GCH1 and hyperinsulinemic hypoglycemia, familial, 4: When taken together with the data presented herein that demonstrates the ability of MitoTEMPO and sepiapterin to individually normalise the decrease in BH4, and the increase in ROS in Gch1 siRNA-treated cells, this shows strong evidence that BH4-deficiency, and consequent mitochondrial ROS generation, negatively affect the abundance of these selected cellular enzymatic antioxidants.