Because the infant's brain is to a large extent dependent on glucose utilization, hypoglycemia of infants can have grave effects on brain function, and it is important to diagnose it and, when possible, treat it promptly. Causes of hypoglycemia in infants are (a) excess insulin secretion, (b) factitious hyperinsulinemia, (c) GH or ACTH deficiency, (d) primary glucocorticoid deficiency, (e) defects of the enzymes involved in hepatic glucose production, or (f) defects in hepatic fatty acid oxidation.