IDH1 R132H point mutations are generally associated with secondary GBM and more indolent tumor behavior than tumors that are IDH1 wildtype. IDH1 status is a component of the WHO 2016 criteria for certain astrocytomas including GBM. IDH is an enzyme that normally converts isocitrate to alpha-ketoglutarate as part of the TCA cycle. This evidence concerns the gene IDH1 and glioblastoma.