Update in growth hormone therapy of children

Although recombinant human GH (rhGH) has been available since 1985, there are several questions related to its use that remain unanswered. The Entrez-PubMed search engine was used to conduct a review of publications appearing since 2007 that address growth and GH treatment. Recent publications related to the diagnosis of GH deficiency, genetics of growth, the use of rhGH in different genetic conditions, in idiopathic short stature, and in puberty, and strategies to adjust rhGH dose were reviewed. New studies investigating the genetics of growth and the response to rhGH therapy in different groups are helping in the understanding of the physiology of normal growth. Although in most children treated with rhGH there is a short-term benefit, the clinical relevance of the benefits after long-term treatment in some conditions remains unclear. The challenges are to define milder forms of GH deficiency and to assess the relevance of the benefits, if any, caused by rhGH in different patient populations and the best therapeutic approach for these patients. Well-designed long-term studies using anthropometric, genetic, and laboratory data that will also assess long-term quality of life benefits are needed to help clinicians select patients to initiate treatment with rhGH and to adjust treatment to improve outcome.

Clinical and molecular evaluation of SHOX/PAR1 duplications in Leri-Weill dyschondrosteosis (LWD) and idiopathic short stature (ISS)

CONTEXT

Léri-Weill dyschondrosteosis (LWD) is a skeletal dysplasia characterized by disproportionate short stature and the Madelung deformity of the forearm. SHOX mutations and pseudoautosomal region 1 deletions encompassing SHOX or its enhancers have been identified in approximately 60% of LWD and approximately 15% of idiopathic short stature (ISS) individuals. Recently SHOX duplications have been described in LWD/ISS but also in individuals with other clinical manifestations, thus questioning their pathogenicity.

OBJECTIVE

The objective of the study was to investigate the pathogenicity of SHOX duplications in LWD and ISS.

DESIGN AND METHODS

Multiplex ligation-dependent probe amplification is routinely used in our unit to analyze for SHOX/pseudoautosomal region 1 copy number changes in LWD/ISS referrals. Quantitative PCR, microsatellite marker, and fluorescence in situ hybridization analysis were undertaken to confirm all identified duplications.

RESULTS

During the routine analysis of 122 LWD and 613 ISS referrals, a total of four complete and 10 partial SHOX duplications or multiple copy number (n > 3) as well as one duplication of the SHOX 5' flanking region were identified in nine LWD and six ISS cases. Partial SHOX duplications appeared to have a more deleterious effect on skeletal dysplasia and height gain than complete SHOX duplications. Importantly, no increase in SHOX copy number was identified in 340 individuals with normal stature or 104 overgrowth referrals.

CONCLUSION

MLPA analysis of SHOX/PAR1 led to the identification of partial and complete SHOX duplications or multiple copies associated with LWD or ISS, suggesting that they may represent an additional class of mutations implicated in the molecular etiology of these clinical entities.

The jumping SHOX gene--crossover in the pseudoautosomal region resulting in unusual inheritance of Leri-Weill dyschondrosteosis

CONTEXT

During meiosis I, the recombination frequency in the pseudoautosomal region on Xp and Yp (PAR1) in males is very high. As a result, mutated genes located within the PAR1 region can be transferred from the Y-chromosome to the X-chromosome and vice versa.

PATIENTS

Here we describe three families with SHOX abnormalities resulting in Leri-Weill dyschondrosteosis or Langer mesomelic dysplasia.

RESULTS

In about half of the segregations investigated, a transfer of the SHOX abnormality to the alternate sex chromosome was demonstrated.

CONCLUSIONS

Patients with an abnormality of the SHOX gene should receive genetic counseling as to the likelihood that they may transmit the mutation or deletion to a son as well as to a daughter.

Short stature caused by isolated SHOX gene haploinsufficiency: update on the diagnosis and treatment

Heterozygous SHOX defects are observed in about 50 to 90% of patients with Leri-Weill dyschondrosteosis (LWD), a common dominant inherited skeletal dysplasia; and in 2 to 15% of children with idiopathic short stature (ISS), indicating that SHOX defects are the most important monogenetic cause of short stature. In addition, children selected by disproportionate idiopathic short stature had a higher frequency of SHOX mutations (22%). A careful clinical evaluation of family members with short stature is recommended since it usually revealed LWD patients in families first classified as having ISS or familial short stature. SHOX-molecular analysis is indicated in families with LWD and ISS children with disproportionate short stature. Treatment with recombinant human growth hormone is considered an accepted approach to treat short stature associated with isolated SHOX defect. Here we review clinical, molecular and therapeutic aspects of SHOX haploinsufficiency.

