GH responsiveness in a large multinational cohort of SGA children with short stature (NESTEGG) is related to the exon 3 GHR polymorphism

Genetic Screening for Growth Hormone Therapy in Children Small for Gestational Age: So Much to Consider, Still Much to Discover

Children born small for gestational age (SGA), and failing to catch-up growth in their early years, are a heterogeneous group, comprising both known and undefined congenital disorders. Care for these children must encompass specific approaches to ensure optimal growth. The use of recombinant human growth hormone (rhGH) is an established therapy, which improves adult height in a proportion of these children, but not with uniform magnitude and not in all of them. This situation is complicated as the underlying cause of growth failure is often diagnosed during or even after rhGH treatment discontinuation with unknown consequences on adult height and long-term safety. This review focuses on the current evidence supporting potential benefits from early genetic screening in short SGA children. The pivotal role that a Next Generation Sequencing panel might play in helping diagnosis and discriminating good responders to rhGH from poor responders is discussed. Information stemming from genetic screening might allow the tailoring of therapy, as well as improving specific follow-up and management of family expectations, especially for those children with increased long-term risks. Finally, the role of national registries in collecting data from the genetic screening and clinical follow-up is considered.

The exon3-deleted growth hormone receptor gene polymorphism (d3-GHR) is associated with insulin and spontaneous growth in short SGA children (NESGAS)

OBJECTIVE

The effect of a common polymorphism in the Growth Hormone (GH) receptor (d3-GHR) gene on growth, metabolism and body composition was examined in short children born small for gestational age (SGA) on GH treatment.

DESIGN

In 96 prepubertal, short SGA children treated with high-dose GH (67μg/kg/day) in the NESGAS study, insulin sensitivity (IS), insulin secretion and disposition index (DI) were determined during the first year of treatment. Body composition was analysed by DXA. The d3-GHR locus was determined by simple multiplex PCR.

RESULTS

At baseline, children in the d3-GHR group (d3/fl (n=37), d3/d3 (n=7)) had significantly lower IS (median (25-75 percentile)) (223.3% (154.4-304.8)) vs. (269.7% (185.1-356.7)) (p=0.03) and higher concentrations of glucose (mean (SD)) (4.4mmol/L (0.6) vs. 4.2mmol/L (0.7)) (p=0.03), C-peptide (232.1pmol/L (168.8-304.1) vs. 185.1pmol/L (137.7-253.9)) (p=0.04) and insulin (19.2pmol/L (11.8-32.2)) vs. (13.7pmol/L (9.3-20.8)) (p=0.04) compared to children homozygous for the full length allele (fl/fl-GHR (n=52)). There were no differences in DI or insulin secretion. Postnatal, spontaneous growth was significantly greater in the d3-GHR group compared to the fl/fl-GHR group (p=0.02). There were no significant differences in growth response, body composition or metabolism after one year of GH therapy.

CONCLUSION

Short SGA children carrying the d3-GHR polymorphism had increased spontaneous growth, lower IS and a compensatory increase in glucose, C-peptide and insulin before GH therapy compared to children homozygous for the full-length allele.

GH deficiency status combined with GH receptor polymorphism affects response to GH in children

Meta-analysis has shown a modest improvement in first-year growth response to recombinant human GH (r-hGH) for carriers of the exon 3-deleted GH receptor (GHRd3) polymorphism but with significant interstudy variability. The associations between GHRd3 and growth response to r-hGH over 3 years in relation to severity of GH deficiency (GHD) were investigated in patients from 14 countries. Treatment-naïve pre-pubertal children with GHD were enrolled from the PREDICT studies (NCT00256126 and NCT00699855), categorized by peak GH level (peak GH) during provocation test: ≤4 μg/l (severe GHD; n=45) and >4 to <10 μg/l mild GHD; n=49) and genotyped for the GHRd3 polymorphism (full length (fl/fl, fl/d3, d3/d3). Gene expression (GE) profiles were characterized at baseline. Changes in growth (height (cm) and SDS) over 3 years were measured. There was a dichotomous influence of GHRd3 polymorphism on response to r-hGH, dependent on peak GH level. GH peak level (higher vs lower) and GHRd3 (fl/fl vs d3 carriers) combined status was associated with height change over 3 years (P<0.05). GHRd3 carriers with lower peak GH had lower growth than subjects with fl/fl (median difference after 3 years -3.3 cm; -0.3 SDS). Conversely, GHRd3 carriers with higher peak GH had better growth (+2.7 cm; +0.2 SDS). Similar patterns were observed for GH-dependent biomarkers. GE profiles were significantly different between the groups, indicating that the interaction between GH status and GHRd3 carriage can be identified at a transcriptomic level. This study demonstrates that responses to r-hGH depend on the interaction between GHD severity and GHRd3 carriage.

Influence of the exon 3 deletion of GH receptor and IGF-I level at diagnosis on the efficacy and safety of treatment with somatotropin in adults with GH deficiency

PURPOSE

The treatment of adults with GH deficiency (GHD) with human recombinant growth hormone has interindividual variability and several factors influence it. The aims of this study were : 1-to analyze the GH receptor (GHR) genotype in terms of exon 3 deletion GHR (d3-GHR) in adults with GHD; 2-to assess the effects of d3-GHR on initial IGF-I levels; 3-to evaluate whether d3-GHR and/or initial IGF-I levels were associated with adverse effects and/or treatment discontinuation.

METHODS

Forty-four adult patients with GHD were included. Demographic, clinical and biochemical characteristics were retrospectively evaluated at baseline and 6 months, 1 and 3 years after the initiation of treatment. d3-GHR was analyzed in 35 patients.

