The influence of microgravity and re-entry landing on the endocrine sy
stem of adult Japanese quail were studied. The reaction of organisms w
as expressed as changes in plasma levels of: estradiol, testosterone,
thyroxine (T-4), triiodothyronine (T-3) and corticosterone. The result
s were compared with those obtained m synchronous and laboratory contr
ol groups. Flight conditions caused elevated estradiol and decreased t
estosterone and T-4 levels, while the concentration of corticosterone
was not changed. Experimental conditions in synchronous group induced
similar changes as in flight experiment with the exception of T-3 elev
ation and a corticosterone decrease.