Trisomy of the short stature homeobox-containing gene (SHOX) due to duplication/deletion of the X chomosome: clinical implications on the stature

BACKGROUND

The karyotypes of 2 patients with abnormal stature and different phenotypes revealed one similar structural abnormality in the X chromosome by conventional cytogenetic studies and fluorescence in situ hybridization analysis (FISH). FISH strongly suggested the presence of two copies of the SHOX gene in the der(X) chromosome.

PATIENTS AND RESULTS

Patient 1 is a teenager girl with tall stature, behavioral disturbances and normal pubertal development. The abnormal X chromosome was present in all cells studied. Parent's karyotypes were normal. Patient 2 is a girl with gonadal dysgenesis, mild Turner syndrome phenotype and short stature. The karyotype was a mosaic 45,X/46,X,r(X) and der(X) chromosome presented in most metaphases of the cell lines. Parent's karyotypes were normal. Nearly all duplication of Xp and partial deletion of the long arm (Xq) from Xq27 or Xq21 to Xqter, in cases 1 and 2, respectively, were observed. In both patients, duplication of Xp translocated to deleted Xq occurred leading to a triplication of the pseudoautosomal region 1 (PAR1) where the SHOX gene is located (Xp22.3).

CONCLUSIONS

We propose that in some cases of trisomy for the SHOX gene, the effect of overdosage per se may affect the stature, even in patients with preserved ovarian function (case 1), and that estrogen deprivation may not always be a contributor for tall stature (case 2).

Epidemiology of SHOX deficiency

Deletion of short stature homeobox-containing (SHOX) gene, in the pseudoautosomal region (PAR1) of X and Y chromosomes, is an important cause of short stature. Homozygous loss of SHOX results in the more severe Langer mesomelic dysplasia, while SHOX haploinsufficiency cause a wide spectrum of short stature phenotypes, including patients with Turner syndrome, Leri Weill dyschondrosteosis (LWD), and idiopathic short stature (ISS). In Turner syndrome, haploinsufficiency of SHOX gene, as well as short stature, are present in 100%; nevertheless, SHOX deficiency accounts for only two-thirds of Turner patients' short stature. In LWD the prevalence of SHOX gene anomalies varies from 56% to 100%. This wide range might be due to different factors such as selection criteria of patients, sample size, and method used for screening SHOX mutations. The real challenge is to establish the prevalence of SHOX deficiency in ISS children given that published studies have reported this association with a very broad frequency range varying from 1.5% to 15%. An important variable in these studies is represented by the method used for screening SHOX mutations and sometimes by differences in patient selection. Short stature is present by definition in 3 out of 100 subjects; if we consider a frequency of SHOX defects of 3% among ISS, we should expect a population prevalence of 1 in 1000. This prevalence would be higher than that of GH deficiency (1:3,500) and of Turner syndrome (1:2,500 females), suggesting that SHOX deficiency could be one of the most frequent monogenetic causes of short stature.

The SHOX region and its mutations

The short stature homeobox-containing (SHOX) gene lies in the pseudoautosomal region 1 (PAR1) that comprises 2.6 Mb of the short-arm tips of both the X and Y chromosomes. It is known that its heterozygous mutations cause Leri-Weill dyschondrosteosis (LWD) (OMIM #127300), while its homozygous mutations cause a severe form of dwarfism known as Langer mesomelic dysplasia (LMD) (OMIM #249700). The analysis of 238 LWD patients between 1998 and 2007 by multiple authors shows a prevalence of deletions (46.4%) compared to point mutations (21.2%). On the whole, deletions and point mutations account for about 67% of LWD patients. SHOX is located within a 1000 kb desert region without genes. The comparative genomic analysis of this region between genomes of different vertebrates has led to the identification of evolutionarily conserved non-coding DNA elements (CNE). Further functional studies have shown that one of these CNE downstream of the SHOX gene is necessary for the expression of SHOX; this is considered to be typical "enhancer" activity. Including the enhancer, the overall mutation of the SHOX region in LWD patients does not hold in 100% of cases. Various authors have demonstrated the existence of other CNE both downstream and upstream of SHOX regions. The resulting conclusion is that it is necessary to reanalyze all LWD/LMD patients without SHOX mutations for the presence of mutations in the 5'- and 3'-flanking SHOX regions.

