Insulin Like Growth Factor-1 as a Screening Tool to Differentiate Between Idiopathic Short Stature and Growth Hormone Deficiency.

Measurement of serum insulin-like growth factor-1 (IGF-1) is a useful screening test for growth hormone deficiency (GHD) because unlike growth hormone, it has minimal circadian variation. In this retrospective study, the authors compared IGF-1 concentrations in children with GHD vs. idiopathic short stature (ISS) to define IGF-1 cut-off to differentiate the two. Of the 75 children studied, 38 were GHD and 37 ISS. Weight, height, BMI Z-scores, bone age: age ratio, IGF-1 concentrations and IGF-1 Z-scores were significantly lower in the GHD group. The best IGF-1 Z-score cut-off was -2.41 (sensitivity: 74.3% and specificity: 89.2%). Many children who are non-GH deficient fail growth hormone stimulation tests and get wrongly diagnosed as GHD and receive a lesser dose of GH leading to suboptimal response. In such patients, if the IGF-1 is well above the cut-off (-2.41), other diagnostic possibilities including ISS may be considered for GH dose adjustment.