Effects of dose and gender on the growth and growth factor response to GH in GH-deficient children: implications for efficacy and safety

Evaluation of insulin-like growth factor-1 in Indian growth hormone-deficient children on growth hormone therapy

OBJECTIVE

To evaluate the impact of recombinant human growth hormone therapy (GHT) on serum insulin-like growth factor 1 (IGF-1) concentrations in Indian children with growth hormone deficiency.

METHODS

Data on anthropometry and serum IGF-1 concentrations were collected from 28 growth hormone-deficient prepubertal children (8.6 ± 2.9 years) on growth hormone therapy, 6 monthly over the period of 2 years.

RESULTS

Height z-scores showed a steady increase from baseline to 24 months. However, IGF-1 z-scores showed a plateau after the first 6 months and then a small dip followed by a rise. The pattern of increase of IGF-1 z-scores was dissimilar to that of the height z-scores.

CONCLUSION

The change in serum IGF-1 z-scores in response to GHT in Indian children may not be a good indicator for monitoring growth hormone responsiveness.

Factors influencing the one- and two-year growth response in children treated with growth hormone: analysis from an observational study

To assess gender-, pubertal-, age-related differences in change from baseline height standard deviation score (ΔHSDS), data from 5,797 growth hormone (GH) naïve pediatric patients (<18 years) with growth hormone deficiency (GHD), multiple pituitary hormone deficiency (MPHD), Turner syndrome (TS), small for gestational age (SGA), Noonan syndrome (NS), and idiopathic short stature (ISS) were obtained from the ANSWER (American Norditropin Studies: Web-enabled Research) Program registry. For patients with SGA, ΔHSDS at year 1 was significantly greater for males versus females (P = .016), but no other gender differences were observed. For patients with GHD, ΔHSDS was greater in prepubertal than in pubertal patients. Younger patients for both genders (<11 years for boys; <10 years for girls) showed a greater ΔHSDS (P < .05 for GHD, MPHD, and ISS). Overall, positive ΔHSDSs were observed in all patients, with greater growth responses in younger prepubertal children, emphasizing the importance of starting GH treatment early.

Genetic causes and treatment of isolated growth hormone deficiency-an update

Isolated growth hormone deficiency is the most common pituitary hormone deficiency and can result from congenital or acquired causes, although the majority of cases are idiopathic with no identifiable etiology. Known genes involved in the genetic etiology of isolated growth hormone deficiency include those that encode growth hormone (GH1), growth-hormone-releasing hormone receptor (GHRHR) and transcription factor SOX3. However, mutations are identified in a relatively small percentage of patients, which suggests that other, yet unidentified, genetic factors are involved. Among the known factors, heterozygous mutations in GH1 remain the most frequent cause of isolated growth hormone deficiency. The identification of mutations has clinical implications for the management of patients with this condition, as individuals with heterozygous GH1 mutations vary in phenotype and can, in some cases, develop additional pituitary hormone deficiencies. Lifelong follow-up of these patients is, therefore, recommended. Further studies in the genetic etiology of isolated growth hormone deficiency will help to elucidate mechanisms implicated in the control of growth and may influence future treatment options. Advances in pharmacogenomics will also optimize the treatment of isolated growth hormone deficiency and other conditions associated with short stature, for which recombinant human growth hormone is a licensed therapy.

A national study of physician recommendations to initiate and discontinue growth hormone for short stature

OBJECTIVES

Overall growth hormone (GH) use depends on decisions to both initiate treatment and continue treatment. The determinants of both are unclear. We studied how physicians decided to begin GH in idiopathic short stature and how, after an initial course of treatment, they decided to continue, intensify (increase the dose), or terminate treatment.

METHODS

We used a national census study of 727 pediatric endocrinologists involving a structured questionnaires with a factorial experimental design. Main outcome measures were GH recommendations for previously untreated children and those children who were treated with GH for 1 year.

RESULTS

The response rate was 90%. In previously untreated children, recommendations to initiate GH were consistent with guidelines and also influenced by family preferences and physician attitudes (P<.001). In children treated with GH, recommendations on whether to continue GH were influenced by the growth response to therapy (P<.01) but were divided regarding course of action. With identical growth responses to treatment, physician decisions diverged (intensify versus discontinue GH) and were driven by independent, nonphysiologic, and contextual factors (eg, physician attitudes, family preferences, and GH-initiation recommendation; each P<.001). Together, attitudinal and contextual factors exerted more influence on continuation decisions than did the growth response to therapy.

