hormone (rhGH) therapy for treatment of short stature has raised concerns of the early onset of puberty. Puberty is initiated by the activation of the hypothalamus-pituitary-gonad axis. Insulin-like growth factor-1 (IGF1) has been known to mediate physiologic effects of GH. To understand the mechanism of precocious sexual maturation following prepubertal GH therapy, the effects of rhGH on the hypothalamus-pituitary-gonad axis were examined in the immature male rats.

METHODS

Immature male rats were given by daily injection of rhGH (1 or 2 IU/kg) from postnatal day (PND) 21 to PND 23 or 30. The effects of rhGH on kisspeptin-GnRH-LH system in the hypothalamus-pituitary axis, systemic and testicular IGF1, spermatogenesis, steroidogenesis, and circulating testosterone levels were examined. The effects of rhGH on the IGF1 expression and steroidogenesis were examined in progenitor LCs in vitro.

RESULTS

Testicular steroidogenic pathway and spermatogenesis marker mRNA levels, number and size of 17β-hydroxysteroid dehydrogenase (+) LCs, and blood testosterone levels of rhGH rats were significantly higher than those of controls on PNDs 24 and 31. Hypothalamic Kiss1 and Gnrh1 mRNA of rhGH rats were significantly higher than those of controls on PND 24, indicating early activation of hypothalamic kisspeptin-GnRH neurons by rhGH. Hypothalamic Igf1 mRNA levels of rhGH rats were significantly higher than those of controls on PND 24 but significantly lower than those of controls on PND 31. Testicular Igf1 mRNA levels were significantly higher in rhGH rats than in the controls on PNDs 24 and 31 whereas circulating IGF1 levels were not. In progenitor LCs, rhGH significantly increased Igf1 and steroidogenic pathway mRNA levels and testosterone production.

CONCLUSIONS

Local increases in testicular IGF1 might be an important mediator of gonadal maturation via activation of LCs steroidogenesis in immature rats given rhGH.

Treatment of Short Stature in Aggrecan-deficient Patients With Recombinant Human Growth Hormone: 1-Year Response

CONTEXT

Patients with aggrecan (ACAN) deficiency present with dominantly inherited short stature, often with advanced skeletal maturation and premature growth cessation. There is a paucity of information on the effects of growth-promoting interventions.

OBJECTIVE

The aim of this study was to evaluate the efficacy and safety of recombinant human growth hormone (rhGH) therapy on linear growth in children with ACAN deficiency.

METHODS

Open-label, single-arm, prospective study at Cincinnati Children's Hospital Medical Center. Ten treatment-naïve patients were recruited. Inclusion criteria were a confirmed heterozygous mutation in ACAN, age ≥2 years, prepubertal, bone age (BA) ≥chronological age (CA), and normal insulin-like growth factor I concentration. Treatment was with rhGH (50 µg/kg/day) over 1 year. Main outcomes measured were height velocity (HV) and change in (Δ) height SD score (HtSDS).

RESULTS

Ten patients (6 females) were enrolled with median CA of 5.6 years (range 2.4-9.7). Baseline median HtSDS was -2.5 (range -4.3 to -1.1). Median baseline BA was 6.9 years (range 2.5-10.0), with median BA/CA of 1.2 (range 0.9-1.5). Median pretreatment HV was 5.2 cm/year (range 3.8-7.1), increased to 8.3 cm/year (range 7.3-11.2) after 1 year of therapy (P = .004). Median ΔHtSDS after 1 year was +0.62 (range +0.35 to +1.39) (P = .002). Skeletal maturation did not advance inappropriately (median ΔBA/CA -0.1, P = .09). No adverse events related to rhGH were observed.

CONCLUSION

Treatment with rhGH improved linear growth in a cohort of patients with short stature due to ACAN deficiency.

Copy number variations residing outside the SHOX enhancer region are involved in Short Stature and Léri-Weill dyschondrosteosis

Background

SHOX enhancer CNVs, affecting one or more of the seven recognized evolutionary conserved non‐coding elements (CNEs) represent one of the most frequent cause of SHOX‐haploinsufficiency. During the diagnostic workflow deletions/duplications have been identified downstream SHOX not including any of the these CNEs.

Methods

Fine tiling aCGH and breakpoint PCR were used to characterize the critical interval and to search for novel alterations in a cohort of selected patients.

Results

Screening of 252 controls provided evidence that duplications in this area represent likely benign variants whereas none of the deletions were detected. These findings suggested that other alterations relevant for SHOX‐haploinsufficiency might be missed by the standard diagnostic methods. To identify such undisclosed elements, the aCGH was used to reanalyze 52 unresolved cases with clinical features strongly suggestive of SHOX‐haploinsufficiency. This analysis followed by the screening of 210 patients detected two partially overlapping small deletions of ~12 and ~8 kb in four unrelated individuals, approximately 15 kb downstream SHOX, that were absent in 720 normal stature individuals.

Conclusion

Our results strengthen the hypothesis that alterations of yet unidentified cis‐regulatory elements residing outside those investigated through conventional methods, might explain the phenotype in ISS/LWD patients thus enlarging the spectrum of variants contributing to SHOX‐haploinsufficiency.

Human Growth and Growth Hormone: From Antiquity to the Recominant Age to the Future

Since antiquity Man has been fascinated by the variations in human (and animal) growth. Stories and art abound about giants and little people. Modern genetics have solved some of etiologies at both extremes of growth. Serious study began with the pathophysiology of acromegaly followed by early attempts at treatment culminating in modern endoscopic surgery and multiple pharmacologic agents. Virtually at the same time experiments with the removal of the pituitary from laboratory animals noted the slowing or stopping of linear growth and then over a few decades the extraction and purification of a protein within the anterior pituitary that restored, partially or in full, the animal's growth. Human growth hormone was purified decades after those from large animals and it was noted that it was species specific, that is, only primate growth hormone was metabolically active in primates. That was quite unlike the beef and pork insulins which revolutionized the care of children with diabetes mellitus. A number of studies included mild enzymatic digestion of beef growth hormone to determine if those "cores" had biologic activity in primates and man. Tantalizing data showed minimal but variable metabolic efficacy leading to the "active core" hypothesis, for these smaller peptides would be amenable to peptide synthesis in the time before recombinant DNA. Recombinant DNA changed the landscape remarkably promising nearly unlimited quantities of metabolically active hormone. Eight indications for therapeutic use have been approved by the Food and Drug Administration and a large number of clinical trials have been undertaken in multiple other conditions for which short stature in childhood is a sign. The future predicts other clinical indications for growth hormone therapy (and perhaps other components of the GH?IGF-1 axis), longer-acting analogues and perhaps a more physiologic method of administration as virtually all methods at present are far from physiologic.

