INTRODUCTION: Recombinant human growth hormone (r-hGH) enhances somatic growth and body composition, yet its short-term effects on aerobic capacity and myocardial function remain unclear in short-statured children. OBJECTIVE: To assess changes in aerobic performance and cardiac morphology/function in prepubertal children with short stature undergoing r-hGH therapy, using conventional and speckle tracking echocardiography (STE). MATERIAL AND METHODS: This prospective longitudinal study included 30 prepubertal children (18 with GH deficiency [GHD], 12 non-GHD including 6 small for gestational age [SGA] and 6 idiopathic short stature [ISS]). Participants received r-hGH for 12 months. Assessments at baseline, 6, and 12 months included anthropometry, VO2max (Bruce protocol), and cardiac function (including global longitudinal strain [GLS] and strain rate [GLSR] via STE). Adherence was monitored electronically. RESULTS: r-hGH significantly increased IGF-1 and left ventricular mass indices. VO2max showed no overall improvement; a significant decrease was observed in GHD children, particularly girls, despite high adherence. Only GHD males exhibited supranormal VO2max values at baseline, and this pattern persisted at 12 months. GLSR improved significantly at 6 months in GHD patients, indicating early myocardial response to GH therapy, although GLS remained unchanged. No correlation was found between VO2max evolution and cardiac parameters. CONCLUSIONS: While r-hGH therapy led to favorable cardiac remodeling and early subclinical improvements in myocardial contractility in GHD children, no enhancement in aerobic capacity was observed over one year. STE proved valuable for detecting early cardiac adaptations to GH therapy. Further studies with longer follow-up and larger cohorts are warranted to clarify the functional implications of these structural changes.