Characterization and prevalence of severe primary IGF1 deficiency in a large cohort of French children with short stature.

OBJECTIVE:The prevalence of severe primary IGF1 deficiency (IGFD) is unclear. IGFD must be identified promptly as treatment with recombinant human IGF1 (rhIGF1) is now available. Our objective was to characterize and assess the prevalence of severe primary IGFD in a large cohort of patients evaluated for short stature at a pediatric endocrinology unit in France. DESIGN:Observational study in a prospective cohort. METHODS:Consecutive patients referred to our unit between 2004 and 2009 for suspected slow statural growth were included. Patients were classified into eight etiological categories. IGFD was defined by height ≤-3 SDS, serum IGF1 levels <2.5th percentile, GH sufficiency, and absence of causes of secondary IGFD. RESULTS:Out of 2546 patients included, 337 (13.5%) were born small for gestational age and 424 (16.9%) had idiopathic short stature. In these two categories, we identified 30 patients who met our criterion for IGFD (30/2546, 1.2%). In these 30 patients, we assessed the response to IGF1 generation test, time course of IGF1 levels, and efficiency of GH replacement therapy. The results indicated that only four of the 30 children were definite or possible candidates for rhIGF1 replacement therapy. CONCLUSION:The prevalence of severe primary IGFD defined using the standard criterion for rhIGF1 treatment was 1.2%, and only 0.2% of patients were eligible for rhIGF1 therapy.