Elevated glutathione levels may reflect an accumulation resulting from impaired recycling, often due to deficiencies in NADPH, selenium, or riboflavin (vitamin B2). This indicates a disruption in the redox balance rather than Question 22 139 pl the enzyme glutathione reductase Table 1 from Medications and Glucose 6 Phosphate NADPH homeostasis in cancer: functions, mechanisms and therapeutic implications Signal Transduction and Targeted Therapy