The Auxological and Biochemical Continuum of Short Children Born Small for Gestational Age (SGA) or with Normal Birth Size (Idiopathic Short Stature)

Efficacy and Safety Evaluation of Human Growth Hormone Therapy in Patients with Idiopathic Short Stature in Korea - A Randomised Controlled Trial

BACKGROUND

This trial evaluated the efficacy and safety of growth hormone (GH) therapy (Norditropin®; Novo Nordisk, Bagsværd, Denmark) in paediatric patients with idiopathic short stature (ISS) in Korea.

METHODS

This was an open-label, parallel-group, multicentre, interventional trial (ClinicalTrials.gov identifier: NCT01778023). Pre-pubertal patients (mean age 6.2 years; height, 107.1 cm) were randomised 2:1 to 12 months' GH treatment (0.469 mg/kg/week; group A, n=36) or 6 months untreated followed by 6 months' GH treatment (group B, n=18). Safety analysis was based on adverse events (AEs) in all GH-treated patients.

RESULTS

After 6 months, height velocity (Ht-V), change in both height standard deviation score (Ht-SDS) and insulin-like growth factor 1 (mean difference [95% confidence interval {CI}]: 5.15 cm/year [4.09, 6.21]; 0.57 [0.43, 0.71]; 164.56 ng/mL [112.04, 217.08], respectively; all p<0.0001) were greater in group A than in group B. Mean difference in Ht-V for 0-6 months versus 6-12 months was 2.80 cm/year (95% CI 1.55, 4.04) for group A and -4.60 cm/year (95% CI -6.12, -3.09; both p<0.0001) for group B. No unexpected AEs were reported.

CONCLUSIONS

During the first 6 months, height was significantly increased in GH-treated patients versus untreated patients with ISS. Safety of GH was consistent with the known safety profile.

Phenotypic Features and Response to GH Treatment of Patients With a Molecular Defect of the IGF-1 Receptor

CONTEXT

The phenotype and response to GH treatment of children with an IGF1R defect is insufficiently known.

OBJECTIVE

To develop a clinical score for selecting children with short stature for genetic testing and evaluate the efficacy of treatment.

DESIGN AND SETTING

Case series with an IGF1R defect identified in a university genetic laboratory.

PATIENTS AND INTERVENTIONS

Of all patients with sufficient clinical data, 18 had (likely) pathogenic mutations (group 1) and 7 had 15q deletions including IGF1R (group 2); 19 patients were treated with GH.

MAIN OUTCOME MEASURES

Phenotype and response to GH treatment.

RESULTS

In groups 1 and 2, mean (range) birth weight, length, and head circumference (HC) SD scores (SDSs) were -2.1 (-3.7 to -0.4), -2.7 (-5.0 to -1.0), and -1.6 (-3.0 to 0.0), respectively. At presentation, height, HC, and serum IGF-1 SDSs were -3.0 (-5.5 to -1.7), -2.5 (-4.2 to -0.5), and +1.2 (-1.3 to 3.2), respectively. Feeding problems were reported in 15 of 19 patients. A clinical score with 76% sensitivity is proposed. After 3 years of GH treatment [1.1 (0.2) mg/m2/d] height gain in groups 1 (n = 12) and 2 (n = 7) was 0.9 SDS and 1.3 SDS (at a mean IGF-1 of 3.5 SDS), less than reported for small for gestational age (1.8 SDS).

CONCLUSION

A clinical score encompassing birth weight and/or length, short stature, microcephaly, and IGF-1 is useful for selecting patients for IGF1R analysis. Feeding problems are common and the growth response to GH treatment is moderate.

Idiopathic short stature and growth hormone sensitivity in prepubertal children

OBJECTIVE

We compared growth hormone sensitivity to an insulin-like growth factor I (IGF-I) generation test in children with idiopathic short stature (ISS) and of normal stature (NS) across the birthweight range.

METHODS

Forty-six prepubertal children (~7.1 years) born at term were studied: ISS (n = 23; 74% boys) and NS (n = 23; 57% boys). Children underwent a modified IGF-I generation test with recombinant human growth hormone (rhGH; 0.05 mg/kg/d) over four consecutive days. Hormonal concentrations were measured at baseline and day 5.

RESULTS

Children with idiopathic short stature were 1.90 SDS lighter (P < 0.0001) but had 4.5% more body fat (P = 0.0007) than NS children. Overall, decreasing birthweight SDS across the normal range (-1.9 to +1.5 SDS) was associated with lower percentage IGF-I response to rhGH stimulation in univariable (r = 0.45; P = 0.002) and multivariable models (β = 24.6; P = 0.006). Plasma IGF-I concentrations rose in both groups with rhGH stimulation (P < 0.0001). GHBP levels (P = 0.002) were suppressed in ISS children (-19%; P = 0.029) but increased among NS children (+18%; P = 0.028), with contrasting responses also observed for leptin and IGFBP-1. Further, the increase in insulin concentrations in response to rhGH stimulation was ~3-fold greater in NS children (142% vs 50%; P = 0.006).

