Towards optimal treatment with growth hormone in short children and adolescents: evidence and theses

Molecular diagnosis is an important indicator for response to growth hormone therapy in children with short stature

BACKGROUND

Significant differences have been observed in the efficacy of recombinant human growth hormone (rhGH) treatment for short children. The present study aimed to identify the genetic etiology of short stature and to assess the role of molecular diagnosis in predicting responses to rhGH treatment.

METHODS

A total of 407 short children were included in the present study, 226 of whom received rhGH treatment. Whole-exome sequencing (WES) was conducted on short children to identify the underlying genetic etiology. Correlations between molecular diagnosis and the efficacy of rhGH treatment were examined.

RESULTS

Pathogenic or likely pathogenic mutations were identified in 86 of the 407 patients (21.1%), including 36 (41.9%) novel variants. Among the multiple pathways affecting short stature, genes involved in fundamental cellular processes (38.7%) play a larger role, especially the RAS-MAPK pathway. In general, patients without pathogenic mutations responded better to rhGH than those with mutations. Furthermore, patients with hormone signaling pathway mutations had a better response to rhGH, while those with paracrine factor mutations had a worse response to rhGH.

CONCLUSIONS

This study highlights the utility of WES in identifying genetic etiology in children with short stature. Identifying likely causal mutations is an important factor in predicting rhGH response.

Safety and Efficacy of Pediatric Growth Hormone Therapy: Results From the Full KIGS Cohort

CONTEXT

The Kabi/Pfizer International Growth Database (KIGS) is a large, international database (1987-2012) of children treated with recombinant human growth hormone (rhGH) in real-world settings.

OBJECTIVE

This work aimed to evaluate the safety and efficacy of rhGH from the full KIGS cohort.

METHODS

Data were collected by investigators from children with growth disorders treated with rhGH (Genotropin [somatropin]; Pfizer). Safety was evaluated in all treated patients, and efficacy in those treated for 1 year or more. A subgroup included patients treated for 5 years or more (≥ 2 years prepubertal) who had reached near-adult height (NAH). Main outcomes included adverse events (AEs), serious AEs (SAEs), and height growth.

RESULTS

The full KIGS cohort (N = 83 803 [58% male]) was treated for idiopathic GH deficiency (IGHD; 46.9%), organic GHD (10.0%), small for gestational age (SGA; 9.5%), Turner syndrome (TS; 9.2%), idiopathic short stature (ISS; 8.2%), and others (16.2%). Median rhGH treatment duration was 2.7 years and observation 3.1 years. SAEs occurred in 3.7% of patients and death in 0.4%. The most common SAEs were recurrence of craniopharyngioma (n = 151), neoplasm (n = 99), and cancer (n = 91); and scoliosis (n = 91). Median first-year delta height-SD score (SDS) (Prader) in prepubertal patients was 0.66 (IGHD), 0.55 (ISS), 0.58 (TS), and 0.71 (SGA). Median gains in NAH-SDS were 1.79 (IGHD), 1.37 (ISS), and 1.34 (SGA) for boys, and 2.07 (IGHD), 1.62 (ISS), 1.07 (TS), and 1.57 (SGA) for girls.

CONCLUSION

Data from KIGS, the largest and longest running international database of rhGH-treated children, show that rhGH is safe and increases short-term height gain and adult height across GHD and non-GHD conditions.

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

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

An eHealth Framework for Managing Pediatric Growth Disorders and Growth Hormone Therapy

Background

The use of technology to support health and health care has grown rapidly in the last decade across all ages and medical specialties. Newly developed eHealth tools are being implemented in long-term management of growth failure in children, a low prevalence pediatric endocrine disorder.

Objective

Our objective was to create a framework that can guide future implementation and research on the use of eHealth tools to support patients with growth disorders who require growth hormone therapy.

Methods

A total of 12 pediatric endocrinologists with experience in eHealth, from a wide geographical distribution, participated in a series of online discussions. We summarized the discussions of 3 workshops, conducted during 2020, on the use of eHealth in the management of growth disorders, which were structured to provide insights on existing challenges, opportunities, and solutions for the implementation of eHealth tools across the patient journey, from referral to the end of pediatric therapy.

Results

A total of 815 responses were collected from 2 questionnaire-based activities covering referral and diagnosis of growth disorders, and subsequent growth hormone therapy stages of the patient pathway, relating to physicians, nurses, and patients, parents, or caregivers. We mapped the feedback from those discussions into a framework that we developed as a guide to integration of eHealth tools across the patient journey. Responses focused on improved clinical management, such as growth monitoring and automation of referral for early detection of growth disorders, which could trigger rapid evaluation and diagnosis. Patient support included the use of eHealth for enhanced patient and caregiver communication, better access to educational opportunities, and enhanced medical and psychological support during growth hormone therapy management. Given the potential availability of patient data from connected devices, artificial intelligence can be used to predict adherence and personalize patient support. Providing evidence to demonstrate the value and utility of eHealth tools will ensure that these tools are widely accepted, trusted, and used in clinical practice, but implementation issues (eg, adaptation to specific clinical settings) must be addressed.