RESULTS

37.1% of patients were d3-GHR carriers (31.4% heterozygous, 5.7% homozygous). IGF-I at baseline was low in 64% of patients and was not related to d3-GHR status. There was no association between the d3-GHR allele and baseline IGF-I (p = 0.14). Although adverse events were more frequent in the d3-GHR carriers (30.7 vs. 18.2% in fl/fl) and in patients with normal IGF-I levels at diagnosis (43.7 vs. 17.8% in patients with low IGF-I levels), this association was not statistically significant. d3-GHR status was not related to the incidence of adverse events (p = 0.4) or treatment discontinuation (p = 0.47). Baseline IGF-I levels were neither associated with adverse events (p = 0.08) nor treatment discontinuation (p = 0.75).

CONCLUSIONS

The d3-GHR allele was not related to baseline levels of IGF-I. Neither d3-GHR nor baseline IGF-I level was related to adverse events or treatment discontinuation.

The growth hormone receptor exon 3 polymorphism is not associated with height or metabolic traits in healthy young adults

CONTEXT

The GHR polymorphisms contribution to the interindividual variability in prenatal and postnatal growth as well as to metabolic traits is controversial.

OBJECTIVE

The aim of this study is to analyze the association of the GHRfl/d3 polymorphism with prenatal and postnatal growth and metabolic outcomes in adult life and to compare the genotype distribution in different populations.

DESIGN

385 community healthy subjects followed from birth to adult life (23-25years old) were grouped according to birth size: small-SGA (n=130, 62 males), appropriate-AGA (n=162, 75 males) and large for gestational age-LGA (n=93, 48 males). GHRfl/d3 genotype distribution and its potential association with anthropometric (at birth, childhood and adult life) and metabolic features (in adult life) were analyzed and compared with data obtained from a systematic review of GHRfl/d3 association studies (31 articles).

RESULTS

The frequency of the GHR d3/d3 genotype was lower in the LGA (χ2 p=0.01); SGA and AGA subjects exhibited an increased chance of the d3/d3 genotype (OR=3.58; 95%CI: 1.55; 8.24) and (OR=2.39; 95%CI: 1.02; 5.62), respectively. Despite the different prevalence among different birth size groups, in adults, GHRfl/d3 genotype was not associated with height, plasma IGF1 levels or metabolic phenotype and cardiovascular risk. GHRfl/d3 genotype distributions in AGA, SGA and LGA groups were comparable with those found in subjects of European origin but not with those of Asian ancestry.

CONCLUSIONS

The GHRd3 genotype was negatively associated with birth size but it was not associated with adult height or weight, plasma IGF1, metabolic phenotype or any marker of increased cardiovascular risk in young adults.

Growth hormone receptor polymorphism and growth hormone therapy response in children: a Bayesian meta-analysis

Recombinant human growth hormone (rhGH) therapy is used in the long-term treatment of children with growth disorders, but there is considerable treatment response variability. The exon 3-deleted growth hormone receptor polymorphism (GHR(d3)) may account for some of this variability. The authors performed a systematic review (to April 2011), including investigator-only data, to quantify the effects of the GHR(fl-d3) and GHR(d3-d3) genotypes on rhGH therapy response and used a recently established Bayesian inheritance model-free approach to meta-analyze the data. The primary outcome was the 1-year change-in-height standard-deviation score for the 2 genotypes. Eighteen data sets from 12 studies (1,527 children) were included. After several prior assumptions were tested, the most appropriate inheritance model was codominant (posterior probability = 0.93). Compared with noncarriers, carriers had median differences in 1-year change-in-height standard-deviation score of 0.09 (95% credible interval (CrI): 0.01, 0.17) for GHR(fl-d3) and of 0.14 (95% CrI: 0.02, 0.26) for GHR(d3-d3). However, the between-study standard deviation of 0.18 (95% CrI: 0.10, 0.33) was considerable. The authors tested by meta-regression for potential modifiers and found no substantial influence. They conclude that 1) the GHR(d3) polymorphism inheritance is codominant, contrasting with previous reports; 2) GHR(d3) genotypes account for modest increases in rhGH effects in children; and 3) considerable unexplained variability in responsiveness remains.

Predicting response to growth hormone treatment

Despite extensive experience over the past 25 y in managing growth failure with growth hormone (rhGH), predicting treatment efficacy in individual children remains a challenge. In this paper, the authors present the methods that are currently available to clinicians for predicting the growth response, and other more sophisticated techniques which have the potential to pave the way for individualised therapy in the future.

IV. Growth Failure in Institutionalized Children

Children within institutional care settings experience significant global growth suppression, which is more profound in children with a higher baseline risk of growth impairment (e.g., low birth weight [LBW] infants and children exposed to alcohol in utero). Nutritional insufficiencies as well as suppression of the growth hormone-insulin-like growth factor axis (GH-IGF-1) caused by social deprivation likely both contribute to the etiology of psychosocial growth failure within these settings. Their relative importance and the consequent clinical presentations probably relate to the age of the child. While catch-up growth in height and weight are rapid when children are placed in a more nurturing environment, many factors, particularly early progression through puberty, compromise final height. Potential for growth recovery is greatest in younger children and within more nurturing environments where catch-up in height and weight is positively correlated with caregiver sensitivity and positive regard. Growth recovery has wider implications for child well-being than size alone, because catch-up in height is a positive predictor of cognitive recovery as well. Even with growth recovery, persistent abnormalities of the hypothalamic-pituitary-adrenal system or the exacerbation of micronutrient deficiencies associated with robust catch-up growth during critical periods of development could potentially influence or be responsible for the cognitive, behavioral, and emotional sequelae of early childhood deprivation. Findings in growth-restricted infants and those children with psychosocial growth are similar, suggesting that children experiencing growth restriction within institutional settings may also share the risk of developing the metabolic syndrome in adulthood (obesity, Type 2 diabetes mellitus, hypertension, heart disease). Psychosocial deprivation within any care-giving environment during early life must be viewed with as much concern as any severely debilitating childhood disease.

