Introduction: The aim of this study was to investigate the consequences of 20 d of physical inactivity using head-down bed rest (HDBR) at -6 degrees on leptin, ghrelin, and counter-regulatory hormone responses.
Methods: Eight male volunteers were subjected to HDBR for 20 d. Variables measured before, during, and after HDBR included plasma cortisol, insulin, glucose, leptin, ghrelin, thyroid stimulating hormone (TSH), free thyroxine (fT4), and free triiodothyronine (fT3).
Results: No changes in ghrelin and leptin concentrations were observed during HDBR. Glucose concentration decreased significantly on the 20th day of HDBR compared to the pre-value (day 0) of HDBR (87.6 +/- 2.0 vs. 93 +/- 1.6 mg x dl(-1)). Significant correlation was observed between glucose and leptin concentrations.
Discussion: The results provide the first evidence that 20 d of HDBR is not associated with an alteration in ghrelin concentration. Leptin, insulin, and cortisol concentrations did not differ during 20 d of HDBR.