CONCLUSIONS

Physician decisions to initiate GH are largely consistent with evidence-based medicine. However, decisions about continuing GH vary and are strongly influenced by factors other than response to treatment. With a potential market of 500 000 US children and costs exceeding $10 billion per year, changes in GH use may depend on potentially modifiable physician attitudes and family preferences as much as physiologic evidence.

The continuum of growth hormone-IGF-I axis defects causing short stature: diagnostic and therapeutic challenges

The growth hormone (GH)-IGF-I axis is essential for normal foetal and childhood growth. Defects at different sites in the axis frequently result in short stature which may compromise adult height. We describe a continuum of clinically relevant abnormalities from GH deficiency through to GH resistance and discuss the implementation and interpretation of investigations. We consider appropriate therapy for patients with abnormal auxology and subnormal adult height prognosis, highlighting new data to clarify therapeutic choices leading to optimal clinical outcome.

Variable degree of growth hormone (GH) and insulin-like growth factor (IGF) sensitivity in children with idiopathic short stature compared with GH-deficient patients: evidence from an IGF-based dosing study of short children

CONTEXT

We recently showed that, in IGF-based GH therapy, the IGF-I target chosen affects GH dose requirements, and higher IGF-I targets are associated with more robust growth parameters.

OBJECTIVE

The objective of the study was to compare the response of GH-deficient (GHD) vs. idiopathic short-stature (ISS) children to IGF-based GH therapy.

DESIGN

This was a 2-yr, open-label, randomized trial.

SETTING

The setting was multicenter and outpatient.

PATIENTS

Prepubertal short children [height sd score (SDS) < -2] with low IGF-I levels (<or=-1 SDS), subclassified based on the peak stimulated serum GH concentration at baseline, into two subgroups: GHD (n = 63, GH < 7 ng/ml) and ISS (n = 102, GH >or= 7 ng/ml).

INTERVENTIONS

Patients were randomized 2:2:1 to three treatment groups: IGF-I target of 0 SDS (IGF0T), 2 SDS (IGF2T), or a conventional weight-based GH dosing of 40 microg/kg x d (Conv).

MAIN OUTCOME MEASURES

Change in (Delta) height SDS, IGF-I SDS, and GH dose was measured.

RESULTS

ISS subjects required higher GH doses than GHD patients in the IGF2T (but not IGF0T) arm (medians 119 and 65 microg/kg x d, respectively), indicating that ISS represents a partial GH-insensitive state that manifests during treatment with higher doses of GH. GHD children grew more than those with ISS in both IGF-targeted dosage groups despite similar IGF-I levels (suggesting a degree of IGF insensitivity in ISS subjects): Delta height SDS of 2.04 +/- 0.17 for GHD and 1.33 +/- 0.09 for ISS groups in IGF2T, 1.41 +/- 0.13 for children with GHD, and 0.84 +/- 0.07 for those with ISS in IGF0T.

CONCLUSION

IGF-based GH dosing is clinically feasible in both GHD and ISS patients, although GH dose requirements and auxological outcomes are distinct between these groups. This suggests a degree of both GH and IGF insensitivity in subjects with ISS that requires specific management strategies to optimize growth during GH therapy.

Growth hormone: health considerations beyond height gain

The therapeutic benefit of growth hormone (GH) therapy in improving height in short children is widely recognized; however, GH therapy is associated with other metabolic actions that may be of benefit in these children. Beneficial effects of GH on body composition have been documented in several different patient populations as well as improvements in lipid profile. Marked augmentation of bone mineral density also seems evident in many pediatric populations. Some of these benefits may require continued therapy past the acquisition of adult height. With long-term therapy of any kind, the adverse consequences of treatment should also be considered. Fortunately, long-term GH treatment seems to be safe and well-tolerated. This review describes the long-term metabolic effects of GH treatment in the pediatric population and considers how these may benefit children who are treated with GH.

Gender bias in children receiving growth hormone treatment

BACKGROUND

About twice as many boys than girls are treated with GH. Ascertainment bias is a possible explanation.

HYPOTHESES

For ascertainment bias, the gender least frequently treated should be relatively shorter, and in an unbiased population sample, equal numbers of boys and girls should be eligible for GH treatment.

SUBJECTS AND SETTING

In 2007 a total of 1485 Australian children received GH (OZGROW database). Heights were also obtained from two recent unbiased surveys consisting of 3596 and 4794 Australian children.

METHODS

Numbers of boys and girls treated with GH were determined for each treatment indication. Height sd scores (SDS) at first presentation for GH-treated boys and girls were assessed. Frequency of boys and girls from two unbiased populations with height SDS less than -2.326 were recorded.

