The Metabolic Response to Exercise and Exhaustion in Normal and Growth-Hormone-Deficient Children

The effects of exhausting bicycle exercise at close to maximal work capacity upon circulating levels of hormones and energy substrates in 4 fasting growth-hormone-deficient and 15 fasting healthy subjects (aged 13–18 years) have been studied. As expected, only the healthy subjects showed a rise in plasma growth hormone (GH) levels. In both groups plasma insulin tended to fall, but the decline was more prolonged in the GH-de-ficient group. Plasma Cortisol levels rose in both groups with the exception of one adrenocorticotropin (ACTH)-deficient subject. Blood sugar levels were well-maintained in all but this ACTH-deficient subject, whereas both groups showed marked lactate accumulation. Both groups demonstrated an initial fall and then a secondary rise in serum free fatty acid concentrations; however, fatty acid levels were lower in the GH-deficient group and there was no post-exercise overshoot, suggesting a possible reduction in the effectiveness of lipid mobilization.