Diagnosis and management of growth hormone deficiency in childhood and adolescence--part 2: growth hormone treatment in growth hormone deficient children

Quality of Life of Children and Adolescents with Short Stature: The Twofold Contribution of Physical Growth and Adaptive Height-Related Cognitive Beliefs

This study aimed to examine the health-related quality of life (HrQoL), coping, height-related beliefs, and social support of children/adolescents with short stature, the sociodemographic, clinical, and psychosocial variables associated with HrQoL, and the moderating role of sociodemographic and clinical variables on the associations between psychosocial variables and HrQoL. 114 Portuguese children/adolescents with short stature, aged 8-18 years old, completed the Quality of Life in Short Stature Youth questionnaire and the Satisfaction with Social Support Scale. Regression analyses explained 54% of the variance of HrQoL, with significant main effects of current height deviation and height-related beliefs, and a significant interaction effect between beliefs and diagnosis. Results suggest that a multidisciplinary therapeutic approach, not only focused on hormone treatment to boost physical growth, but also including psychosocial interventions focused on the modification of height-related beliefs, may contribute to improve the HrQoL of pediatric patients with short stature.

Absorption, metabolism and excretion of once-weekly somapacitan, a long-acting growth hormone derivative, after single subcutaneous dosing in human subjects

Somapacitan is a reversible albumin-binding growth hormone (GH) derivative in clinical development for once-weekly administration in patients with adult GH deficiency (AGHD) and children with GH deficiency (GHD). To date, the use of somapacitan in AGHD or severe AGHD has been approved in the USA and Japan, respectively. This study (ClinicalTrials.gov, NCT02962440) investigated the absorption, metabolism and excretion, as well as the pharmacokinetics (PK), of tritium-labelled somapacitan ([³H]-somapacitan). Seven healthy males received a single subcutaneous dose of 6 mg somapacitan containing [³H]-somapacitan 20 MBq. Blood, serum, plasma, urine, faeces, and expired air were collected for radioactivity assessment. Metabolites were identified and quantified in plasma and urine collected. The PK of plasma components were determined, and the radioactive peaks of the most abundant plasma metabolites and urine metabolites were selected for analysis. Twenty-eight days after dosing, 94.0% of the administered dose was recovered as [³H]-somapacitan-related material, most of which was excreted in urine (80.9%); 12.9% was excreted in faeces, and an insignificant amount (0.2%) was exhaled in expired air. PK properties of [³H]-somapacitan-related material appeared to be consistent across plasma, serum and blood. Three abundant plasma metabolites (P1, M1 and M1B) and two abundant urine metabolites (M4 and M5) were identified. The total exposure of intact somapacitan accounted for 59% of the total exposure of all somapacitan-related material, P1 accounted for 21% and M1 plus M1B accounted for 12%. M4 and M5 were the most abundant urine metabolites and accounted for 37% and 8% of the dosed [³H]-somapacitan radioactivity, respectively. No intact somapacitan was found in excreta. Two subjects had six adverse events (AEs); all were mild in severity and unlikely to be related to trial product. The majority of dosed [³H]-somapacitan (94%) was recovered as excreted metabolites. Urine was the major route for excretion of somapacitan metabolites, followed by faeces, and exhalation in expired air was negligible. The low molecular weights of identified urine metabolites demonstrate that somapacitan was extensively degraded to small residual fragments that were excreted (fully biodegradable). The extensive metabolic degradation and full elimination of metabolites in excreta were the major clearance pathways of somapacitan and the key elements in its biological fate. A single dose of 6 mg somapacitan (containing [³H]-somapacitan) in healthy male subjects was well tolerated with no unexpected safety issues identified.

Growth hormone deficiency and the transition from pediatric to adult care

OBJECTIVE

To discuss the approach to patients diagnosed with growth hormone deficiency (GHD) in childhood during the transition period from puberty to adulthood, focusing on the following: (1) physiology; (2) effects of recombinant human GH (rhGH) interruption/reinstitution after adult height achievement; (3) re-evaluation of somatrotropic axis; (4) management of rhGH reinstitution, when necessary.

SOURCE OF DATA

Narrative review of the literature published at PubMed/MEDLINE until September 2020 including original and review articles, systematic reviews and meta-analyses.