The exon 3-deleted growth hormone receptor: molecular and functional characterization and impact on GH/IGF-I axis in physiological and pathological conditions

The GH receptor (GHR) plays a key role in the the function of the GH/IGF-I axis and is the major effector of human growth. A common polymorphic variant consisting of genomic exon 3 deletion or retention (d3-GHR and full-length GHR, respectively), described in 2000, has been linked with increased receptor activity due to enhanced signal transduction. Subsequent pharmacogenetic studies have addressed a possible role of GHR polymorphism on the response to recombinant human GH treatment first in short children and then in adults, many of them suggesting that growth response to GH may be influenced, at least in some aspects, by this polymorphism. Similar studies, performed in patients with acromegaly, assumed an influence of the d3- GHR variant in the relationship between GH and IGF-I levels. More recently, some studies have investigated the relation between GHR genotype and treatment with the GHR antagonist pegvisomant, suggesting a better clinical response to therapy related to d3-GHR genotype. This review provides a summary of the main pharmacogenetic studies performed on this current and still open topic.

Common polymorphisms in the GH/IGF-1 axis contribute to growth in extremely tall subjects

CONTEXT/OBJECTIVE

The growth hormone (GH)/insulin-like growth factor-1(IGF-1) axis is the key regulator of somatic growth in humans and its genes are plausible candidates to study the genetics of height variation. Here, we studied polymorphic variation in the GH/IGF-1 axis in the extremely tall Dutch.

METHODS

Case-control study of 166 tall cases with height >2 SDS and 206 controls with normally distributed height <2 SDS. Excluded were subjects with endocrine disorders or growth syndromes. We analyzed genomic DNA at 7 common polymorphisms in the GH-1, GH receptor (GHR), IGF-1 and IGFBP-3 genes.

RESULTS

The association of the GH-1 1663 SNP with tall stature approached statistical significance, with the T-allele more present in the tall (allele frequency (AF): 0.44 vs. 0.36; p=0.084). Moreover, haplotype frequencies at this locus were significantly different between cases and controls, with the GGT haplotype most commonly seen in cases (p=0.01). Allele frequencies of GHR polymorphisms were not different. For the IGF-1 CA-repeat we observed a higher frequency of homozygous 192-bp carriers among tall males compared to control males (AF: 0.62 vs. 0.55; p=0.02). The IGFBP-3 -202 C-allele occurred more frequently in cases than in controls (AF: 0.58 vs. 0.50; p=0.002). Within cases, those carrying one or two copies of the -202 C-allele were significantly taller than AA genotype carriers (AC, p=0.028 and CC, p=0.009). Serum IGFBP-3 levels were highest in AA genotype carriers, the -202 SNP explained 5.8% of the variation.

CONCLUSION

Polymorphic variation in the GH-1, IGF-1 and IGFBP-3 genes is associated with extremely tall stature. In particular, the IGFBP-3 -202 SNP is associated not only with being very tall but also with height variation within the tall.

IV. Growth Failure in Institutionalized Children

Children within institutional care settings experience significant global growth suppression, which is more profound in children with a higher baseline risk of growth impairment (e.g., low birth weight [LBW] infants and children exposed to alcohol in utero). Nutritional insufficiencies as well as suppression of the growth hormone-insulin-like growth factor axis (GH-IGF-1) caused by social deprivation likely both contribute to the etiology of psychosocial growth failure within these settings. Their relative importance and the consequent clinical presentations probably relate to the age of the child. While catch-up growth in height and weight are rapid when children are placed in a more nurturing environment, many factors, particularly early progression through puberty, compromise final height. Potential for growth recovery is greatest in younger children and within more nurturing environments where catch-up in height and weight is positively correlated with caregiver sensitivity and positive regard. Growth recovery has wider implications for child well-being than size alone, because catch-up in height is a positive predictor of cognitive recovery as well. Even with growth recovery, persistent abnormalities of the hypothalamic-pituitary-adrenal system or the exacerbation of micronutrient deficiencies associated with robust catch-up growth during critical periods of development could potentially influence or be responsible for the cognitive, behavioral, and emotional sequelae of early childhood deprivation. Findings in growth-restricted infants and those children with psychosocial growth are similar, suggesting that children experiencing growth restriction within institutional settings may also share the risk of developing the metabolic syndrome in adulthood (obesity, Type 2 diabetes mellitus, hypertension, heart disease). Psychosocial deprivation within any care-giving environment during early life must be viewed with as much concern as any severely debilitating childhood disease.

Different relationships between the first 2 years on growth hormone treatment and the d3-growth hormone receptor polymorphism in short small-for-gestational-age (SGA) children

BACKGROUND

There has been controversy in recent years on whether the d3 polymorphism of the GH receptor is associated with a better growth response to GH in idiopathic short children born small for gestational age (SGA).

METHODS

In this prospective study, we evaluated exon 3-GHR polymorphisms in 142 (62 f, 80 m) short prepubertal children born SGA (birth length and/or weight of ≤-2 SD for GA) and treated with rhGH (mean dose of 0·30 mg/kg/week) in 24 centres in Germany. A growth prediction for the first year of therapy was calculated for each child according to Ranke and co-workers. The index of responsiveness (IOR) was calculated by dividing the response (observed growth minus predicted growth) by the standard error of the prediction. All analyses were performed in one centre on samples collected and shipped on filter paper. The DNA fragment containing or missing exon 3 of the GHR was amplified by multiplex PCR.

