Effect of Growth Hormone Replacement on Cardiac Autonomic Functions in Childhood: A Pilot Study

Purpose Growth hormone (GH), which has been used for many years for various indications, has been extensively studied because of its systemic effects. One notable effect is on the cardiovascular system. Heart rate variability (HRV) is a widely used noninvasive tool for understanding environmental factors, diseases, and treatment effects, providing insights into the autonomic nervous system (ANS). This study aimed to examine the effects of childhood GH replacement treatment (GHRT) on HRV parameters and their implications for the ANS. Methods The study included 10 pediatric patients (mean age 12.01 ± 1.38 years) evaluated for short stature and diagnosed with isolated GH deficiency (GHD). Time‐domain parameters of HRV were examined in patients with a 24 h Holter monitoring before GHRT and after six months of treatment. Results Root mean square of the successive normal sinus R–R interval difference (RMSSD) and percentage of successive normal sinus R–R intervals longer than 50 milliseconds (pNN50), which are known to correlate with the parasympathetic nervous system, decreased significantly after 6 months of treatment compared to baseline. No significant changes were observed in the other time‐domain parameters, the standard deviation of all normal sinus R–R intervals (SDNN), and the standard deviation of the averages of R–R intervals in all 5 min segments of the recording (SDANN). Conclusion GHRT in childhood was associated with significant reductions in vagally mediated HRV parameters, suggesting an effect on autonomic regulation during the early phase of treatment. Long‐term studies are required to determine whether these changes persist or normalize over time. This appears to be the first study to investigate the effects of GHRT on ANS function in children with GHD.