A Proposal to Develop New References for Serum IGF-I Levels in Children

Wit and collaborators (1) have again approached the issue of the value of IGF-I serum levels as a tool for diagnosing growth hormone deficiency (GHD).They have thoughtfully reviewed the existing literature and deliberated that the cutoff in terms of standard deviation (SD) score (SDS) should be interpreted based on the pre-test likelihood of GHD.I recommend reading this interesting article.In short, the authors concluded: In the case the pre-test likelihood for GHD -based on anamnestic information, physical findings, anthropometric measurements and laboratory results not specifically related to GHD -is high (>50%) further testing (including measurements of GH secretion) is recommended even if IGF-I levels are in the normal range.However, if the pre-test likelihood is low (<10%) only very low IGF-I levels (<-2 SDS) qualify these children for a further diagnostic work-up.The diagnosis of GHD in childhood is in fact complex and is subject to an ongoing, partly controversial discussion (2).A number of -often rather less well-defined terms -have been used to subclassify GHD, including congenital, acquired, idiopathic, with or without (isolated) other pituitary hormone deficits, severe, less severe, total, and partial GHD (3).In addition, the clinical picture, as well as the diagnostic tools and criteria applied, are dependent on the age of the patient.The key issue remains the methodologically difficult quantification of GH secretion, which means defining the individual GH secretion as being insufficient (deficient) compared to normal.Components of the IGF system [IGF-I, IGF-binding protein-3 (IGFBP-3), and others] are qualitatively dependent on GH secretion.Their serum