RESULTS

The fl-GHR isoform was most common with a frequency of 47·8%, followed by the d3/fl isoform with 38% and the d3-GHR isoform with 14·2%. There were no significant differences regarding gestational age, birth weight and birth length, mid parental height-SDS, chronological age at start of therapy, height-SDS, BMI-SDS, height velocity and GH dose between the different subgroups according to the genotype. After the first treatment year, height (H)-SDS (P < 0·05), height velocity (HV) (P < 0·01), HV-SDS (P < 0·001) and delta-H-SDS (P < 0·05) were significantly higher in patients with d3-GHR than in those with fl-GHR. The mean IOR was above 0 in children with at least one d3 allele, and highest, with 0·54, in those with the d3-GHR isoform. After the second year on GH, no differences between the different GHR-isoforms were found.

CONCLUSIONS

According to our results, the exon 3-deleted GHR explains the better growth response to GH only for the first and not for the second year.

Correlation of fl/d3 polymorphism of growth hormone receptor with the first- and second-year response to recombinant human growth hormone therapy in pre-pubertal Greek children with idiopathic isolated growth hormone deficiency

BACKGROUND

fl/d3 polymorphism in human GH receptor was correlated with the response to GH therapy in different groups of children with short stature.

AIM

This is a 2-yr retrospective study which evaluates the influence of fl/d3 polymorphism to the 1st-and 2nd-year response to GH replacement therapy in Greek children with isolated GH deficiency (GHD).

SUBJECTS AND METHODS

A total number of 195 pre-pubertal Greek children were studied (121 controls and 74 patients with GH peak <10 ng/ml). Patients with deficiency were treated with exogenous GH at a mean dose of 28.8 μg/kg.d. Multiplex PCR was used to genotype all children for fl/d3 polymorphism, followed by statistical analysis. The main parameters which were used to assess the association of genotype with the response to GH replacement were height SD score (SDS), height gain SDS, and growth velocity (GV) expressed as cm/yr and SDS.

RESULTS

Our results revealed that the frequency of d3-homozygosity in the Greek population was 8.26%. No association was detected between the presence or abcense of GHD and genotype. Moreover, no connection between genotype and sex was observed. First-year height SDS, height gain SDS, and GV SDS were significantly higher in d3-carriers (p<0.05). However, this difference did not appear in the 2nd year of treatment.

CONCLUSIONS

In our study, the d3-polymorphism seems to be associated with a higher efficacy to GH replacement, at least at the beginning of the treatment.

The distribution of exon 3-deleted/full-length growth hormone receptor polymorphism in the Turkish population

OBJECTIVE

The exon 3-deleted/full-length (d3/fl) growth hormone receptor (d3/fl-GHR) polymorphism has been associated with responsiveness to GH therapy in some children and also with adult height variation in the general population. We aimed to evaluate the distribution of d3/fl-GHR polymorphism in a Turkish population.

METHODS

The study included 477 (54 females/423 males) healthy adults with a mean±SD age of 31.1±9.0 years (range: 18-57). Height and body mass index (BMI) were expressed as standard deviation score (SDS) according to national standards. All adults had normal height and BMI SDSs (between -2 and +2). GHR exon 3 isoforms were studied by simple multiplex polymerase chain reaction method. Insulin-like growth factor-1 (IGF-1) and IGF-binding protein-3 (IGFBP-3) values were also measured and expressed as SDS.

RESULTS

The distribution of the GHR exon 3 genotypes in the Turkish healthy adults was 35% (n=167) for fl/fl, 39% (n=186) for fl/d3, and 26% (n=124) for d3/d3. There was no difference between genders in GHR exon 3 genotypes. Frequencies of fl allele and d3 allele were 54.5% and 45.5%, respectively. There were no differences in height SDS and BMI SDS among the three d3/fl-GHR genotype groups. There was a significant difference in IGFBP-3 SDS between fl/fl and fl/d3 groups (p=0.022).

CONCLUSIONS

This study presents the results of GHR polymorphism in a Turkish population as a reference for further studies. The distribution was similiar to European populations. There were no correlations between GHR isoforms and height SDS or other clinical/biochemical characteristics of the individuals except for higher IGFBP-3 levels in the fl/d3 group as compared to the fl/fl group. Whether this finding implies an abnormality, needs further investigation.

Uniparental disomies 7 and 14

Normally, one inherits one chromosome of each pair from one parent and the second chromosome from the other parent. Uniparental disomy (UPD) describes the inheritance of both homologues of a chromosome pair from the same parent. The biological basis of UPD syndromes is disturbed genomic imprinting. The consequences of UPD depend on the specific chromosome/segment involved and its parental origin. Phenotypes range from unapparent to unmasking of an autosomal-recessive disease to presentation as a syndromic imprinting disorder. Whilst paternal UPD(7) is clinically unapparent, maternal UPD(7) is one of several causes of Silver-Russell syndrome. Presentation of paternal UPD(14) ("Kagami syndrome") is a thoracic dysplasia syndrome with mental retardation and limited survival. Findings in maternal UPD(14) ("Temple") syndrome show an age-dependent overlap with the well-known maternal UPD(15) (Prader-Willi) syndrome and are dominated by initial failure to thrive followed by obesity, learning difficulties and precocious puberty. Diagnostic strategies to tackle the genetic heterogeneity of UPD(7) and UPD(14) syndromes will be explained. Management issues in UPD(7) and UPD(14) patients will be discussed, and finally areas requiring further research will be outlined.

Should short children born small for gestational age with a distance to target height <1 standard deviation score be excluded from growth hormone treatment?

CONTEXT

The criteria for starting growth hormone (GH), an approved treatment for short children born small for gestational age (SGA), differ between Europe and the USA. One European requirement for starting GH, a distance to target height (DTH) of > or =1 standard deviation score (SDS), is controversial.