Pubertal boy presenting with mild disproportionate short stature

A boy aged 12 years was referred with short stature. He was born at term, of adequate weight (10-25th centile) and length (10-25th centile), which settled to just below the third centile from 18 months of age, with a growth deceleration in the last 6 months (growth velocity -2.1 standard deviation score, according to Tanner charts). He was otherwise asymptomatic. His mother's height was 155 cm, and father's height 158 cm, and he was growing near his target height centile (-2.26 SDS, <3rd centile).On examination, his height was -2.22 SDS, with normal weight and body mass index (BMI). Pubertal stage corresponded to Tanner 2, with a testicular volume of 4 mL. His legs and forearms appeared shorter, with arm span/height ratio 0.93 (normal value >0.965) and sitting height/height ratio 0.56 (slightly above the normal upper value of 0.55). He resembled his father, whose wrists were abnormally curved (figure 1). The patient's hand X-ray showed that bone age was similar to chronological age.

SHOX deficiency in children with growth impairment: evaluation of known and new auxological and radiological indicators

Background

The phenotypic features of SHOX deficiency (SHOX-D) are highly variable and can be very mild, especially in young children. The aim of this retrospective study was to evaluate auxological and radiological indicators that could be predictive of SHOX-D in children.

Methods

Molecular analysis of the SHOX gene was performed in 296 subjects with growth impairment or skeletal disproportion, without alternative diagnosis. Auxological variables and radiographs of the hand, wrist and forearm were evaluated.

Results

SHOX mutations (88% inherited, 12% de novo) were identified in 52 subjects. The most predictive auxological indicators of SHOX-D were an increased sitting height/height ratio and a decreased arm span/height ratio. The convexity of distal radial metaphysis at X-ray, not yet reported in literature, was also found to be predictive of SHOX-D. In young children, stratification of data by bone age also highlighted ulnar tilt, lucency of the ulnar border of the distal radius and enlarged radius as the radiological signs most related to SHOX-D .

Conclusions

In this study, the analysis of auxological and radiological indicators in SHOX-D children allowed to identify an additional early radiological sign and underlines the importance of family auxological evaluation.

Clinical and Genetic Characteristics of 23 Korean Patients with Haploinsufficiency of the Short-stature Homeobox-containing Gene

BACKGROUND

The short-stature homeobox-containing gene (SHOX) is one of the major growth genes in humans. The clinical spectrum of SHOX haploinsufficiency ranges from Léri-Weill dyschondrosteosis to idiopathic short stature. Herein, we describe the clinical and genetic characteristics of 23 Korean patients with SHOX deficiency disorders.

METHODS

Medical records of 23 patients (19 females and 4 males) from 15 unrelated families who were genetically confirmed to have SHOX deficiency were retrospectively reviewed. SHOX gene deletions or mutations were determined by sequence analyses using multiplex ligation-dependent probe amplification, chromosomal microarray, and/or Sanger sequencing methods.

RESULTS

In the 15 families, 9 probands were de novo cases. All 23 patients showed mesomelia. Madelung deformity and tibia vara were observed in 13 (56.5%) and 3 (13.1%) patients, respectively. Genetically, 11 (73.3%) of the 15 families showed SHOX deletions of various sizes, and the other 4 families harboured SHOX sequence variants. Four patients had undergone orthopaedic surgeries (3 for tibia vara and 1 for Madelung deformity). Among 7 patients who had received growth hormone treatment for ≥1 year, 5 showed good responses, with a median first-year change-in-height standard deviation score of +0.6. There were no significant differences in the clinical characteristics of the deletion and point mutation groups.

CONCLUSIONS

A high index of suspicion and the genetic confirmation of SHOX deficiency are helpful for the timely management of the condition and are needed to provide genetic counselling to the family members of the patients.

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.

NPR2 Variants Are Frequent among Children with Familiar Short Stature and Respond Well to Growth Hormone Therapy

CONTEXT

The C-type natriuretic peptide receptor encoded by the NPR2 gene is a paracrine regulator of the growth plate; heterozygous NPR2 variants cause short stature with possible presence of different signs of bone dysplasia. To date, the effect of growth hormone (GH) treatment has been described in a few individuals with NPR2 gene variants with inconsistent results.

OBJECTIVES

To identify NPR2 gene variants among children with familial short stature (FSS) and to describe their phenotype, including GH treatment response.

DESIGN, SETTINGS AND PATIENTS

Out of 747 patients with short stature treated with GH in a single center, 87 with FSS met the inclusion criteria (pretreatment height ≤ -2 standard deviation in both the patient and the shorter parent, unknown genetic etiology). Next-generation sequencing methods were performed to search for NPR2 gene variants. The results were evaluated using the American College of Medical Genetics and Genomics guidelines. The GH treatment response (growth velocity improvement and height standard deviation score development over the first 5 years of treatment) was evaluated.

RESULTS

In 5/87 children (5.7%), a (likely) pathogenic variant in the NPR2 gene was identified (p.Ile558Thr [in 2], p.Arg205*, p.Arg557His, p.Ser603Thr). Two children had disproportionate short-limbed short stature, 1 a dysplastic 5th finger phalanx. The growth velocity in the first year of GH treatment accelerated by 3.6 to 4.2 cm/year; the height improved by 1.2 to 1.8 SD over 5 years of treatment.

CONCLUSIONS

NPR2 gene variants cause FSS in a significant proportion of children. Their GH treatment response is promising. Studies including final height data are necessary to assess the long-term efficacy of this therapy.

