Reference values for serum levels of insulin-like growth factor-I and insulin-like growth factor binding protein-3 in Korean children and adolescents

Age- and sex-specific reference intervals across life span for insulin-like growth factor binding protein 3 (IGFBP-3) and the IGF-I to IGFBP-3 ratio measured by new automated chemiluminescence assays

CONTEXT

Measurement of IGF-binding protein-3 (IGFBP-3) can aid the diagnosis of GH-related diseases. Furthermore, epidemiological studies suggest that IGFBP-3 and the molar IGF-I to IGFBP-3 ratio are associated with clinical end points like cancer or cardiovascular disease. However, their clinical use is limited by the lack of validated reference intervals.

OBJECTIVE

The objective of the study was the establishment of age- and sex-specific reference intervals for IGFBP-3 and the molar IGF-I to IGFBP-3 ratio by newly developed automated immunoassays.

SETTING

This was a multicenter study with samples from 11 cohorts from the United States, Canada, and Europe.

PARTICIPANTS

A total of 14 970 healthy subjects covering all ages from birth to senescence participated in the study.

MAIN OUTCOME MEASURES

Concentrations of IGFBP-3 and the IGF-I to IGFBP-3 ratio as determined by the IDS iSYS IGF-I and IGFBP-3 assays were measured.

RESULTS

Both the concentration of IGFBP-3 and the IGF-I to IGFBP-3 ratio are mainly determined by age. IGFBP-3 concentrations increase until the age of 22 years, with a plateau being visible between 15 and 25 years. Determined by the high peripubertal peak in IGF-I, the peak in the IGF-I to IGFBP-3 ratio occurs already around the age of 15 years, with a slightly earlier and higher peak in females. Beyond the age of 60 years, IGFBP-3 concentrations remain higher in females, whereas IGF-I as well as the IGF-I to IGFBP-3 ratio remains significantly higher in males.

CONCLUSIONS

We present an extensive set of assay-specific age- and sex-adjusted normative data for concentrations of IGFBP-3 and the molar IGF-I to IGFBP-3 ratio and demonstrate distinct sex specific differences across the life span.

Factors that predict a positive response on gonadotropin-releasing hormone stimulation test for diagnosing central precocious puberty in girls

PURPOSE

The rapid increase in the incidence of precocious puberty in Korea has clinical and social significance. Gonadotropin-releasing hormone (GnRH) stimulation test is required to diagnose central precocious puberty (CPP), however this test is expensive and time-consuming. This study aimed to identify factors that can predict a positive response to the GnRH stimulation test.

METHODS

Clinical and laboratory parameters, including basal serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), and estradiol (E2), were measured in 540 girls with clinical signs of CPP.

RESULTS

Two hundred twenty-nine of 540 girls with suspected CPP had a peak serum LH level higher than 5 IU/L (the CPP group). The CPP group had advanced bone age (P<0.001), accelerated yearly growth rate (P<0.001), increased basal levels of LH (P=0.02), FSH (P<0.001), E2 (P=0.001), and insulin-like growth factor-I levels (P<0.001) compared to the non-CPP group. In contrast, body weight (P<0.001) and body mass index (P<0.001) were lower in the CPP group. Although basal LH was significantly elevated in the CPP group compared to the non-CPP group, there was considerable overlap between the 2 groups. Cutoff values of basal LH (0.22 IU/L) detected CPP with 87.8% sensitivity and 20.9% specificity.

CONCLUSION

No single parameter can predict a positive response on the GnRH stimulation test with both high sensitivity and specificity. Therefore, multiple factors should be considered in evaluation of sexual precocity when deciding the timing of the GnRH stimulation test.

Arsenic exposure affects plasma insulin-like growth factor 1 (IGF-1) in children in rural Bangladesh

BACKGROUND

Exposure to inorganic arsenic (As) through drinking water during pregnancy is associated with lower birth size and child growth. The aim of the study was to assess the effects of As exposure on child growth parameters to evaluate causal associations.