OBJECTIVE

To investigate the influence of DTH on growth during GH treatment in short SGA children and to ascertain whether it is correct to exclude children with a DTH <1 SDS from GH.

PATIENTS

A large group of short prepubertal SGA children (baseline n = 446; 4 years GH n = 215).

MEASUREMENTS

We analysed the prepubertal growth response during 4 years of GH. We investigated the influence of the continuous variable DTH SDS on growth response and a possible DTH SDS cut-off level below which point the growth response is insufficient.

RESULTS

Height gain SDS during 4 years of GH showed a wide variation at every DTH SDS level. Multiple regression analyses demonstrated that, after correction for other significant variables, an additional DTH of 1 SDS resulted in 0.13 SDS more height gain during 4 years of GH. We found no significant differences in height gain below and above certain DTH SDS cut-off levels.

CONCLUSIONS

DTH SDS had a weak positive effect on height gain during 4 years of GH, while several other determinants had much larger effects. We found no support for using any DTH cut-off level. Based on our data, excluding children with a DTH <1 SDS from GH treatment is not justified.

d3-GHR genotype does not explain heterogeneity in GH responsiveness in hypopituitary adults

OBJECTIVE

Heterogeneity in growth hormone (GH) responsiveness in adult hypopituitary patients receiving recombinant human GH (rhGH) is poorly understood; doses vary up to fourfold between individuals. Deletion of exon 3 in the GH receptor (d3-GHR) has been linked to enhanced rhGH responsiveness in children. We investigated the role of the d3-GHR polymorphism in determining adult rhGH responsiveness.

METHODS

One hundred and ninety-four patients treated with an identical rhGH dosing protocol in a single centre were genotyped for the d3-GHR, and the results correlated with changes in serum IGF-I and clinical parameters of GH responsiveness after 6 and 12 months of GH replacement therapy.

RESULTS

Allele frequencies for homozygous full length (fl/fl), heterozygous d3 (fl/d3) and homozygous d3 (d3/d3) were 52%, 38.7% and 9.3%, respectively, and were in Hardy-Weinberg equilibrium. Baseline IGF-I and DeltaIGF-I at 6 months were comparable between groups. DeltaIGF-I at 12 months was significantly greater in the d3/d3 group (P = 0.028). No difference was detected between fl/d3 and fl/fl groups. Regression analyses of DeltaIGF-I at 12 months and DeltaIGF-I/rhGH dose confirmed a significant relationship of d3/d3 genotype on rhGH response. There was no difference between groups in maintenance rhGH dose between genotypes.

CONCLUSION

Homozygosity for d3-GHR confers a marginal increase in GH responsiveness at 12 months but without a detectable change in maintenance rhGH dose required. Both d3 alleles are required to achieve this response; given that only 10% of the population are d3 homozygotes, the d3GHR does not explain the marked heterogeneity of GH responsiveness in hypopituitary adults.

Rapid and high throughput genotyping of the growth hormone receptor exon 3 deleted/full-length polymorphism using a tagSNP

OBJECTIVE

The growth hormone (GH) receptor (GHR) exon 3 deleted/full-length (d3/fl) polymorphism has been suggested to affect GH sensitivity. The conventional genotyping method used for this polymorphism (multiplex PCR with fragment detection by gel electrophoresis) is laborious and requires large amount of DNA template. This has restricted analysis of this polymorphism to small cohorts. Our aim was to evaluate the accuracy of using a tagging single nucleotide polymorphism (tagSNP) as a marker for the d3/fl polymorphism.

DESIGN

The d3/fl polymorphism was analyzed using TaqMan SNP genotyping of the tagSNP rs6873545 in 183 patients with adult GH deficiency (GHD). The results were compared to d3/fl genotypes determined by the conventional method.

RESULTS

Genotyping success rate for the tagSNP was 100%. Frequency of the d3-allele was 24.0% (d3/d3 7.7%, d3/fl 32.2% and fl/fl 60.1%) and the results from the two different methods were identical. Moreover, three samples previously undetermined when genotyped using the conventional method were successfully analyzed using the tagSNP.

CONCLUSION

The GHR d3/fl polymorphism can be studied by TaqMan SNP genotyping. Use of the tagSNP facilitates investigations of the effects of the d3/fl polymorphism in large cohorts.

d3-Growth hormone receptor polymorphism in acromegaly: effects on metabolic phenotype

OBJECTIVE

A common polymorphic variant of the growth hormone receptor (GHR) is because of genomic deletion of exon 3 and has been linked with increased responsiveness to exogenous GH. The impact of this polymorphism in acromegaly, a disease characterized by endogenous excess of GH and partial loss of IGF-I feedback on tumoural GH secretion, is not clear. The aim of this study was to investigate possible influences of d3GHR on the GH/IGF-I relationship and metabolic parameters in acromegaly.

DESIGN AND METHODS

Retrospective study on 76 acromegalic patients. Genotype analysis was carried out on leucocyte DNA by multiplex PCR assay. Clinical, hormonal and biochemical parameters at diagnosis were collected from patients' medical records.

RESULTS

Forty-two patients (55.3%) were homozygotes for the allele encoding the full-length GHR (fl/flGHR), 27 patients were heterozygotes (fl/d3) and seven homozygotes (d3/d3) for the genomic deletion of exon 3. Heterozygotes and homozygotes for the d3 allele were considered together (d3GHR) and compared with fl/flGHR patients. d3GHR and fl/flGHR patients showed no difference in GH and IGF-I levels or in the relationship between these two parameters. Patients bearing d3GHR had a lower body mass index (BMI) than patients bearing fl/flGHR (25.8 +/- 2.1 vs. 28.1 +/- 4.8 kg/m(2), P < 0.05). Diabetes mellitus and hypertension were equally distributed, but more d3GHR patients had a normal glucose tolerance (66.7%vs. 56.3%, P < 0.05). The presence of d3GHR allele, and not BMI or age, was a significant negative predictor of insulin levels 120 min after oral glucose load (beta = -80.8, P < 0.05).

