Reduced exercise-induced growth hormone secretion among children with attention-deficit hyperactivity disorder

Purpose: Attention-deficit/hyperactivity disorder (ADHD) is typically a chronic, often lifelong condition. Data suggest that ADHD itself and its treatment may be associated with dysregulated growth, including height and BMI. The reason for this association is yet unknown. The objective of this study was to examine differences in growth hormone (GH) response to exercise between children who had received a diagnosis of ADHD and age- and gender-matched controls. We reasoned that the normal increase in circulating GH seen in response to exercise would be blunted in children with ADHD. Methods: We recruited 13 treatment-naïve children with newly diagnosed ADHD and 14 age-matched controls (all male) and measured GH response to an exercise test in which the work was scaled to each subject's physical capability. Results: There was no difference in the peak heart rate achieved during exercise between controls and ADHD participants (196.6 ± 1.5 vs. 196.5 ± 2.1 bpm, respectively) and lactate response to exercise (53.8 ± 5.0 vs. 47.9 ± 3.8 mg/dl, respectively). After exercise, GH increased significantly in the control subjects (p < 0.005), while GH responses were substantially blunted in the ADHD group (p = NS) even though the work performed did not differ from controls. Conclusions: Our data suggest that GH excretion after exercise challenge in children with ADHD is impaired. This can be detected using a minimally invasive, nonpharmacologic challenge and may link ADHD with growth impairment in some children.