Early retesting by GHRH + arginine test shows normal GH response in most children with idiopathic GH deficiency

Purpose: Most children with idiopathic isolated GH deficiency (IGHD) normalize GH response to stimulation tests when retested at the completion of growth. The objective of this study was to test the effectiveness of early retesting in challenging the diagnosis of idiopathic IGHD and critically review the diagnostic workup leading to this diagnosis in children with short stature. Methods: We cross-sectionally retested 38 children with idiopathic IGHD and still on GH treatment. The initial diagnosis of idiopathic IGHD was based on subnormal GH responses to two stimulation tests and normal brain imaging or minor/nonspecific findings at magnetic resonance. The GH response normalization at retesting was considered as the main outcome measure. Clinical features of children who were falsely classified as idiopathic IGHD based on first GH testing were retrospectively analyzed. Results: GH secretion was normal in 36/38 children (95 %). Two children showed slightly reduced peak GH responses and normal IGF-I levels. Fourteen children underwent GH retesting before puberty, 24 children during puberty. Conclusion: The diagnostic process should be improved to minimize the rate of false positive at GH testing and, in case of unsatisfactory response to GH treatment, the diagnosis of isolated idiopathic GHD should be challenged with early retesting.