Role of Signal Transduction Pathways and Transcription Factors in Cartilage and Joint Diseases

Osteoarthritis and rheumatoid arthritis are common cartilage and joint diseases that globally affect more than 200 million and 20 million people, respectively. Several transcription factors have been implicated in the onset and progression of osteoarthritis, including Runx2, C/EBPβ, HIF2α, Sox4, and Sox11. Interleukin-1 β (IL-1β) leads to osteoarthritis through NF-ĸB, IκBζ, and the Zn²⁺-ZIP8-MTF1 axis. IL-1, IL-6, and tumor necrosis factor α (TNFα) play a major pathological role in rheumatoid arthritis through NF-ĸB and JAK/STAT pathways. Indeed, inhibitory reagents for IL-1, IL-6, and TNFα provide clinical benefits for rheumatoid arthritis patients. Several growth factors, such as bone morphogenetic protein (BMP), fibroblast growth factor (FGF), parathyroid hormone-related protein (PTHrP), and Indian hedgehog, play roles in regulating chondrocyte proliferation and differentiation. Disruption and excess of these signaling pathways cause genetic disorders in cartilage and skeletal tissues. Fibrodysplasia ossificans progressive, an autosomal genetic disorder characterized by ectopic ossification, is induced by mutant ACVR1. Mechanistic target of rapamycin kinase (mTOR) inhibitors can prevent ectopic ossification induced by ACVR1 mutations. C-type natriuretic peptide is currently the most promising therapy for achondroplasia and related autosomal genetic diseases that manifest severe dwarfism. In these ways, investigation of cartilage and chondrocyte diseases at molecular and cellular levels has enlightened the development of effective therapies. Thus, identification of signaling pathways and transcription factors implicated in these diseases is important.

GH and IGF-1 Replacement in Children

In this chapter, we want to give an overview on what we have learned from more than 30 years ago on the use of recombinant human growth hormone (rhGH) and later recombinant human IGF-1 which was introduced for the treatment of short children and what are the safety issues concerned with this treatment. However, rhGH is used not solely in conditions where short stature is the consequence of GH deficiency but also in various disorders without a proven GH deficiency. In clinical studies, growth responses to various forms of rhGH therapy were analyzed, adding to our concept about the physiology of growth. Most patients under rhGH treatment show a considerable short-term effect; however, the long-term gain of height in a child obtained by a year-long treatment until final height remains controversial in some of the growth disorders that have been treated with rhGH or IGF-1. Today the first studies on the long-term safety of rhGH treatment have been published and raising some questions whether this treatment is similarly safe for all the patient groups treated with rhGH. Although there is a long-standing safety record for these hormone replacement therapies, in the face of the considerable costs involved, the discussion about the risk to benefit ratio is continuing. Newer developments of rhGH treatment include long-term preparations, which have only to be injected once a week. Although some of these drugs already have proven their non-inferiority to conventional rhGH treatment, we have to await further results to see whether they show improvements in treatment adherence of the patients and prove their long-term safety.

SHOX gene deletion screening by FISH in children with short stature and Madelung deformity and their characteristics

Background The short stature homeobox-containing (SHOX) gene strongly affects height. Therefore, a better understanding of SHOX haploinsufficiency could be advantageous to early diagnosis and treatment. We investigated the rate of SHOX haploinsufficiency in patients of short stature and documented their anthropometric measurements. Methods Between 2010 and 2017, we evaluated 86 patients (70 females, 16 males; age 4.3-18 years) with clinical diagnoses of short stature and Madelung deformity (MD). Clinical abnormalities are presented for patients with MD with and without SHOX haploinsufficiency as determined by fluorescence in situ hybridisation (FISH). Results According to our inclusion criteria, 78 of 86 patients (70 females, 16 males) had short stature (height <-2.5 standard deviation [SD]) and a family history suggestive of short stature. Eight patients had short stature, a family history suggestive of short stature and MD. MD was obvious in eight children in radiographic examinations. Although five of these had no deletion of SHOX, three had deletion of this gene. The deletion detection rate was 37.5% in the individuals with short stature and MD, i.e. Leri-Weill dyschondrosteosis syndrome (LWS), whilst no deletions were detected in the individuals with only short stature. One individual responded well to growth hormone (GH) treatment for the first 2 years but then developed an intolerance with persistently elevated insulin-like growth factor-1 (IGF-1) levels. Conclusions As we likely missed cases due to our methodology, the routine analysis for SHOX screening should be firstly multiplex ligation-dependent probe amplification (MLPA). The incidence of MD may have been higher in the cohort if X-rays were performed in all individuals. GH treatment was not well tolerated in one case due to persistently elevated IGF-1 levels, and long-term evaluations of patients with SHOX deficiency are required.

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.

Improving clinical diagnosis in SHOX deficiency: the importance of growth velocity

BackgroundThe aim of this study was to estimate the prevalence of haploinsufficiency of short stature homeobox containing gene (SHOX) deficiency (SHOXD) in a population of short-statured children, and to analyze their phenotype and the performance of clinical scores.MethodsScreening for SHOXD was performed in 281 children with short stature by direct sequencing and multiplex ligation probe-dependent amplification. Subjects with SHOXD were compared with 117 matched short patients without SHOXD. We calculated the cutoff of growth velocity associated with the highest sensitivity and specificity as a screening test for SHOXD by receiver operating characteristic curves.ResultsThe prevalence of SHOXD was 6.8%. Subjects with SHOXD showed a lower growth velocity (P<0.05) and a higher prevalence of dysmorphic signs. The best cutoff for growth velocity was -1.5 standard deviation score (SDS) both in the whole population and in subjects with a Rappold score <7 and <4 points. Growth velocity was ≤-1.5 SDS or Rappold score was >7/>4 points in 17/17 of 19 children with SHOXD and in 49/65 of 117 subjects without SHOX mutations.ConclusionsGrowth rate ≤-1.5 SDS, even with negative Rappold score, may be useful to detect precociously children with SHOXD. Selecting children deserving the genetic test by using growth velocity or the Rappold score significantly increases the sensitivity in detecting mutations and decreases the specificity.

Growth response to growth hormone treatment in patients with SHOX deficiency can be predicted by the Cologne prediction model

Background Growth hormone (GH) treatment in children with short stature homeobox-containing gene (SHOX) deficiency is recognized to increase height velocity (HV) and adult height. Prediction of growth response continues to be a challenge. A comparatively accurate method is the Cologne prediction model developed in children with GH deficiency. The aim was to investigate whether this model also applies to patients with SHOX deficiency. Methods Included were 48 patients with SHOX deficiency confirmed by DNA analysis and treated with 0.05 mg/kg/day of somatropin. Prediction by the Cologne model uses the following variables: relative bone age (BA) retardation, baseline insulin-like growth factor-I (IGF-I), urinary deoxypyridinoline (DPD) cross-links at 4 weeks and HV at 3 months. Results HV and height standard deviation scores (SDS) increased significantly during the first year of treatment. Predicted and observed HV (cm/year) showed a Pearson correlation coefficient of 0.50 (p<0.001; root-mean-square error=1.63) and for first-year change in height SDS a Pearson correlation coefficient of 0.751 (p<0.001; root-mean-square error=0.32). Poor response could be adequately predicted using SDS change, with sensitivity and specificity both above 70% for certain thresholds.

