Serial GH measurement after intravenous catheter placement alone can detect levels above stimulation test thresholds in children

Context: GH stimulation testing is limited by poor specificity and reproducibility in identifying GH deficiency. Intravenous line placement (IVP) in pediatrics may be a stimulus for GH secretion. Objective: The objective of the studywasto determine whether the measurement ofGHat baseline as well as 15 and 30 minutes after IVP detects additional patients with sufficient peak GH concentrations who are not identified by a subsequent insulin tolerance test (ITT). Methods: The ITT protocol was modified to include GH measurement at the time of IVP (t-0) and 15 (t = 15) and 30 (t = 30) minutes later. Insulin was administered at t = 30, and an ITT was performed as per standard protocols. Children were grouped according to the indication for ITT: initial evaluation of GH deficiency (group 1); and GH deficiency at transition to adulthood (group 2). Results: Ninety-seven patients were included (76 in group 1, 21 in group 2). Of these, 27 (28%) had a peak GH concentration of 7 ng/mL or greater (19 in group 1, eight in group 2) either after IVP or ITT. Thirteen subjects (11 in group 1, two in group 2) had GH concentrations of 7 ng/mL or greater after IVP, without exceeding this on a subsequent ITT. Among the 11 group 1 patients, three of these GH peaks of 7 ng/mL or greater occurred at t = 0, 5 at t = 15, and 5 at t = 30, including one patient who had a peak GH of 7 ng/mL or greater at all three time points. Conclusion: Some children will not have a sufficient GH response to pharmacological stimuli but will have a robust response to IVP. We recommend GH measurement after IVP in children undergoing GH stimulation testing, particularly when there is a delay between IVP and the administration of the pharmacological stimulus.