Impact of Ondansetron Timing on Symptom Burden and Diagnostic Performance During Pediatric Growth Hormone Stimulation Testing.

Introduction: Growth hormone (GH) stimulation testing using levodopa/carbidopa often causes nausea and vomiting. Ondansetron is commonly used for symptom control, but its effect on GH test accuracy is unclear.

Methods: We retrospectively studied 129 children (ages 2-16) who underwent GH stimulation testing with arginine-levodopa/carbidopa. Ondansetron timing was categorized as none, early (0-30 minutes), or late (31-120 minutes). We assessed the association between ondansetron timing and GH test response, incorporating clinical, auxological, and biochemical characteristics into multivariable regression models. Primary outcomes were peak GH concentration and GH deficiency classification (<10 μg/L).

Results: Ondansetron timing was not associated with peak GH or GH deficiency. Nausea/vomiting was more common in the late group (51%) than early (38%) or none (25%) (p = .019), possibly reflecting selection bias. Higher BMI SDS was associated with lower peak GH (β = -0.302, p < .001) and increased odds of GH deficiency (OR = 1.81, p = .016).

Discussion: Ondansetron does not affect GH test outcomes and may reduce symptoms. BMI standard deviation scores (SDS) is an independent predictor of GH response and should be considered in interpreting test results.