SYNTHESIS OF DATA

Growth hormone is crucial for the attainment of normal growth and for adequate somatic development, which does not end concomitantly with linear growth. Retesting adolescents who already meet the criteria that predict adult GHD with high specificity is not necessary. Patients with isolated GHD have a high likelihood of normal response to GH testing after puberty. Adolescents with confirmed GHD upon retesting should restart rhGH replacement and be monitored according to IGF-I levels, clinical parameters, and complementary exams.

CONCLUSION

Patients with isolated idiopathic GHD in childhood are a special group who must be reevaluated for GHD as many of them have normal GH provocative tests upon retesting after puberty. Patients who confirm the persistence of GHD in the transition period should maintain rhGH replacement in order to reach an ideal peak bone mass, satisfactory body composition, lipid and glucose profiles, and quality of life.

Neuroendocrine manifestations of Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a rare inflammatory myeloid neoplasia that can affect any organ or system in the human body. It is usually diagnosed during childhood but can also affect adults. Recent studies have demonstrated involvement of the hypothalamo-pituitary axis (HPA) in a significant proportion of patients with deficiencies in both anterior and posterior pituitary function that in the majority of cases are permanent and require specific hormone replacement regimes. Central diabetes insipidus is considered the most frequent abnormality of HPA involvement in LCH and can be encountered either as isolated deficiency or along with other pituitary deficiencies. Complete hormonal evaluation of pituitary hormones and long-term follow-up of LCH patients are strongly recommended, especially when pituitary involvement is established.

Deciphering short stature in children

Short stature is a common reason for referral to pediatric endocrinologists. Multiple factors, including genetic, prenatal, postnatal, and local environmental factors, can impair growth. The majority of children with short stature, which can be defined as a height less than 2 standard deviation score below the mean, are healthy. However, in some cases, they may have an underlying relevant disease; thus, the aim of clinical evaluation is to identify the subset of children with pathologic conditions, for example growth hormone deficiency or other hormonal abnormalities, Turner syndrome, inflammatory bowel disease, or celiac disease. Prompt identification and management of these children can prevent excessive short stature in adulthood. In addition, a thorough clinical assessment may allow evaluation of the severity of short stature and likely growth trajectory to identify the most effective interventions. Consequently, appropriate diagnosis of short stature should be performed as early as possible and personalized treatment should be started in a timely manner. An increase in knowledge and widespread availability of genetic and epigenetic testing in clinical practice in recent years has empowered the diagnostic process and appropriate treatment for short stature. Furthermore, novel treatment approaches that can be used both as diagnostic tools and as therapeutic agents have been developed. This article reviews the diagnostic approach to children with short stature, discusses the main causes of short stature in children, and reports current therapeutic approaches and possible future treatments.

Growth hormone therapy in children; research and practice - A review

Short stature remains the most common reason for referral to a pediatric Endocrinologist and its management remains a challenge. One of the main controversies is the diagnosis of idiopathic short stature and the role of new technologies for genetic investigation of children with inadequate growth. Complexities in management of children with short stature includes selection of who should receive interventions such as recombinant human growth hormone, and how should this agent dose be adjusted during treatment. Should anthropometrical data be the primary determinant or should biochemical and genetic data be used to improve growth response and safety? Furthermore, what is considered a suboptimal response to growth hormone therapy and how should this be managed? Treatment of children with short stature remains a "hot" topic and more data is needed in several areas. These issues are reviewed in this paper.

Children's psychosocial functioning and parents' quality of life in paediatric short stature: The mediating role of caregiving stress

OBJECTIVES

On the basis of the multidimensional model of the caregiving process, this study aimed (a) to compare the levels of quality of life (QoL) and psychological problems of children with short stature and the levels of caregiving stress and QoL of their parents, between diagnostic, treatment, and current height deviation groups, and (b) to examine the direct and indirect links, via caregiving stress, between children's psychosocial functioning and their parents' QoL.

METHOD

The sample was collected in 5 European countries and comprised 238 dyads of 8- to 18-year-old children and adolescents with a clinical diagnosis of growth hormone deficiency or idiopathic short stature and one of their parents. The children completed self-report measures of height-related QoL (Quality of Life in Short Stature Youth Core Module) and psychological problems (Strengths and Difficulties Questionnaire); the parents reported on their own QoL (EUROHIS-QOL-8 Index) and caregiving stress (Quality of Life in Short Stature Youth Effects on Parents subscale).

