Failure of IGF-I and IGFBP-3 to diagnose growth hormone insufficiency

Background-Growth hormone insufficiency (GHI) is diagnosed conventionally b y short stature and slow growth, and is confirmed by diminished peak GH res ponse to a provocation test. Insulin-like growth factor I (IGF-I) and IGF b inding protein 3 (IGFBP-3) have previously been considered individually Objective-To test the hypothesis that the combined analysis of IGF-I and IG FBP-3 could act as a surrogate marker for the diagnosis of GHI. Design-Reference ranges for IGF-I and IGFBP-3 were calculated using 521 nor mal individuals. A retrospective analysis was performed on 318 children ref erred for investigation of short stature. Results-No significant difference was found between either the IGF-I or IGF BP-3 standard deviation scores (SDSs) in children with and without GHI. If the requirement were for both tests to be positive (< -2 SDS) for a diagnos is of GHI, then 99% of children without GHI would be correctly identified; however, the sensitivity of the test was only 15%. Conclusions Neither IGF-I nor IGFBP-3 alone is a marker for GHI. In additio n, they cannot be used as an effective screening test in combination.