HMP Pathway Simplified: NADPH Role & G6PD Deficiency Explained Glucose 6 Phosphate Dehydrogenase Deficiency (G6PD) In G6PD deficiency (XR), we have increased oxidative damage to RBCs, leading to intravascular hemolysis with decreased serum haptoglobin. We have decreased NADPH production, which means decreased conversion of oxidized ( S S ) glutathione Hepatic Glucose 6 Phosphate Dehydrogenase (G6PD) plays a pivotal role in the Pentose Phosphate Pathway, generating NADPH for antioxidant defense and supporting nucleotide & amino acid biosynthesis.