Different approaches in the molecular analysis of the SHOX gene dysfunctions

Deficit of the short stature homeobox containing gene (SHOX) accounts for 2.15% of cases of idiopathic short stature (ISS) and 50-100% of cases of Leri-Weill dyschondrosteosis (LWD). It has been demonstrated that patients with SHOX deficit show a good response to treatment with GH. Thus, the early identification of SHOX alterations is a crucial point in order to choose the best treatment for ISS and LWD patients. In this study, we analyze the most commonly used molecular techniques for the detection of SHOX gene alterations. multiple ligation-dependent probe amplification analysis appears to represent the gold standard for the detection of deletion involving the SHOX gene or the enhancer region, being able to show both alterations in a single assay.

Auxological and anthropometric evaluation in skeletal dysplasias

Anthropometry is the technique of expressing body shape in quantitative terms. The measurements are compared with the standard growth curves for the general population and expressed as a SD score or percentiles. The comparison of the different parameters with normal standards requires: standardized landmarks on the body, standardized methods of taking measurements, and standard equipment. Skeletal dysplasias generally present with disproportionate short stature, that may be caused primarily by a short trunk or short limbs. If short limbs are observed, the reduction may affect the proximal (rhizomelic), the middle (mesomelic) or distal (acromelic) segments. Anthropometric measurements should include all the segments of the arms and the legs with a comparison with the normal standards for height age. Short stature homeobox- containing (SHOX) gene defects determine a highly variable phenotype, that includes an osteochondrodysplasia with mesomelic short stature and Madelung deformity, but also presentations without evident malformations. Anthropometric indicators of SHOX deficiency are: disproportionate short stature, reduction of lower limb, reduction of the ratio between arm span and forearm length with respect to height, increase in the sitting/ height stature ratio, increase in limb circumference (arm, forearm, thigh, and leg) with respect to height and increased body mass index. In some forms of skeletal dysplasias and in particular in SHOX gene anomalies that have many characteristics superimposable to idiopathic short stature, only an accurate auxo-anthropometric and dysmorphologic evaluation enable us to propose, fairly accurately, the subjects for the gene study.

Bone dysplasias: the A, B, C of radiographic interpretation

The skeletal dysplasias are a group of genetic disorders affecting skeletal development and maintenance, usually manifesting in childhood with disproportionate short stature. Although individually rare, they are not infrequent as a group. An accurate diagnosis is crucial for prevention and/or treatment of complications, estimate of child's growth, and proper genetic counseling. Radiology is the mainstay of diagnosis. Recognition of single radiographic signs or patterns of anomalies is required to reach the correct diagnosis. The radiographic features of Leri-Weill syndrome and Langer mesomelic dwarfism, two skeletal dysplasias caused by a defect in the short stature homeobox-containing gene, are briefly discussed.

The SHOX gene: a new indication for GH treatment

Short stature homeobox-containing (SHOX) gene mutations causing haploinsufficiency have been reported in idiopathic short stature, but the real prevalence of this defect in the population with growth failure is debated. Based on current data, the prevalence of SHOXdefect (SHOX-D) has been calculated to have occurred in at least 1 in 2,000 children. This occurrence rate is higher than that of classic GH deficiency or Turner syndrome. In all probability, the real prevalence of SHOX-D will increase in the future with the improvement of the genetic analysis with investigations for point mutations in the enhancer sequences or for deletions in other parts of this region. A selection criterion to individuate the most appropriate candidates eligible for the SHOX region analysis has been suggested based on the evaluation of a disproportional short stature. The efficacy of GH treatment in these patients has recently been demonstrated with results that are similar to those observed in Turner syndrome.

A short history of the initial discovery of the SHOX gene

Already in 1981 Davis had reported that small Yp terminal deletion resulted in short stature and, basing his findings on Davis's results, on the results of other publications, and on his own observations that Xp terminal deletions normally result in short stature regardless of the breakpoints, in 1993 Ogata suggested that a growth gene was located in the pseudoautosomal region (PAR) and that haploinsufficiency of the growth gene actually caused short stature as a dominant phenotype. Rao et al. in 1997 cloned a gene from the distal part of the PAR and gave it the name SHOX for "short stature homeobox-containing" gene. SHOX is expressed from an inactive X chromosome and an active X and a normal Y chromosome, indicating that SHOX produces the dosage effect in sex chromosome aberrations. In the same year, both Ellison and Rao demonstrated that SHOX is most clearly expressed in bone marrow fibroblasts, thus suggesting that SHOX has a particular importance in bone growth and maturation.

