Corticotroph axis sensitivity after exercise in endurance-trained athletes.
OBJECTIVE
The present study was conducted in order to describe human hypothalamo-pituitary adrenal (HPA) axis adaptation in a model of repeated physical stress (endurance training) that causes a moderate increase in cortisol levels.


METHODS
We performed the same stimulation tests (adrenal stimulation with ACTH or pituitary stimulation with combined CRH/LVP) in a population of 8 endurance-trained athletes in two distinct situations: resting (baseline cortisol values) and 2 h after the end of strenuous exercise (increased cortisol values) to evaluate the HPA axis sensitivity to endogenous sustained increases in cortisol concentrations.


METHODS
During these tests, saliva and plasma cortisol (Fs and Fp, respectively) were assessed and compared.


RESULTS
Cortisol values in both plasma and saliva at the end of 2 h of exercise were significantly higher than in rested controls: Fs 11.5 +/- 1.3 vs 6.5 +/- 0.8 nmol.l-1 and Fp 428 +/- 36 vs 279 +/- 27 nmol.l-1 (post exercise vs post rest sessions, respectively, P < 0.001 for both). After either hormone test (CRH/LVP or ACTH), cortisol levels in plasma and saliva increased similarly when rest was compared to post exercise. Saliva variations (delta %) under exogenous hormone stimulation were dramatically greater than plasma variations. For example, under ACTH stimulation, the relative increments in cortisol were on control day: delta Fs 980 +/- 139 vs delta Fp 218 +/- 43% (saliva vs plasma, respectively, P < 0.05) and on exercise day: delta Fs 605 +/- 89 vs delta Fp 102 +/- 14% (saliva vs plasma, respectively, P < 0.05).


CONCLUSIONS
In endurance-trained athletes, displaying a moderate but sustained endogenous cortisol increase: (1) ACTH responses following pituitary stimulation are not blunted, (2) cortisol responses following maximal adrenal stimulation are not blunted. Our results favour the hypothesis of a decreased pituitary sensitivity to cortisol negative feedback whereas the hypothesis of a major decreased adrenal sensitivity to ACTH was discarded. The greater ability of saliva assays to detect a cortisol increase strongly supports its use in the study of HPA physiology, whether under basal or dynamic conditions.
Duclos
M
M
Laboratoire de Biologie Appliquée à L'Education Physique et aux Sports et Laboratoire Performance Sportive et Santé, Université de Bordeaux II, France. Martine.Duclos@biosport.U-Bordeaux2.fr
Corcuff
J B
JB
Arsac
L
L
Moreau-Gaudry
F
F
Rashedi
M
M
Roger
P
P
Tabarin
A
A
Manier
G
G
D000324:Adrenocorticotropic Hormone; D000328:Adult; D003346:Corticotropin-Releasing Hormone; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis / Q000097:blood / Q000378:metabolism*; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000502:physiology*; D008236:Lypressin; D008297:Male; D010807:Physical Endurance / Q000502:physiology*; D012420:Running / Q000502:physiology*; D012463:Saliva / Q000737:chemistry; D018709:Statistics, Nonparametric; D013268:Stimulation, Chemical; D013312:Stress, Physiological / Q000097:blood*
D008236:Lypressin; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D006854:Hydrocortisone