Conclusions

The use of eHealth in growth hormone therapy has major potential to improve the management of growth disorders along the patient journey. Combining objective clinical information and patient adherence data is vital in supporting decision-making and the development of new eHealth tools. Involvement of clinicians and patients in the process of integrating such technologies into clinical practice is essential for implementation and developing evidence that eHealth tools can provide value across the patient pathway.

Short and Long-Term Effects of Growth Hormone in Children and Adolescents With GH Deficiency

The syndrome of impaired GH secretion (GH deficiency) in childhood and adolescence had been identified at the end of the 19^th century. Its non-acquired variant (naGHD) is, at childhood onset, a rare syndrome of multiple etiologies, predominantly characterized by severe and permanent growth failure culminating in short stature. It is still difficult to diagnose GHD and, in particular, to ascertain impaired GH secretion in comparison to levels in normally-growing children. The debate on what constitutes an optimal diagnostic process continues. Treatment of the GH deficit via replacement with cadaveric pituitary human GH (pit-hGH) had first been demonstrated in 1958, and opened an era of therapeutic possibilities, albeit for a limited number of patients. In 1985, the era of recombinant hGH (r-hGH) began: unlimited supply meant that substantial long-term experience could be gained, with greater focus on efficacy, safety and costs. However, even today, the results of current treatment regimes indicate that there is still a substantial fraction of children who do not achieve adult height within the normal range. Renewed evaluation of height outcomes in childhood-onset naGHD is required for a better understanding of the underlying causes, whereby the role of various factors - diagnostics, treatment modalities, mode of treatment evaluation - during the important phases of child growth - infancy, childhood and puberty - are further explored.

A Genome-Wide Pharmacogenetic Study of Growth Hormone Responsiveness

CONTEXT

Individual patients vary in their response to growth hormone (GH). No large-scale genome-wide studies have looked for genetic predictors of GH responsiveness.

OBJECTIVE

To identify genetic variants associated with GH responsiveness.

DESIGN

Genome-wide association study (GWAS).

SETTING

Cohorts from multiple academic centers and a clinical trial.

PATIENTS

A total of 614 individuals from 5 short stature cohorts receiving GH: 297 with idiopathic short stature, 276 with isolated GH deficiency, and 65 born small for gestational age.

INTERVENTION

Association of more than 2 million variants was tested.

MAIN OUTCOME MEASURES

Primary analysis: individual single nucleotide polymorphism (SNP) association with first-year change in height standard deviation scores. Secondary analyses: SNP associations in clinical subgroups adjusted for clinical variables; association of polygenic score calculated from 697 genome-wide significant height SNPs with GH responsiveness.

RESULTS

No common variant associations reached genome-wide significance in the primary analysis. The strongest suggestive signals were found near the B4GALT4 and TBCE genes. After meta-analysis including replication data, signals at several loci reached or retained genome-wide significance in secondary analyses, including variants near ST3GAL6. There was no significant association with variants previously reported to be associated with GH response nor with a polygenic predicted height score.

CONCLUSIONS

We performed the largest GWAS of GH responsiveness to date. We identified 2 loci with a suggestive effect on GH responsiveness in our primary analysis and several genome-wide significant associations in secondary analyses that require further replication. Our results are consistent with a polygenic component to GH responsiveness, likely distinct from the genetic regulators of adult height.

Adult height prediction by bone age determination in children with isolated growth hormone deficiency

BACKGROUND

The precision of adult height prediction by bone age determination in children with idiopathic growth hormone deficiency (IGHD) is unknown.

METHODS

The near adult height (NAH) of patients with IGHD in the KIGS database was compared retrospectively to adult height prediction calculated by the Bayley-Pinneau (BP) prediction based on bone age by Greulich-Pyle (GP) in 315 children and based on the Tanner-Whitehouse 2 (TW2) method in 121 children. Multiple linear regression analyses adjusted for age at GH start, age at puberty, mean dose and years of of GH treatment, and maximum GH peak in stimulation test were calculated.

RESULTS

The mean underestimation of adult height based on the BP method was at baseline 4.1 ± 0.7 cm in girls and 6.1 ± 0.6 cm in boys, at 1 year of GH treatment 2.5 ± 0.5 cm in girls and 0.9 ± 0.4 cm in boys, while at last bone age determination adult height was overestimated in mean by 0.4 ± 0.6 cm in girls and 3.8 ± 0.5 cm in boys. The mean underestimation of adult height based on the TW2 method was at baseline 5.3 ± 2.0 cm in girls and 7.9 ± 0.8 cm in boys, at 1 year of GH treatment adult height was overestimated in girls 0.1 ± 0.6 cm in girls and underestimated 4.1 ± 0.4 cm in boys, while at last bone age determination adult height was overestimated in mean by 3.1 ± 1.5 cm in girls and 3.6 ± 0.8 cm in boys.

CONCLUSIONS

Height prediction by BP and TW2 at onset of GH treatment underestimates adult height in prepubertal IGHD children, while in mean 6 years after onset of GH treatment these prediction methods overestimated adult height.