OUTCOMES

OUTCOMES included gender frequencies and height SDSs. HYPOTHESES were formed before interrogation of preexisting databases.

RESULTS

More boys than girls received GH (P = 3.68 x 10(-20)). By indication: biochemical GH deficiency (P = 0.001), cranial irradiation (P = 0.002), slow growing (P = 2.09 x 10(-16)), and chronic renal failure (P = 0.061). Approximately equal numbers of girls and boys were treated for hypoglycemia (P = 0.543). Slow-growing girls were relatively shorter than boys for ages spanning 4.50-8.49 yr (P = 3.80 x 10(-4)), but boys were relatively shorter in the 6.00- to 17.99-month age group (P = 0.011). Biochemical boys were relatively shorter than girls (P = 0.023). In the two unbiased surveys, boys outnumbered girls 11 to six and 16 to eight for height SDS less than -2.326.

CONCLUSIONS

There is a gender bias in this GH-treated population. Ascertainment bias does not appear to be the major cause.

Proteins related to lipoprotein profile were identified using a pharmaco-proteomic approach as markers for growth response to growth hormone (GH) treatment in short prepubertal children

Background

The broad range in growth observed in response to growth hormone (GH) treatment is mainly caused by individual variations in both GH secretion and GH sensitivity. Individual GH responsiveness can be estimated using evidence-based models that predict the response to GH treatment; however, these models can be improved. High-throughput proteomics techniques can be used to identify proteins that may potentially be used as variables in such models in order to improve their predictive ability. Previously we have reported that proteomic analyses can identify biomarkers that discriminate between short prepubertal children with idiopathic short stature (ISS) who show good or poor growth in response to GH treatment. In this study we used a pharmaco-proteomic approach to identify novel factors that correlate with the growth response to GH treatment in prepubertal children who are short due to GH deficiency or ISS. The study included 128 short prepubertal children receiving GH treatment, of whom 39 were GH-deficient and 89 had ISS. Serum protein expression profiles at study start and after 1 year of GH treatment were analyzed using SELDI-TOF. Cross-validated regression and random permutation analyses were performed to identify significant correlations between protein expression patterns and the 2-year growth response to GH treatment.

Results

At start of treatment we identified a combination of seven protein peaks that correlated with the 2-year growth response in the GH-deficient group (R² = 0.73). After 1 year of treatment, a combination of four peaks in the GH-deficient group (R² = 0.64), eight peaks in the ISS group R² = 0.47) and eight peaks in the total study group correlated with the 2-year growth response R² = 0.38).

The peaks identified corresponded to apolipoproteins A-I, A-II, C-I, C-III, transthyretin and serum amyloid A 4, which are all part of the high-density lipoprotein.

Conclusion

Using a proteomic approach we identified biomarkers related to the lipoprotein profile that could be used to predict growth response to GH treatment in prepubertal children who are short as a result of GH-deficiency or who have ISS.

These results support our previous findings that apolipoproteins and transthyretin may have a role in GH sensitivity.

The first-year growth response to growth hormone treatment predicts the long-term prepubertal growth response in children

Background

Pretreatment auxological variables, such as birth size and parental heights, are important predictors of the growth response to GH treatment. For children with missing pretreatment data, published prediction models cannot be used.

The objective was to construct and validate a prediction model for children with missing background data based on the observed first-year growth response to GH. The accuracy and reliability of the model should be comparable with our previously published prediction model relying on pretreatment data. The design used was mathematical curve fitting on observed growth response data from children treated with a GH dose of 33 μg/kg/d.

Methods

Growth response data from 162 prepubertal children born at term were used to construct the model; the group comprised of 19% girls, 80% GH-deficient and 23% born SGA. For validation, data from 205 other children fulfilling the same inclusion and treatment criteria as the model group were used. The model was also tested on data from children born prematurely, children from other continents and children receiving a GH dose of 67 μg/kg/d.

Results

The GH response curve was similar for all children, but with an individual amplitude. The curve SD score depends on an individual factor combining the effect of dose and growth, the 'Response Score', and time on treatment, making prediction possible when the first-year growth response is known. The prediction interval (± 2 SD_res) was ± 0.34 SDS for the second treatment year growth response, corresponding to ± 1.2 cm for a 3-year-old child and ± 1.8 cm for a 7-year-old child. For the 1–4-year prediction, the SD_res was 0.13 SDS/year and for the 1–7-year prediction it was 0.57 SDS (i.e. < 0.1 SDS/year).

