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Serial GH Measurement After Intravenous Catheter Placement Alone Can Detect Levels Above Stimulation Test Thresholds
C P Hawkes1, M Mavinkurve1, M Fallon1
1Division of Endocrinology and Diabetes (C.P.H., A.G.), The Children's Hospital of Philadelphia, and Department of Pediatrics (A.G.), Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104; and The National Children's Research Centre (C.P.H.) and Department of Paediatric Endocrinology (M.M., M.F., D.C.C.), Our Lady's Children's Hospital, Crumlin 12, Ireland.
Insights
Intravenous line placement (IVP) can stimulate growth hormone (GH) secretion in children. Measuring GH after IVP may identify more cases of GH deficiency than standard tests alone.
Area of Science:
- Pediatric Endocrinology
- Growth Hormone Physiology
- Diagnostic Testing
Background:
- Growth hormone (GH) stimulation testing often lacks specificity and reproducibility for diagnosing GH deficiency.
- Intravenous line placement (IVP) may inadvertently stimulate GH secretion in pediatric patients.
Purpose of the Study:
- To assess if measuring GH levels post-IVP identifies additional children with sufficient peak GH concentrations.
- To compare GH levels after IVP with those obtained during a subsequent insulin tolerance test (ITT).
Main Methods:
- Modified the insulin tolerance test (ITT) protocol to include GH measurements at baseline (t=0), 15 minutes (t=15), and 30 minutes (t=30) after IVP.
- Administered insulin at t=30 minutes for a standard ITT.
- Grouped 97 pediatric patients based on the indication for testing: initial GH deficiency evaluation (group 1) or transition to adulthood (group 2).
Main Results:
- 27% of patients (19 in group 1, 8 in group 2) achieved a peak GH concentration of ≥7 ng/mL after either IVP or ITT.
- 13 patients (11 in group 1, 2 in group 2) showed adequate GH response to IVP but not to ITT.
- In group 1, GH peaks ≥7 ng/mL occurred at t=0, t=15, and t=30 minutes post-IVP, with one patient responding at all time points.
Conclusions:
- Some children exhibit a robust GH response to IVP, even without responding adequately to pharmacological stimuli.
- Recommends measuring GH levels following IVP in children undergoing GH stimulation testing.
- This approach is particularly valuable when delays occur between IVP and the administration of pharmacological agents.
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 study was to determine whether the measurement of GH at 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.
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