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

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

Treatment with Growth Hormone in Noonan Syndrome Observed during 25 Years of KIGS: Near Adult Height and Outcome Prediction

BACKGROUND/AIMS

There is little information how rhGH treatment affects height in NS. This study aims to analyze data from the NS patients assembled in KIGS over 25 years.

PATIENTS/METHODS

Of 613 (389 m/224 f) NS patients documented, 476 (302 m/174 f) were treated for 1 year, 237 (160 m/77 f) of which served to develop a 1st year height velocity (HV) prediction algorithm. One-hundred and forty (74 m/66 f) had reached near adult height (NAH). Factors affecting NAH on rhGH were determined.

RESULTS

At the start of rhGH, the NAH groups were (median, m, f) 11.0 and 10.3 years, with a height SDS of -3.2 and -3.8 SDS (Prader), respectively. The total gain after 6.3 and 5.6 years on rhGH (0.27 and 0.30 mg/kg/week) was 1.2 and 1.3 SDS. Age at the start of rhGH (negative), height at the start of rhGH, rhGH dose, number of rhGH injections/wk and birth weight (all positive) explained 36% of the variability of 1st year HV. Height at the start of rhGH, 1st year growth on rhGH, birth weight, and gender explained 74% of the variability of NAH. Causes for rhGH treatment discontinuation and adverse events were also analyzed.

CONCLUSION

rhGH treatment increases NAH in NS. Prediction algorithms may optimize treatment in the future.

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

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

Needle-Free and Needle-Based Growth Hormone Therapy in Children: A Pooled Analysis of Three Long-Term Observational Studies

BACKGROUND

Treatment with growth hormone (GH) is standard clinical practice in children with GH deficiency (GHD) or Turner syndrome (TS). Hitherto, no long-term data on auxological outcome and safety of Zomacton® have been published. Data comparing needle-free administration (NF) and needle injection (NI) of GH are very sparse.

AIMS

To analyse longitudinal auxological outcome and safety data of GH treatment-naïve patients diagnosed with GHD or TS and to compare NF and NI in a real-life setting.

METHODS

Pooled auxological data and safety information from three consecutive prospective observational Zomacton® studies covering 22 years of treatment were analysed and NF was compared to NI.

RESULTS

The safety cohort comprised 1,595 patients who received at least one GH dose. The auxological outcome cohort comprised 856 treatment-naïve patients with follow-up data ≥12 months. Height-SDS and height velocity improved significantly during the first 3 years of treatment. Documented choice of device was available for 658 patients (NF 69.1%, NI 30.9%). NF administration was non-inferior to NI. No previously unknown safety signals occurred.

CONCLUSION

Real-life data show that treatment with Zomacton® improves auxological outcome parameters without new safety concerns. NF administration of GH represents a useful alternative to NI in children with growth disorders.

Criteria for First-Year Growth Response to Growth Hormone Treatment in Prepubertal Children With Growth Hormone Deficiency: Do They Predict Poor Adult Height Outcome?

Objective: Several criteria for first-year growth response (FYGR) to growth hormone (GH) treatment have been proposed. We explored which FYGR criteria predicted best the final height outcome after GH treatment in prepubertal children with GH deficiency (GHD). Design and methods: Height data of 129 GHD children (83 boys) who attained adult height and had been treated with GH for at least 4 consecutive years with at least 1 year before pubertal onset, were retrieved from the Belgian GH Registry. The FYGR parameters were: (1) increase in height (ΔHt) SDS, (2) height velocity (HV) SDS, (3) ΔHV (cm/year), (4) index of responsiveness (IoR) in KIGS prediction models, (5) first-year HV SDS based on the KIGS expected HV curve (HV KIGS SDS), (6) near final adult height (nFAH) prediction after first-year GH treatment. Poor final height outcome (PFHO) criteria were: (1) total ΔHt SDS <1.0, (2) nFAH SDS <-2.0, (3) nFAH minus midparental height SDS <-1.3. ROC curve analyses were performed to define the optimal cut-off for FYGR parameters to predict PFHO. Only ROC curves with an area under the curve (AUC) of more than 70% were further analyzed. Results: Twelve, 22 and 10% of the children had respectively a total ΔHt SDS <1, nFAH SDS <-2, and nFAH minus midparental height SDS <-1.3. The AUC's ranged between 73 and 85%. The highest AUC was found for first-year ΔHt SDS to predict total ΔHt SDS <1, and predicted nFAH SDS to predict nFAH SDS <-2. The currently used FYGR criteria had low specificities and sensitivities to detect PFHO. To obtain a 95% specificity, the cut-off value (and sensitivity) of FYGR parameters were: ΔHt SDS <0.35 (40%), HV SDS <-0.85 (43%), ΔHV <1.3 cm/year (36%), IoR <-1.57 (17%), HV KIGS SDS <-0.83 (40%) to predict total ΔHt SDS <1; predicted nFAH SDS (with GH peak) <-1.94 (25%), predicted nFAH SDS (without GH peak) <-2.02 (25%) to predict nFAH SDS <-2. At these cut-offs, the amount of correctly diagnosed poor final responders equals the amount of false positives. Conclusion: First-year growth response criteria perform poorly as predictors of poor final height outcome after long-term GH treatment in prepubertal GHD children.

