Vitamin E Supplementation in Hyperinsulinism/Hyperammonemia Syndrome

Subjects will take an oral Vitamin E (alpha-tocopherol) supplement once daily with a fat-containing meal for 2 weeks. The dose will be based on subject age (150 IU if 1-3 years old, 300 IU if 4-8 years old, 450 IU if 9-17 years old, 600 IU if \>17 years old). Formulations include 50 IU/mL liquid and 200 IU capsules. The liquid formulation will be used for subjects who will receive \<600 IU daily, or for any subjects who prefer liquid medication to capsules.