Clinical characteristics and growth hormone treatment response in children with borderline versus lower peak growth hormone stimulation test responses.

OBJECTIVE: Peak GH responses of 7-<10 ng/mL on growth hormone stimulation testing (GHST) represent a diagnostic grey zone in pediatric GH deficiency (GHD). Whether children in this borderline range differ clinically from those with peak GH <7 ng/mL and whether their growth response to rhGH therapy is comparable remain poorly characterized. METHODS: This retrospective cohort study included treated children with confirmed GHD who had available first-year growth velocity data and were categorized as Group 1 (peak GH <7 ng/mL, n = 121) and Group 2 (peak GH 7-<10 ng/mL, n = 74) at King Abdulaziz University Hospital between 2014 and 2022. Baseline characteristics, first- and second-year growth velocities, and Spearman correlations between peak GH, BMI SDS, and growth velocity were analyzed. RESULTS: Group 1 had higher BMI (median 16.1 vs 15.0 kg/m2, P < 0.001) and lower IGF-1 SDS (median - 1.4 vs -1.0, P = 0.047). First-year growth velocity did not differ significantly between groups (7.5 vs 7.3 cm/year, P = 0.417), nor did second-year growth velocity (7.0 vs 6.5 cm/year, P = 0.534). Peak GH did not correlate with first-year growth velocity (Spearman's ρ = -0.027, P = 0.746) and was not an independent predictor on multivariable regression (adjusted β = -0.59, P = 0.174). CONCLUSION: Peak GH level was not associated with first-year rhGH treatment response in children with confirmed GHD. These findings support interpreting GHST results within the broader clinical, auxological, biochemical, and body-composition context rather than relying on peak GH thresholds alone.