Diagnosis of Idiopathic GHD in Children Based on Response to rhGH Treatment: The Importance of GH Provocative Tests and IGF-1

Purpose: Serum IGF-1 (Insulin like growth factor 1) and Growth Hormone (GH) provocative tests are reasonable tools for screening and diagnosis of idiopathic GH Deficiency (IGHD). However, the average cut-off points applied on these tests have a lower level of evidence and produce large amounts of false results. The aim of this study is to evaluate the sensitivity, specificity, and accuracy of IGF-1 and GH stimulation tests as diagnostic tools for IGHD, using clinical response to recombinant human GH (rhGH) treatment as diagnostic standard [increase of at least 0.3 in height standard deviation (H-SD) in 1 year]. Methods: We performed a prospective study with 115 children and adolescents presenting short stature (SS), without secondary SS etiologies such as organic lesions, genetic syndromes, thyroid disorders. They were separated into Group 1 [patients with familial SS or constitutional delay of growth and puberty (CDGP), not treated with rhGH], Group 2 (patients with suspicion of IGHD with clinical response to rhGH treatment), and Group 3 (patients with suspicion of IGHD without growth response to rhGH treatment). Then, they were assessed for diagnostic performance of IGF-1, Insulin Tolerance Test (ITT) and clonidine test (CT) alone and combined at different cut-off points. Results: Based on the ROC curve, the best cut-off points found for IGF-1, ITT, and CT when they were used isolated were -0.492 SDS (sensitivity: 50%; specificity: 53.8%; accuracy: 46.5%), 4.515 μg/L (sensitivity: 75.5%; specificity: 45.5%; accuracy: 52.7%), and 4.095 μg/L (sensitivity: 54.5%; specificity: 52.6%; accuracy: 56.9%), respectively. When we had combined IGF-1 with-2SD as cut-off alongside ITT or CT, we found 7 μg/L as the best cut-off point. In this situation, ITT had sensitivity, specificity and accuracy of 93.9, 81.8, and 90.1%, while CT had 93.2, 68.4, and 85.7%, respectively. Conclusion: Our data suggest that diagnosis of IGHD should be established based on a combination of clinical expertise, auxologic, radiologic, and laboratorial data, using IGF-1 at the -2SD threshold combined, with ITT or CT at the cut-off point of 7 μg/L. Additional studies, similar to ours, are imperative to establish cut-off points based on therapeutic response to rhGH in IGHD, which would be directly related to a better treatment outcome.

Poor growth response during the first year of growth hormone treatment in short prepubertal children with growth hormone deficiency and born small for gestational age: a comparison of different criteria

Background

There is no consensus on the definition of poor growth response after the first year of growth hormone (GH) treatment. We determined the proportion of poor responders identified by different criteria in children with GH deficiency (GHD) and born small for gestational age (SGA). The second aim was to analyze the IGF-1 response in poor growth responders.

Methods

First-year height data of 171 SGA and 122 GHD children who remained prepubertal during the first GH treatment year were retrieved from the BESPEED database and analyzed. Criteria for poor first-year response/responsiveness were: change in height (∆Ht) SDS<0.3 or<0.5, height velocity (HV) SDS<0.5 or <1 based on the population reference, HV SDS<- 1 based on the KIGS expected HV curve (HV Ranke SDS), studentized residual (SR) <- 1 in the KIGS first-year prediction model.

Results

∆Ht SDS<0.5 gave the highest percentage poor responders (37% SGA, 26% GHD). Although % poor responders were comparable for ∆Ht SDS<0.3, HV SDS<+ 0.5, HV SDS<+ 1, SR<- 1, and HV Ranke SDS<- 1, these criteria did not always identify the same patients as poor responders. Among the poor growth responders 24% SGA and 14% GHD patients had an IGF-1 increase < 40%.

Conclusions

The different response criteria yield high but comparable percentages poor responders, but identify different patients. This study does not provide evidence that one criterion is better than another. A limited IGF-1 generation is not the major reason for a poor growth response in the first year of GH treatment in SGA and GHD children.

Trial registration

Retrospectively registered.

[Efficacy and safety of replacement treatment in isolated growth hormone deficiency]

INTRODUCTION

Growth in patients with isolated growth hormone (GH) deficiency is heterogeneous despite treatment due to the low specificity of diagnostic tests, making it necessary to define efficacy variables.

AIMS

To evaluate efficacy of hormone replacement therapy in children with isolated GH deficiency.

METHODS

Observational-ambispective study of patients treated in our department in the last 14 years for isolated GH deficiency. This was defined as a GH level less than 7.4mg/dl in response to 2 stimulation tests in patients with height<2SD and a decreased growth rate.

RESULTS

The study included a total 97 patients, of whom 69% were boys. The large majority (89.58%) achieved final height. None of them had side effects. The median dose of GH used was 0.028mg/kg/day (0.03-0.025). There was a gain of 1.17 SD in final height. Around three-quarters (71.13%) of the patients were reassessed in adulthood, of whom 39.4% maintained the deficiency, and 79.31% achieved target range height. Target height, estimated height, and the total pubertal gain were positively correlated with final height, while the bone age/chronological age ratio and the initial insulin-like growth factor-1 showed a negative correlation.