RESULTS

Children who were treated and who achieved normal height reported better QoL compared to those untreated and with current short stature. Parents of children with idiopathic short stature and current short stature presented greater caregiving stress than parents of children with growth hormone deficiency and achieved normal height. Children's better psychosocial functioning was indirectly associated with parents' better QoL, via less caregiving stress, and these links were invariant across diagnoses, treatment status, and current height deviation.

CONCLUSIONS

These results suggest that, along with growth hormone treatments, multidisciplinary interventions in paediatric endocrinology should be family-centred, by targeting both the children's psychosocial functioning and the parents' stress, in order to improve individual and family adaptation.

Growth monitoring as an early detection tool: a systematic review

Growth monitoring of apparently healthy children aims at early detection of serious underlying disorders. However, existing growth-monitoring practices are mainly based on suboptimal methods, which can result in delayed diagnosis of severe diseases and inappropriate referrals. We did a systematic review to address two key and interconnected questions underlying growth monitoring: which conditions should be targeted, and how should abnormal growth be defined? We systematically searched for studies reporting algorithms for growth monitoring in children and studies comparing the performance of new WHO growth charts with that of other growth charts. Among 1556 identified citations, 69 met the inclusion criteria. Six target conditions have mainly been studied: Turner syndrome, coeliac disease, cystic fibrosis, growth hormone deficiency, renal tubular acidosis, and small for gestational age with no catch-up after 2 or 3 years. Seven algorithms to define abnormal growth have been proposed in the past 20 years, but their level of validation is low, and their overall sensitivities and specificities vary substantially; however, the Grote and Saari clinical decision rules seem the most promising. Two studies reported that WHO growth charts had poorer performance compared with other existing growth charts for early detection of target conditions. Available data suggest a large gap between the widespread implementation of growth monitoring and its level of evidence or the clinical implications of early detection of serious disorders in children. Further investigations are needed to standardise the practice of growth monitoring, with a consensus on a few priority target conditions and with internationally validated clinical decision rules to define abnormal growth, including the selection of appropriate growth charts.

Associations between Psychological Problems and Quality of Life in Pediatric Short Stature from Patients' and Parents' Perspectives

Short stature has been associated with psychosocial impairments, but whether treatments and achieved height impact on health-related quality of life (HrQoL) and psychological functioning of children/adolescents is still controversial. This study aimed to examine the effects of height deviation and treatment status on psychosocial adaptation outcomes and to identify clinical and psychosocial determinants of internalizing/externalizing problems in a large cohort of short statured children/adolescents from seven European countries. Participants were 345 children aged 8–18 years with a clinical diagnosis of short stature and 421 parents of 4–18 year-old patients. Children and parents reported on psychological problems (Strengths and Difficulties Questionnaire), generic (KIDSCREEN) and condition-specific HrQoL (QoLISSY). According to analyses of covariance, children/adolescents with current short stature presented more parent-reported internalizing problems and lower self- and parent-reported condition-specific HrQoL, compared to patients with an achieved height above -2SD. Treated children self-reported better HrQoL than the untreated group. Hierarchical regression analysis showed that, rather than height–related clinical variables, children’s sex, younger age and poorer HrQoL were the best predictors of psychological problems, explaining 39% of the variance in patient- and 42% in parent-reported internalizing problems, and 22% of the variance in patient- and 24% in parent-reported externalizing problems. Treatment status also moderated the negative links between patient-reported HrQoL and internalizing problems, explaining 2% of additional variance. These results suggest that children with current short stature are at greater risk for internalizing problems. Routine assessment of HrQoL in pediatric healthcare may help identify children for referral to specialized psychological assessment and intervention.

