Serum levels of free insulin-like growth factor (IGF)-I and IGF-binding protein-1 in prepubertal children with idiopathic short stature

LCN2 is a new diagnostic biomarker and potential therapeutic target in idiopathic short stature

Idiopathic short stature (ISS) is the most common paediatric endocrine disease. However, the underlying pathology of ISS remains unclear. Currently, there are no effective diagnostic markers or therapeutic strategies available for ISS. In this study, we aimed to identify differential plasma protein expression and novel biomarkers in patients with ISS, and elucidate the biological functions of candidate proteins in ISS pathogenesis. Four specimen pairs from four ISS children and age‐/sex‐matched control individuals were subjected to proteomics analysis, and 340 samples of children with a mean age 9.73 ± 0.24 years were utilized to further verify the differentially expressed proteins by enzyme‐linked immunosorbent assay (ELISA). The receiver‐operating characteristic (ROC) curve and the area under the ROC curve (AUC) were plotted. A total of 2040 proteins were identified, of which 84 were differentially expressed. In vitro and in vivo experiments confirmed the biological functions of these candidate proteins. LCN2 overexpression in ISS was verified using ELISA. Meanwhile, LCN2 showed high sensitivity and specificity in discriminating children with ISS from those with growth hormone deficiency, precocious puberty and normal control individuals. The upregulated expression of LCN2 not only suppressed food intake but also impaired chondrocyte proliferation and bone growth in chondrocytes and rats. As a result, the rats presented a short‐stature phenotype. Subsequently, we found that bone growth inhibition recovered after LCN2 overexpression was stopped in immature rats. To our knowledge, this is the first study to report that LCN2 may be a significant target for ISS diagnosis and treatment.

Obstructive sleep apnea syndrome and growth failure

Obstructive sleep apnea syndrome is a common problem among children and is recognized as a cause of significant medical morbidity. Since the 1980s, it has been suggested that obstructive sleep apnea syndrome is a risk factor for growth failure in children. In many cases, it has been shown that growth failure is reversible once the obstructive sleep apnea syndrome is resolved. The objectives of this study were to analyze and compare growth failure prevalence in a Mediterranean population of children with obstructive sleep apnea syndrome and healthy children matched in age and sex, and to assess the effectiveness of tonsillectomy and adenoidectomy in resolving growth retardation. We compared 172 children with obstructive sleep apnea syndrome (apnea-hypopnea index ≥ 3) who had undergone tonsillectomy and adenoidectomy with 172 healthy controls in terms of key anthropometric parameters. Most of the criteria used for growth failure were higher to a statistically significant degree in the study group vs the control group: height-for-age ≤ 3rd percentile (7.56% vs 2.91%; p = 0.044), weight-for-age ≤ 5th percentile (9.30% vs 2.33%; p = 0.005), weight-for-age ≤ 3rd percentile (8.14% vs 2.33%; p = 0.013) and height and/or weight for-age ≤ 5th percentile (13.95% vs 5.81%; p = 0.009). The height-for-age ≤ 5th percentile was almost at the limit of statistical significance (8.72% for the study group vs 4.65% for the control group; p = 0.097). At one-year post-surgery follow-up, 10 of 15 children with height-for-age ≤ 5th percentile had achieved catch-up growth (66.6%), and 14 of 24 children with height- and/or weight-for-age ≤ 5th percentile had normalized growth (58.33%). For children with failure to thrive or who have growth failure, physicians should consider the possibility of obstructive sleep apnea. A significant number of children with obstructive sleep apnea concurrent with growth failure could benefit from tonsillectomy and adenoidectomy to recover and normalize their growth rate.

Posttonsillectomy weight loss in adults

OBJECTIVE

To analyze and determine the incidence and severity of weight loss in adult tonsillectomies.

STUDY DESIGN

Case series with chart review.

SETTING

Adult tonsillectomy is performed for a variety of indications. Anecdotally, patients report a 10- to 15-pound weight loss in the postoperative period; however, no supporting research has been documented. The pediatric population has a well-documented weight gain postoperatively.