Conclusion

The model based on the observed first-year growth response on GH is valid worldwide for the prediction of up to 7 years of prepubertal growth in children with GHD/ISS, born AGA/SGA and born preterm/term, and can be used as an aid in medical decision making.

[Mathematical models for predicting growth responses to growth hormone replacement therapy]

Growth prediction models are algorithms derived from multiple regression analyses including variables that influence growth responses to GH therapy in a defined group of subjects over a defined period of time. Mathematical equations can be derived from the knowledge acquired with the relative importance of each variable, which provide objective measurements of each subject's growth potential in response to GH therapy on different situations. Therefore, these equations can be used as tools to improve evidence-based decision regarding to growth promoting treatment strategies to be used in each child, optimizing cost-effectiveness with the lowest cumulative GH dose. Several models have already been developed to predict growth responses to GH for different short stature causes, but they still have low clinical usefulness, due to their low predictive power and low prevision accuracy. This has lead to a growing interest in the addition of new variables, such as biochemical or genetic markers, which could improve prevision accuracy and then allow, in the future, GH therapy individualization according to the specific needs of each child.

Height velocity targets from the national cooperative growth study for first-year growth hormone responses in short children

CONTEXT

Although GH has been used to treat short stature in GH deficiency (GHD) and other conditions for more than 40 yr, criteria for satisfactorily defining targets for GH responsiveness have never been developed.

OBJECTIVE

The objective of this study was to present the first-year growth expressed as height velocity (HV) for prepubertal boys and girls with idiopathic GHD, organic GHD, idiopathic short stature, or Turner syndrome from Genentech's National Cooperative Growth Study to derive age-specific targets for GH responsiveness for each etiology and gender.

DESIGN AND POPULATION

Using data from the National Cooperative Growth Study, we constructed curves of response to GH during the first year of treatment with standard daily doses in naive-to-treatment prepubertal children with idiopathic GHD (2323 males, 842 females), organic GHD (582 males, 387 females), idiopathic short stature (1392 males, 465 females), or Turner syndrome (1367 females).

MAIN OUTCOME MEASURE

For each category, mean pretreatment and mean +/-1 and +/-2 sd for the first-year HV on GH were assessed. Mean and mean +/- 1 sd for HV were plotted vs. age at baseline (initiation of GH treatment) and compared with mean pretreatment HV.

RESULTS

HV plots for each category as a factor of age at baseline are presented. Mean - 2 sd HV plots approximated the pretreatment HV.

CONCLUSION

Using baseline age- and gender-specific targets will assist clinicians in assessing a patient's first-year growth response. We propose that HV below the mean - 1 sd on these plots be considered a "poor" response. These curves may be used to identify patients who may benefit from GH dose adjustment, to assess compliance issues, or to challenge the original diagnosis.

Models predicting the growth response to growth hormone treatment in short children independent of GH status, birth size and gestational age

Background

Mathematical models can be used to predict individual growth responses to growth hormone (GH) therapy. The aim of this study was to construct and validate high-precision models to predict the growth response to GH treatment of short children, independent of their GH status, birth size and gestational age. As the GH doses are included, these models can be used to individualize treatment.

Methods

Growth data from 415 short prepubertal children were used to construct models for predicting the growth response during the first years of GH therapy. The performance of the models was validated with data from a separate cohort of 112 children using the same inclusion criteria.

Results

Using only auxological data, the model had a standard error of the residuals (SD_res), of 0.23 SDS. The model was improved when endocrine data (GH_max profile, IGF-I and leptin) collected before starting GH treatment were included. Inclusion of these data resulted in a decrease of the SD_res to 0.15 SDS (corresponding to 1.1 cm in a 3-year-old child and 1.6 cm in a 7-year old). Validation of these models with a separate cohort, showed similar SD_res for both types of models. Preterm children were not included in the Model group, but predictions for this group were within the expected range.

Conclusion

These prediction models can with high accuracy be used to identify short children who will benefit from GH treatment. They are clinically useful as they are constructed using data from short children with a broad range of GH secretory status, birth size and gestational age.

Insulin growth factor-based dosing of growth hormone therapy in children: a randomized, controlled study

CONTEXT

Weight-based dosing of GH is the standard of care for short children, although IGF-I is thought to be the main mediator of GH actions on growth.

OBJECTIVE

The objective of the study was to test whether IGF-I levels achieved during GH therapy are determinants of the growth responses to GH treatment.

