Plasma thyroxine changes of the Apollo Crewman.

Blood drawn from Apollo crew member; to the mission, at recovery, and postmission was used to examine the effect Apollo mission activities have on tyroid hormone levels. At recovery, statistically significant increases in thyroxine and the free thyroxine index were found. Serum cholesterol and triglycerides were decreased. No change of statistical significance was found in the T3 binding percentage, total serum proteins, and albumin. We conclude that apollo activities and environment caused the postmission increase in serum cholesterol may be one result of the increased thyroxine activity.