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Endocrine responses to acute and chronic high-altitude exposure (4,300 meters): modulating effects of caloric restriction

¹Clinical Studies Unit and Medical Service, Veterans Affairs Palo Alto Health Care System; ²Department of Medicine and Program in Human Biology, Stanford University, Palo Alto, California; ³Center for Aerospace and Hyperbaric Medicine, Oklahoma State University Health Science Center, Tulsa, Oklahoma; ⁴Thermal and Mountain Medicine Division, United States Army Research Institute for Environmental Medicine, Natick; ⁵Department of Exercise Science, University of Massachusetts, Amherst, Massachusetts; and ⁶Department of Kinesiology, University of Colorado, Boulder, Colorado

Submitted 15 September 2005 ; accepted in final form 12 December 2005

High-altitude anorexia leads to a hormonal response pattern modulated by both hypoxia and caloric restriction (CR). The purpose of this study was to compare altitude-induced neuroendocrine changes with or without energy imbalance and to explore how energy sufficiency alters the endocrine acclimatization process. Twenty-six normal-weight, young men were studied for 3 wk. One group [hypocaloric group (HYPO), n = 9] stayed at sea level and consumed 40% fewer calories than required to maintain body weight. Two other groups were deployed to 4,300 meters (Pikes Peak, CO), where one group (ADQ, n = 7) was adequately fed to maintain body weight and the other [deficient group (DEF), n = 10] had calories restricted as above. HYPO experienced a typical CR-induced reduction in many hormones such as insulin, testosterone, and leptin. At altitude, fasting glucose, insulin, and epinephrine exhibited a muted rise in DEF compared with ADQ. Free thyroxine, thyroid-stimulating hormone, and norepinephrine showed similar patterns between the two altitude groups. Morning cortisol initially rose higher in DEF than ADQ at 4,300 meters, but the difference disappeared by day 5. Testosterone increased in both altitude groups acutely but declined over time in DEF only. Adiponectin and leptin did not change significantly from sea level baseline values in either altitude group regardless of energy intake. These data suggest that hypoxia tends to increase blood hormone concentrations, but anorexia suppresses elements of the endocrine response. Such suppression results in the preservation of energy stores but may sacrifice the facilitation of oxygen delivery and the use of oxygen-efficient fuels.

altitude; hypoxia; hormones; energy balance; acclimatization; caloric restriction

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				A. Benso, F. Broglio, G. Aimaretti, B. Lucatello, F. Lanfranco, E. Ghigo, and S. Grottoli Endocrine and metabolic responses to extreme altitude and physical exercise in climbers Eur. J. Endocrinol., December 1, 2007; 157(6): 733 - 740. [Abstract] [Full Text] [PDF]