The presence of the d3-growth hormone receptor polymorphism is negatively associated with fetal growth but positively associated with postnatal growth in healthy subjects

A common deletion in the growth hormone receptor gene (d3-GHR) in the offspring is related to maternal placental GH levels during pregnancy

BACKGROUND

A common growth hormone receptor polymorphism with deletion of exon 3 (d3-GHR) has previously been linked to increased postnatal growth on the one hand and decreased fetal growth on the other. Regulation of fetal growth is positively dependent on secretion of placental GH (hGH-V).

OBJECTIVE

We explored the effect of the fetal d3-GHR genotype on maternal serum levels of hGH-V and fetal growth. The cellular localization of hGH-V synthesis and the GH receptors were determined in normal placentas.

METHODS

43 healthy mother-child pairs were examined during pregnancy with measurements of hGH-V during third trimester, and serial ultrasound measurements determined fetal growth rate. Birth anthropometrics were obtained. The GHR genotype of the child was analysed postnatally. Immunohistochemical (IHC) analysis was conducted on four placentas.

RESULTS

The presence of the d3-GHR genotype was associated with a markedly reduced concentration of hGH-V in maternal serum (β -0.52, SE 0.24, p = 0.04) compared to those who had a fl/fl genotype. Accordingly, a tendency towards reduced fetal growth rate during third trimester (β -25.8, SE 12.7, p = 0.05) and a lower birth weight were found among carriers of the d3-GHR allele, but these associations did not reach statistical significance (p = 0.08). IHC analysis showed expression of placental GH and GHR in the villous syncytiotrophoblast, the extravillous trophoblast, and the decidual cells and smooth muscle cells in chorionic vessels.

CONCLUSIONS

The presence of the d3-GHR polymorphism in the fetus was associated with lower maternal serum levels of hGH-V, decreased fetal growth rate in third trimester and lower birth weight compared to the wildtype.

MECHANISMS IN ENDOCRINOLOGY: Clinical and pharmacogenetic aspects of the growth hormone receptor polymorphism

Pharmacogenetics aims to maximize the beneficial effects of a medical therapy by identifying genetic finger prints from responders and non-responders and, thereby improving safety and efficacy profile of the drug. Most subjects who are deficient in growth hormone (GHD) are candidates for recombinant human GH (rhGH) therapy. To date, it is well established that even after adjustments for several clinical variables, such as age, gender, body composition and the age at onset of the GHD, response to rhGH treatment is highly variable among individuals, part of which is believed to be due to genetic factors within the GH system. As the first genetic variant to potentially influence the individual response to rhGH therapy in children with growth disorders, polymorphism in the GH receptor (GHR) has attracted a great interest as a target for pharmacogenetics. Studies have been conducted to compare the functional and molecular effects of the full-length GHR (fl-GHR) isoform with the exon 3 deleted (d3-GHR) isoform in children and adults treated with rhGH therapy. Additionally, the impact of the GHR polymorphism has been investigated in relation to the clinical status and response to medical treatment in acromegaly, especially to the GHR antagonist drug pegvisomant. We have performed a narrative review of the studies performed to date on the association of GHR polymorphism with rhGH response in children and adults, and its potential influence in the medical management of acromegaly. In addition, data from studies on the general population and in other chronic diseases examining a role of this genetic variant in the regulation of growth and metabolism are summarized.

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.

Cognitive ability in adolescents born small for gestational age: Associations with fetal growth velocity, head circumference and postnatal growth

BACKGROUND

Small size at birth may be associated with impaired cognitive ability later in life. The aim of this study was to examine the effect of being born small for gestational age (SGA), with or without intrauterine growth restriction (IUGR) on cognitive ability in late adolescence.