Psychometric performance of the Quality of Life in Short Stature Youth (QoLISSY) questionnaire in the Netherlands

The European Quality of Life in Short Stature Youth (QoLISSY) questionnaire is a disease-specific instrument assessing quality of life (QoL) in children with short stature from the child and parent perspectives. In order to use the QoLISSY in Dutch samples, a translation process and psychometric testing is needed. Children diagnosed with short stature (8 to 18 years) and their parents were recruited from a Dutch growth clinic. Reliability was assessed using Cronbach's α and intraclass correlation coefficients (ICCs). Pearsons' correlations with the generic KIDSCREEN and a confirmatory factor analysis (CFA) were performed to test validity. Scales showed good internal consistency with α ranging from 0.80 to 0.94 (child report) and from 0.85 to 0.95 (parent report). Test-retest reliability (ICC) ranged from 0.15 to 0.91 (child report) and from 0.14 to 0.83 (parent report). Correlations with the KIDSCREEN in the mean range indicated criterion validity. The models' goodness of fit was confirmed by CFA results in the Dutch and in comparison with the European sample.

CONCLUSION

The Dutch QoLISSY is a psychometrically reliable and valid short stature-specific QoL measure. It is now available for use in clinical research and practice to evaluate well-being and possible effects of growth hormone treatment and psychological interventions in the Netherlands.

Efficacy and safety of Samtropin™ recombinant human growth hormone; a double-blind randomized clinical trial

Background

Recombinant human growth hormone (rhGH) can increase the growth rate in growth hormone deficient children (GHD). In this randomized clinical trial, we compared the efficacy and side effects of an Iranian brand; Samtropin with Norditropin.

Methods

The GHD children were randomly treated either with standard dose of Samtropin or Norditropin rhGH for one year. Upstanding height, height standard deviation score (HSDS), growth velocity (GV), serum levels of insulin like growth factor-1 (IGF-1), and bone age (BA) were determined before and during one year treatment concomitant side effects of treatment.

Results

We evaluated 22 subjects; 12 on Samtropin and, 10 on Norditropin. In each group, mean age was 12 yr and 50% of them were male. The mean differences in height, HSDS, IGF-1 and BA by Norditropin before and after 12 months were 8.8 cm, 0.5, 49 ng/ml and 2.8 yr, respectively. These measures by Samtropin were 9.1 cm, 0.6, 133 ng/ml, and 1.7 yr, respectively without any significant difference. The mean of GV by Samtropin was 9.1 vs. 8.8 cm by Norditropin without significant difference. Since the efficacy of Samtropin was found to be similar to Norditropin after 12 months; we switched to use only Samtropin for the next 12 months. The mean differences in height, HSDS, GV and BA in 20 children between months 12 and 24 were 7.0 cm, 1.6, 2.1 cm/yr and 1.0 yr, respectively (P < 0.001). We also found a non-significant decrease in IGF-1 levels. No side effects were observed.

Conclusions

We need to conduct a post marketing surveillance with a large sample size in order to confirm our findings.

Trial registration

Registration code number in the Iranian Registry of Clinical Trials (IRCT): IRCT1138901181414N11.

HRQoL of European children and adolescents with short stature as assessed with generic (KIDSCREEN) and chronic-generic (DISABKIDS) instruments

Short stature may be associated with impairments in health-related quality of life (HRQoL). This study compared the HRQoL of children/adolescents diagnosed with short stature to population norms and examined the effects of height deviation and treatment status on HRQoL.

METHOD

We cross-sectionally assessed 110 children/adolescents aged 8-18, with current short stature (height deviation ≤-2 standard-deviation (SD)) or normal height achieved since diagnosis, and 98 parents, using the generic KIDSCREEN and the chronic-generic DISABKIDS instruments.

RESULTS

Generic HRQoL of patients was similar to population norms. Patients with achieved normal height reported better chronic-generic HRQoL when untreated, while patients with current short stature reported better HRQoL upon receiving treatment. Parents reported better HRQoL for treated patients, especially for girls.

CONCLUSION

Although their HRQoL is not significantly compromised, patients diagnosed with short stature may profit from growth-hormone treatment. Specific instruments are needed to adequately assess the effectiveness of treatment.

Efficacy of short-term growth hormone treatment in prepubertal children with idiopathic short stature

PURPOSE

It has been reported that daily recombinant human growth hormone (GH) treatment showed beneficial effects on growth in prepubertal children with idiopathic short stature (ISS). The present study aimed to validate the GH (Eutropin®) effect on growth promotion and safety after short-term GH treatment.

