Persistent effects of a marathon run on the pituitary-testicular axis.

Plasma levels of testosterone (T), LH, FSH, prolactin (PRL), cortisol (F), dehydroepiandrosterone sulfate (DHAS), noradrenaline (NA), NA sulfate (NAS), adrenaline (A) and A sulfate (AS) were measured in 7 adult males before and immediately after a marathon run as well as every morning for 5 days after the run. While plasma T levels fell significantly on the first and the second postmarathon day, those of LH rose significantly during the first 3 postrun days. Plasma PRL and F values increased significantly only at the end of the marathon. Plasma levels of NA and NAS rose significantly at the end of the run and again on days 2 and 5 postmarathon, respectively. A similar pattern was observed for A and AS except for the second peak of free A. These results show that a strenuous physical exercise leads to a persistent relative insensitivity to LH of the testicular T biosynthetic machinery, while the feedback mechanisms operating at the hypothalamic-pituitary level are normal. Furthermore, they suggest that catecholamines may be responsible for the prolonged inhibitory effect of stress on T biosynthesis.