To test our hypothesis, we used an established murine model of isolated endocrine IGF-1 deficiency: knockdown of IGF-1 specifically in the liver using Cre-lox technology (Igf1f/f + TBG-Cre-AAV8) (Tarantini et al., 2017c). The gene discussed is IGF1; the disease is hyperinsulinemic hypoglycemia, familial, 4.