Some studies found no evidence of insulin-like growth factor 1 (IGF-I), insulin-like growth factor binding protein 1 (IGFBP1), IGFBP2, IGFBP-3, or IGF-I/IGFBP3 ratio being associated with glioma risk (9, 12, 21, 22). This evidence concerns the gene IGFBP3 and glioma.