Decrease in serum free triiodothyronine after jejuno-ileal bypass for obesity.

Seventeen patients with stable body-weights who had undergone a jejuno-ileal bypass for obesity, and 25 obese patients matching in sex, age and height were studied. Median serum concentration of free triiodothyronine (3.7 pmol/l) in the jejuno-ileal bypass patients was significantly (P less than 0.001) decreased by 18 per cent (95 per cent confidence limits: 11-27 per cent). Correspondingly median serum concentration of total triiodothyronine (1.47 nmol/l) was significantly (P less than 0.0001) decreased by 18 per cent (95 per cent confidence limits:11-27 per cent). The medium serum concentrations of free thyroxine (27.5 pmol/l) and total thyroxine 94 nmol/l) were of equal size in jejuno-ileal bypass patients and obese patients. In the bypass patients the median serum concentration of thyroxine-binding prealbumin (3.9 micromol/l) ws significantly (P less than 0.05) decreased by 13 per cent (95 per cent confidence limits: 7-27 per cent), whereas no significant changes could be demonstrated in thyroxine-binding globulin.