CONCLUSIONS

A majority of patients reached target size, although only a few of them maintained the deficiency in adulthood. Target size, estimated adult height, and pubertal variables are directly related to adult height, while bone age/chronological age and insulin-like growth factor-1 were inversely related, and these can be used as efficacy variables. No adverse effects were observed in the sample with the doses used for the treatment.

Growth hormone - past, present and future

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

Pre-treatment growth and IGF-I deficiency as main predictors of response to growth hormone therapy in neural models

Mathematical models have been applied in prediction of growth hormone treatment effectiveness in children since the end of 1990s. Usually they were multiple linear regression models; however, there are also examples derived by empirical non-linear methods. Proposed solution consists in application of machine learning technique - artificial neural networks - to analyse this problem. This new methodology, contrary to previous ones, allows detection of both linear and non-linear dependencies without assuming their character a priori The aims of this work included: development of models predicting separately growth during 1st year of treatment and final height as well as identification of important predictors and in-depth analysis of their influence on treatment's effectiveness. The models were derived on the basis of clinical data of 272 patients treated for at least 1 year, 133 of whom have already attained final height. Starting from models containing 17 and 20 potential predictors, respectively for 1st year and final height model, we were able to reduce their number to 9 and 10. Basing on the final models, IGF-I concentration and earlier growth were indicated as belonging to most important predictors of response to GH therapy, while results of GH secretion tests were automatically excluded as insignificant. Moreover, majority of the dependencies were observed to be non-linear, thus using neural networks seems to be reasonable approach despite it being more complex than previously applied methods.

Individualised growth response optimisation (iGRO) tool: an accessible and easy-to-use growth prediction system to enable treatment optimisation for children treated with growth hormone

BACKGROUND

Growth prediction models (GPMs) exist to support clinical management of children treated with growth hormone (GH) for growth hormone deficiency (GHD), Turner syndrome (TS) and for short children born small for gestational age (SGA). Currently, no prediction system has been widely adopted.

CONTENT

The objective was to develop a stand-alone web-based system to enable the widespread use of an 'individualised growth response optimisation' (iGRO) tool across European endocrinology clinics. A modern platform was developed to ensure compatibility with IT systems and web browsers. Seventeen GPMs derived from the KIGS database were included and tested for accuracy.

SUMMARY

The iGRO system demonstrated prediction accuracy and IT compatibility. The observed discrepancies between actual and predicted height may support clinicians in investigating the reasons for deviations around the expected growth and optimise treatment.

CONCLUSIONS

This system has the potential for wide access in endocrinology clinics to support the clinical management of children treated with GH for these three indications.

Managing Transition in Patients Treated with Growth Hormone

Growth hormone (GH) promotes growth in children, but is also essential for bone strength, body composition, metabolic factors, such as lipid profile, and maintenance of quality of life. The Merck KGaA (Germany) funded "360° GH in Europe" meeting, held in Lisbon, Portugal, in June 2016, comprised three sessions entitled "Short Stature Diagnosis and Referral," "Optimizing Patient Management and Adherence," and "Managing Transition." The scientific program covered all stages of pediatric GH treatment, and reported here are the outcomes of the third session of the meeting, which considered transition from pediatric GH treatment to teenage and young adult GH therapy. A large number of patients with chronic diseases, including GH deficiency, drop out of therapy during the transition period. Multiple factors are associated with this, such as lack of understanding of the disease process, insufficient knowledge of treatment options, the patient becoming more independent, and requirement for interaction with a new set of health-care workers. Education regarding disease management and treatment options should be provided from an early age and right through the transition period. However, endocrine specialists will view the transition period differently, depending on whether they are pediatric endocrinologists who mainly deal with congenital diseases, in which auxology is important, or adult endocrinologists who are more concerned with body composition and metabolic factors. View points of both a pediatric and an adult endocrine specialist are presented, together with a case study outlining practical aspects of transition. It was noted in the meeting discussion that having one person to guide a patient through transition from an early age is important, but may be constrained by various factors such as finances, and options will differ by country.

Validation of Prediction Models for Near Adult Height in Children with Idiopathic Growth Hormone Deficiency Treated with Growth Hormone: A Belgian Registry Study

BACKGROUND/AIM

To validate prediction models for near final adult height (nFAH) by Ranke et al. [Horm Res Paediatr 2013;79:51-67].

METHODS

Height data of 127 (82 male) idiopathic growth hormone (GH)-deficient children, treated with GH until nFAH, were retrieved from the database of the Belgian Society for Pediatric Endocrinology and Diabetology (BESPEED). nFAH was predicted after first-year GH treatment, applying prediction models by Ranke et al. Bland-Altman plots and Clarke error grid analyses were performed to assess clinical significance of the differences between observed and predicted nFAH.

