Serum thyroid hormones changes in patients undergoing Caesarean section under general or regional anaesthesia

The effects of anaesthesia on serum thyroid hormones were studied in 32 pregnant young women undergoing Caesarean section at term. Eighteen patients received general anaesthesia and 14 lumbar extradural blockade. Maternal serum concentrations of thyrotrophin (TSH), thyroxine (T4), triiodothyronine (T3) and reverse triiodothyronine (rT3) were measured using radioimmunoassay at 0, delivery and 24 h. There were no significant changes in TSH in the two groups. T4 concentrations decreased significantly at 24 h in the general anaesthesia group but regional anaesthesia produced a significant decrease only at the time of delivery. T3 concentrations decreased with both techniques. Reverse T3 increased markedly with general anaesthesia only at 24 h.