STUDY DESIGN

A follow-up study of a former cohort included 123 participants (52 males); 47 born SGA and 76 born appropriate for gestational age (AGA). Fetal growth velocity (FGV) was determined by serial ultrasound measurements during the third trimester. A control group matched for age and birthplace was included. The original Wechsler Adult Intelligence Scale (WAIS) was administered, and verbal, performance and full-scale Intelligence Quotient (IQ) scores were calculated.

RESULTS

There was no difference in IQ between adolescents born SGA and AGA. FGV or IUGR during the third trimester did not influence cognitive ability in late adolescence. Full-scale IQ was positively related to head circumference (HC) in adolescence (B: 1.30, 95% CI: 0.32-2.28, p=0.01). HC at birth and three months was positively associated with full-scale IQ. Catch-up growth in the group of SGA children was associated with a significantly increased height, larger HC, increased levels of insulin-like growth factor-I (IGF-I) and increased full-scale IQ compared to those born SGA without catch-up growth.

CONCLUSION

SGA and IUGR may not be harmful for adult cognitive ability, at least not in individuals born at near-term. However, known risk factors of impaired fetal growth may explain the link between early growth and cognitive ability in adulthood.

Rapid method for growth hormone receptor exon 3 delete (GHRd3) SNP genotyping from archival human placental samples

Analysis of archival samples from cohorts of pregnant women may be key to discovering prognosticators of stillbirth and pregnancy/perinatal complications. Growth hormone (GH) and its receptor (GHR) are pivotal in feto-placental development and pregnancy maintenance. We report a rapid, optimized method for genotyping the GHR full-length versus exon 3-deleted isoform (GHRd3). TaqMan single nucleotide polymorphism (SNP) genotyping proved superior to standard multiplex polymerase chain reaction (PCR) in allele detection and GHR genotyping from archived samples, including those with poor genomic deoxyribonucleic acid quality/quantity such as formalin fixed, paraffin embedded, blood, and serum. Furthermore, this assay is suitable for high through put 96 or 384-well plate quantitative PCR machines with automated genotype calling software. The TaqMan genotyping assay can increase the data obtained from precious archival human samples.

The growth hormone receptor exon 3-deleted/full-length polymorphism and response to growth hormone therapy in prepubertal idiopathic short children

OBJECTIVE

The primary aim of the study was to evaluate d3-GHR as a possible cause of increased GH sensitivity in children with delayed infancy-childhood transition (DICT). The secondary aim was to investigate the impact of the GHR exon 3 deleted/full-length (d3/fl) polymorphism on GH treatment response in prepubertal children classified as having idiopathic short stature (ISS).

DESIGN

Study subjects included 167 prepubescent longitudinally followed children classified as having ISS. Children were randomized to standard-dose GH treatment (33 μg kg(-1) day(-1)), to double-dose treatment (67 μg kg(-1) day(-1)), or to an untreated control group. Growth and metabolic outcome were evaluated at birth (n = 166), after one year of treatment (n = 59) and at adult height (n = 145). Genotyping of the GHR d3/fl polymorphism was performed using TaqMan SNP genotyping of tagSNP rs6873545.

RESULTS

Birth and early growth data did not reach the predetermined level of statistical significance for difference between genotypes. Growth and IGF-1 response after one year of GH treatment did not differ between genotypes. IGFBP-3SDS was higher in untreated d3-GHR carriers than in untreated fl/fl individuals, whereas there was insufficient evidence for higher IGFBP-3SDS in treated d3-GHR carriers. Genotype did not explain the growth response to treatment, and no differences in heightSDS, height gain, or difference in height to midparental heightSDS between genotype groups were found at adult height.

CONCLUSION

The common GHR d3/fl polymorphism is probably not a cause of DICT in children with ISS, and our results do not suggest that the d3-GHR genotype is associated with increased sensitivity to GH in children with ISS.

GH signaling in skeletal muscle and adipose tissue in healthy human subjects: impact of gender and age

OBJECTIVE

The mechanisms underlying the impact of age and gender on the GH-IGF1 axis remain unclear. We tested the hypothesis that age and gender have impacts on GH signaling in human subjects in vivo.