METHODOLOGY/FINDINGS

Children born in a longitudinal mother-child cohort in rural Bangladesh were studied at 4.5 years (n=640) as well as at birth (n=134). Exposure to arsenic was assessed by concurrent and prenatal (maternal) urinary concentrations of arsenic metabolites (U-As). Associations with plasma concentrations of insulin-like growth factor 1 (IGF-1), calcium (Ca), vitamin D (Vit-D), bone-specific alkaline phosphatase (B-ALP), intact parathyroid hormone (iPTH), and phosphate (PO4) were evaluated by linear regression analysis, adjusted for socioeconomic factor, parity and child sex. Child U-As (per 10 µg/L) was significantly inversely associated with concurrent plasma IGF-1 (β=-0.27; 95% confidence interval: -0.50, -0.0042) at 4.5 years. The effect was more obvious in girls (β=-0.29; -0.59, 0.021) than in boys, and particularly in girls with adequate height (β=-0.491; -0.97, -0.02) or weight (β=-0.47; 0.97, 0.01). Maternal U-As was inversely associated with child IGF-1 at birth (r=-0.254, P=0.003), but not at 4.5 years. There was a tendency of positive association between U-As and plasma PO4 in stunted boys (β=0.27; 0.089, 0.46). When stratified by % monomethylarsonic acid (MMA, arsenic metabolite) (median split at 9.7%), a much stronger inverse association between U-As and IGF-1 in the girls (β=-0.41; -0.77, -0.03) was obtained above the median split.

CONCLUSION

The results suggest that As-related growth impairment in children is mediated, at least partly, through suppressed IGF-1 levels.

Final height and insulin-like growth factor-1 in children with medulloblastoma treated with growth hormone

PURPOSE

Medulloblastoma is a highly malignant childhood brain tumor. Survival from medulloblastoma is increasing. This study was performed to examine growth outcomes, insulin-like growth factor-1(IGF-1), and response to growth hormone (GH) treatment in children with medulloblastoma.

METHODS

Retrospective analysis of 34 children treated with GH for medulloblastoma was performed. We evaluated serum IGF-1 and insulin-like growth factor binding protein-3 concentrations. Further, we examined growth status and changes with GH treatment according to treatment modality.

RESULTS

GH deficiency was observed in 28 patients (82 %). The initial height at the start of GH treatment was -2.35 ± -1.53 standard deviation score (SDS) and increased to -1.85 ± -1.28 SDS by 1 year, -1.64 ± -1.46 SDS by 2 years, and -1.42 ± -1.49 SDS by 3 years after GH treatment. The final height was -1.54 ± -1.06 SDS. Gender, surgical method, tumor location, tumor size, and type of radiation did not correlate with height gain. A younger age at the initiation of GH treatment correlated with height gain. The initial serum IGF-1 concentration was -1.73 ± -0.42 and increased significantly to -0.74 ± -0.21 SDS by 1 year after GH treatment. The serum IGF-1 SDS increment correlated significantly with height gain.

CONCLUSIONS

Beginning GH treatment at a younger age was an important prognostic factor for growth outcome. Serum IGF-1 increment correlated with height gain during GH treatment. Thus, early GH treatment and analysis of serum IGF-1 might be helpful for improving final height or growth outcome.

Efficacy and safety of LB03002, a once-weekly sustained-release human GH for 12-month treatment in Korean children with GH deficiency

PURPOSE

The purpose of this study was to investigate the efficacy and safety of LB03002, a sustained-release human GH (SR-hGH), compared with that of daily rhGH for 12 months in children with GH deficiency (GHD).

METHODS

A total of 73 children with GHD were screened and 63 eligible subjects were randomized in a 1:1 ratio of LB03002 (SR-hGH) to daily rhGH treatment group. LB03002 was administered once weekly at a dose of 0.5 mg/kg while daily rhGH was administered for 6 consecutive days with equally divided doses to make a total of 0.21 mg/kg per week. Treatments were given for 12 months by s.c. injections. Injection site reactions and adverse events were investigated throughout the study period.

RESULTS

The mean (S.D.) height velocity (HV) SHOWED a clinically significant increase after the 6-month treatment: 3.00 (1.15) cm/year at screening to 9.78 (1.98) cm/year at 6 months in the LB03002 group; 2.39 (1.63) cm/year at screening to 10.56 (2.65) cm/year at 6 months in the daily rhGH group. The increased HV at 12 months was still maintained in both the groups: 9.06 (1.63) cm/year at 12 months in the LB03002 group; 9.72 (2.32) cm/year at 12 months in the daily rhGH group. Most of the adverse drug reactions were mild and tolerable. No subjects were withdrawn due to adverse events.

CONCLUSION

Weekly injection of LB03002 at a dose of 0.5 mg/kg per week was confirmed to have comparable efficacy to daily injection of rhGH at a dose of 0.21 mg/kg per week. Both formulations were well tolerated.