Salivary but not plasma cortisone tracks the plasma cortisol response to exercise: effect of time of day.

INTRODUCTION: The cortisol, cortisone, corticosterone, and CBG responses to exercise in the AM and PM have not been described. This study examined the response of these glucocorticoids and CBG to intense exercise in 12 endurance-trained men in plasma (Pl) and saliva (Sa).

METHODS: Each subject completed treadmill exercise in the morning and evening. Paired blood and Sa samples were obtained at rest before and after exercise.

RESULTS: Significant time effect existed for Pl-cortisol and Sa-cortisol from baseline in the AM and PM (p < 0.01). Pl-cortisone and CBG significantly increased in the PM (p < 0.01). Pl-corticosterone increased in the AM and PM (p < 0.01). Unlike Pl-cortisone, Sa-cortisone was significantly higher in the AM compared to the PM, increasing in the AM and PM (All p < 0.01). Strong associations were found between Pl-cortisol and Sa-cortisol (r = 0.81, p < 0.0001), Pl-cortisol and Sa-cortisone (r = 0.81, p < 0.0001).

CONCLUSIONS: (1) Intense EX induces a similar increase in Pl-cortisone (~90 %) and corticosterone (~200 %) in the AM and PM, whereas exercise increases CBG in the PM, but not in the AM; (2) vigorous exercise increases Sa-cortisone; (3) Sa-cortisone and cortisol are equally strongly correlated to Pl-cortisol, suggesting a significant role for Sa-cortisone as a novel marker of free cortisol during exercise.