DESIGN

A total of 20 healthy non-obese adults ('young group'<30 years (5F/5M) and 'old group'>60 years (5F/5M)) were studied after: i) an i.v. GH bolus (0.5 mg) and ii) saline.

METHODS

Muscle and fat biopsies were obtained after 30 and 120 min. Total and phosphorylated STAT5B proteins, gene expression of IGF1, SOCS1, SOCS2, SOCS3 and CISH, body composition, VO2max, and muscle strength were measured.

RESULTS

In the GH-unstimulated state, women displayed significantly elevated levels of CISH mRNA in muscle (P=0.002) and fat (P=0.05) and reduced levels of IGF1 mRNA in fat. Phosphorylated STAT5B (pSTAT5b) was maximally increased in all subjects 30 min after GH exposure and more pronounced in women when compared with men (P=0.01). IGF1, SOCS1, SOCS2, SOCS3, and CISH mRNA expression increased significantly in muscle after 120 min in all subjects with no impact of age and gender. GH-induced pSTAT5b correlated inversely with lean body mass (LBM; r=-0.56, P=0.01) and positively with the CISH mRNA response (r=0.533, P=0.05).

CONCLUSION

i) GH signaling in muscle and fat after a single GH bolus in healthy human subjects is age independent, ii) we hypothesize that constitutive overexpression of CISH may contribute to the relative GH resistance in women, and iii) experimental studies on the impact of sex steroid administration and physical training on GH signaling in human subjects in vivo are required.

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.

Association between GH receptor polymorphism (exon 3 deletion), serum IGF1, semen quality, and reproductive hormone levels in 838 healthy young men

INTRODUCTION

GH activity may be involved in male reproductive function. A common genetic polymorphism in the gene encoding the GH receptor (GHR) results in deletion of the entire exon 3 sequence (GHRd3 isoform). The short GHRd3/d3 isoform seems more sensitive compared with full-length receptors (GHRfl/fl).

AIM

TO INVESTIGATE THE ASSOCIATIONS BETWEEN GH ACTIVITY, EVALUATED BY EXON 3 GHR POLYMORPHISM, AND SERUM IGF1 VS REPRODUCTIVE HORMONES, SEMEN QUALITY, AND PRE- AND POSTNATAL GROWTH IN HEALTHY YOUNG MALES (N=838, MEAN AGE: 19.4 years).

RESULTS

Compared with GHRfl/fl homozygous individuals (n=467) GHRd3/d3 homozygous individuals (n=69) tended to have larger semen volume (3.2 (2.4-4.3) vs 3.6 (2.6-4.7) ml, P=0.053) and higher serum inhibin-B levels (208 pg/ml (158-257) vs 227 pg/ml (185-264), P=0.050). Semen quality, levels of gonadotropins, testosterone, estradiol, sex hormone-binding globulin, and IGF1 were not associated with GHRd3 genotype. A twofold increase in serum IGF1 was associated with a 13% (4-23) increase in calculated free testosterone (P=0.004). By contrast IGF1 was inversely associated with serum inhibin-B (P=0.027), but showed no associations to semen quality. GHR genotype and serum IGF1 were not associated with size at birth or final height.

CONCLUSIONS

GHRd3 polymorphism seemed only to have a weak influence on male reproductive function of borderline significance. The sensitive GHRd3/d3 genotype may slightly increase testicular function, as evaluated by semen volume and levels of inhibin-B, but does not seem to influence Leydig cell steroidogenesis. GHR genotype did not influence pre- and postnatal growth.

