An Evaluation of Growth Hormone and IGF-1 Responses in Neonates with Hyperinsulinaemic Hypoglycaemia

Background. Hyperinsulinaemic Hypoglycaemia (HH) is the most common cause of severe and persistent hypoglycemia in the neonatal period. It has been shown that the neonates with HH fail to generate adequate serum cortisol counterregulatory response to symptomatic hypoglycemia. However the role played by growth hormone (GH) and Insulin-like Growth Factor 1 (IGF-1) is not clear. Objectives. To compare the serum GH, IGF-1, and IGFBP3 responses to HH in neonates undergoing diagnostic fasting studies. Population and Methods. Data was retrospectively collected on full-term neonates who presented with severe and persistent hypoglycemia and were confirmed to have HH. Neonates born with intrauterine growth retardation or those on medical therapy (diazoxide or octreotide) were excluded. Results. 31 neonates with HH (mean gestational age: 38 weeks and mean birth weight: 3.9 kg) were included in the study. The mean age at the time of diagnostic fast was 4 weeks, the mean glucose concentration during the fast was 2.2 mmol/L (SEM ± 0.09), and the mean insulin level was 11.9 mU/L (±2.12). The mean serum GH concentration during the hypoglycaemia was 12.5 µg/L (±1.53). The mean serum IGF-1 and Insulin-like Growth Factor Binding Protein 3 (IGFBP3) levels were 29.2 ng/ml (±7.8) and 1.21 mg/L (±0.13), respectively. The mean cortisol concentration was 201 nmol/L (±33). Conclusions. Whilst the serum IGF-1 and IGFBP3 levels are relatively low during hypoglycaemia, the serum GH level does reflect an appropriate counterregulatory response to HH. The serum cortisol counterregulatory hormonal responses are blunted. Further studies are required to understand the mechanism(s) of these hormonal alterations in neonates with HH.