Kristensen et al. investigated the physiological effects and correlation between renin-angiotensin system (RAS) activity, the endogenous release of erythropoietin (EPO), and cognitive function during hypoglycemia in a crossover study of induced hypoglycemia and maintained normoglycemia in nine T1DM patients with high RAS activity and nine T1DM patients with low RAS activity [27]. The gene discussed is EPO; the disease is type 1 diabetes mellitus.