Acute Response to Endurance Exercise Stress: Focus on Catabolic/Anabolic Interplay Between Cortisol, Testosterone, and Sex Hormone Binding Globulin in Professional Athletes

Summary Background: Endocrine system plays a major role in both permissive and regulatory activities in order to adequately respond to physical stress of exercise. But level and direction of activation depend on many factors and are not easily interpreted. Methods: We tested a group of male professional athletes (21 water polo players and 15 wrestlers), together with 20 sedentary controls matched by age. All participants took a continuous progressive exercise stress test on a treadmill until exhaustion and plateau of oxygen consumption (VO 2 ). Blood samples for cortisol, sex hormone binding globulin (SHBG) and testosterone were drawn in four time points: baseline (B), start of the test (S), point of maximal strain (MAX) and in the 3 rd minute of recovery period (R). Results: Cortisol levels significantly increased in both groups, but the response between S and MAX was more pronounced in controls (p=0.036). The athletes had significantly higher levels of cortisol in all points in test, except during R (p=0.118), when their cortisol levels gradually started to decline. Significant increase in total testosterone was in great deal a consequence of increase in SHBG level (p<0.01 for both). Consequently, calculated free testosterone significantly decreased during test (p=0.008), and the drop was more pronounced in athletes. This was in concordance with significant correlation between SHBG and cortisol level demonstrated in athletes, but not in controls. Conclusions: It seems that high intensity endurance exercise favors catabolic response, but the level of response highly depends on a previous level of training.