CONCLUSIONS

This study supports the hypothesis that the d3GHR is functionally different from the fl/fl variant mostly for the effects on body weight regulation and on glucose metabolism.

The growth hormone receptor (GHR) polymorphism in growth-retarded children with Cushing disease: lack of association with growth and measures of the somatotropic axis

Pediatric Cushing disease (CD) often presents with short stature, but we have observed significant inter-individual variability in the growth delay caused by endogenous hypercortisolism. Glucocorticoids cause growth retardation by affecting the growth hormone (GH) - insulin-like growth factor-1 (IGF 1) somatotropic axis, but also other, GH-independent sites. Recently, the GH receptor (GHR) gene was found to have a common polymorphism (P) that leads to a deletion (d3) or retention of exon 3. In this study, we tested the hypothesis that the GH receptor polymorphism (GHR-P) maybe one of the significant variants that determines the degree of growth delay among patients with CD. GHR genotyping was performed on 56 children with newly diagnosed CD (24 females, 32 males, mean age of 12.9+/-3.3 years) who were followed at our institution between the years 1997-2007. Correlation analysis included genotype, measures of growth and the somatotropic axis, and anthropometrics. Within the group, 31 (12 girls, 19 boys) expressed the full length GHR allele, 10 (4 girls, 6 boys) were d3-GHR homozygotes and 15 (7 girls, 8 boys) were d3-GHR heterozygotes. No significant differences were found between the GHR genotypes and patient's height and/or growth velocity, or any other measures that we evaluated. The presence of a well-studied and common GHR polymorphism does not appear to be responsible for the variability of growth delay observed in patients with Cushing disease.

The common exon 3 polymorphism of the growth hormone receptor gene and the effect of growth hormone therapy on growth in Korean patients with Turner syndrome

OBJECTIVE

Recombinant human growth hormone (GH) can achieve final adult height gain in girls with Turner syndrome (TS), but its efficacy varies widely across individuals. The exon 3-deleted polymorphism of growth hormone receptor (d3-GHR) has been reported to be associated with responsiveness to GH therapy. The short-term growth response of Turner patients to GH therapy was analysed according to their GHR-exon 3 polymorphism genotype.

DESIGN AND PATIENTS

This was a retrospective study of 175 TS patients. Auxological and endocrine parameters were measured, and the GHR-exon 3 genotype was analysed. Allelic frequencies of GHR-exon 3 genotype were compared between patients with TS and control individuals. GH had been administered to 147 patients, 115 of which remained pre-pubertal after the first follow-up year. Changes in height standard deviation score (SDS), height velocity (HV), body mass index (BMI), IGF-1 and IGF binding protein-3 (IGFBP-3) concentrations were compared between these patients, grouped according to genotype, after the first follow-up year.

RESULTS

There was no difference in GHR-exon 3 genotype frequency between the TS and control groups of Koreans. According to the GHR-exon 3 genotype (fl/fl group vs. d3/fl and d3/d3 group), HV gain and height SDS gain did not differ significantly at the first year of GH therapy. Moreover, changes in IGF-1, IGFBP-3 concentration and BMI showed no significant difference between the groups with and without d3-GHR after 1 year of GH therapy.

CONCLUSION

The distribution of the GHR-exon 3 genotype was similar in the TS and control groups in a Korean population. The growth promotion efficacy of GH therapy did not differ significantly between TS patients with and without the d3-GHR allele. These findings indicate that the GHR-exon 3 genotype may not be a major factor to affect the GH response in Korean Turner patients.

Impact of the exon 3-deleted growth hormone (GH) receptor polymorphism on baseline height and the growth response to recombinant human GH therapy in GH-deficient (GHD) and non-GHD children with short stature: a systematic review and meta-analysis

CONTEXT

The exon-3 deleted GH receptor (GHR(d3)) polymorphism is associated with an increased growth response to recombinant human GH (rhGH) therapy in some, but not all, studies in GH-deficient (GHD) and non-GHD children with short stature.

OBJECTIVE

The aim of the study was to assess the effects of GHR(d3) on baseline height and the first year's growth response to rhGH treatment in prepubertal GHD and non-GHD children with short stature.

DESIGN

We conducted a systematic review and meta-analysis.

METHODS

Fifteen studies reporting the effect of GHR(d3) on growth parameters were included. Principal outcomes were baseline height sd score (SDS) and the weighted average of change in growth velocity (Delta cm/yr) and height gain (Delta height SDS) after 1 yr of rhGH.

RESULTS

In GHD, not in non-GHD, baseline height SDS was 0.159 sd higher [95% confidence interval (CI), 0.020, 0.298] in GHR(d3) compared with GHR(wt-wt). In GHR(d3), rhGH therapy resulted in a higher increase in growth velocity (0.521 cm/yr; 95% CI, 0.196, 1.015) and height gain (0.075 sd; 95% CI, 0.007, 0.143) compared with GHR(wt-wt). Meta-regression demonstrated a larger difference between GHR(d3) and GHR(wt-wt) in studies using lower rhGH doses and carried out at a higher age, independently of the cause of short stature.

CONCLUSIONS

This meta-analysis in prepubertal children with short stature indicates that GHR(d3) is associated with increased baseline height in GHD, but not in non-GHD. Furthermore, GHR(d3) stimulates growth velocity by an additional effect of approximately 0.5 cm during the first year of rhGH treatment, and this effect is more pronounced at lower doses of rhGH and higher age.