CONCLUSIONS

The results demonstrate that the Cologne model can be used to predict growth response in patients with SHOX deficiency with reasonable precision in the first treatment year, comparable to prediction in patients with GH deficiency.

Mortality in Children Receiving Growth Hormone Treatment of Growth Disorders: Data From the Genetics and Neuroendocrinology of Short Stature International Study

CONTEXT

Although pediatric growth hormone (GH) treatment is generally considered safe for approved indications, concerns have been raised regarding potential for increased risk of mortality in adults treated with GH during childhood.

OBJECTIVE

To assess mortality in children receiving GH.

DESIGN

Prospective, multinational, observational study.

SETTING

Eight hundred twenty-seven study sites in 30 countries.

PATIENTS

Children with growth disorders.

INTERVENTIONS

GH treatment during childhood.

MAIN OUTCOME MEASURE

Standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) using age- and sex-specific rates from the general population.

RESULTS

Among 9504 GH-treated patients followed for ≥4 years (67,163 person-years of follow-up), 42 deaths were reported (SMR, 0.77; 95% CI, 0.56 to 1.05). SMR was significantly elevated in patients with history of malignant neoplasia (6.97; 95% CI, 3.81 to 11.69) and borderline elevated for those with other serious non-GH-deficient conditions (2.47; 95% CI, 0.99-5.09). SMRs were not elevated for children with history of benign neoplasia (1.44; 95% CI, 0.17 to 5.20), idiopathic GHD (0.11; 95% CI, 0.02 to 0.33), idiopathic short stature (0.20; 95% CI, 0.01 to 1.10), short stature associated with small for gestational age (SGA) birth (0.66; 95% CI, 0.08 to 2.37), Turner syndrome (0.51; 95% CI, 0.06 to 1.83), or short stature homeobox-containing (SHOX) gene deficiency (0.83; 95% CI, 0.02 to 4.65).

CONCLUSIONS

No significant increases in mortality were observed for GH-treated children with idiopathic GHD, idiopathic short stature, born SGA, Turner syndrome, SHOX deficiency, or history of benign neoplasia. Mortality was elevated for children with prior malignancy and those with underlying serious non-GH-deficient medical conditions.

Heterozygous Deletion in Exons 4-5 of SHOX Gene in a Patient Diagnosed as Idiopathic Short Stature

Introduction: Isolated Short Stature Homeobox (SHOX) gene haploinsufficiency can be found in 2-15% of individuals diagnosed with idiopathic short stature determining different skeletal phenotypes.

Case presentation: We present the history of an 11-year-old female patient diagnosed with idiopathic short stature. Clinically, she was moderately disproportionate, with cubitus valgus and palatum ogivale. Her breast development was in Tanner stage 1 at the time of diagnosis. The endocrine diagnostic tests did not reveal any abnormalities except a slightly elevated thyroid stimulating hormone. We have also assessed the bone radiological findings. Multiplex Ligation-dependent Probe Amplification technique used for the identification of SHOX gene haploinsufficiency showed a heterozygous deletion spanning exons 4-5 of SHOX gene.

Conclusions: This case is determined by deletions in exons 4-5 of SHOX gene and indicates the necessity of screening for SHOX deletions in patients diagnosed with idiopathic short stature, especially in children having increased sitting height-to-height ratio or decreased extremities-to-trunk ratio.

Short Stature Homeobox-Containing Haploinsufficiency in Seven Siblings with Short Stature

Deficiency of the short stature homeobox-containing (SHOX) gene is a frequent cause of short stature in children (2–15%). Here, we report 7 siblings with SHOX deficiency due to a point mutation in the SHOX gene. Index case was a 3-year-old male who presented for evaluation of short stature. His past medical history and birth history were unremarkable. Family history was notable for multiple individuals with short stature. Physical exam revealed short stature, with height standard deviation score (SDS) of −2.98, as well as arm span 3 cm less than his height. His laboratory workup was noncontributory for common etiologies of short stature. Due to significant familial short stature and shortened arm span, SHOX gene analysis was performed and revealed patient is heterozygous for a novel SHOX gene mutation at nucleotide position c.582. This mutation is predicted to cause termination of the SHOX protein at codon 194, effectively causing haploinsufficiency. Six out of nine other siblings were later found to also be heterozygous for the same mutation. Growth hormone was initiated in all seven siblings upon diagnosis and they have demonstrated improved height SDS.

Growth Promotion Ethics and the Challenge to Resist Cosmetic Endocrinology

The advancement of "human growth hormone (hGH)-for-height" - increasing height attainment in children short for reasons other than GH deficiency - arose from intuitive, deep-seated assumptions about the disability of short stature, its improvement with hGH-mediated height gain, and the safety of escalating dosages of hGH in healthy children. Evidence challenging these assumptions now strengthens criticism of hGH-for-height as cosmetic endocrinology. To counter this characterization, collective acceptance of guidelines is needed that advise nontreatment of the vast majority of short children, support strategies that minimize treatment duration and dosage, and restrain enhancement of normal adult stature. Through a clinical case analysis, ethical issues underlying these recommendations are explored. These include duties to provide informed assent and re-assent, protect children from unnecessary treatment, consider fairness to nontreated children, and allocate healthcare resources responsibly. Informed assent for hGH-for-height should ensure awareness of modest, variable height gain expectations, limited evidence for psychosocial benefit, ongoing studies for potential posttreatment adverse effects, and options for less expensive/invasive approaches, including nontreatment and counseling. Approaching growth pro-motion in this way fosters therapeutic restraint, resists the al lure of enhancement therapy, and minimizes contributions to society's perception that to be taller is to be better.
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Achondroplasia: Development, pathogenesis, and therapy

Autosomal dominant mutations in fibroblast growth factor receptor 3 (FGFR3) cause achondroplasia (Ach), the most common form of dwarfism in humans, and related chondrodysplasia syndromes that include hypochondroplasia (Hch), severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN), and thanatophoric dysplasia (TD). FGFR3 is expressed in chondrocytes and mature osteoblasts where it functions to regulate bone growth. Analysis of the mutations in FGFR3 revealed increased signaling through a combination of mechanisms that include stabilization of the receptor, enhanced dimerization, and enhanced tyrosine kinase activity. Paradoxically, increased FGFR3 signaling profoundly suppresses proliferation and maturation of growth plate chondrocytes resulting in decreased growth plate size, reduced trabecular bone volume, and resulting decreased bone elongation. In this review, we discuss the molecular mechanisms that regulate growth plate chondrocytes, the pathogenesis of Ach, and therapeutic approaches that are being evaluated to improve endochondral bone growth in people with Ach and related conditions. Developmental Dynamics 246:291-309, 2017. © 2016 Wiley Periodicals, Inc.