Growth hormone therapy in patients with short stature homeobox-gene (SHOX) deficiency

Short stature homeobox (SHOX) gene is located in the pseudoautosomal region 1 on the distal end of the X and Y chromosomes at Xp22.3 and Yp11.3. The haploinsufficiency of SHOX is correlated with short stature, Leri-Weill dyschondrosteosis, and Langer mesomelic dysplasia. Subjects with Turner syndrome (TS) present a SHOX haploinsufficiency that appears to be substantially responsible for their short stature. Several studies have shown a positive response to GH therapy in patients with TS. Short children with SHOX haploinsufficiency do not spontaneously catch up to attain a normal final height. Considering the positive effects obtained in patients with TS, GH therapy has been proposed for short stature due to isolated SHOX haploinsufficiency. The aim of this paper is to summarize the current data on GH administration in patients with SHOX haploinsufficiency. The conclusion is that GH therapy, at the same dosage used in patients with TS, induces a sustained catch-up growth and a height velocity and adult height gain in short patients with SHOX haploinsufficiency.

SHOX mutation as a rare disease: molecular diagnosis and growth hormone treatment supported by the Italian public health system

Short stature homeobox-containing (SHOX) gene deficiency is acknowledged under the term "dyschondrosteosis", which is included in the family of congenital osteodystrophies. Under current regulations, the cost of the genetic testing and treatment with GH in children with short stature, and SHOX gene deficiency may be reimbursed. Prescription of costs exemption is subject to the identification of the regional centers qualified to diagnose congenital osteodystrophies (RNG060). The centers qualified to diagnose and treat "dyschondrosteosis" have been identified in only a few regions, whereas in other regions centers for the diagnosis and treatment of congenital osteodystrophies have been identified, and in still others, no specific centers have been identified yet. Treatment with GH as indicated by European Medicines Agency (EMEA) for people with short stature and evidence of SHOX gene deficiency is governed by Agenzia Italiana del Farmaco (AIFA) note number 39. The latest version does not provide for the medication to be directly reimbursed by the National Health Service, although it may be prescribed for patients with well-defined auxological characteristics, subject to the prior authorization of the regional commission qualified to monitor the use of the GH. Therefore, a diagnostic/ therapeutic course for patients with short stature with SHOX gene mutation has been proposed. The healthcare course relating to such patients has not been thoroughly defined in terms of implementation and is affected by regional organizational approaches. Implementing specific healthcare courses for such patients may provide a model for treating other patients with short stature and rare diseases with GH.

Improved molecular diagnostics of idiopathic short stature and allied disorders: quantitative polymerase chain reaction-based copy number profiling of SHOX and pseudoautosomal region 1

CONTEXT

Short stature has an incidence of three in 100 in children. Reliable molecular genetic testing may be crucial in the context of beneficial disease management. Deletions spanning or surrounding the SHOX gene account for a significant proportion of patients with idiopathic short stature (ISS) and allied disorders, such as Leri-Weill dyschondrosteosis.

OBJECTIVE

Several shortcomings of current strategies for copy number profiling of the SHOX region prompted us to develop an improved test for molecular diagnostics of the SHOX region.

DESIGN AND RESULTS

We introduced a quantitative PCR (qPCR)-based copy number profiling test, consisting of 11 amplicons targeting clinically relevant regions, i.e. the SHOX gene and regulatory regions. To ensure an optimal sensitivity and specificity, this test was validated in 32 controls and 18 probands with previously identified copy number changes. In addition, 152 probands with SHOX-associated phenotypes were screened, revealing 10 novel copy number changes.

CONCLUSION

This highly validated qPCR test supersedes other approaches for copy number screening of the SHOX region in terms of reliability, accuracy, and cost efficiency. In addition, another strong point is the fact that it can be easily implemented in any standard equipped molecular laboratory. Our qPCR-based test is highly recommended for molecular diagnostics of idiopathic short stature and allied disorders.

Approach to the patient with Turner syndrome

Turner syndrome (TS) occurs in about 1:4000 live births and describes females with a broad constellation of problems associated with loss of an entire sex chromosome or a portion of the X chromosome containing the tip of its short arm. TS is associated with an astounding array of potential abnormalities, most of them thought to be caused by haploinsufficiency of genes that are normally expressed by both X chromosomes. A health care checklist is provided that suggests screening tests at specific ages and intervals for problems such as strabismus, hearing loss, and autoimmune thyroid disease. Four areas of major concern in TS are discussed: growth failure, cardiovascular disease, gonadal failure, and learning disabilities. GH therapy should generally begin as soon as growth failure occurs, allowing for rapid normalization of height. Cardiac imaging, preferably magnetic resonance imaging, should be performed at diagnosis and repeated at 5- to 10-yr intervals to assess for congenital heart abnormalities and the emergence of aortic dilatation, a precursor to aortic dissection. Hypertension should be aggressively treated. For those with gonadal dysgenesis, hormonal replacement therapy should begin at a normal pubertal age and be continued until the age of 50 yr. Transdermal estradiol provides the most physiological replacement. Finally, nonverbal learning disabilities marked by deficits in visual-spatial-organizational skills, complex psychomotor skills, and social skills are common in TS. Neuropsychological testing should be routine and families given support in obtaining appropriate therapy, including special accommodations at school.