DESIGN

This was a 2-yr, open-label, randomized, IGF-I concentration-controlled trial. Prepubertal short children [n = 172, mean age 7.53 yr, mean height sd score (HT-SDS) -2.64] with low IGF-I levels (mean IGF-I SDS -3.56) were randomized to receive one of two GH dose-titration arms in which GH dosage was titrated to achieve an IGF-I SDS at the mean [IGF((low)) group, n = 70] or the upper limit of the normal range [+2 SDS, IGF((high)) group, n = 68] or to a comparison group of conventional GH dose of 40 microg/kg/d (n = 34).

SETTING

The study was conducted in a multicenter, outpatient setting.

PRIMARY OUTCOME MEASURE

Change in HT-SDS over 2 yr was measured.

RESULTS

One hundred forty-seven patients completed the trial. Target IGF-I levels were achieved in the dose-titration arms within 6-9 months. The changes in HT-SDS were +1.0, +1.1, and +1.6 for conventional, IGF((low)), and IGF((high)), respectively, with IGF((high)) showing significantly greater linear growth response (P < 0.001, compared with the other two groups). The IGF((high)) arm required higher doses (>2.5 times) than the IGF((low)) arm, and these GH doses were highly variable (20-346 microg/kg/d). Multivariate analyses suggested that the rise in the IGF-I SDS significantly impacted height outcome along with the GH dose and the pretreatment peak-stimulated GH level.

CONCLUSION

IGF-I-based GH dosing is clinically feasible and allows maintaining serum IGF-I concentrations within the desired target range. Titrating the GH dose to achieve higher IGF-I targets results in improved growth responses, although at higher average GH doses.

Prediction of adult height in growth-hormone-treated children with growth hormone deficiency

CONTEXT

Several studies have searched for factors that significantly influence adult height (AH) of children with GH deficiency (GHD) who have been treated with biosynthetic GH, but a prediction model for AH has not yet been presented.

OBJECTIVE

Our objective was to develop models for prediction of AH, using information available at the start of GH treatment or after 1 yr of treatment.

DESIGN AND SETTING

For this retrospective study, data were collected from the National Registry of Growth Hormone Treatment in Children, which contained data of Dutch children treated with GH.

PATIENTS/INTERVENTION

Patients included males born before 1985 and females born before 1987 with either diagnosis of GHD (syndromes, tumors, and other diseases were excluded) or a maximal GH response during provocation tests of less than 11 ng/ml, treated with biosynthetic GH for at least 1 yr. To be able to use the complete group of 342 children for the development of the models, multiple imputation was used for missing values.

MAIN OUTCOME MEASURE

We assessed AH sd scores (SDS).

RESULTS

Each prediction model contained both target height SDS and current height SDS. The change in height SDS during the first year proved an important predictor for AH. In all models, addition of GH dose was not significant. The percent explained variance, after correction for overfitting, ranged from 37% (prepubertal children, prediction at start) to 60% (pubertal children, prediction after 1 yr).

CONCLUSION

The presented prediction models give accurate predictions of AH for children with GHD at start and after 1 yr of GH treatment. They are useful tools in the treatment of these children.

Growth hormone therapy improves bone mineral density in children with cerebral palsy: a preliminary pilot study

CONTEXT

Cerebral palsy is associated with osteopenia, increased fracture risk, short stature, and decreased muscle mass, whereas GH therapy is associated with increased bone mineral density (BMD) and linear growth and improvement in body composition.

OBJECTIVE

We conducted a pilot study to evaluate the effect of 18 months of GH therapy on spinal BMD, linear growth, biochemical markers, and functional measures in children with cerebral palsy.

DESIGN AND SETTING

The study was a randomized control trial, conducted from 2002-2005 at the University of California, Los Angeles, Orthopedic Hospital's Center for Cerebral Palsy.

PATIENTS

Patients included 12 males with cerebral palsy, ages 4.5-15.4 yr.

INTERVENTION

We compared 18 months of GH (50 microg daily) vs. no treatment.

PRIMARY OUTCOME MEASURES

Spinal BMD (dual-energy x-ray absorptiometry scan), height, growth factors, and bone markers were assessed.

RESULTS

Ten subjects (five in each group) completed the study. Pre- and post-average height z-scores were -1.47 +/- 0.23 and 0.8 +/- 0.2 (GH-treated group) vs. -1.35 +/- 1.26 and -1.36 +/- 1.27 (control group) (Delta SD score, 0.67 vs. -0.01; P = 0.01). Average change in spinal BMD z-score (Delta SD score corrected for height) was 1.169 +/- 0.614 vs. 0.24 +/- 0.25 in the treated and control groups, respectively (P = 0.03). Osteocalcin, IGF-I, and IGF-binding protein 3 levels increased during GH therapy. There was no change in quality of life scores as measured by the Pediatric Orthopedic Disability Inventory.

