Endocrine and metabolic responses to extreme altitude and physical exercise in climbers.
BACKGROUND
Chronic hypoxia induces complex metabolic and endocrine adaptations. High-altitude (HA) exposure is a physiological model of hypoxia.


OBJECTIVE
To further investigate the endocrine and metabolic responses to extreme HA.


METHODS
We studied nine male elite climbers at sea level and at 5200 m after climbing Mt. Everest.


RESULTS
After 7 weeks at HA, body weight was reduced (P<0.05); regarding endocrine variables we observed: a) an increase of 2-h mean GH concentration (P<0.05) as well as of total IGF-I and IGF binding protein-3 levels (P<0.05 for both); b) a prolactin increase (P<0.05) coupled with testosterone decrease (P<0.01) and progesterone increase (P<0.05) without any change in estradiol levels: c) no change in cortisol, ACTH, and dehydroepiandrosterone sulfate (DHEAS) levels; d) an increase in free thyroxine (P<0.05) and free tri-iodothyronine (T(3)) decrease (P<0.05) but no change in TSH levels; e) a plasma glucose decrease (P<0.05) without any change in insulin levels; f) an increase in mean free fatty acid levels (P<0.05); g) despite body weight loss, leptin levels showed non-significant trend toward decrease, while ghrelin levels did not change at all.


CONCLUSIONS
The results of the present study in a unique experimental human model of maximal exposure to altitude and physical exercise demonstrate that extreme HA and strenuous physical exercise are coupled with specific endocrine adaptations. These include increased activity of the GH/IGF-I axis and a low T(3) syndrome but no change in ghrelin and leptin that was expected taking into account body weight decrease. These findings would contribute to better understanding human endocrine and metabolic physiology in hypoxic conditions.
Benso
Andrea
A
Division of Endocrinology and Metabolism, Department of Internal Medicine, Molinette Hospital, University of Turin, Corso Dogliotti 14, 10126 Turin, Italy.
Broglio
Fabio
F
Aimaretti
Gianluca
G
Lucatello
Barbara
B
Lanfranco
Fabio
F
Ghigo
Ezio
E
Grottoli
Silvia
S
D000328:Adult; D000531:Altitude; D001835:Body Weight / Q000502:physiology; D004958:Estradiol / Q000097:blood; D015444:Exercise / Q000502:physiology*; D019382:Human Growth Hormone / Q000097:blood; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D020738:Leptin / Q000097:blood; D008297:Male; D010907:Pituitary Hormones / Q000378:metabolism*; D011374:Progesterone / Q000097:blood; D011388:Prolactin / Q000097:blood; D013739:Testosterone / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D018972:Insulin-Like Growth Factor Binding Protein 3; D020738:Leptin; D010907:Pituitary Hormones; D014284:Triiodothyronine; D019382:Human Growth Hormone; D013739:Testosterone; D011374:Progesterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D011388:Prolactin; D013974:Thyroxine