Association of the exon 3 deleted/full-length GHR polymorphism with recombinant growth hormone dose in growth hormone-deficient adults

Aims: Contradictory reports exist regarding the influence of the exon 3 deleted (d3)/full-length (fl) growth hormone receptor (GHR) polymorphism on responsiveness to recombinant human growth-hormone therapy in idiopathic short stature, small for gestational age and GH-deficient children, Turner syndrome patients and GH-deficient adults. In some of these studies, the d3 allele was associated with increased responsiveness to GH. The aim of this study was to test this association in a group of GH-deficient adult patients receiving recombinant GH treatment. Materials & methods: Patients were derived from the prospective German Pfizer International Metabolic Study (KIMS) Pharmacogenetics Study. The GHRd3/fl polymorphism was determined in 133 German adult patients (66 men and 67 women; mean age: 45.4 years ± 13.1 standard deviation; majority Caucasian) with a GH-deficiency of different origin. Patients received GH treatment for 12 months with a finished dose-titration of GH and standardized insulin-like growth factor (IGF)-1 measurements in one central laboratory. GH dose after 1 year of treatment, IGF-1 serum concentrations, IGF-1 standard deviation score (SDS) values and anthropometric data were analyzed by GHRd3/fl genotypes. Results: After 1 year of GH treatment, the individually required GH dose was significantly lower in GH-deficient patients carrying one or two d3 alleles, compared with patients with the full-length receptor (p = 0.04). Genotype groups (d3-allele carriers vs noncarriers) showed no significant differences in IGF-1 serum concentrations (p = 0.51), IGF-1 SDS (p = 0.36) nor in gender (p = 0.53), age (p = 0.28), weight (p = 0.13), height (p = 0.53) or BMI (p = 0.15). Conclusion: The d3-allele carriers required approximately 25% less exogenous GH compared with the homozygous fl-allele carriers, which may express an increased responsiveness to exogenous GH. Variability of the individually required GH dose in adult GH-deficient patients may therefore be partly due to the GHRd3/fl polymorphism. Further studies are required to confirm these results.

Influence of the exon 3-deleted/full-length growth hormone (GH) receptor polymorphism on the response to GH replacement therapy in adults with severe GH deficiency

CONTEXT

There is considerable individual variation in the clinical response to GH replacement therapy in GH deficient (GHD) adults. Useful predictors of treatment response are lacking.

OBJECTIVE

The aim of the study was to assess the influence of the exon 3-deleted (d3-GHR) and full-length (fl-GHR) GH receptor isoforms on the response to GH replacement therapy in adults with severe GHD.

DESIGN AND PATIENTS

A total of 124 adult GHD patients (79 men; median age, 50 yr) were studied before and after 12 months of GH therapy. GHD patients were divided into those bearing fl/fl alleles (group 1) and those bearing at least one d3-GHR allele (group 2), and the genotype was related to the effects of GH therapy on IGF-I levels and total body fat (BF).

INTERVENTION

GH dose was individually titrated to obtain normal serum IGF-I levels.

MAIN OUTCOME MEASURES

GHR genotype was determined by PCR amplification, IGF-I levels by immunoassay, and BF by a four-compartment model.

RESULTS

Seventy-two (58%) patients had fl/fl genotype and were classified as group 1, whereas 52 (42%) had at least one d3-GHR allele and were classified as group 2 (40 were heterozygous and 12 were homozygous). At baseline, there were no significant differences in the study groups. Changes in IGF-I and BF after 12 months of GH treatment did not differ significantly between the two genotype groups.

CONCLUSION

The presence of d3-GHR allele did not influence the response to GH replacement therapy in our cohort of adults with severe GHD.

Growth hormone (GH1) gene variation and the growth hormone receptor (GHR) exon 3 deletion polymorphism in a West-African population

Among Europeans, functionally significant GH1 gene variants occur not only in individuals with idiopathic growth hormone (GH) deficiency and/or short stature but also fairly frequently in the general population. To assess the generality of these findings, 163 individuals from Benin, West Africa were screened for mutations and polymorphisms in their GH1 genes. A total of 37 different sequence variants were identified in the GH1 gene region, 24 of which occurred with a frequency of >1%. Although four of these variants were novel missense substitutions (Ala13Val, Arg19His, Phe25Tyr and Ser95Arg), none of these had any measurable effect on either GH function or secretion in vitro. Some 37 different GH1 promoter haplotypes were identified, 23 of which are as yet unreported in Europeans. The mean in vitro expression level of the GH1 promoter haplotypes observed in the African population was significantly higher than that previously measured in Britons (p<0.001). A gene conversion in the GH1 promoter, previously reported in a single individual of British origin, was found to occur at polymorphic frequency (5%) in the West-African population and was associated with a 1.7-fold increase in promoter activity relative to the wild-type. The d3 allele of the GHR exon 3 deletion polymorphism, known to be associated with increased GH responsiveness, was also found to occur at an elevated frequency in these individuals from Benin. We speculate that both elevated GH1 gene expression and increased GHR-mediated GH responsiveness may constitute adaptive responses to the effects of scarce food supply in this West-African population since increased circulating GH appears to form part of a physiological response to nutritional deprivation.