Safety Outcomes and Near-Adult Height Gain of Growth Hormone-Treated Children with SHOX Deficiency: Data from an Observational Study and a Clinical Trial

BACKGROUND/AIMS

To assess auxological and safety data for growth hormone (GH)-treated children with SHOX deficiency.

METHODS

Data were examined for GH-treated SHOX-deficient children (n = 521) from the observational Genetics and Neuroendocrinology of Short Stature International Study (GeNeSIS). For patients with near-adult height information, GeNeSIS results (n = 90) were compared with a clinical trial (n = 28) of SHOX-deficient patients. Near-adult height was expressed as standard deviation score (SDS) for chronological age, potentially increasing the observed effect of treatment.

RESULTS

Most SHOX-deficient patients in GeNeSIS had diagnoses of Leri-Weill syndrome (n = 292) or non-syndromic short stature (n = 228). For GeNeSIS patients with near-adult height data, mean age at GH treatment start was 11.0 years, treatment duration 4.4 years, and height SDS gain 0.83 (95% confidence interval 0.49-1.17). Respective ages, GH treatment durations and height SDS gains for GeNeSIS patients prepubertal at baseline (n = 42) were 9.2 years, 6.0 years and 1.19 (0.76-1.62), and for the clinical trial cohort they were 9.2 years, 6.0 years and 1.25 (0.92-1.58). No new GH-related safety concerns were identified.

CONCLUSION

Patients with SHOX deficiency who had started GH treatment before puberty in routine clinical practice had a similar height gain to that of patients in the clinical trial on which approval for the indication was based, with no new safety concerns.

Prevalence of SHOX haploinsufficiency among short statured children

BACKGROUND

The aim of this clinical study was to determine the prevalence of SHOX haploinsufficiency in a population of short stature patients and describe their anthropometric measurements.

METHODS

574 short statured patients were evaluated in a single center (1992-2015). SHOX copy number was detected by quantitative polymerase chain reaction (qPCR) in 574 subjects, followed by multiplex ligation-dependent probe amplification (MLPA) and DNA sequencing in subjects with SHOX haploinsufficiency. We evaluated anthropometric measurements at birth, and at first examination. Skeletal abnormalities were recorded for patients with SHOX haploinsufficiency.

RESULTS

Thirty-two patients were excluded due to Turner syndrome (n = 28), SRY-positive 46,XX male karyotype (n = 1), or lacked clinical follow-up information (n = 3). The prevalence of SHOX haploinsufficiency was 9 out of 542 (1.7%). The nine children had decreased height -2.85 (0.6) SD scores (SDS) (mean (SD)) and weight -2.15 (1.36) SDS, P < 0.001 and P = 0.001, respectively. The sitting height/height ratio was increased, P = 0.04. Madelung deformity was diagnosed in three patients. Mean height was -2.9 (0.4) SDS at baseline and increased by 0.25 (0.2) SDS, P = 0.046, after 1 y of growth hormone (GH) treatment.

CONCLUSION

The prevalence of SHOX haploinsufficiency was 1.7%. The clinical findings indicating SHOX haploinsufficiency among the nine children were disproportionate short stature and forearm anomalies.

A Track Record on SHOX: From Basic Research to Complex Models and Therapy

SHOX deficiency is the most frequent genetic growth disorder associated with isolated and syndromic forms of short stature. Caused by mutations in the homeobox gene SHOX, its varied clinical manifestations include isolated short stature, Léri-Weill dyschondrosteosis, and Langer mesomelic dysplasia. In addition, SHOX deficiency contributes to the skeletal features in Turner syndrome. Causative SHOX mutations have allowed downstream pathology to be linked to defined molecular lesions. Expression levels of SHOX are tightly regulated, and almost half of the pathogenic mutations have affected enhancers. Clinical severity of SHOX deficiency varies between genders and ranges from normal stature to profound mesomelic skeletal dysplasia. Treatment options for children with SHOX deficiency are available. Two decades of research support the concept of SHOX as a transcription factor that integrates diverse aspects of bone development, growth plate biology, and apoptosis. Due to its absence in mouse, the animal models of choice have become chicken and zebrafish. These models, therefore, together with micromass cultures and primary cell lines, have been used to address SHOX function. Pathway and network analyses have identified interactors, target genes, and regulators. Here, we summarize recent data and give insight into the critical molecular and cellular functions of SHOX in the etiopathogenesis of short stature and limb development.

Investigation of SHOX Gene Mutations in Turkish Patients with Idiopathic Short Stature

OBJECTIVE

The frequency of mutations in the short stature homeobox (SHOX) gene in patients with idiopathic short stature (ISS) ranges widely, depending mostly on the mutation detection technique and inclusion criteria. We present phenotypic and genotypic data on 38 Turkish patients with ISS and the distinctive features of 1 patient with a SHOX deletion.

METHODS

Microsatellite markers (MSMs) DXYS10092 (GA repeats) and DXYS10093 (CT repeats) were used to select patients for fluorescent in situ hybridisation (FISH) analysis and to screen for deletions in the SHOX gene. The FISH analysis was applied to patients homozygous for at least one MSM. A Sanger sequencing analysis was performed on patients with no deletions according to FISH to investigate point mutations in the SHOX gene.

RESULTS

One patient (2.6%) had a SHOX mutation.

CONCLUSION

Although the number of cases was limited and the mutation analysis techniques we used cannot detect all mutations, our findings emphasize the importance of the difference in arm span and height when selecting patients for SHOX gene testing.