MATERIALS AND METHODS

This study was an open-label, multicenter, interventional study conducted at nine university hospitals in Korea between 2008 and 2009. Thirty six prepubertal children with ISS were enrolled in this study to receive 6-month GH treatment. Yearly growth rate, height standard deviation score (SDS), and adverse events were investigated during treatment.

RESULTS

After 26 weeks of GH treatment, the height velocity significantly increased by 6.36±3.36 cm/year (p<0.001). The lower end of one-sided 95% confidence interval was 5.22 cm/year, far greater than the predefined effect size. The gain in height SDS at week 26 was 0.57±0.27 (p<0.0001). Bone age significantly increased after GH treatment, however, bone maturation rate (bone age for chronological age) showed limited advancement. This 26-week GH treatment was effective in increasing serum levels of insulin-like growth factor (IGF)-I and IGF binding protein (IGFBP)-3 from baseline (p<0.0001). Eutropin was well tolerated and there were no withdrawals due to adverse events. No clinically significant changes in laboratory values were observed.

CONCLUSION

This 6-month daily GH treatment in children with ISS demonstrated increased height velocity, improved height SDS, and increased IGF-I and IGFBP-3 levels with a favorable safety profile.

The association between growth response to growth hormone and baseline body composition of children with growth hormone deficiency

OBJECTIVE

We wanted to examine the relationship between initial growth response to recombinant human Growth Hormone (rhGH) treatment and body composition in children with growth hormone deficiency (GHD).

DESIGN AND METHODS

Forty-two patients (21 boys and 21 girls) aged between 5.7-15.5 years (mean age: 10.8 ± 2.6 years) with isolated GHD. The auxological and laboratory data (GH and IGF-I levels) and results of bioelectrical impedance analyses were evaluated. Children with GHD were followed up for 12 months and categorized according to growth response to rhGH into good and poor responders (change in height of > 0.7 SDS or < 0.7 SDS over one year respectively). Mean doses of rhGH per kg of fat free mass (FFM) were calculated.

RESULTS

Forty-eight percent of patients showed a good growth response to rhGH therapy. At study entry, mean age, height SDS, weight SDS, serum IGF-1 SDS, IGFBP-3 SDS, growth velocity prior to rhGH therapy, GH after clonidine and l-dopa were similar in the two groups. At baseline, BMI SDS and waist-hip ratio were significantly higher in good responders (p = 0.02 and p = 0.006, respectively). Good responders had lower percentages of FFM (73.4 ± 8.9 vs. 83.1 ± 5.9) and total body water (TBW) (56.5 ± 5.3 vs. 63.1 ± 4.4), compared to poor responders (p < 0.05). There were significant correlations between changes in height SDS over one year and baseline body composition in children with GHD on rhGH treatment (r = -0.617 for percentage of FFM, r = -0.629 for percentage of TBW, p < 0.001). A correlation between BMI SDS, waist-hip ratio, mean rhGH dose per FFM and growth response was observed only in prepubertal subjects.

CONCLUSION

Baseline body composition data in children with GHD can be used to predict the growth response to rhGH treatment. A management strategy that involves titrating rhGH dose according to FFM as a means of optimizing the growth response to intervention requires further study.

Neuropsychological recovery and quality-of-life in children and adolescents with growth hormone deficiency following TBI: a preliminary study

OBJECTIVE

To compare neurocognition and quality-of-life (QoL) in a group of children and adolescents with or without growth hormone deficiency (GHD) following moderate-to-severe traumatic brain injury (TBI).

STUDY DESIGNS

Thirty-two children and adolescents were recruited from the TBI clinic at a children's hospital. Growth hormone (GH) was measured by both spontaneous overnight testing and following arginine/glucagon stimulation administration. Twenty-nine subjects participated in extensive neuropsychological assessment.

RESULTS

GHD as measured on overnight testing was significantly associated with a variety of neurocognitive and QoL measures. Specifically, subjects with GHD had significantly (p < 0.05) lower scores on measures of visual memory and health-related quality-of-life. These scores were not explained by severity of injury or IQ (p > 0.05). GHD noted in response to provocative testing was not associated with any neurocognitive or QoL measures.

CONCLUSIONS

GHD following TBI is common in children and adolescents. Deficits in neurocognition and QoL impact recovery after TBI. It is important to assess potential neurocognitive and QoL changes that may occur as a result of GHD. It is also important to consider the potential added benefit of overnight GH testing as compared to stimulation testing in predicting changes in neurocognition or QoL.