The growth hormone receptor polymorphism in patients with acromegaly: relationship to BMI and glucose metabolism

The aim of this study was to investigate association between the frequencies of Growth Hormone receptor (d3GHR) gene polymorphisms and some clinical parameters of acromegalic patients. Total of 35 acromegalic patients were enrolled to study. The d3GHR polymorphism was identified by using polymerase chain reaction from peripheral blood samples. The levels of systolic and diastolic blood pressure, BMI, fasting plasma glucose (FPG), Fasting insulin, HOMA-IR, IGF-I, GH, IGFBP3, triglyceride, HDL and LDL cholesterol concentrations were evaluated. The frequencies of d3GHR genotypes were found as follows; 5 (14.3%) subjects had d3/d3, 11 (31.4%) had d3/fl and 19 (54.3%) had fl/fl in patients. The prevalence of the d3 and fl alleles was 30 and 70%, respectively. Systolic blood pressure, fasting insulin and HOMA-IR was found significantly increased in homozygote d3GHR genotype group compared to d3/fl subjects (P < 0.05). In addition, BMI was observed significantly different among three genotypes (P = 0.007) and in the subjects with d3/d3 genotype, BMI was found significantly higher than d3/fl and fl/fl genotypes groups. As well as, no significant difference was found between the d3 and fl alleles group in terms of the clinical parameters except for BMI (P = 0.002). It can be said that the d3GHR gene polymorphism may affect BMI, systolic blood pressure and insulin regulation. At the same time we can say homozygote d3GHR genotype and d3 allele carriers may have more risk than other genotypes for high BMI.

Serum IGF1 and insulin levels in girls with normal and precocious puberty

OBJECTIVE

IGF1 plays an important role in growth and metabolism during puberty. IGF1 levels are increased in girls with central precocious puberty (CPP). However, the relationship with insulin before and during gonadal suppression is unknown. In addition, the influence of the exon 3-deleted GH receptor gene (GHRd3) on IGF1 levels was evaluated.

DESIGN

Nine hundred and eleven healthy and 23 early pubertal girls (15 with CPP) participated and were evaluated by dual-energy X-ray absorptiometry (DXA) scans, fasting and oral glucose-stimulated insulin levels, IGF1 levels, and GHR genotyping. Fifteen girls with early puberty (13 with CPP) were treated with GNRH agonists and reevaluated after 3 and 12 months.

RESULTS

IGF1 and insulin levels were higher in girls with CPP compared with healthy controls after adjustment for age, bone age, and breast development (all P≤0.02). IGF1 levels were only significantly positively correlated with insulin levels in girls with CPP at baseline (P≤0.03). During gonadal suppression, changes in IGF1 levels were inversely associated with changes in insulin levels (P=0.04). The GHRd3/d3 genotype was associated with significantly higher IGF1 levels (P=0.01) but not with earlier pubertal timing in healthy girls. The distribution of the GHRd3 genotypes among girls with CPP did not differ significantly from healthy girls (P=0.2).

CONCLUSION

The increased IGF1 and insulin levels in girls with CPP may be causally interrelated. In addition, the GHRd3 allele positively influences IGF1 levels in a copy number-response relationship but not pubertal timing in healthy girls.

The growth hormone receptor gene deleted for exon three (GHRd3) polymorphism is associated with birth and placental weight

CONTEXT

Human growth hormone receptor (GHR) transcripts have two isoforms, full-length (GHRfl) or exon 3 deleted (GHRd3). An association of these isoforms has been found with small for gestational age (SGA) infants but does not influence adult height. The role of this polymorphism in the birth size spectrum in the general population is unclear.

OBJECTIVE

To determine the association of maternal and infants GHR exon 3 polymorphism with antenatal growth, birth size and early postnatal growth in two large, normal white European birth cohorts.

STUDY DESIGN

Pregnant women from white European families were recruited by the University College London Foetal Growth Study (n = 774) and the Moore normal pregnancy cohort (n = 274). GHR variants, wild-type (fl) and deleted for exon 3 (d3) were analysed using multiplex PCR.

