In 2005, the FDA approved IGF-1 therapy (administered as a twice-daily subcutaneous injection) for treatment of patients with severe primary IGF-1 deficiency (IGFD) (in whom GH therapy is not effective), many of whom have GH resistance due to variants in the GH receptor (Laron syndrome or GH insensitivity syndrome), defects in the post-GH receptor signaling pathway, or variants in the IGF-1 gene (9, 10). This evidence concerns the gene GHR and growth delay due to insulin-like growth factor type 1 deficiency.