Long-duration Space Flight and Bed Rest Effects on Testosterone and Other Steroids

J Clin Endocrinol Metab. 2012 Jan;97(1):270-8. doi: 10.1210/jc.2011-2233. Epub 2011 Nov 2.


Context: Limited data suggest that testosterone is decreased during space flight, which could contribute to bone and muscle loss.

Objective: The main objective was to assess testosterone and hormone status in long- and short-duration space flight and bed rest environments and to determine relationships with other physiological systems, including bone and muscle.

Design: Blood and urine samples were collected before, during, and after long-duration space flight. Samples were also collected before and after 12- to 14-d missions and from participants in 30- to 90-d bed rest studies.

Setting: Space flight studies were conducted on the International Space Station and before and after Space Shuttle missions. Bed rest studies were conducted in a clinical research center setting. Data from Skylab missions are also presented.

Participants: All of the participants were male, and they included 15 long-duration and nine short-duration mission crew members and 30 bed rest subjects.

Main outcome measures: Serum total, free, and bioavailable testosterone were measured along with serum and urinary cortisol, serum dehydroepiandrosterone, dehydroepiandrosterone sulfate, and SHBG.

Results: Total, free, and bioavailable testosterone was not changed during long-duration space flight but were decreased (P < 0.01) on landing day after these flights and after short-duration space flight. There were no changes in other hormones measured. Testosterone concentrations dropped before and soon after bed rest, but bed rest itself had no effect on testosterone.

Conclusions: There was no evidence for decrements in testosterone during long-duration space flight or bed rest.

Publication types

  • Clinical Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adult
  • Bed Rest* / adverse effects
  • Bone and Bones / metabolism
  • Bone and Bones / physiology
  • Gonadal Steroid Hormones / analysis
  • Gonadal Steroid Hormones / blood
  • Gonadal Steroid Hormones / metabolism*
  • Gonadal Steroid Hormones / urine
  • Humans
  • Male
  • Middle Aged
  • Space Flight*
  • Testosterone / analysis
  • Testosterone / blood
  • Testosterone / metabolism*
  • Testosterone / urine
  • Time Factors
  • Weightlessness


  • Gonadal Steroid Hormones
  • Testosterone