Radiological Features in Patients with Short Stature Homeobox-Containing (SHOX) Gene Deficiency and Turner Syndrome before and after 2 Years of GH Treatment

BACKGROUND/AIMS

The short stature homeobox-containing (SHOX) gene is one of many genes that regulate longitudinal growth. The SHOX deficiency (SHOX-D) phenotype, caused by intragenic or regulatory region defects, ranges from normal stature to mesomelic skeletal dysplasia. We investigated differences in radiological anomalies between patients with SHOX-D and Turner syndrome (TS) and the effect of 2 years of growth hormone (GH) treatment on these anomalies.

METHODS

Left hand/wrist, forearm and lower leg radiographs were assessed at baseline and after 2 years in children with genetically confirmed SHOX-D (GH-treated and untreated groups) and TS (GH-treated) in a randomised, controlled, multinational study.

RESULTS

Radiological anomalies of hand, wrist and forearm were common in SHOX-D and TS. Radial bowing appeared more prevalent in SHOX-D, while lower leg anomalies were more common in TS. There were no significant differences in radiological findings between GH-treated and untreated patients with SHOX-D after 2 years.

CONCLUSION

GH treatment had no systematic effect on skeletal findings in SHOX-D, based on limited radiological differences between the GH-treated and untreated groups at 2 years. Bone age radiographs allow assessment of radiological signs indicating a potential diagnosis of SHOX-D and may lead to earlier genetic confirmation and initiation of GH therapy.

SHOX gene variants: growth hormone/insulin-like growth factor-1 status and response to growth hormone treatment

CONTEXT

Short stature homeobox-containing gene (SHOX) variants of unknown clinical significance occur frequently among children with short stature, yet their growth hormone (GH)/insulin-like growth factor-1 (IGF-1) status and response to GH have not been studied.

OBJECTIVE

To define GH and IGF-1 status in children with SHOX variants and assess their response to GH.

PATIENTS AND METHODS

This is a retrospective review of children with short stature. Children with SHOX variants were compared to those with no variants. Height standard deviation scores (SDS) and IGF-1 SDS at baseline and during GH treatment at 6, 12, and 24 months were analyzed. Growth velocity (GV), maximum GH dose, IGF-BP3, and changes in height SDS, IGF-1 SDS, and GV were compared.

RESULTS

Among 355 children, 83 (23%) had SHOX variants. Nineteen different SHOX variants were detected. There was no difference in age, height SDS, IGF-1 SDS, or IGF-BP3 between children with SHOX variants and those with normal SHOX. Height SDS, IGF-1 SDS, IGF-BP3, GV, and GH dose were not different between patients with SHOX variants and those without.

CONCLUSIONS

The GH and IGF-1 characteristics of children with short stature were not different between children with SHOX+ variants and children with no variants. Although these findings suggest that SHOX variants are polymorphisms, studies prospectively comparing individual SHOX variants are needed.

Short and tall stature: a new paradigm emerges

In the past, the growth hormone (GH)-insulin-like growth factor 1 (IGF-1) axis was often considered to be the main system that regulated childhood growth and, therefore, determined short stature and tall stature. However, findings have now revealed that the GH-IGF-1 axis is just one of many regulatory systems that control chondrogenesis in the growth plate, which is the biological process that drives height gain. Consequently, normal growth in children depends not only on GH and IGF-1 but also on multiple hormones, paracrine factors, extracellular matrix molecules and intracellular proteins that regulate the activity of growth plate chondrocytes. Mutations in the genes that encode many of these local proteins cause short stature or tall stature. Similarly, genome-wide association studies have revealed that the normal variation in height seems to be largely due to genes outside the GH-IGF-1 axis that affect growth at the growth plate through a wide variety of mechanisms. These findings point to a new conceptual framework for understanding short and tall stature that is centred not on two particular hormones but rather on the growth plate, which is the structure responsible for height gain.

The growth response to GH treatment is greater in patients with SHOX enhancer deletions compared to SHOX defects

OBJECTIVE

Short stature caused by point mutations or deletions of the short stature homeobox (SHOX) gene (SHOX haploinsufficiency (SHI)) is a registered indication for GH treatment. Patients with a SHOX enhancer deletion (SED) have a similar phenotype, but their response to GH is unknown. It is uncertain if duplications of SHOX or its enhancer (SDUP) cause short stature. This study aimed to describe the clinical characteristics and growth response to GH treatment in patients with aberrations of SHOX and its enhancers.

DESIGN

In this retrospective multi-center study (2002-March 2014) clinical information was available from 130 patients (72 SHI, 44 SED, and 14 SDUP) of whom 52 patients were treated with GH. We evaluated height, sitting height (SH), arm span, dysmorphic features and indicators of the growth response to GH (delta height SDS, height velocity, and index of responsiveness).

RESULTS

Patients with SEDs showed similar HtSDS to patients with SHI (-2.3 and -2.6, respectively, P=0.2), but they were less disproportionate (SH/height ratio SDS 2.0 vs 3.1 (P<0.01) and extremities/trunk ratio 2.57 vs 2.43 (P=0.03)). The 1st year growth response to GH treatment was significantly greater in prepubertal patients with SEDs than SHI. None of the patients with an SDUP was disproportionate and SDUP cosegregated poorly with short stature; their growth response to GH treatment (n=3) was similar to the other groups.

CONCLUSIONS

Patients with SEDs are equally short, but less disproportionate than patients with SHI, and show a greater response to GH.

A Leri-Weill dyschondrosteosis patient confirmed by mutation analysis of SHOX gene

Leri-Weill dyschondrosteosis is characterized by SHOX deficiency, Madelung deformity, and mesomelic short stature. In addition, SHOX deficiency is associated with idiopathic short stature, Turner syndrome, and Langer mesomelic dysplasia. We report the first case of a Leri-Weill dyschondrosteosis patient confirmed by SHOX gene mutation analysis in Korea. The patient, who was a 7-year-old female, showed short stature. Her height and weight were 108.9 cm (<3rd percentile) and 19.7 kg (5th-10th percentile), respectively. Her arm span, height of trunk, leg length, and sitting length were 100.5 cm, 58 cm, 50.9 cm, and 62.5 cm, respectively. Her body proportion was 1.13:1. Extremities to trunk ratio was 2.61. Her hand radiograph showed Madelung deformity. And the growth hormone stimulation test showed a normal response. Furthermore, because of Madelung deformity with idiopathic short stature, she was suspected of SHOX deficiency. We performed SHOX gene mutation analysis and found a c.491G>A (p.W164X) mutation of the SHOX gene. Accordingly, this patient was diagnosed with Leri-Weill dyschondrosteosis. Recently, many mutations have been reported in the SHOX gene. However, to date, mutation analysis of the SHOX gene for Leri-Weill dyschondrosteosis has not been reported in Korea as yet. We report the first case of a Leri-Weill dyschondrosteosis patient confirmed by mutation analysis of the SHOX gene.