SUBJECTS

In total, 138 adults (aged 18-40 years) receiving tonsillectomy at Naval Medical Center Portsmouth (NMCP) between 2008 and 2013.

METHODS

A retrospective study was performed using an S3 surgery scheduling system search of all adult tonsillectomies at NMCP between 2008 and 2013. A subsequent electronic medical record search (AHLTA) of preoperative and postoperative weights and demographics was performed.

RESULTS

Data analysis revealed a significant difference found between preoperative and postoperative weight across all age groups (4.77 pounds, P < .005). Analysis of variance was performed to determine if there is a significant difference between these age and body mass index (BMI) groups. The highest amount of weight loss was observed in the oldest population group (5.72 pounds in subjects aged >40 years, 4.95 pounds in 31- to 40-year-olds, and 5.44 pounds in 20- to 30-year-olds, P = .03). Age comparisons were statistically significant. There was no statistically significant association between BMI and postoperative weight loss.

CONCLUSIONS

These results indicate that there is evidence of a roughly 5-pound weight loss in the postoperative period following tonsillectomy in adults with subsequent return to baseline weight after roughly 5 months. These findings are significant since this could lead to further research into changes in obesity-associated disease.

Growth hormone/insulin-like growth factor-1 axis as related to body mass index in patients with idiopathic short stature

OBJECTIVE

Idiopathic short stature (ISS) is a heterogeneous disorder. An impairment of growth hormone (GH)/insulin-like growth factor 1 (IGF-1)/IGF-1 receptor (IGF-1 R) axis is postulated. To evaluate the somatotropic axis in relation to body mass index (BMI), serum IGF-1, IGF-binding protein-3 (IGFBP-3) and the expression of IGF-1 R genes in patients with ISS.

METHODS

Fifty-five ISS patients (24 F/31 M) aged 14.6 ± 5.5 years (range 3.5-28.5 years) and 25 BMI- and pubertal stage-matched peers were enrolled in the study. The ISS patients underwent a four-day standard GH stimulation test to evaluate IGF-1 generation. mRNA expression of the IGF-1 R gene in peripheral blood leukocytes was evaluated. ISS patients and controls were compared with respect to anthropometric and laboratory data. The results were also analyzed after subdividing the two groups into low-normal [BMI standard deviation score (SDS) between -2 to -1)] and normal (BMI SDS between -1 to +1) BMI subgroups.

RESULTS

Basal serum IGF-1 concentrations were lower in ISS subjects compared to controls who had similar BMI SDS values (p=0.000). Subgroup analyses revealed that there were no significant differences between low-normal BMI ISS subjects and low-normal BMI controls with respect to serum IGF-1 and IGFBP-3 concentrations. However, in the normal BMI ISS subgroup, basal and stimulated IGF-1 levels were significantly lower than the basal values in their control counterparts (basal: p=0.000; stimulated: p=0.007). mRNA expression of IGF-1 R gene was not found to be significantly different in ISS subjects and controls.

CONCLUSIONS

ISS patients were found to have lower IGF-1 concentrations than BMI-matched peers, a finding supporting presence of an impairment in the somatotropic axis. IGF-1 R expression does not seem to be impaired in ISS patients. ISS patients with low-normal BMI SDS also tend to display a relative IGF-1 resistance, whereas those with normal BMI SDS tend to be less GH-sensitive than healthy peers.

Growth failure and sleep disordered breathing: a review of the literature

OBJECTIVE

While otolaryngologists consider growth failure an absolute indication for tonsillectomy and adenoidectomy (T&A), they may not be accustomed to screening for poor growth, and thus unlikely to consider it when recommending a T&A. This paper will (a) familiarize otolaryngologists with the definition, prevalence, and etiology of growth failure and (b) review the published findings that examine the inter-relationship among sleep disordered breathing, growth failure, and adentonsillar hypertrophy in children.