CONCLUSIONS

This small pilot study suggests that 18 months of GH therapy is associated with statistically significant improvement in spinal BMD and linear growth.

The insulin-like growth factor-I response to growth hormone is increased in prepubertal children with obesity and tall stature

CONTEXT

Children with obesity [body mass index (BMI) > +2 sd score (SDS)] and children with constitutional tall stature [CTS; height > +2 SDS)] have normal-high serum IGF-I levels, associated with a low and broad range of GH secretion, respectively. This suggests increased sensitivity to GH, whereas children with idiopathic short stature (ISS; height < -2 SDS) are believed to have decreased GH sensitivity. OBJECTIVE, DESIGN, AND MAIN OUTCOME MEASURE: To compare the responsiveness to GH in 62 prepubertal children (43 females, 19 males) with obesity, CTS, or ISS and 26 controls (15 females, 11 males; height and BMI -2 to +2 SDS), we used an IGF-I generation test and studied the IGF-I concentration 24 h after a single injection of GH (2 mg/m2).

PATIENTS

Twenty patients with obesity, 20 with CTS, 22 with ISS, and 26 controls were studied. The mean age was 8.3 +/- 2.9 yr, with no difference in age or gender between groups.

RESULTS

Compared with controls, the mean IGF-I increment was 80% higher in obese children and 36% higher in tall children (P < 0.05 obese or tall vs. control children; P = 0.05 obese vs. tall children). Conversely, the IGF-I increment was similar in short compared with control children, despite a mean baseline IGF-I 62% lower in short children (P < 0.05 vs. controls). In all groups, the IGF-I increment was correlated with the BMI SDS or the fat mass percentage (r = 0.51-0.58, P < 0.05).

CONCLUSION

Obese children tend to have greater GH responsiveness than tall children, and both have greater GH responsiveness than controls. GH responsiveness was similar in controls and short children, despite a lower baseline IGF-I in short children. Whether the differences in the IGF-I response to GH between these children reflect differences in the respective anabolic (growth promotion) and metabolic (i.e. insulin action modulation) roles of circulating IGF-I is unknown.

Controversy in clinical endocrinology: problems with reclassification of insulin-like growth factor I production and action disorders

CONTEXT

Recent developments in the IGF field have raised questions on whether this is the right time to redefine IGF deficiency.

OBJECTIVE

In this controversy, arguments are made against the need for redefining IGF deficiency at this moment, suggesting instead to wait for further clinical developments.

CASE

Although a number of rare case reports of IGF deficiency with precise molecular etiologies have been described, the vast majority of the cases remain clinically defined and without a genetic diagnosis.

INTERVENTIONS

Because IGF products are now available for clinical use in IGF-deficient patients, we are still using GH stimulation and static IGF levels as our only clinical diagnostic and classification tools. POSITIONS: We need to develop additional clinical tools, side by side with molecular tools, for the diagnosis and subclassification of IGF deficiency. Chief among these are the IGF-generation test for identification of GH-insensitive patients and genetic panels of polymorphic changes in relevant genes.

CONCLUSIONS

Until further progress is made in the clinical classification of IGF deficiency, we should not change the current classification, and, when we do, it should be the responsibility of the relevant societies in the field to conduct a consensus statement on the topic first.

Effect of growth hormone (GH) treatment on the near-final height of 1258 patients with idiopathic GH deficiency: analysis of a large international database

CONTEXT

Treatment with GH has been used to correct the growth deficit in children with GH deficiency (GHD). Although successful in increasing height velocity, such treatment often falls short of helping patients achieve full genetic height potential.

OBJECTIVE

This study set out to analyze near-final height (FH) data from a cohort of GH-treated children with idiopathic GHD.

DESIGN, SETTING, AND PARTICIPANTS

Of 1258 evaluable patients in the Pfizer International Growth Database (KIGS) with GHD, 980 were of Caucasian origin, and 278 were of Japanese origin; 747 had isolated GHD (IGHD), and 511 had multiple pituitary hormone deficiencies (MPHD).

MAIN OUTCOME MEASURES

Near-FH, relation to midparental height, and factors predictive of growth outcomes were the main outcome measures.