RESULTS

In males, the predicted nFAH was higher than the observed nFAH (difference: 0.2 ± 0.7 SD; p < 0.01). In females, there was no significant difference. Bland-Altman analyses showed that the means of the differences between observed and predicted nFAH were close but not equal to zero, with overprediction for smaller heights and underprediction for taller heights. Clarke error grid analysis: in males, 59-61% of the predicted nFAH were within 0.5 SDS and 88% within 1.0 SDS from the observed nFAH; in females, 40-44% of the predicted nFAH were within 0.5 SDS and 76-78% within 1.0 SDS from the observed nFAH.

CONCLUSION

Ranke's models accurately predicted nFAH in females and overpredicted nFAH in males by about 1.5 cm. In most individuals, the predicted nFAH was within 1 SDS of observed nFAH. These models can be of help in giving realistic expectations of adult height. © 2016 S. Karger AG, Basel.

Dynamic response of C-type natriuretic peptide and its aminoterminal propeptide (NTproCNP) to growth hormone treatment in children with short stature

OBJECTIVE

C-type natriuretic peptide (CNP) and its aminoterminal propeptide (NTproCNP) are potential biomarkers of recombinant human growth hormone (rhGH) efficacy. The objective of this study was to describe the pharmacodynamics of plasma CNP and NTproCNP levels in response to rhGH treatment and to identify the optimal time of sampling after starting rhGH.

DESIGN

This was a prospective, observational study. Subjects were treated with rhGH for 1 year, with blood sampled at regular intervals.

PATIENTS

Eighteen prepubertal children, eight with low levels of GH on biochemical testing and ten with idiopathic short stature, completed the study.

MEASUREMENTS

Blood levels of CNP, NTproCNP, GH, insulin-like growth factor-I, leptin and bone-specific alkaline phosphatase were measured. Anthropometrics were obtained.

RESULTS

Plasma levels of both CNP and NTproCNP reached peak levels 7-28 days after starting rhGH treatment and then declined to intermediate levels through the first year. Plasma NTproCNP levels after 14 days trended towards a correlation with height velocity after 6 and 12 months of treatment. Unexpectedly, serum GH levels measured 2 and 28 days after starting rhGH correlated strongly with height velocity after 6 and 12 months of treatment.

CONCLUSIONS

This study identified 14 days after starting rhGH treatment as the optimal time for assessing CNP and NTproCNP levels as biomarkers of rhGH efficacy. Additionally, we identified GH levels as a potential biomarker. Larger, prospective studies are now needed to test the clinical utility of these biomarkers.

Low Treatment Adherence in Pubertal Children Treated with Thyroxin or Growth Hormone

BACKGROUND

Treatment outcome depends largely on treatment adherence (TA). However, studies analyzing TA in chronic endocrine diseases are scarce and controversial in childhood.

PATIENTS AND METHODS

We studied TA in 103 children treated subcutaneously with growth hormone (GH) and 97 children treated orally with thyroxin. TA was calculated based on the prescription refill rates. The number of GH injections was recorded by an autoinjector device in 23 children treated with GH.

RESULTS

The correlation between recorded TA and calculated TA based on prescription refill rates was very good (p < 0.001, r = 0.83). TA was lower (p < 0.01) in pubertal children compared to prepubertal children and in children self-administering their medication compared to those whose drug was administered by their parents, both in GH- and thyroxin-treated children. Overall, 67% of the pubertal children treated with GH and 58% of the pubertal children treated with thyroxin missed at least 1 dose per week. TA was higher (p < 0.001) in children with thyroxin treatment compared to children treated with recombinant human GH (8 vs. 26% missed >3 doses/week).

DISCUSSION

Puberty and self-administration of drugs were negative predictors of TA. Therefore, in puberty, prevention and treatment efforts should be undertaken to improve TA, especially when adolescents administer their drugs themselves.

Early cessation and non-response are important and possibly related problems in growth hormone therapy: An OZGROW analysis

OBJECTIVE

To investigate growth hormone (GH) treatment and treatment cessation with respect to efficacy and efficiency. To identify factors that best classify or predict cessation type: completed treatment (CT), early cessation (EC), or non-response (NR).

DESIGN

Observational study (1990-2013) of the Australian GH Program comparing CT, EC, and NR groups with respect to demographic, clinical, and response criteria. All patients treated for GH deficiency (GHD; 909), short stature and slow growth (SSSG; 2144), and Turner Syndrome (TS; 626) were included. Information was retrieved from the OZGROW database.

RESULTS

51.9% of patients were EC, 40.7% CT and 7.4% NR.Median treatment durations for NR patients were often longer than patients who completed treatment. EC and NR groups were both associated with poor growth response with males overrepresented.Socioeconomic status differentiated NR (higher) and EC (lower) groups.

CONCLUSIONS

EC was observed at very high rates and appears, generally, to be a little-recognised but frequent problem in GH therapy.EC and delayed recognition of NR may be interrelated being differentiated by the decision to cease or continue treatment following poor response.Poor treatment compliance is likely a major causal factor in EC.Strategies to address poor response and compliance have been developed, however, given the scale of these problems, it may be that long acting GH formulations or individualized treatment need consideration.