Assessing the quality of life of health-referred children and adolescents with short stature: development and psychometric testing of the QoLISSY instrument

BACKGROUND

When evaluating the outcomes of treatment in paediatric endocrinology, the health-related quality of life (HrQoL) of the child is to be taken into consideration. Since few self-reported HrQoL instruments exist for children with diagnosed short stature (dSS), the objective of this study was to develop and psychometrically test a targeted HrQoL instrument for use in multinational clinical research.

METHODS

The target population were short stature (height<-2 SDS) children and adolescents (age 8-12 and 13-18 years) with a diagnosis of growth hormone deficiency (GHD) or idiopathic short stature (ISS), differing in growth hormone treatment status. Focus group discussions for concept and item generation, piloting of the questionnaire with cognitive debriefing, and instrument field testing with a retest were conducted simultaneously in five countries. After qualitative and preliminary quantitative analyses, psychometric testing of field test data in terms of reliability and validity including confirmatory factor analyses (CFA) was performed.

RESULTS

Following item generation from focus group discussions, 124 items were included in a pilot test with a cognitive debriefing exercise providing preliminary feedback on item and domain operating characteristics. A field test with 268 participants showed high internal consistency reliabilities (alpha 0.82-0.95), good correlations with generic measures (up to r=.58), significant known group differences (e.g. in height: F=32, df 244, p<0.001) and an acceptable CFA model fit suggesting construct validity of the three-domain core structure with 22 items, supplemented by three mediator domains with 28 items.

CONCLUSIONS

The QoLISSY questionnaire is a promising step forward in assessing the impact of dSS on HrQoL. It is based on items generated from the subjective experience of short stature children referred for endocrine investigation, is validated for use in five languages and it is easy to administer in clinical and research settings.

The benefits of growth hormone therapy in patients with Turner syndrome, Noonan syndrome and children born small for gestational age

This review will summarize the effects of growth hormone (GH) on height, body composition, bone and psychosocial parameters in children with Turner syndrome or Noonan syndrome and those born small for gestational age. The safety of GH treatment in children with these diagnoses is also reported. Despite the reported efficacy and safety of GH in these indications, however, not all children achieve their target height potential, due in some part to poor adherence to GH therapy regimens; indeed up to 50% of children are less than fully compliant with treatment. With this in mind the present and future administration of GH therapy is discussed with respect to advances being made in the presentation of GH for injection and advances in GH injection devices. It is hoped that such progress, aimed at making the administration of GH easier and less painful for the patient will improve treatment adherence and outcome benefits.

Adult height after growth hormone treatment in Japanese children with idiopathic growth hormone deficiency: analysis from the KIGS Japan database

OBJECTIVE

To identify factors affecting adult height in Japanese patients with idiopathic growth hormone deficiency (GHD), who received growth hormone (GH) treatment during childhood.

METHODS

A retrospective pharmaco-epidemiological study of the effect of GH treatment on adult height standard deviation scores (SDS) was conducted in 374 Japanese patients with idiopathic GHD. During childhood, GH (0.146 +/- 0.023 mg/kg/week) was administered for a mean of 6.4 +/- 2.6 years.

RESULTS

The mean adult height was 160.6 +/- 6.3 cm (-1.75 SD; n = 232) in boys and 146.9 +/- 7.3 cm (-2.20 SD; n = 158) in girls after GH therapy. The mean increases in height SDS in boys and girls with severe GHD were 2.13 SD and 1.66 SD, respectively (p < 0.05). These increases were greater than those observed in patients with moderate GHD and mild GHD. The mean adult height of male patients with GHD and gonadotropin deficiency (166.8 cm) was significantly higher (p < 0.05) than that of isolated GHD patients who were either receiving (159.1 cm) or not receiving (160.5 cm) gonadal suppression therapy. The mean adult heights of female patients were 149.6, 146.7, and 146.9 cm, respectively, and these values did not significantly differ.

CONCLUSION

Linear multiple regression analyses of Japanese patients with severe GHD (n = 61) revealed three independent variables that influenced adult height: gonadotropin deficiency, initial height SDS and height velocity during the first year after the initiation of GH therapy.

