FH and cancer: Other intrinsic factors include altered glutaminolysis,22 activated mitochondrial electron transport chain (ETC) function23, 24 altered tricarboxylic acid (TCA) cycle in many cancer types,25 mutations in enzymes such as isocitrate dehydrogenases 1 and 2 (IDH1, IDH2),26 succinate dehydrogenase (SDH) and (fumarate hydratase) FH.27, 28