Insulin-like growth factor binding-protein-3 (IGFBP-3)

The IGF system comprises two IGFs (IGF-1, IGF-2), two IGF-receptors (IGF-R1, IGF-R2), and six IGF binding proteins (IGFBPs) with a high affinity for IGFs. The IGFBPs, of which IGFBP-3 is the most abundant in postnatal blood, link with IGFs and prevent them from being degraded; they also facilitate IGF transport through body compartments. The interaction between IGFs and their specific receptors is partly regulated by structural modifications inherent to the IGFBPs. IGFBPs also have IGF-independent biological effects. Since serum IGFBP-3 is GH-dependent and correlates quantitatively with GH secretion, its measurement is useful in tests of abnormal GH secretion. Particularly during childhood, IGFBP-3 values play an important role in ascertaining alterations in GH secretion and action (i.e., primary IGF deficiency states). A new role for IGFBP-3 and other IGFBPs with natural or altered structures is likely to be established through current studies investigating their application in promoting apoptotic processes in malignancies.

Growth hormone dose-dependent pubertal growth: a randomized trial in short children with low growth hormone secretion

BACKGROUND/AIMS

Growth hormone (GH) treatment regimens do not account for the pubertal increase in endogenous GH secretion. This study assessed whether increasing the GH dose and/or frequency of administration improves pubertal height gain and adult height (AH) in children with low GH secretion during stimulation tests, i.e. idiopathic isolated GH deficiency.

METHODS

A multicenter, randomized, clinical trial (No. 88-177) followed 111 children (96 boys) at study start from onset of puberty to AH who had received GH 33 µg/kg/day for ≥1 year. They were randomized to receive 67 µg/kg/day (GH(67)) given as one (GH(67×1); n = 35) or two daily injections (GH(33×2); n = 36), or to remain on a single 33 µg/kg/day dose (GH(33×1); n = 40). Growth was assessed as heightSDSgain for prepubertal, pubertal and total periods, as well as AHSDS versus the population and the midparental height.

RESULTS

Pubertal heightSDSgain was greater for patients receiving a high dose (GH(67), 0.73) than a low dose (GH(33×1), 0.41, p < 0.05). AHSDS was greater on GH(67) (GH(67×1), -0.84; GH(33×2), -0.83) than GH(33) (-1.25, p < 0.05), and heightSDSgain was greater on GH(67) than GH(33) (2.04 and 1.56, respectively; p < 0.01). All groups reached their target heightSDS.

CONCLUSION

Pubertal heightSDSgain and AHSDS were dose dependent, with greater growth being observed for the GH(67) than the GH(33) randomization group; however, there were no differences between the once- and twice-daily GH(67) regimens. © 2014 S. Karger AG, Basel.

Human monoclonal antibody fragments targeting matrilin-3 in growth plate cartilage

PURPOSE

Many genetic disorders, including chondrodysplasias, and acquired disorders impair growth plate function, resulting in short and sometimes malformed bones. There are multiple endocrine and paracrine factors that promote chondrogenesis at the growth plate, which could potentially be used to treat these disorders. Targeting these growth factors specifically to the growth plate might augment the therapeutic skeletal effect while diminishing undesirable effects on non-target tissues.

METHODS

Using yeast display technology, we selected single-chain variable antibody fragments that bound to human and mouse matrilin-3, an extracellular matrix protein specifically expressed in cartilage tissue. The ability of the selected antibody fragments to bind matrilin-3 and to bind cartilage tissue in vitro and in vivo was assessed by ELISA and immunohistochemistry.

RESULTS

We identified antibody fragments that bound matrilin-3 with high affinity and also bound with high tissue specificity to cartilage homogenates and to cartilage structures in mouse embryo sections. When injected intravenously in mice, the antibody fragments specifically homed to cartilage.

CONCLUSIONS

Yeast display successfully selected antibody fragments that are able to target cartilage tissue in vivo. Coupling these antibodies to chondrogenic endocrine and paracrine signaling molecules has the potential to open up new pharmacological approaches to treat childhood skeletal growth disorders.

Is growth hormone treatment in children associated with weight gain?--longitudinal analysis of KIGS data

OBJECTIVE

Growth hormone (GH) increases lean body mass and reduces fat mass. However, the long-term changes in weight status during growth hormone treatment, according to age and weight status at onset of treatment, have not previously been reported in large data sets.

METHODS

Changes in BMI-SDS between starting GH treatment and attaining near adult height (NAH) were analysed in 2643 children with idiopathic GH deficiency (IGHD), 281 children small for gestational age (SGA), 1661 girls with Turner syndrome (TS), and 142 children with Prader-Willi syndrome (PWS) in the KIGS database.

RESULTS

BMI-SDS increased significantly between onset of GH treatment and NAH (IGHD:+0·29, SGA:+0·69, TS:+0·48) except in PWS (-0·02). These increases were greater in children with younger age at onset of GH treatment (significant in all indications) and with lower doses of GH treatment (significant in IGHD & TS) in multiple linear regression analyses also including gender, duration of GH treatment, BMI-SDS and height-SDS at onset of treatment, and birth weight-SDS. Obese children at onset of GH treatment decreased their BMI-SDS, while underweight and normal weight children at onset of GH treatment increased their BMI-SDS independently of GH treatment indication.

