Biochemical studies in patients with hyperinsulinaemic hypoglycaemia.

Hyperinsulinaemic hypoglycaemia (HH) is characterised by the dysregulated secretion of insulin from the pancreatic β-cell. It is a major cause of severe and persistent hypoglycaemia in the newborn period. There have been no previous studies assessing the various biochemical alterations at the time of hypoglycaemia in relation to the severity of the hypoglycaemia. Biochemical and clinical data were collected on 90 neonates (gestational age range, 32-42 weeks) with a diagnosis of HH [(based on glucose requirement  > 8 mg/kg/min) and the biochemical profile of insulin action (low beta-hydroxybutyrate and fatty acid concentrations)] who had undergone fasting studies. The results showed that (a) the serum insulin level measured at the time of hypoglycaemia had no correlation with the severity of hypoglycaemia, (b) the serum insulin level was undetectable despite severe hypoglycaemia in a significant proportion of patients, (c) there was no correlation between the birth weight and the insulin level at the time of hypoglycaemia, (d) the suppression of ketogenesis was more marked than that of the non-esterified fatty acids. This study suggests that the diagnosis of HH should not rely solely on a raised serum insulin level at the time of hypoglycaemia but on the constellation of clinical and biochemical findings.