Growth hormone treatment for short stature in children born small for gestational age

Children born small for gestational age (SGA) who do not show catch-up in the first 2 years generally remain short for life. Although the majority of children born SGA are not growth hormone (GH) deficient, GH treatment is known to improve average growth in these children.Early studies using GH in children born SGA demonstrated increased height velocity, but these effects tended to be short-term with effects decreasing when GH treatment stopped. With refined GH regimens, significant effects on height have been shown, with gains of approximately 1 standard deviation score after 2 years. Studies have also shown that long-term continuous GH therapy can significantly increase final height to within the normal range. GH treatment of children born SGA does not appear to unduly affect bone age or pubertal development. Growth prediction models have been used to identify various factors involved in the response to GH therapy with age at start, treatment duration, and GH dose showing strong effects. Genetic factors such as the exon 3 deletion of the GH receptor may contribute to short stature of children born SGA and may also be involved in the responsiveness to GH treatment, but there remain other unknown genetic and/or environmental factors. No unexpected safety concerns have arisen in GH therapy trials. In particular, no long-term adverse effects have been seen for glucose metabolism, and positive effects have been shown for lipid profiles and blood pressure.GH treatment in short children born SGA has shown a beneficial, growth-promoting effect in both the short-and long-term, and has become a recognized indication in both the US and Europe. Further studies on individualized treatment regimens and long-term safety are ongoing.

The exon 3-deleted/full-length growth hormone receptor polymorphism does not influence the effect of puberty or growth hormone therapy on glucose homeostasis in short non-growth hormone-deficient small-for-gestational-age children: results from a two-year controlled prospective study

CONTEXT

The exon 3-deleted/full-length (d3/fl) GH receptor polymorphism (d3/fl-GHR) has been associated with responsiveness to GH therapy in short small-for-gestational-age (SGA) patients, although consensus is lacking. However, its influence on glucose homeostasis, at baseline or under GH therapy, has not been investigated.

OBJECTIVE

Our objective was to evaluate whether the d3/fl-GHR genotypes influence insulin sensitivity in short SGA children before or after puberty onset or during GH therapy.

DESIGN

We conducted a 2-yr prospective, controlled, randomized trial.

SETTING

Thirty Spanish hospitals participated. Auxological, GH secretion, and glucose homeostasis evaluation was hospital based, whereas molecular analyses and data computation were centralized.

PATIENTS

Patients included 219 short SGA children [body mass index sd score (SDS) < or = 2.0]; 159 were prepubertal (group 1), and 60 had entered puberty (group 2).

INTERVENTION

Seventy-eight patients from group 1 were treated with GH (66 microg/kg.d) for 2 yr (group 3).

MAIN OUTCOME MEASURES

Previous and 2-yr follow-up auxological and biochemical data were recorded, d3/fl-GHR genotypes determined, and data analyzed.

RESULTS

In groups 1 and 2, fasting glucose, insulin, homeostasis model assessment (HOMA), and quantitative insulin sensitivity check index (QUICKI) were similar in each d3/fl-GHR genotype. Group 2 glucose, insulin, and HOMA were significantly higher and QUICKI lower than in group 1. In group 3 GH-treated patients, height SDS, growth velocity SDS, fasting glucose, insulin, and HOMA significantly increased as did body mass index SDS at the end of the second year, and QUICKI decreased during the first and second years, with no differences among the d3/fl-GHR genotypes.

CONCLUSION

In short SGA patients, the d3/fl-GHR genotypes do not seem to influence prepubertal or pubertal insulin sensitivity indexes or their changes over 2 yr of GH therapy (66 mug/kg.d).

[Growth hormone therapy for short children born small for gestational age]

Approximately 10% of all children born small for gestational age (SGA) fail to achieve sufficient catch-up growth and remain with short stature throughout childhood and adult life. Abnormalities of the GH/IGF-1 axis are not always identified. Several studies have demonstrated that GH is an effective and well-tolerated therapy and most children will reach a normal adult height. In this review, it can be seen the encouraging results of GH treatment in growth-retarded children born SGA highlighting the benefits of early treatment.

GH receptor d3 polymorphism in Dutch patients with MPHD and IGHD born small or appropriate for gestational age

OBJECTIVE

GH acts through the GH receptor (GHR). The GHR gene contains a genetic polymorphism caused by a deletion of exon 3 (d3), with high frequency in the normal population. There is a continuing controversy whether the presence or absence of the exon 3 deletion (d3+ vs. d3-) affects the effect of GH in human growth.

DESIGN, PATIENTS AND MEASUREMENTS

For 144 patients with idiopathic isolated GH deficiency (IGHD, n = 72) or multiple pituitary hormone deficiency (MPHD, n = 72), amplification of the region around exon 3 of the GHR gene was performed. Clinical data and response to GH treatment were compared between GHR d3+and d3- IGHD and MPHD patients born either small for gestational age (SGA) or appropriate for gestational age (AGA).

RESULTS

IGHD patients born SGA had a significantly higher d3+frequency (82%) than IGHD patients born AGA (35%, P = 0.006). Within the group of IGHD patients born SGA, d3- patients showed a slightly better spontaneous catch up growth before start of GH treatment than d3+ patients (1.1 +/- 1.1 SD vs. 0.6 +/- 1.1 SDS, P = 0.040) There was no difference in patients first year's response to GH treatment between GHR d3+ and d3- patients.

CONCLUSIONS

In IGHD and MPHD patients, response to GH treatment was independent of GHR genotype. GHR-d3 was significantly more frequent among IGHD patients born SGA. As we are the third to report an association between birth size and GHR d3 status, it is conceivable that the GHR-d3 might affect prenatal growth in IGHD patients by a yet unknown mechanism.

Individualization of growth hormone therapy

Short children born small for gestational age account for 20% of patients with short stature. These children should be investigated individually to identify treatable causes of their short stature and any associated neurodevelopmental problems. Randomized controlled growth hormone therapy trials demonstrate growth acceleration in childhood and improved adult height. The individualization of therapy is increasingly possible with insight from the available prediction models. These identify the main modifiable factors such as dose of growth hormone and age at the start of therapy. Non-modifiable factors including target height standard deviation score (SDS), weight SDS at the start of therapy, and first year response to therapy also play a significant role.