CONCLUSIONS

Long-term GH treatment was associated with changes in weight status, which were beneficial for underweight and obese children independent of the indication for GH. However, the increase in BMI-SDS in normal weight children treated with GH needs to be investigated in future prospective longitudinal studies to analyse whether this represents an increase of fat mass, lean body mass or both.

Pharmacogenomics related to growth disorders

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

Constitutional delay influences the auxological response to growth hormone treatment in children with short stature and growth hormone sufficiency

In a retrospective, population based cohort study, we examined whether constitutional delay was associated with the growth response to growth hormone (GH) in children with short stature and normal GH responses. 70 patients were treated with 21 GH iu/m2/week from 1975 to 2013 throughout New Zealand. Demographic and auxological data were prospectively collected and standard deviation scores (SDS) were calculated for height (HtSDS), yearly growth velocity (GV-SDS), body mass index (BMI-SDS) and predicted adult height (PAH-SDS) at time of the last available bone age. In the first year, GH was associated with marked increase in HtSDS (+0.46 (0.19, 0.76), p < 0.001) and GV-SDS (from −1.9 (−3.6, −0.7) to +2.7 (0.45, 4.2), p < 0.001). The increase in HtSDS but not in GV-SDS was greatest with younger patients and greater bone age delay, with no effect of sex, BMI-SDS or baseline HtSDS. PAH-SDS increased with treatment (+0.94 (0.18, 1.5)); increased PAH-SDS was associated with less bone age delay and greater initial increase in HtSDS. This study shows that greater bone age delay was associated with greater initial improvement in height but less improvement in predicted adult heights, suggesting that children with very delayed bone ages may show accelerated maturation during GH treatment.

Pediatric perspective on pharmacogenomics

The advances in high-throughput genomic technologies have improved the understanding of disease pathophysiology and have allowed a better characterization of drug response and toxicity based on individual genetic make up. Pharmacogenomics is being recognized as a valid approach used to identify patients who are more likely to respond to medication, or those in whom there is a high probability of developing severe adverse drug reactions. An increasing number of pharmacogenomic studies are being published, most include only adults. A few studies have shown the impact of pharmacogenomics in pediatrics, highlighting a key difference between children and adults, which is the contribution of developmental changes to therapeutic responses across different age groups. This review focuses on pharmacogenomic research in pediatrics, providing examples from common pediatric conditions and emphasizing their developmental context.

Isolated growth hormone deficiency (GHD) in childhood and adolescence: recent advances

The diagnosis of GH deficiency (GHD) in childhood is a multistep process involving clinical history, examination with detailed auxology, biochemical testing, and pituitary imaging, with an increasing contribution from genetics in patients with congenital GHD. Our increasing understanding of the factors involved in the development of somatotropes and the dynamic function of the somatotrope network may explain, at least in part, the development and progression of childhood GHD in different age groups. With respect to the genetic etiology of isolated GHD (IGHD), mutations in known genes such as those encoding GH (GH1), GHRH receptor (GHRHR), or transcription factors involved in pituitary development, are identified in a relatively small percentage of patients suggesting the involvement of other, yet unidentified, factors. Genome-wide association studies point toward an increasing number of genes involved in the control of growth, but their role in the etiology of IGHD remains unknown. Despite the many years of research in the area of GHD, there are still controversies on the etiology, diagnosis, and management of IGHD in children. Recent data suggest that childhood IGHD may have a wider impact on the health and neurodevelopment of children, but it is yet unknown to what extent treatment with recombinant human GH can reverse this effect. Finally, the safety of recombinant human GH is currently the subject of much debate and research, and it is clear that long-term controlled studies are needed to clarify the consequences of childhood IGHD and the long-term safety of its treatment.

Comparison of weight- vs body surface area-based growth hormone dosing for children: implications for response

OBJECTIVE

To compare weight (per kg)- vs body surface area (BSA, per m(2) )-based growth hormone (GH) dosing formats in children and to derive a useful conversion formula between the two formats.

PATIENTS AND DESIGN

Growth hormone doses (>33,000) from 1874 children were obtained from the national Australian database (OZGROW) and used to derive conversion formulae and to confirm the accuracy of a conversion formula based on a weight-only BSA estimate. A further 27,000 doses were used to test the accuracy of all formulae. The best conversion formula was used to compare weight- and surface area-based GH dosing, which included an analysis of first year response (∆SDS height or growth velocity, GV).

MEASUREMENTS

Growth hormone doses in mg/m(2) /wk and mg/kg/wk, dose estimates, residuals, first year ∆SDS, first year GV.

RESULTS

The formula, [Formula: see text] based on a weight-only BSA estimate, provides accurate dose conversion (mean residual, 0·005 mg/kg/week). A constant mg/m(2) /week dose expressed in terms of mg/kg/week declines quickly with increasing body weight to approximately 15 kg after which the decline continues although less dramatically. For Australian patients, despite an increase in mean per m(2) dose with increased starting weight/age, the per kg dose decreased. This was associated with a greater decline in first year GV than estimated if a per kg dose had been maintained.

CONCLUSIONS

Growth hormone doses can be accurately converted between formats. Surface area-based GH dosing is likely to result in a reduced height response as children become heavier when compared with weight-based GH dosing.