Hormone replacement therapy in children: The use of growth hormone and IGF-I

Recombinant human GH (rhGH) has been available since 1985. This article gives an overview, what has been achieved over the past 30 years in respect to optimization of rhGH treatment for the individual child with GH deficiency and what are the safety issues concerned with this treatment. In the last twenty years significant scientific progress has been made in the diagnosis of GH deficiency, the genetic disorders that are associated with pituitary GH deficiency and the genetics that influence growth in general. On the other hand rhGH is not only used in states of GH deficiency but also various conditions without a proven GH deficiency by classical standards. Clinical studies that investigated both the genetics of growth and the individual responses to rhGH therapy in these patient populations were able to refine our concept about the physiology of normal growth. In most patients under rhGH treatment there is a considerable short-term effect, however the overall gain in growth obtained by a long-term treatment until final height still remains a matter of debate in some of the conditions treated. Also first studies on the long-term safety risks of rhGH treatment have raised the question whether this treatment is similarly safe for all the patient groups eligible for such a treatment. Therefore even in the face of a longstanding safety record of this drug replacement therapy the discussion about the right cost and risk to benefit ratio is continuing. Consequently there is still a need for carefully conducted long-term studies that use modern anthropometric, genetic, and laboratory techniques in order to provide the necessary information for clinicians to select the patients that will benefit best from this valuable treatment without any long term risk.

Pharmacogenomics related to growth disorders

Growth disorders resulting in short stature are caused by a wide range of underlying pathophysiological processes. To improve height many of these conditions are treated with recombinant human growth hormone (rhGH). However, substantial inter-individual variability in growth response both in the short and long-term is recognised. Over the last decade, disease-specific growth prediction models have been developed that the clinician can use to define a child's potential response to rhGH and to optimise starting and maintenance doses of rhGH. These models, however, are not able to predict all the variations in treatment response. There has, therefore, been recent interest in using genetic information to contribute to the evaluation of responses to rhGH, including high-throughput technologies for assessing DNA markers (genome) and mRNA transcripts (transcriptome) as pharmacogenomic tools. This review will focus on how these pharmacogenomic approaches are being applied to growth disorders.

Short stature before puberty: which children should be screened for SHOX deficiency?

OBJECTIVE

We studied the prevalence of deficiency in the short stature homeobox containing gene (SHOX) in prepubertal short-statured children and analyzed the clinical and radiological signs.

METHODS

Screening for SHOX deficiency was performed in 449 prepubertal short-statured children (54% females, aged 4-10 years) by direct sequencing and multiplex ligation probe-dependent amplification. Children with SHOX deficiency were compared to 1:2 age- and gender-matched prepubertal children without SHOX deficiency with respect to left-hand radiographs and anthropometrics including different ratios to height and proposed scores.

RESULTS

We identified 22 (4.9%) patients with SHOX deficiency (64% point mutations). Children with SHOX deficiency demonstrated a mesomelic shortening of extremities. Lower leg lengths but not forearm length was reduced in children <8 years with SHOX deficiency. 36% of all children and none of the children <8 years with SHOX deficiency demonstrated any typical radiologic sign. Increased sitting height-to-height ratio and decreased extremities-to-trunk ratio demonstrated the best positive and negative predictive values to identify SHOX deficiency.

CONCLUSIONS

Screening for SHOX deficiency seems rational, especially in children with increased sitting height-to-height ratio or decreased extremities-to-trunk ratio. These criteria were also valid in young children.

Identification of novel SHOX target genes in the developing limb using a transgenic mouse model

Deficiency of the human short stature homeobox-containing gene (SHOX) has been identified in several disorders characterized by reduced height and skeletal anomalies such as Turner syndrome, Léri-Weill dyschondrosteosis and Langer mesomelic dysplasia as well as isolated short stature. SHOX acts as a transcription factor during limb development and is expressed in chondrocytes of the growth plates. Although highly conserved in vertebrates, rodents lack a SHOX orthologue. This offers the unique opportunity to analyze the effects of human SHOX expression in transgenic mice. We have generated a mouse expressing the human SHOXa cDNA under the control of a murine Col2a1 promoter and enhancer (Tg(Col2a1-SHOX)). SHOX and marker gene expression as well as skeletal phenotypes were characterized in two transgenic lines. No significant skeletal anomalies were found in transgenic compared to wildtype mice. Quantitative and in situ hybridization analyses revealed that Tg(Col2a1-SHOX), however, affected extracellular matrix gene expression during early limb development, suggesting a role for SHOX in growth plate assembly and extracellular matrix composition during long bone development. For instance, we could show that the connective tissue growth factor gene Ctgf, a gene involved in chondrogenic and angiogenic differentiation, is transcriptionally regulated by SHOX in transgenic mice. This finding was confirmed in human NHDF and U2OS cells and chicken micromass culture, demonstrating the value of the SHOX-transgenic mouse for the characterization of SHOX-dependent genes and pathways in early limb development.

Unexpected high frequency of skeletal dysplasia in idiopathic short stature and small for gestational age patients

OBJECTIVE

To assess the prevalence of skeletal dysplasias (SDs) in patients with idiopathic short stature (ISS) or small for gestational age (SGA) status.

SETTING

Rare Endocrine/Growth Diseases Center in Paris, France.

DESIGN

A prospective study on consecutive patients with ISS and SGA enrolled from 2004 to 2009.

METHOD

We used a standardized workup to classify patients into well-established diagnostic categories. Of 713 patients with ISS (n=417) or SGA status (n=296), 50.9% underwent a skeletal survey. We chose patients labeled normal or with a prepubertal slowdown of growth as a comparison group.

