THE INFLUENCE OF VARIOUS ANESTHETICS ON THE RELEASE AND METABOLISM OFTHYROID-HORMONES - RESULTS OF 2 CLINICAL-STUDIES

Normal functioning of the thyroid gland during surgery is important, b ut few data are available on the possible interactions between anesthe sia and thyroid hormones. In two independent studies we examined the i nfluence of different types of general anesthesia on the plasma levels of the thyroid hormones. They revealed an intraoperative increase of free thyroxine (fT(4)) and total thyroxine (tT(4)) in plasma to approx imately 150% of preanesthesia levels when enflurane was used. No incre ase in thyroid-stimulating hormone (TSH) secretion was noted prior to this. The increase was not due to a quantitative change in the binding proteins. The plasma levels of fT(4) and tT(4) returned to normal pos toperatively; however, no accompanying increase in plasma triiodothyro nine levels was observed. Hence we assume the increase to be due to ho rmone release from thyroid and/or extrathyroidal stores-an intercompar tmental shifting.