Effectiveness of the combined recombinant human growth hormone and gonadotropin-releasing hormone analog therapy in pubertal patients with short stature due to SHOX deficiency

CONTEXT

Isolated heterozygous SHOX defects are the most frequent monogenic cause of short stature, and combined therapy with recombinant human GH (rhGH) and GnRH analog (GnRHa) in pubertal patients has been suggested, but there are no data on final height.

OBJECTIVE

The aim of the study was to analyze adult height after rhGH and GnRHa therapy in patients with SHOX haploinsufficiency.

PATIENTS

Ten peripubertal patients with isolated SHOX defects participated in the study.

INTERVENTION

Five patients were followed without treatment, and five were treated with rhGH (50 mug/kg/d) and depot leuprolide acetate (3.75 mg/month).

MAIN OUTCOME MEASURES

Adult height sd score (SDS) was measured.

RESULTS

All patients followed without treatment had marked downward growth shift during puberty (height SDS, -1.2 +/- 0.7 at 11.4 +/- 1.4 yr; adult height SDS, -2.5 +/- 0.5). Conversely, four of five patients treated with rhGH for 2 to 4.9 yr associated to GnRHa for 1.4 to 5.8 yr improved their height SDS from -2.3 +/- 1.3 at 11.8 +/- 2.1 yr to a final height SDS of -1.7 +/- 1.6. The difference between the mean height SDS at the first evaluation and final height SDS was statistically significant in nontreated vs. treated patients (mean height SDS change, -1.2 +/- 0.4 vs. 0.6 +/- 0.4, respectively; P <0.001).

CONCLUSION

A gain in adult height of patients with isolated SHOX defects treated with combined rhGH and GnRHa therapy was demonstrated for the first time, supporting this treatment for children with SHOX defects who have just started puberty to avoid the loss of growth potential observed in these patients during puberty.

Effect of growth hormone therapy on severe short stature and skeletal deformities in a patient with combined Turner syndrome and Langer mesomelic dysplasia

BACKGROUND

Homozygous mutation of the short stature homeobox-containing gene, SHOX, results in Langer mesomelic dysplasia (LMD). Our case presented with severe short stature and skeletal deformities with Turner syndrome (TS) and a SHOX gene abnormality due to a downstream allele deletion in her normal X chromosome. Medical literature review did not reveal similar cases that were treated with GH therapy.

METHOD

We present an 11-yr-old with combined TS and LMD with severe short stature and skeletal deformities. She was studied for the effect of GH therapy on stature and skeletal deformities. Karyotype testing showed 45,X/46,X,idic(X). Genetic analysis of SHOX gene testing did not detect any exonic mutations. Interestingly, both alleles of the flanking marker DXYS233, a marker downstream of the 3' end of SHOX coding sequence, were absent with resultant LMD. GH therapy in the mean dose of 0.321 mg/kg/wk was administered for 4 yr (0.287, 0.355, 0.317, and 0.327 mg/kg/week in the first, second, third, and fourth years, respectively). Clinical data were reviewed.

RESULT

The growth rates of 3.46, 3.87, 2.3, and 0.7 cm/yr were observed in the first, second, third, and fourth years of the GH therapy, respectively. There was no clinical deterioration of the skeletal deformities.

CONCLUSION

There was a failure to achieve growth improvements with GH therapy for 4 years, but there was no worsening of the skeletal deformities. We conclude that GH therapy may not be beneficial in severe short stature due to combined TS and LMD resulting from homozygous SHOX deficiency.

Deletion of Xpter encompassing the SHOX gene and PAR1 region in familial patients with Leri-Weill Dyschondrosteosis syndrome

Heterozygote deletions or mutations of pseudoautosomal 1 region (PAR1) encompassing the short stature homeobox-containing (SHOX) gene cause Leri-Weill Dyschondrosteosis (LWD), which is a dominantly inherited osteochondroplasia characterized by short stature with mesomelic shortening of the upper and lower limbs and Madelung deformity of the wrists. SHOX is expressed by both sex chromosomes in males and females and plays an important role in bone growth and development. Clinically, the LWD expression is variable and more severe in females than males due to sex differences in oestrogen levels. Here, we report two familial cases of LWD with a large Xp terminal deletion (approximately 943 kb) of distal PAR1 encompassing the SHOX gene. In addition, the proband had mental retardation which appeared to be from recessive inheritance in the family.