Since both clinical and experimental findings indicate that fibrosis is a primary factor in the respiratory dysfunction and cardiomyopathy that are the leading causes of death in dystrophin-deficient dystrophy, the extended lifespan of nNOS Tg+/dko mice may reflect the decreased fibrosis that occurred in respiratory and cardiac muscles. Here, NOS1 is linked to hyperinsulinemic hypoglycemia, familial, 4.