Diagnostic Significance of Serum IGF-I Level in Growth Hormone Deficiency

Son, Byeong Hee; Chung, Woo Yeong

Abstract

PURPOSE
Insuline-like growth factor I(IGF-I) is polypeptide mitogen and mediate growth effect of growth hormone(GH). It's serum level is regulated by GH. The aim of this study is to evaluate whether -2 standard deviation of IGF-I level in normal short stature after insuline and L-dopa stimulation test has any diagnostic significance in GH deficiency. METHOD:We included 64 children with GH deficiency(complete GH deiciency 18 cases, partial GH deficiency 46 cases). Their height was below 10 percentile of korean children's standard growth chart. Control group was 175 children whose test results were normal after insuline and L-dopa stimulation test. Serum growth hormone level was measured by IRMA(immunoradiometric assay) with "Daiichi" kit(Japan) and serum IGF-I level was measured with 125I RIA kit (U.S.A).
RESULTS
1)Serum IGF-I level in normal stimulation test result group was increased with the age and the level was higher in female than that of male. 2)Using the cut-off value of -2SD of IGF-I level in control group, sensitivity was 17.2%, specificity was 98.86%, positive predictive value was 84.62%, negative predictive value was 76.55%, and test accuracy was 76.99%. Sensitivity and test accuracy was 44.44% and 93.26% in th complete GH deficiency, respectively. 3)Serum IGF-I level was significantly correlated with peak GH level with insuline stimulation test in control and GH deficiency group(Y=0.018889X+11.32 r= 0.23930 P=0.0014, Y=0.008592X+4.189 r=0.28141 P=0.0267). But serum IGF-I level was was not correlated with peak GH level with L-dopa stimulation test(Y= 0.005609X+13.88 r=0.06625 P=0.3823, Y=0.008293X+2.98 r=0.20895 P=0.1031).
CONCLUSION
Serum IGF-I level in GH deficiency group was lower than that of control group and had wide variation of normal range. Based upon above results IGF-I level has limited clinical value in the diagnosis of GH deficiency.