RESULTS

There was a significant underrepresentation of infants wild-type fl/fl (36%) and overrepresentation of d3/d3 (14%) genotypes in the SGA infants within the cohorts (χ(2) = 11·2, P = 0·003, df = 2). Fl/fl was overrepresented in large for gestational age (LGA) infants (χ(2) = 6·1, P = 0·047, df = 2). There was a significant association of infants GHR isoforms with placental weight (P < 0·001) and birth weight standard deviation scores (P = 0·04) with the fl/fl genotype associated with a larger placental and birth weight. In multiple regression analysis, the GHR isoform type, maternal booking weight and parity influenced placental weight (R(2) = ·35; P < 0·001, df = 7). The GHR isoform type was not related to antenatal anthropometric measurements or growth in infancy.

CONCLUSION

These data suggest that the GHR isoforms are associated with placental and birth weight.

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.

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 gene is associated with small birth size and early pubertal onset in healthy boys

CONTEXT

The GH/IGF-I axis influences gonadal development and function. Recently, a deletion of exon 3 in the GH receptor gene (GHRd3) has been linked to increased responsiveness to GH.

OBJECTIVE

Our objective was to evaluate the influence of the GHRd3 gene on birth size and pubertal onset.

DESIGN AND SETTING

We conducted a cross-sectional study, part of The COPENHAGEN Puberty Study, at a tertiary center for pediatric endocrinology.

PARTICIPANTS

Participants included 618 healthy boys aged 6.1-19.8 yr.

MAIN OUTCOME MEASURES

We assessed pubertal onset by genital staging and testicular palpation and parental reported birth weight and length. GHR genotypes were determined by multiplex PCR.

RESULTS

Age at onset of genital development (G2+) was significantly earlier in the GHRd3 homozygotes (GHRd3/d3) [10.86 (10.35-11.37) yr, mean (95% confidence interval)] compared with the full-length homozygotes (GHRfl/fl) [11.76 (11.35-12.00) yr, P = 0.002]. The odds ratio of having detectable testosterone levels for a given age was significantly higher in GHRd3/d3 compared with GHRfl/fl group (odds ratio = 3.1; 95% confidence interval = 1.2-8.9; P = 0.036). The GHRd3/d3 group the higher prepubertal IGF-I levels compared with the GHRfl/fl group (9.2% (0.1-18.1%), P = 0.048) after adjustment for IGF-binding protein-3 levels. Lower gestational-age-adjusted birth weight and length were found in the GHRd3/d3 group compared with the GHRfl/fl group and the GHRfl/d3 group, respectively (all P < or = 0.018).

CONCLUSION

The GHRd3/d3 genotype was associated with smaller birth size and earlier age at pubertal onset compared with the GHRfl/fl genotype. Thus, this common polymorphism could play a role for prenatal growth and gonadal development in boys.

Growth hormone receptor d3-variant, insulin-like growth factor binding protein-1 -575G/A polymorphism and postnatal catch-up growth: association with parameters of glucose homeostasis in former extremely low birth weight preterm infants

BACKGROUND

Low birth weight predisposes to the development of insulin resistance. In addition to auxological parameters such as rapid catch-up growth, low IGFBP-1 serum levels in childhood have been linked to an increased risk of insulin resistance later in life. Concerning postnatal growth, we previously reported the GHRd3-variant to be associated with catch-up growth in preterm infants. In children born small for gestational age, a common IGFBP-1 promoter polymorphism -575G/A has been linked to IGFBP-1 serum levels and has been suggested to be an additional player in the interaction between the IGF-IGFBP-axis and metabolism.

STUDY DESIGN

We analyzed postnatal growth, metabolic parameters, and genotypes for the GHRd3-variant and IGFBP-1 -575G/A in 51 former extremely low birth weight preterm infants (mean age 5.9 years).