Consensus statement on the diagnosis and treatment of children with idiopathic short stature: a summary of the Growth Hormone Research Society, the Lawson Wilkins Pediatric Endocrine Society, and the European Society for Paediatric Endocrinology Workshop

OBJECTIVE

Our objective was to summarize important advances in the management of children with idiopathic short stature (ISS).

PARTICIPANTS

Participants were 32 invited leaders in the field.

EVIDENCE

Evidence was obtained by extensive literature review and from clinical experience.

CONSENSUS

Participants reviewed discussion summaries, voted, and reached a majority decision on each document section.

CONCLUSIONS

ISS is defined auxologically by a height below -2 sd score (SDS) without findings of disease as evident by a complete evaluation by a pediatric endocrinologist including stimulated GH levels. Magnetic resonance imaging is not necessary in patients with ISS. ISS may be a risk factor for psychosocial problems, but true psychopathology is rare. In the United States and seven other countries, the regulatory authorities approved GH treatment (at doses up to 53 microg/kg.d) for children shorter than -2.25 SDS, whereas in other countries, lower cutoffs are proposed. Aromatase inhibition increases predicted adult height in males with ISS, but adult-height data are not available. Psychological counseling is worthwhile to consider instead of or as an adjunct to hormone treatment. The predicted height may be inaccurate and is not an absolute criterion for GH treatment decisions. The shorter the child, the more consideration should be given to GH. Successful first-year response to GH treatment includes an increase in height SDS of more than 0.3-0.5. The mean increase in adult height in children with ISS attributable to GH therapy (average duration of 4-7 yr) is 3.5-7.5 cm. Responses are highly variable. IGF-I levels may be helpful in assessing compliance and GH sensitivity; levels that are consistently elevated (>2.5 SDS) should prompt consideration of GH dose reduction. GH therapy for children with ISS has a similar safety profile to other GH indications.

The role of sex steroids in controlling pubertal growth

Longitudinal growth, which is primarily due to chondrocytic activity at the level of the epiphyseal growth plate, is influenced by many hormones and growth factors in an endocrine and paracrine manner. Their influence is even more complex during the accelerated growth period of puberty that accounts for about 20% of final adult height. Although abnormalities of growth during puberty are very common, the underlying mechanisms that govern the beginning and cessation of pubertal growth at the level of the growth plate are poorly understood. Sex steroids play a crucial role in pubertal growth both at the systemic level via the GH/IGF-1 axis and at the local level of the epiphyseal growth plate. In both sexes it is now accepted that oestrogen is the critical hormone in controlling growth plate acceleration and fusion. This paper reviews the mechanisms that influence pubertal growth and the problems that are associated with disorders of gonadal function.

Growth hormone treatment of non-growth hormone-deficient growth disorders

Although a large body of data on efficacy and safety of growth hormone (GH) treatment for various non-growth hormone-deficient (GHD) growth disorders has accumulated from a combination of clinical trial and postmarketing sources in the last 20 years or more, there remain limitations. Clinical trial data have the advantage of direct comparison of well-matched, randomized patient groups receiving treatment (or not) under comparable conditions and, as such, provide the highest quality evidence of efficacy. Clinical trials, however, are typically too small for any statistically valid assessment for safety, which is more comprehensively addressed using postmarketing data. Consequently, while the efficacy of GH treatment in children with non-GHD growth disorders has been solidly established and, based on the combination of the rigor of the clinical trial data and numerical power of the postmarketing data, no major concerns exist regarding safety, additional long-term data are required.

Use of growth hormone in children

The introduction of recombinant DNA-derived human growth hormone (rhGH) in the mid-1980s allowed studies to be undertaken in a number of growth disorders other than the classic indication--growth-hormone deficiency (GHD). In patients with GHD, optimizing the dose and frequency of rhGH administration, and early instigation of therapy, has led to near-normalization of final height. The use of rhGH in the treatment of Turner syndrome, Prader-Willi syndrome, intrauterine growth restriction, and chronic renal failure demonstrated the efficacy of therapy, although the increase in final height (5-7 cm) is less than that achieved in GHD. Cost-benefit implications need to be considered in the next phases of evaluating the role of rhGH therapy in these indications. To date, rhGH has only received approval for the management of idiopathic short stature in the US; as with the other wider growth indications, the lack of formal randomized, controlled trials hampers the full evaluation of efficacy, and a cautious approach should, therefore, be adopted for this particular indication. rhGH has a good safety record, although there are current concerns about the possible long-term increased risk of colonic and lymphatic malignancy, which will require monitoring through national cancer registries.

