Recurrent spontaneous hypoglycaemia causes loss of neurogenic and neuroglycopaenic signs in infants with congenital hyperinsulinism.

OBJECTIVE: Hypoglycaemia-associated autonomic failure (HAAF) with impaired neurogenic and neuroglycopaenic responses occurs in adults following recent, repeated hypoglycaemia. We aimed to evaluate whether HAAF also occurs in patients with infant-onset congenital hyperinsulinism (CHI). DESIGN, PATIENTS: A controlled fast was performed in (i) seven CHI infants with initial symptomatic hypoglycaemia and three recent episodes of spontaneous recurrent hypoglycaemia each lasting <5 min and in (ii) seven infants with idiopathic ketotic hypoglycaemia for control. MEASUREMENTS: At the time of hypoglycaemia (blood glucose <3 mmol/l or clinical signs), blood was drawn for serum insulin, cortisol, glucagon, adrenalin and nor-adrenalin. Signs of hypoglycaemia were documented. In CHI patients, the ABCC8 and KCNJ11 genes were analysed by denaturing high performance liquid chromatography (DHPLC) and/or direct bidirectional sequencing.
RESULTS: Two CHI patients had a paternal ABCC8 mutation, five had no mutations. When repeated hypoglycaemia was provoked, all CHI patients exhibited a complete loss of clinical signs of hypoglycaemia, along with a global blunting of the counter-regulatory hormones cortisol, glucagon, growth hormone, adrenalin and nor-adrenalin responses (median values 256 nmol/l, 23 pmol/l, 5·6 mU/l, 390 pmol/l and 2·9 nmol/l, respectively), irrespective of mutational status. In the controls, hypoglycaemia was always clinically overt with normal counter-regulatory cortisol, glucagon, adrenalin and nor-adrenalin responses (530 nmol/l, 60, 920 pmol/l and 4·0 nmol/l, respectively).
CONCLUSION: Recurrent hyperinsulinaemic hypoglycaemia even of short duration blunts the autonomic, neuroglycopaenic and glucose counter-regulatory hormonal responses in patients with infant-onset CHI resulting in clinically silent hypoglycaemia. Tight, or continuous, glucose monitoring is therefore recommended, especially in conservatively treated patients.