ESPE Abstracts

Introduction: Insulin stress test (IST) to diagnose growth hormone (GH) deficiency is rarely used by paediatric endocrine teams in the United Kingdom, due to concerns over safety. We share our experience of undertaking modified IST in children, with regards to safety and outcomes.

Methods: We adapted the protocol for insulin stress test, proposed by Galloway et al to undertake pituitary stimulation test for our cohort of patients with suspected growth hormone deficiency. The exclusion criteria were were strictly adhered to and comprised the following: children less than 5 years of age, history of seizures, suspected or established adrenal insufficiency and suspected pan-hypopituitarism. An informed consent was taken from the parent(s) prior to undertaking the test and sex-steroid priming was done as per British Society for Paediatric Endocrinology and Diabetes (BSPED) guidance. Each test was supervised by specialist endocrine nurse and consultant. We evaluated the number of modified ISTs undertaken between February 2020 and June 2022. Data was gathered relating to any adverse events, degree of hypoglycaemia achieved, timing of peak responses for GH and cortisol.

Results: 22 ISTs were performed during the study period. The age range of patients was 5.6-16.2 years (15 males and 7 females). 11 patients (50%) had suboptimal GH response based on BSPED cut-off of 6.7 mcg/l. 1 patient (5%) had suboptimal GH and cortisol response and 10 patients (45%) had appropriate GH and cortisol response. Majority of patients (27%) achieved peak GH response at 45 minutes (range 30-150 minutes), post insulin administration. The peak cortisol response was observed at 60 minutes post insulin administration in 50% of patients (range 0-120 minutes). BG dropped to below 3 mmol/l in 19 patients (range 0.7-2.9 mmol/l). The two patients who did not achieve the desired drop in blood glucose (4.2 and 3.4 mmol/l) showed appropriate responses to GH (11.5 and 9.2 mcg/l respectively) and cortisol (849 and 543 nmol/l respectively). Apart from hunger and tiredness, no adverse effect was observed in any of the patient.

Conclusion: Modified IST can be undertaken relatively safely in children over 5 years of age with strict adherence to exclusion criteria and appropriate supervision. Adequate hypoglycaemia was achieved in 86% of cases. Modified IST can eliminate the need for a second stimulation test saving time and cost.