RESULTS

Diagnoses were ISS (16.9%), SGA (13.5%), normal growth (24.5%), transient growth rate slowing (17.3%), endocrine dysfunction (12%), genetic syndrome (8.9%), chronic disease (5.1%), and known SD (1.8%). SD was found in 20.9% of SGA and 21.8% ISS patients and in only 13.2% in our comparison group. SD prevalence was significantly higher in the ISS group than in the comparison group, especially (50%) for patients having at least one parent whose height was <-2 SDS. Dyschondrosteosis and hypochondroplasia were the most frequently identified SD, and genetic anomaly was found in 61.5 and 30% respectively. Subtle SD was found equally in the three groups and require long-term growth follow-up to evaluate the impact on final height.

CONCLUSION

SD may explain more than 20% of cases of growth retardation ascribed to ISS or SGA, and this proportion is higher when parental height is <-2 SDS. A skeletal survey should be obtained in patients with delayed growth in a context of ISS or SGA.

Growth hormone treatment in non-growth hormone-deficient children

Until 1985 growth hormone (GH) was obtained from pituitary extracts, and was available in limited amounts only to treat severe growth hormone deficiency (GHD). With the availability of unlimited quantities of GH obtained from recombinant DNA technology, researchers started to explore new modalities to treat GHD children, as well as to treat a number of other non-GHD conditions. Although with some differences between different countries, GH treatment is indicated in children with Turner syndrome, chronic renal insufficiency, Prader-Willi syndrome, deletions/mutations of the SHOX gene, as well as in short children born small for gestational age and with idiopathic short stature. Available data from controlled trials indicate that GH treatment increases adult height in patients with Turner syndrome, in patients with chronic renal insufficiency, and in short children born small for gestational age. Patients with SHOX deficiency seem to respond to treatment similarly to Turner syndrome. GH treatment in children with idiopathic short stature produces a modest mean increase in adult height but the response in the individual patient is unpredictable. Uncontrolled studies indicate that GH treatment may be beneficial also in children with Noonan syndrome. In patients with Prader-Willi syndrome GH treatment normalizes growth and improves body composition and cognitive function. In any indication the response to GH seems correlated to the dose and the duration of treatment. GH treatment is generally safe with no major adverse effects being recorded in any condition.

Height outcome of the recombinant human growth hormone treatment in patients with SHOX gene haploinsufficiency: a meta-analysis

Background: Patients with mutations or deletions of the SHOX gene present variable growth impairment, with or without mesomelic skeletal dysplasia. If untreated, short patients with SHOX haplodeficiency (SHOXD) remain short into adulthood. Although recombinant human growth hormone (rhGH) treatment improves short-term linear growth, there are episodic data on the final height of treated SHOXD subjects. Patients & methods: After a thorough search of the published literature for pertinent studies, we undertook a meta-analysis evaluation of the efficacy and safety of rhGH treatment in SHOXD patients. Results: In SHOXD patients, administration of rhGH progressively improved the height deficit from baseline to 24 months, although the major catch-up growth was detected after 12 months. The rhGH-induced growth appeared constant until final height. Conclusion: Our meta-analysis suggested rhGH therapy improves height outcome of SHOXD patients, though future studies using carefully titrated rhGH protocols are needed.

Original submitted 29 October 2012; Revision submitted 22 February 2013

Height matters-from monogenic disorders to normal variation

Height is a classic polygenic quantitative trait with a high level of heritability. As it is a simple and stable parameter to measure, height is a model for both common, complex disorders and monogenic, Mendelian disease. In this Review, we examine height from the perspective of monogenic and complex genetics and discuss the lessons learned so far. We explore several examples of rare sequence variants with large effects on height and compare these variants to the common variants identified in genome-wide association studies that have small effects on height. We discuss how copy number changes or genetic interactions might contribute to the unidentified aspects of the heritability of height. We also ask whether information derived from genome-wide association studies on specific loci in the vicinity of genes can be used for further research in clinical paediatric endocrinology. Furthermore, we address key challenges that remain for gene discovery and for the transition of moving from genomic localization to mechanistic insights, with an emphasis on using next-generation sequencing to identify causative variants of people at the extremes of height distribution.

A pilot study of discontinuous, insulin-like growth factor 1-dosing growth hormone treatment in young children with FGFR3 N540K-mutated hypochondroplasia

OBJECTIVE

To assess the growth promoting effect of a recombinant growth hormone (rGH) treatment protocol adjusted on insulin-like growth factor 1 (IGF-1) dosing in children affected by the most severe forms of FGFR3 N540K-mutated hypochondroplasia.

STUDY DESIGN

Midterm results of an open-label, single-center, nonrandomized, 2003-2020 pilot trial to final stature, including 6 children (mean age, 2.6 ± 0.7 years; mean height SDS, -3.0 ± 0.5) with the N540K mutation of FGFR3 gene who received an rGH dosage titrated to an IGF-1 level close to 1.5 SDS of the normal range. rGH therapy was interrupted 1 day per week, 1 month per year, and 6 months every 2 years.

RESULTS

The mean height SDS increased by 1.9 during the 6.1 ± 0.9-year study period, reaching -0.8 to -1.3 at age 8.7 ± 1 years. The mean±SDS baseline IGF-1 value was -1.6 ± 0.5 before rGH treatment and 1.4±0.3 during the last year of observation. The average cumulative rGH dose was 0.075 ± 0.018 mg/kg/day (range, 0.059-0.100 mg/kg/day). Trunk/leg disproportion was improved.

CONCLUSION

IGF-1-dosing rGH treatment durably improves growth and reduces body disproportion in children with severe forms of hypochondroplasia.

Use of the MLPA assay in the molecular diagnosis of gene copy number alterations in human genetic diseases

Multiplex Ligation-dependent Probe Amplification (MLPA) assay is a recently developed technique able to evidence variations in the copy number of several human genes. Due to this ability, MLPA can be used in the molecular diagnosis of several genetic diseases whose pathogenesis is related to the presence of deletions or duplications of specific genes. Moreover, MLPA assay can also be used in the molecular diagnosis of genetic diseases characterized by the presence of abnormal DNA methylation. Due to the large number of genes that can be analyzed by a single technique, MLPA assay represents the gold standard for molecular analysis of all pathologies derived from the presence of gene copy number variation. In this review, the main applications of the MLPA technique for the molecular diagnosis of human diseases are described.