CONCLUSIONS

A progressive decrease in birthweight SDS was associated with a reduction in GH sensitivity in both NS and ISS children. Thus, the lower IGF-I response to rhGH stimulation in association with decreasing birthweight indicates that the ISS children at the lower end of the birthweight spectrum may have partial GH resistance, which may contribute to their poorer growth.

Growth hormone therapy in children born small for gestational age: results from the ANSWER program

Growth hormone (GH) is used to treat short stature and growth failure associated with growth disorders. Birth size and GH status variably modulate response to GH therapy. The aim of this study was to determine the effect of birth size on response to GH therapy, and to determine the impact of GH status in patients born small for gestational age (SGA) on response to GH therapy. Data from the prospective, non-interventional American Norditropin® Studies: Web-Enabled Research (ANSWER) Program were analyzed for several growth outcomes in response to GH therapy over 3 years. GH-naïve children from the ANSWER Program were included in this analysis: SGA with peak GH ≥10 ng/mL (20 mIU/l), SGA with peak GH <10 ng/mL (20 mIU/l), isolated growth hormone deficiency (IGHD) born SGA, IGHD not born SGA, and idiopathic short stature. For patients with IGHD, those who did not meet criteria for SGA at birth showed greater improvements in height SDS and BMI SDS than patients with IGHD who met criteria for SGA at birth. For patients born SGA, response to GH therapy varied with GH status. Therefore, unlike previous guidelines, we recommend that GH status be established in patients born SGA to optimize GH therapy.

Assessment of pathogenicity of natural IGFALS gene variants by in silico bioinformatics tools and in vitro functional studies

Acid-labile subunit (ALS) is essential for stabilization of IGF-I and IGFBP-3 in ternary complexes within the vascular system. ALS deficient (ALS-D) patients and a subset of children with idiopathic short stature (ISS), presenting IGFALS gene variants, show variable degree of growth retardation associated to IGF-I and IGFBP-3 deficiencies. The aim of this study was to evaluate the potential pathogenicity of eleven IGFALS variants identified in ALS-D and ISS children using in silico and in vitro approaches. We were able to classify seven of these variants as pathogenic since they present impaired synthesis (p.Glu35Lysfs*87, p.Glu35Glyfs*17, p.Asn276Ser, p.Leu409Phe, p.Ser490Trp and p.Cys540Arg), or partial impairment of synthesis and lack of secretion (p.Leu213Phe). We also observed significant reduction of secreted protein for variants p.Ala330Asp, Ala475Val and p.Arg548Trp, while still retaining their ability to form ternary complexes. These findings provide an approach to test the pathogenicity of IGFALS gene variants.

Characterizing short stature by insulin-like growth factor axis status and genetic associations: results from the prospective, cross-sectional, epidemiogenetic EPIGROW study

CONTEXT

Serum IGF-I levels are often low in patients with short stature (SS) without defined etiology. Hence, genetic investigations have focused on the GH-IGF-I axis.

OBJECTIVE

Our objectives were to characterize IGF-I axis status and search for a broader range of genetic associations in children with SS and normal GH.

DESIGN AND SETTING

We conducted a prospective, cross-sectional, epidemiogenetic case-control study in 9 European countries (2008-2010).

PARTICIPANTS

Children (n = 275) aged ≥2 years with SS without defined etiology (≤-2.5 height SD score [SDS]) and ≥1 peak GH ≥7 μg/L) were recruited.

METHODS

Serum IGF-I, IGF-binding protein-3 (IGFBP-3), and acid-labile subunit (ALS) levels were measured in a central laboratory. Candidate gene exome sequencing was performed in this cohort and ethnicity-matched controls.

RESULTS

Serum IGF-I, IGFBP-3, and ALS levels were highly correlated, but there was a discrepancy between prevalence of IGF-I, IGFBP-3, and ALS deficiencies (53%, 30%, and 0.8%, respectively). An insertion-deletion (Indel) on the IGF1 gene (P = 1.2 × 10(-5), Bonferroni-corrected; case vs control frequency: 0.04 vs 0.112), an Indel on NFKB1 (P = 1.36 × 10(-10); case vs control frequency: 0.464 vs 0.272), and 2 single-nucleotide polymorphisms on ZBTB38 (P < 2.3 × 10(-6)) were associated with SS. At P < 10(-4), single-nucleotide polymorphisms on genes related to protein kinase regulation, MAPK, and Fanconi pathways were also associated with SS.

CONCLUSIONS

IGF-I deficiency is a common feature in SS without defined etiology; an Indel in the IGF1 gene was associated with SS. However, genes involved in transcriptional regulation (NFKB1 and ZBTB38) and growth factor signaling were also associated, providing further candidates for genetic investigations on individual patients.