Growth hormone therapy

Growth hormone (GH) therapy has revolutionized treatment of children with growth hormone deficiency (GHD). Improved height outcome with final height in the target height range has been achieved in these children. Identification of Creutzfeldt-Jakob disease, a deadly prion mediated disorder, in recipients of pituitary GH accelerated the transition from pituitary derived GH to recombinant GH. Once daily subcutaneous administration of the freeze-dried preparation at evening is the recommended mode of GH therapy. Studies have led to use of higher dose of GH for improving height outcome (0.33 mg/kg/week or 0.14 IU/kg/day) albeit at a significantly high cost. Growth velocity increases from 3-4 cm/year before therapy to 10-12 cm/year during the first two years of therapy and is maintained at 7-8 cm/year after a period of two years. Close follow-up with regular clinical and laboratory monitoring is essential for achieving a desirable height outcome. A theoretical unlimited supply has led to wide spread use of GH in a variety of disorders other than GHD. Initially started in children with Turner syndrome, GH has now been used in chronic renal failure, idiopathic short stature and intrauterine growth restriction besides a wide array of newly emerging indications.

Estrogen regulation of growth hormone action

GH plays a pivotal role in regulating body growth and development, which is modulated by sex steroids. A close interplay between estrogen and GH leads to attainment of gender-specific body composition during puberty. The physiological basis of the interaction is not well understood. Most previous studies have focused on the effects of estrogen on GH secretion. There is also strong evidence that estrogen modulates GH action independent of secretion. Oral but not transdermal administration of estrogen impairs the metabolic action of GH in the liver, causing a fall in IGF-I production and fat oxidation. This results in a loss of lean tissue and a gain of body fat in postmenopausal women and an impairment of GH effect in hypopituitary women on GH replacement. The negative metabolic sequelae are potentially important because of the widespread use of oral estrogen and estrogen-related compounds. Estrogen affects GH action at the level of receptor expression and signaling. More recently, estrogen has been shown to inhibit Janus kinase/signal transducer and activator of transcription signaling by GH via the induction of suppressor of cytokine signaling-2, a protein inhibitor for cytokine signaling. This represents a novel paradigm of steroid regulation of cytokine receptors and is likely to have significance for a diverse range of cytokine function.

Growth hormone deficiency and related disorders: insights into causation, diagnosis, and treatment

Advances in molecular biology have led to the identification of mutations within several novel genes associated with the phenotype of isolated growth hormone deficiency, combined pituitary hormone deficiency, and syndromes such as septo-optic dysplasia. Progress has also been made in terms of the optimum diagnosis of disorders of stature and their treatment. The use of growth hormone for the treatment of adults with growth hormone deficiency and conditions such as Turner's syndrome, Prader-Willi syndrome, intrauterine growth restriction, and chronic renal failure has changed the practice of endocrinology, although cost-benefit implications remain to be established.

GH1 splicing is regulated by multiple enhancers whose mutation produces a dominant-negative GH isoform that can be degraded by allele-specific small interfering RNA (siRNA)

The majority of mutations that cause isolated GH deficiency type II affect splicing of GH1 transcripts, leading to the production of a dominant-negative GH isoform. Because numerous mutations and polymorphisms throughout the GH1 gene have not yet been tested for aberrant splicing, we used a deletion mutagenesis screen across intron 2-exon 3-intron 3 to identify splicing regulatory sequences. These analyses identified a new enhancer element, ESE2, upstream of the cryptic splice site in exon 3 and further defined a previously described enhancer (ESE1) to include the first seven nucleotides of exon 3. Besides enhancers, the overall size of intron 3 is also crucial for exon inclusion. Given the deleterious effects of the dominant-negative 17.5-kDa isoform, these and previous studies underscore the extent to which splicing regulatory elements serve to prevent exon skipping. Importantly, we show here that small interfering RNAs can be used to specifically degrade exon 3-skipped transcripts, potentially a new avenue of therapeutic intervention in isolated GH deficiency II and other dominant disorders.