RESULTS

Median height sd scores (SDS) at the start of treatment were -2.4 (IGHD) and -2.9 (MPHD) for Caucasian males and -2.6 (IGHD) and -3.4 (MPHD) for females, respectively; comparable starting heights were -2.9 (IGHD) and -3.6 (MPHD) for Japanese males and -3.3 (IGHD) and -4.0 (MPHD) for females, respectively. Corresponding near-adult height SDS after GH treatment were -0.8 (IGHD) and -0.7 (MPHD) for Caucasian males and -1.0 (IGHD) and -1.1 (MPHD) for females, respectively; and -1.6 (IGHD) and -1.9 (MPHD) for Japanese males and -2.1 (IGHD) and -1.8 (MPHD) for females, respectively. Differences between near-adult height and midparental height ranged between -0.6 and +0.2 SDS for the various groups, with the closest approximation to MPH occurring in Japanese males with MPHD. The first-year increase in height SDS and prepubertal height gain was highly correlated with total height gain, confirming the importance of treatment before pubertal onset.

CONCLUSIONS

It is possible to achieve FH within the midparental height range in patients with idiopathic GHD treated from an early age with GH, but absolute height outcomes remain in the lower part of the normal range. Patients with MPHD generally had a slightly better long-term height outcome.

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.

Metabolic effects of the incretin mimetic exenatide in the treatment of type 2 diabetes

Interventional studies have demonstrated the impact of hyperglycemia on the development of vascular complications associated with type 2 diabetes, which underscores the importance of safely lowering glucose to as near-normal as possible. Among the current challenges to reducing the risk of vascular disease associated with diabetes is the management of body weight in a predominantly overweight patient population, and in which weight gain is likely with many current therapies. Exenatide is the first in a new class of agents termed incretin mimetics, which replicate several glucoregulatory effects of the endogenous incretin hormone, glucagon-like peptide-1 (GLP-1). Currently approved in the US as an injectable adjunct to metformin and/or sulfonylurea therapy, exenatide improves glycemic control through multiple mechanisms of action including: glucose-dependent enhancement of insulin secretion that potentially reduces the risk of hypoglycemia compared with insulin secretagogues; restoration of first-phase insulin secretion typically deficient in patients with type 2 diabetes; suppression of inappropriately elevated glucagon secretion to reduce postprandial hepatic output; and slowing the rate of gastric emptying to regulate glucose appearance into the circulation. Clinical trials in patients with type 2 diabetes treated with subcutaneous exenatide twice daily demonstrated sustained improvements in glycemic control, evidenced by reductions in postprandial and fasting glycemia and glycosylated hemoglobin (HbA(1c)) levels. Notably, improvements in glycemic control with exenatide were coupled with progressive reductions in body weight, which represents a distinct therapeutic benefit for patients with type 2 diabetes. Acute effects of exenatide on beta-cell responsiveness along with significant reductions in body weight in patients with type 2 diabetes may have a positive impact on disease progression and potentially decrease the risk of associated long-term complications.

Growth hormone injections improve bone quality in a mouse model of osteogenesis imperfecta

Systemic growth hormone injections increased spine and femur length in a mouse model of OI. Femur BMC, cross-sectional area, and BMD were increased. Smaller gains were produced in vertebral BMC and cross-sectional area. Biomechanical testing showed improvements to structural and material properties in the femur midshaft, supporting expanded testing of growth hormone therapy in children with OI.

INTRODUCTION

Osteoblasts in heterozygous Cola2oim mutant mice produce one-half the normal amounts of the alpha2 strand of type I procollagen. The mice experience a mild osteogenesis imperfecta (OI) phenotype, with femurs and vertebrae that require less force than normal to break in a biomechanical test.

MATERIALS AND METHODS

Subcutaneous injections of recombinant human growth hormone (rhGH) or saline were given 6 days per week to oim/+ mice between 3 and 12 weeks of age, in a protocol designed to simulate a trial on OI children.

RESULTS

rhGH injections promoted significant weight gain and skeletal growth compared with saline-treated control animals. Femur and spine lengths were increased significantly. Significant increases at the femur midshaft in cortical BMD (2.2%), BMC (15.5%), and cross-sectional area (13%) were produced by rhGH treatment. Increases in the same cortical bone parameters were measured in the metaphyseal region of the femur and in tail vertebrae, but lumbar vertebrae showed significant increases in BMC (9.6%) and cross-sectional area (10.1%) of trabecular bone. Three-point bending testing documented functional improvements to the femur mid-shafts. GH treatment produced significant increases in bone stiffness (23.7%), maximum load (30.8%), the energy absorbed by the femurs to the point of maximum load (44.5%), and the energy to actual fracture (40.4%). The ultimate stress endured by the bone material was increased by 14.1%.

CONCLUSIONS

Gains in bone length, cross-sectional area, BMD, BMC, structural biomechanical properties, and strength were achieved without directly addressing the genetic collagen defect in the mice. Results support expanded clinical testing of GH injections in children with OI.

