Transient neonatal hypoglycemia Causes of transient hypoglycemia are Inadequate substrate (eg, glycogen) Immature enzyme function leading to deficient glycogen stores Transient hyperinsulinism Deficiency of glycogen stores at birth is common among preterm infants who have a very low birth weight, infants who are small for gestational age because of placental insufficiency, and infants who have perinatal asphyxia.