Heredity and pituitary response to exercise-related stress in trained men.

To evaluate the role of heredity in the pituitary responses to exercise-related stress, serum ACTH, beta-endorphin, cortisol, GH, and PRL responses to a thirty-minute treadmill exercise at individual anaerobic threshold were evaluated in nine pairs of male monozygotic twin athletes. Hormone evaluations were performed before (-30, -15, 0 pre) and after exercise (0 post, + 15, + 30, + 45, + 60, and + 90 min). The intraclass correlation coefficient (expression of within-pair resemblance) was computed for each hormone before and after exercise as area under curves (AUC), absolute values, and percentage of variation, respectively. The exercise-related stress condition induced a significant increase for all evaluated hormones before (anticipatory response) and/or after exercise. As new data, we observed: 1) A significant within-pair resemblance for exercise-related GH and PRL increase (AUCs and/or absolute values), and for the percentage of variation of cortisol, and 2) the lack of significant resemblance for the observed increase of ACTH, cortisol and absolute beta-endorphin serum concentration. This first co-twin control study supports the hypothesis that, in trained men, there are probably different relative roles for the influence of genetic factors on the pituitary hormones involved in physiological adaptation to exercise-related stress. Furthermore, our findings justify further investigations into this topic.