The effect of methylphenidate on the dopamine and growth hormone response to exercise in children with attention-deficit hyperactivity disorder

Purpose

To assess the growth hormone (GH) and Dopamine (DA) response to exercise in children with attention-deficit hyperactivity disorder (ADHD) with and without methylphenidate (MP). We hypothesized that the GH and DA response to the exercise with MP would be siginicantly lower.

Methods

Twenty children participated in the study (12 males and 8 females, age range 9–13 years). Ten with ADHD and 10 controls. Participants with ADHD performed an exercise test twice, with and without MP while controls performed one exercise test. Blood samples for GH and DA were collected before, at peak, 30 and 60 min after the end of exercise.

Results

Compared to controls, children with ADHD with and without MP, had a significantly lower GH (P < .002) and DA (P < .01) responses to exercise. In participants with ADHD, a significantly greater GH response (p < .04) to exercise was found when MP administered to the children before exercise, yet this response was still significantly lower than controls.

Conclusions

GH and DA excretion after an exercise challenge in children with ADHD is impaired. MP slightly attenuates the GH blunted response. This may link ADHD with growth impairment in some children and explain previous findings indicating that the final adult height is usually not compromised in children with ADHD treated with MP. The combined exercise and stimulant treatment therapeutic effects needs to be further explored.

Trial registration number: NCT00945971