Effect on isoflurane anaesthesia and surgery on thyroid function in man

The effect of isoflurane (Forane) anaesthesia and surgery on thyroid function was investigated in nine male patients. Isoflurane anaesthesia alone for 30 minutes prior to the start of surgery increased plasma triiodothyronine uptake (T3U) and thyroxine (T4) level by 18 and 20 per cent, respectively. Free thyroxine index (FTI) values in blood increased by 62 per cent during the same period. One hour of surgical procedure further elevated these parameters. Our data indicate that isoflurane anaesthesia and surgery increase circulating thyroxine in man.