Short stature and growth hormone

Normal growth and development is a prime concern during childhood. Accurate assessment is essential for differentiating between normal and abnormal growth. Increased accessibility to growth hormone has equipped the pediatrician and pediatric endocrinologist to treat and improve growth in many clinical scenarios. At the same time, there is added responsibility to use this tool judiciously. This review summarizes the basics of proper growth assessment, differentiation of normal and abnormal growth causes of and works up of short stature, and delineation of indications for growth hormone treatment.

Growth hormone treatment in children: review of safety and efficacy

Since the advent of growth hormone (GH), the pediatric applications of GH therapy have expanded. Children with a wide variety of growth disorders have received GH treatment. The therapeutic effects and safety profile of GH in a number of pediatric conditions are reviewed, including GH deficiency (GHD), Turner syndrome, chronic renal failure, children born small for gestational age, Prader-Willi syndrome, juvenile chronic arthritis, and cystic fibrosis. GH therapy has been clearly shown to improve height velocity during childhood in a variety of pediatric conditions in which growth is compromised. There is now data that confirms GH treatment also improves final height in a number of diagnostic subgroups. Early initiation and individualization of GH treatment has the potential to normalize childhood growth in children with idiopathic GHD and enable them to achieve their genetic target height in a cost-effective manner. In children in whom GHD is not the main factor compromising growth, supra-physiological doses of GH have been shown to increase height velocity during childhood and final height. The development of predictive models for these conditions may allow further improvements in height outcome while maintaining an acceptable safety profile. Survivors of childhood malignancy, particularly those who have had craniospinal irradiation, represent a particularly challenging group. They appear to be less responsive to GH than children with idiopathic GHD and have a tendency to enter puberty at an earlier age. Both of these factors have a negative impact on their final height. Strategies that combine GH treatment with suppression of puberty using a gonadotropin releasing hormone analog may result in improved height outcomes. When children with GHD are treated with standard doses of GH there is a strong safety record. Adverse events during GH therapy are uncommon and often not drug related. Continued surveillance into adult life is crucial however, particularly in children receiving supra-physiological doses of GH or whose underlying condition increases their risk of adverse effects.

Indications and strategies for continuing GH treatment during transition from late adolescence to early adulthood in patients with GH deficiency: the impact on bone mass

GH plays an important role in longitudinal bone growth and maturation during childhood and adolescence. However, GH has important metabolic functions other than bone growth, which become more apparent during young adulthood, when growth has been completed. Indeed, GH deficiency (GHD) in adult life is a recognized clinical syndrome which includes symptoms such as increased central adiposity, decreased lean body mass, reduced bone mineral density (BMD), increased atherogenic risk, cerebrovascular and cardiac morbidity and mortality, and reduced quality of life. As approximately one quarter of the children with GHD should continue GH administration in adulthood, it is important to reconfirm GHD at the end of growth in order to select patients with severe GHD who need to resume GH therapy with an appropriate age-related dosage. Some evidence indicates that most peak bone mass (PBM) is achieved by the end of adolescence but small increases in BMD continue during the period of transition from late adolescence to young adulthood. Some young adults with GHD show a persistent increase of lumbar BMD after the completion of growth even after discontinuation of treatment suggesting a spontaneous progression towards lumbar PBM or a continuing effect of the treatment. The data indicates that adolescents with GHD who do not reach lumbar PBM at the time of discontinuation of GH treatment can achieve a BMD lower than their genetic potential if they are not treated during the transition to young adulthood.

Growth hormone deficiency (GHD): A new association in Peters' plus syndrome (PPS)

We report a case of a girl with clinical features of Peters' Plus Syndrome (PPS) (association of anterior eye chamber defects; peculiar facies; cleft lip/palate; brachymelia; developmental delay; growth retardation) and documented growth hormone deficiency (height -3.5 SDS at chronological age 5 years 8 months; low growth factors; bone age delay; growth velocity 4.4 cm/year (<3rd centile); and peak growth hormone levels of 1.7 and 4.7 ng/ml by clonidine and insulin provocative testing, respectively). Treatment with recombinant human growth hormone (0.3 mg/kg/week) resulted in a dramatic increase in growth velocity, increasing the height from -3.5 to -1.5 SDS over 2.3 years of therapy, indicative of an excellent response. Growth retardation is a known association in PPS: a condition that includes other midline facial defects. This case supports a role for GHD in the pathogenesis of the short stature observed in these children; demonstrates the efficacy of GH treatment; and further reinforces the relationship of pituitary anomalies with common congenital defects.