METHODS

This paper is divided into three sections. The first section presents a brief overview of growth failure for the otolaryngologist. The second section reviews the evidence base linking sleep disordered breathing, growth failure, and adenotonsillar hypertrophy in children. The anthropometric outcomes of children presenting for T&A, or having sleep symptoms assessed, are presented. The third section presents pilot data (n=28) on the prevalence of growth failure and sleep disordered breathing among children presenting for T&A at our institution.

RESULTS

Among children presenting for T&A or having sleep symptoms assessed, growth failure was at least twice the expected rate in six of eight published studies. Across these six studies, this rate ranged from a low of 6% of children <3rd percentile for weight and 6% <3rd percentile for height in one study, to a high of 52% who were <3rd percentile in weight in a second study, and 44% who were <or= 5th percentile for height in a third. Among children presenting for T&A at our own institution, 14% were <or=5th percentile in height, and 11% were <or=5th percentile in weight. Among children under 6 years of age, 21% were either <or= 5th percentile in weight and/or height.

CONCLUSIONS

Published studies, as well as our own pilot data support the hypothesis that SDB, secondary to adenotonsillar hypertrophy increases the risk of growth failure in children. Adenotonsillar hypertrophy and sleep disordered breathing may be unrecognized risk factors in the etiology of growth failure. Otolaryngologists can play an important role in identifying growth failure, and referring children to the appropriate specialists.

Elevated circulating insulin-like growth factor binding protein-1 is sufficient to cause fetal growth restriction

IGF binding protein-1 (IGFBP-1) inhibits the mitogenic actions of the IGFs. Circulating IGFBP-1 is elevated in newborns and experimental animals with fetal growth restriction (FGR). To establish a causal relationship between high circulating IGFBP-1 and FGR, we have generated transgenic mice using the mouse alpha-fetoprotein gene promoter to target overexpression of human IGFBP-1 (hIGFBP-1) in the fetal liver. These transgenic mice (AFP-BP1) expressed hIGFBP-1 mainly in the fetal hepatocytes, starting at embryonic d 14.5 (E14.5), with lower levels in the gut. The expression peaked at 1 wk postnatally (plasma concentration, 474 +/- 34 ng/ml). At birth, AFP-BP1 pups were 18% smaller [weighed 1.34 +/- 0.02 g compared with 1.62 +/- 0.04 g for wild type (WT); P < 0.05], and they did not demonstrate any postnatal catch-up growth. The placentas of the AFP-BP1 mice were larger than WT from E16.5 onwards (150 +/- 12 for AFP-BP1 vs. 100 +/- 5 mg for WT at E16.5; P < 0.05). Thus, this model of FGR is associated with a larger placenta, but without postnatal catch-up growth. Overall, these data clearly demonstrate that high concentrations of circulating IGFBP-1 are sufficient to cause FGR.

Spontaneous growth hormone secretion and IGF1:IGFBP3 molar ratios in children born small for gestational age (SGA)

OBJECTIVE

To analyze spontaneous nocturnal GH profiles, IGF1 and IGFBP3 serum levels, as well as IGF1:IGFBP3 molar ratios in SGA children without postnatal catch-up growth.

METHODS

Short statured prepubertal SGA children (n = 24) were matched retrospectively for sex, age and BMI to short statured children born appropriate for gestational age (AGA), who underwent the same diagnostic program. GH deficiency was excluded in all children by a normal increase of GH in 2 stimulation tests (>8 microg/L). For assessment of spontaneous nocturnal GH secretion, GH serum levels were measured every 20 min for 10 h. Pulsatility was analyzed with Pulsar.

RESULTS

None of the Pulsar derived descriptive parameters showed a significant difference between SGA and AGA children. Overall, median IGF1 levels were approximately one SDS below zero SDS (p < 0.001), whereas IGFBP3 levels were normal in both groups. Thus, the IGF1:IGFBP3 molar ratios were significantly lower from zero (p < 0.01) in SGA as well as in AGA children. However, IGF1- and IGFBP3-SDS levels related either to chronological or to bone age did not differ significantly between SGA and AGA children.

