Insulin-like growth factor-I (IGF-I) screening for the diagnosis of growth hormone (GH) deficiency

Growth hormone deficiency (GHD) is a common cause of growth retardation in children and adolescents. Gold standard for the diagnosis of GHD is based upon two standard growth hormone (GH) provocative tests demonstrating a peak serum GH of less than 7 ng/mL. These tests, besides requiring multiple blood samplings, are time-consuming and costly. GH primarily mediates its growth-promoting effect through insulin-like growth factor-I (IGF-I). Hence, basal serum IGF-I level reflects GH status. We studied 47 prepubertal children with or without short stature. Aged ranged between 4.3 and 15.6 years. They were divided into 2 groups based upon 2 standard GH provocative tests. Seventeen Children were classified as having GHD. The remaining 30 were non-GHD. Basal serum IGF-I was obtained before GH testing. The means +/- SE (range) of serum IGF-I concentration were 44.26 +/- 3.19 (19.10-75.63) ng/mL in GHD and 118.42 +/- 10.03 (60.65-235.91) ng/mL in non-GHD which were significantly different (P < 0.001). 88.2 per cent of GHD had serum IGF-I concentration less than 60 ng/mL whereas 100 per cent of non-GHD had serum IGF-I greater than 60 ng/mL. There was no correlation between serum IGF-I and either bone age or chronologic age in children with GHD. These data indicate that serum IGF-I level is a useful screening test to exclude GHD with high sensitivity. We suggest that if serum IGF-I is less than 80 ng/mL in prepubertal children, GH provocative tests should be performed to diagnose GHD. If serum IGF-I is greater than 80 ng/mL, growth rate monitoring is recommended. If growth rate is decreased despite normal IGF-I, GH provocative tests should be obtained to rule out GHD.