INFLUENCES OF OBESITY AND WEIGHT-LOSS ON THYROID-HORMONES - A 3-3.5-YEAR FOLLOW-UP-STUDY ON OBESE SUBJECTS WITH SURGICAL BILIOPANCREATIC BYPASS

The effects of changing body size, energy intake and substrate oxidati on on serum T-4, FT4, T-3, FT3 and TSH were investigated in ten morbid ly obese subjects (4 men/6 women; age. 37 +/- 6 years; BMI: 53.8 +/- 6 .5 kg/m(2); mean +/- SD) who had undergone a surgical bilio-pancreatic by-pass in order to reduce their body weight. The starting value of s erum FT3 was inversely related to the BMI (r = -0.63; p < 0.05). After 1-3 months, all the subjects were losing weight and their intake of c arbohydrates was almost negligible; at this lime a significant reducti on of T-3 (-14.6%; p < 0.0001), T-4 (-19.5%; p < 0.0001), and FT3 (-10 .5%; p < 0.001) was observed. Nine to 16 months after surgery, all the subjects were still losing weight, although there was no carbohydrate restriction; T-3, T-4, and FT3 were lower than prior to surgery but w ere beginning to increase. Finally, after 36-42 months the body weight of all the patients had been stable for at least the previous six mon ths (final BMI, 32.9 +/- 4.1) and their body composition, as assessed by bio-impedance, was almost normal; only the concentrations of FT3 pr oved to be significantly lower than the basal value (-11.2%; p < 0.03) . The change in FT3 proved to be independently influenced by the degre e of fat malabsorption but not by changes in any of the physical chara cteristics considered, All values were always in the normal range; FT4 and TSH did not change significantly during the whole period of study . The final concentrations of TSH proved to be independently related t o the postabsorptive protein oxidation (g/24h) (TSH = 2.37 - 0.018.pro tein oxidation). These results would suggest that nutritional factors have some influence on the blood levels of thyroid hormones, especiall y of FT,, while the removal of obesity does not seem to have any indep endent effect in the long-run. (C) 1997, Editrice Kurtis.