CONCLUSIONS

Building matched pairs of short statured children born either SGA or AGA for sex, age and BMI we did not find any significant differences in spontaneous nocturnal GH secretion, IGF1, IGFBP3, and IGF1:IGFBP3 molar ratios.

Standard and low-dose IGF-I generation tests and spontaneous growth hormone secretion in children with idiopathic short stature

OBJECTIVE

Abnormalities in the GH-IGF-I axis, consistent with GH insensitivity (GHI), have been reported in some patients with idiopathic short stature (ISS). The standard IGF-I generation test (IGFGT) has not demonstrated mild GHI in subjects with ISS. The aim of this study was to investigate the GH-IGF-I axis in ISS by performing standard and novel low-dose IGFGTs together with determination of spontaneous GH secretion.

PATIENTS AND METHODS

Twenty-one (17 male) prepubertal children with ISS, mean age 8.3 years (4.5-12.2), mean height -3.48 SD (-5.40 to -1.79), mean peak GH to provocation with glucagon/clonidine 32.3 mU/l (14.1-66.0) were studied. Serum IGF-I and IGFBP-3 levels were measured during standard (GH 0.033 mg/kg/day x 4) and low (GH 0.011 mg/kg/day x 4) dose IGFGTs at 0, 12, 36 and 84 h. The low-dose IGFGT was performed in seven naive GH-deficient patients (4 male), mean age 8.5 years (range 4.1-11.1). Determination of spontaneous 24-h GH secretion was performed in the 21 ISS patients.

RESULTS

Basal IGF-I and IGFBP-3 standard deviation scores (SDS) in ISS patients were -1.39 (-2.4-1.16) and -0.45 (-1.13-0.38), respectively, IGF-I being lower than IGFBP-3 (P < 0.0001). IGF-I increased in the standard IGFGT at 12 h (P < 0.005), 36 h (P < 0.001) and 84 h (P < 0.001); maximal increment 1.54 (-0.32-3.48), and in the low-dose test at 12 h (P < 0.005), 36 h (P < 0.001) and 84 h (P < 0.005); maximal increment 0.53 (0.08 to -1.23). IGFBP-3 SDS increased in the standard IGFGT at 36 h (P < 0.01) and 84 h (P < 0.001); maximal increment 0.72 (-0.44-1.96), and in the low-dose test at 84 h (P < 0.005); maximal increment 0.33 (-0.08-0.87). Five/19 patients with an IGF-I response > 2 x coefficient of variation (CV) of assay in the standard test failed to respond in the low-dose test, suggestive of mild GHI. In GH-deficient patients, IGF-I increased at each time point (P < 0.05) and IGFBP-3 at 36 h (P < 0.05). Mean GH secretion, expressed in SDS, compared with 66 normal stature controls was: basal GH -0.48 (-0.84-0.93), height of GH peaks compared with zero -0.36 (-1.26-1.51) (both P < 0.05), total GH secretion -0.76 (-1.22-0.42), total GH secretion above baseline -0.67 (-1.21-0.94) (both P < 0.01).

CONCLUSIONS

In children with ISS, basal IGF-I and IGFBP-3 SDS values were below the mean, IGF-I showing a greater response in both IGFGTs. In the standard IGFGT, the IGF-I increase at 36 h was equal to that at 84 h. The low-dose IGFGT, in combination with the standard test, may identify patients with mild GHI.

The GH-IGF-I axis in children with idiopathic short stature

Idiopathic short stature (ISS) is a term used for children in whom the etiology of the short stature is undefined. Investigations of the growth hormone (GH)-insulin-like growth factor I axis have revealed several molecular and endocrinological defects in ISS patients. Abnormalities of GH secretion and action, although not frequent, will help to categorize some children with ISS. Because most diagnostic methods remain crude, however, their modification might be necessary to identify more subtle and yet functionally significant abnormalities of this endocrine axis.