RESULTS

GHRd3 but not IGFBP-1 -575G/A was significantly associated with postnatal growth velocity. Catch-up growth, GHRd3, and IFGBP-1 -575G/A did not influence fasting insulin or HOMA-IR. However, we found significantly higher HbA1c and lower IGFBP-1 concentrations in GHRd3-carriers, a finding not seen with respect to IGFBP-1 -575G/A. Interestingly, HbA1c and IGFBP-1 levels also did not differ between children either with or without catch-up growth.

CONCLUSIONS

In addition to an association with catch-up growth, GHR exon 3 genotype significantly modulates HbA1c and IGFBP-1 concentrations in former ELBW infants. In order to confirm this observation and to clarify whether the GHRd3-variant might be considered as an independent modulator of the low birth weight infant's risk to develop insulin resistance later in life, larger studies extending to later ages are required.

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.

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.

Impact of the growth hormone receptor exon 3 deletion gene polymorphism on glucose metabolism, lipids, and insulin-like growth factor-I levels during puberty

CONTEXT

The GH/IGF-I axis has major impact on insulin sensitivity and insulin secretion. Recently a polymorphism in the GH receptor gene (GHR), a genomic deletion of exon 3 (GHRd3), has been linked to increased responsiveness to GH.

OBJECTIVE

The objective of the present study was to evaluate the impact of the GHRd3 gene polymorphism on insulin sensitivity, insulin secretion, lipids, and IGF-I levels in healthy children and adolescents.

DESIGN

This was cross-sectional and was part of the COPENHAGEN puberty study.

SETTING

The study was conducted at a tertiary center for pediatric endocrinology.

PARTICIPANTS

Participants included 142 healthy Caucasian subjects (65 boys) aged 8.5-16.1 yr.

INTERVENTIONS

Standard 2-h oral glucose tolerance tests were preformed. GHR genotypes were determined by multiplex PCR. Main outcome measures were insulin sensitivity, insulin secretion, serum lipids, and IGF-I levels.

RESULTS

Insulin secretion was higher in children and adolescents with a least one GHRd3 allele, even after adjustment for age, sex, pubertal stage, and insulin sensitivity (P = 0.018). Disposition index was higher in GHRd3-positive subjects (P = 0.026). In addition, the GHRd3 allele was associated with higher triglyceride (P = 0.028), but not IGF-I levels.

CONCLUSION

The presence of at least one GHRd3 allele was associated with higher insulin secretion for a given degree of insulin sensitivity in healthy children and adolescents during puberty. In addition, the presence of the GHRd3 allele was associated with a higher disposition index. Thus, this common polymorphism in the GHR gene might play a role for pancreatic beta-cell compensatory capacity.

Comparison between weight-based and IGF-I-based growth hormone (GH) dosing in the treatment of children with GH deficiency and influence of exon 3 deleted GH receptor variant

OBJECTIVE

Compare the most frequently used weight-based GH dosing with an IGF-I level-based strategy in the treatment of children with severe GH deficiency. Additionally, analyse the influence of the GH receptor exon 3 polymorphism on IGF-I levels during GH therapy.

DESIGN

Thirty children with GH deficiency on treatment with GH for 4.3+/-3.2 yr in a single University Hospital were divided in group W (weight-based GH dosing) and group I (IGF-I-based dosing). In group I, GH doses were changed by 8.3 microg/kg d to maintain IGF-I levels between 0 and +2 SDS, whereas in group W the dose was fixed at 30 microg/kg d in prepubertal and 50 microg/kg d in pubertal patients. Growth velocity was measured after 1 yr, IGF-I and IGFBP3 levels quarterly. GH receptor exon 3 was genotyped by PCR.

