IGSF1 and hyperinsulinemic hypoglycemia, familial, 4: Cortisol production was not evaluated systematically in our kindred; however, transient neonatal hypocortisolism has also been reported in IGSF1 deficiency.9 In this context, it is noteworthy that 3a exhibited neonatal hypoglycaemia; although this is a recognized phenomenon in babies born large for gestational age, we cannot exclude transient cortisol deficiency in the neonatal period although his cortisol production was normal when evaluated in childhood.