PLASMA BETA-ENDORPHIN, CORTICOTROPIN AND GROWTH-HORMONE RESPONSES TO EXERCISE IN PUBERTAL AND PREPUBERTAL CHILDREN

An increase in plasma beta-endorphin concentrations during exercise ha s been reported in adult men and women by several investigators. Howev er, very little is known about this physiological hormonal response to exercise in children. In this study, we investigated plasma beta-endo rphin, ACTH and GH responses to exercise in 40 prepubertal and puberta l children. Subjects were recruited as part of a population of childre n and adolescents presenting growth retardation and were selected on t he basis of the absence of any clinical or biological signs of endocri ne or metabolic disease. There were 16 girls and 24 boys with 24 prepu bertal and 16 pubertal individuals. A standardised 15 min workload on cycloergometer was used to progressively increase the heart rate of th e children up to 90% of the theoretical maximal value. Exercise result ed in a significant increase,(p<0.01) in plasma beta-endorphin (mean+/ -SEM) (4.26+/-0.47 vs 5.74+/-0.56 fmol/ml), ACTH (3.71+/-0.41 vs 6.2+/ -0.62 fmol/ml) and GH (147+/-29 vs 364+/-67 fmol/ml). The percentage o f children with significant hormonal response to exercise was about 75 % for each of the 3 hormones but only 3 of the 40 children studied did not show any hormonal response to exercise. Exercise-induced increase s in plasma beta-endorphin and ACTH were significantly correlated (p<0 .01). By contrast, there was no significant relationship between GH an d beta-endorphin or ACTH values. Furthermore, whereas exercise-induced plasma GH increase was significantly higher in pubertal than in prepu bertal children (p<0.001), corresponding beta-endorphin and ACTH level s were quite similar in the two groups. Our findings give evidence for comparable exercise-induced increase in plasma beta-endorphin levels in either pubertal or prepubertal normal short children. The similarit y of the beta-endorphin responses to exercise between prepubertal and pubertal children does not support the controversial hypothesis that p lasma beta-endorphin modulates GH response to exercise.