Preliminary investigations of urinary thyroxine excretion by young pigs

Total and unconjugated thyroxine were measured in pig urine and the effect of several forms of stress on the urinary thyroxine excretion of young pigs was investigated. There was considerable variation in the daily urinary thyroxine excretion and the rate of excretion tended to increase with age. Handling procedures used to simulate stress had little effect on thyroxine excretion rate but group penning of pigs temporarily altered thyroxine excretion rate. A diurnal variation in the excretion rate of total and unconjugated thyroxine was observed with peaks about 9.00 h, just before feeding.