Hormonal responses to a 160-km race across frozen Alaska.
BACKGROUND
Severe physical and environmental stress seems to have a suppressive effect on the hypothalamic-pituitary-gonadal (HPG) axis in men. Examining hormonal responses to an extreme 160-km competition across frozen Alaska provides a unique opportunity to study this intense stress.


OBJECTIVE
To examine hormonal responses to an ultra-endurance race.


METHODS
Blood samples were obtained from 16 men before and after racing and analyzed for testosterone, interleukin-6 (IL-6), growth hormone (GH) and cortisol. Six subjects (mean (SD) age 42 (7) years; body mass 78.9 (7.1) kg; height 1.78 (0.05) m raced by bicycle (cyclists) and 10 subjects (age 35 (9) years; body mass 77.9 (10.6) kg; height, 1.82 (0.05) m) raced by foot (runners). Mean (SD) finish times were 21.83 (6.27) and 33.98 (6.12) h, respectively.


RESULTS
In cyclists there were significant (p< or =0.05) mean (SD) pre-race to post-race increases in cortisol (254.83 (135.26) to 535.99 (232.22) nmol/l), GH (0.12 (0.23) to 3.21 (3.33) microg/ml) and IL-6 (2.36 (0.42) to 10.15 (3.28) pg/ml), and a significant decrease in testosterone (13.81 (3.19) to 5.59 (3.74) nmol/l). Similarly, in runners there were significant pre-race to post-race increases in cortisol (142.09 (50.74) to 452.21 (163.40) ng/ml), GH (0.12 (0.23) to 3.21 (3.33) microg/ml) and IL-6 (2.42 (0.68) to 12.25 (1.78) pg/ml), and a significant decrease in testosterone (12.32 (4.47) to 6.96 (3.19) nmol/l). There were no significant differences in the hormonal levels between cyclists and runners (p>0.05).


CONCLUSIONS
These data suggest a suppression of the hypopituitary-gonadal axis potentially mediated by amplification of adrenal stress responses to such an ultra-endurance race in environmentally stressful conditions.
Kraemer
W J
WJ
University of Connecticut, Human Performance Laboratory, Storrs, Connecticut 06269-1110, USA. william.kraemer@uconn.edu
Fragala
M S
MS
Watson
G
G
Volek
J S
JS
Rubin
M R
MR
French
D N
DN
Maresh
C M
CM
Vingren
J L
JL
Hatfield
D L
DL
Spiering
B A
BA
Yu-Ho
J
J
Hughes
S L
SL
Case
H S
HS
Stuempfle
K J
KJ
Lehmann
D R
DR
Bailey
S
S
Evans
D S
DS
D000328:Adult; D000413:Alaska; D001642:Bicycling / Q000502:physiology*; D003080:Cold Temperature / Q000009:adverse effects*; D013006:Growth Hormone / Q000097:blood; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism*; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D008875:Middle Aged; D010807:Physical Endurance / Q000502:physiology*; D010913:Pituitary-Adrenal System / Q000378:metabolism*; D012420:Running / Q000502:physiology*; D013739:Testosterone / Q000097:blood
D015850:Interleukin-6; D013739:Testosterone; D013006:Growth Hormone; D006854:Hydrocortisone