Background: Achieving adequate hypoglycaemia during the insulin tolerance test (ITT) is important but excessive hypoglycaemia is undesirable. We aim to evaluate factor affecting insulin sensitivity and hypoglycaemia during ITT.
Patients and method: 106 children (76 males) who had an ITT (Actrapid 0.1 units/kg) performed between 20092013 for evaluation of short stature, poor growth or re-assessment after completion of growth following rhGH therapy. Plasma glucose, cortisol and GH measurements at −30, 0, 15, 30, 60, 90,120 min were studied by a second order negative feedback mathemaciacl model to describe dynamic changes of production rates. The slope of the change in glucose clearance rate vs its concentration was defined as insulin sensitivity. Adequate hypoglycaemia was defined as glucose <2.2 mmol/l.
Results: Median age of the group was 12.7 years (range: 5.719.3), Ht S.D.s-2.8 (−4.2, 1.5), BMISDS −0.1 (−4.0, 4.4). 22 of the 106 (20.7%) did not achieve adequate hypoglycaemia based on measured plasma glucose. The nadir for measured plasma glucose occurred at 15 min (15, 30). However, simulated nadir glucose occurred at 11 min (8, 29) with simulated plasma glucose of 1.44 mmol/l (0.09, 4.75). Of the 22 who did not achieve adequate hypoglycaemia based on measured plasma glucose, 8 (36.4%) achieved adequate simulated hypoglycaemia at 13.5 min (11, 29). Nadir measured plasma glucose was highly associated with nadir simulated glucose (r=0.96, P<0.0001). In a multivariate model, there was a trend for children with GH deficiency to have greater insulin sensitivity (95% CI: 0.00.60). Age, gender, BMISDS, HtSDS, body surface area, puberty were not associated with insulin sensitivity. In multivariate analysis (age, gender, puberty, body surface area, baseline glucose),baseline glucose was the only significant independent factor associated with the extent (P=0.009, 95% CI=0.140.93)and timing of simulated nadir glucose (P=0.005, 95%CI=1.588.79)
Conclusion: 20% of children who underwent ITT were classified as achieving inadequate hypoglycaemia based on plasma glucose. However, based on the simulation model, over one third of these children would have achieved adequate hypoglycaemia. Given that the identification of GH and cortisol deficiency on ITT critically depends on optimal hypoglycaemia, these results have important clinical implications.
01 Oct 2015 - 03 Oct 2015