RESULTS

Most patients in Group I reached target IGF-I levels after 6 months with a GH dose ranging between 25 and 66 microg/kg d (mean+/-SD, 38+/-8). Each change of 8.3 microg/kg d of GH dose, resulted in change of 1.17+/-0.6 SDS of IGF-I levels. Mean IGF-I levels were higher in Group I 0.8+/-0.5 SDS than in Group W -0.3+/-1.9 SDS (p<0.05), but growth velocities were similar, 6.8+/-2.6 cm/yr and 6.9+/-2.6 cm/yr (p=NS), respectively. Serum IGFBP3 levels were similar in both groups and were less useful to individualize GH therapy. Even treated with a similar mean GH dose, patients carrying at least one GH receptor d3-allele reached higher IGF-I levels (0.7+/-1.2 SDS) than those homozygous for the full-length allele (-0.3+/-1.2 SDS; p<0.05), however, growth velocities were not different.

CONCLUSIONS

By adjusting the GH dose, it was feasible to maintain IGF-I in the desired range (0-+2 SDS). Patients carrying at least one GH receptor d3-allele reached higher circulating IGF-I levels than those homozygous for the full-length allele. A multiple regression analysis failed to demonstrate an independent influence of IGF-I levels on GV during the 12 months of observation.

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.

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.

Early childhood predictors of adult body composition

Intra-uterine life has been identified as a possible critical period for the development of obesity risk in both adults and children; others have highlighted the importance of growth and nutrition in the first few years. It is suggested that fetal growth, as assessed by birth weight, may programme lean body mass later in life. Children who are born small for gestational age also have a predisposition to accumulating fat mass, particularly intra-abdominal fat. It is not yet clear whether this predisposition is due to their prenatal growth restraint, their rapid postnatal catch-up growth or a combination of both. Recently, genetic and heritable factors have been shown to contribute to both rapid postnatal growth and childhood obesity risk in children and adults. Future studies should explore their timing of action and potential interactions with markers of antenatal growth restraint.

Fetal growth velocity, size in early life and adolescence, and prediction of bone mass: association to the GH-IGF axis

Poor growth in early life is associated with numerous adverse outcomes later in life. In 123 adolescents 16-18 yr of age, the previous findings of a positive relation between size in early life and later bone mass was confirmed. These associations were mediated by the current height and weight, but it was not confirmed that alterations of the GH-IGF axis cause this.

INTRODUCTION

Numerous studies have found associations between low birth weight and disease later in life, including decreased bone mass.

MATERIALS AND METHODS

A longitudinal cohort of 16- to 19-year-old adolescents (n = 123) with data on third trimester fetal growth velocity (FGV) was assessed by serial ultrasound measurements, birth weight (BW), and weight at 1 yr. A follow-up study included DXA scan, anthropometric measurements, and measurements of the growth hormone (GH) -IGF-I axis in a representative subpopulation (n = 30).

RESULTS

BW and weight at 1 yr were positively associated with whole body BMC (p = 0.02 and p < 0.0001, respectively), lumbar spine BMC (p = 0.001 and p = 0.03, respectively), and lumbar spine BMD (p = 0.04). After correction for adolescent height and weight, no association remained significant. There was no relation between IGF-I and IGF binding protein 3 (IGFBP-3) levels in adolescence and size in early life or bone mass. In the subpopulation, GH secretion (median, 2.58 versus 4.05), GH pulse mass (median, 10.7 versus 19.4 mU/liter), and total GH (median, 74.9 versus 108.8 mU/liter/12 h) were decreased in the small for gestational age (SGA) group compared with the appropriate for gestational age (AGA) group; this did not reach statistical significance. Likewise, there were no differences in IGF-I, IGF-II, and IGFBP-1, -2, and -3 levels between the SGA and AGA groups. A statistically significant positive association between FGV and adolescent IGF-II was found (B = 199.9, p = 0.006). Significant negative associations between GH measurement and BMC, as well as BMD, were found (B = -0.008, p = 0.005 and B = -0.008, p = 0.006, respectively).

CONCLUSIONS

This study confirms the previous findings of a positive relation between size in early life and later BMC, an association apparently independent of the distal part of the GH/IGF-I axis. However, this association may be mediated mainly by postnatal growth determining size of the skeletal envelope rather than an effect of fetal programming on bone mass per se.