Patients with genetic endocrine disorders due to defects such as growth hormone (GH) gene deletion, mutation in GH-releasing hormone (GHRH) receptors, insulin-like growth factor-1 (IGF-1) defects or malformations of the hypothalamic area leading to multiple pituitary hormone deficiencies can present with fasting hypoglycemia. The gene discussed is IGF1; the disease is hyperinsulinemic hypoglycemia, familial, 4.