Hyperinsulinaemic hypoglycaemia (HH) is a major cause of recurrent and persistent hypoglycaemia in infancy and childhood.¹ Rapid diagnosis, avoidance of recurrent and repeated episodes of hypoglycaemia and prompt management of the hypoglycaemia are vital in preventing brain damage and mental retardation.² Unfortunately, a large proportion of children with HH still develop brain damage as a consequence of delayed diagnosis and subsequent management. HH can be either congenital or secondary to certain risk factors (such as intrauterine growth retardation). Congenital hyperinsulinism involves either defects in the genes ABCC8 and KCNJ11 (encoding for the two proteins SUR1 and KIR6.2 of the pancreatic β cell K_ATP channel, respectively) or abnormalities in the enzymes glucokinase, glutamate dehydrogenase and short chain acyl-CoA dehydrogenase (SCHAD). Loss of function mutations in the genes ABCC8 and KCNJ11 cause the most severe forms of HH which are usually medically unresponsive.

HH is also observed in newborns with intrauterine growth retardation, in infants with perinatal asphyxia, in infants of diabetic (gestational and insulin dependent) mothers, in some infants with Beckwith-Weidemann syndrome and, more recently, in infants with no predisposing factors.^3–6 In most of these conditions, the HH is a transient phenomenon and resolves spontaneously. However, some small for gestational age and appropriate for gestational age infants can have prolonged hyperinsulinaemic hypoglycaemia which requires treatment with diazoxide, persists for several months and then resolves spontaneously.^7,8 Recognition of this group of patients is important as they are fully responsive to treatment with oral diazoxide. The underlying mechanisms of the HH in these patient groups are unclear at present.

BIOCHEMICAL BASIS OF HYPERINSULINAEMIC HYPOGLYCAEMIA

The biochemical basis of HH (congenital and secondary) involves dysregulated insulin secretion with …