Effect of 'physiological' doses of triiodothyronine replacement on the hormonal and metabolic adaptation to short-term semistarvation and to low-calorie diet in obese patients.

In four groups of obese patients matched for Body Mass Index (BMI), we studied the effects of different 3-week semi-starvation treatments followed by an 8-week hypocaloric (1008 kcal, protein 20%, carbohydrate 40%) diet with or without low doses of T3 therapy. Dietary intake (formula diet) in the semi-starvation period was 480 kcal, with 66 g protein (P) and 51 g carbohydrate (CHO) in groups I and III and with 33 g P and 84 g CHO in groups II and IV. Moreover, groups III and IV were given low doses (20 micrograms twice a day) of T3 while groups I and II received a placebo. During semi-starvation periods, a similar fall in BMI values was found in all groups, while during the low-calorie diet, T3-treated patients showed the greater BMI reduction. During semi-starvation, nitrogen balance was significantly more negative in low-protein than in high-protein-treated groups; differences between T3-treated (III and IV) and control (I and II) groups were not significant over this relatively short treatment period. No differences in 24 h urinary 3-methylhistidine or alanine excretion were evident between the four groups. During the entire period of study, daily urine creatinine excretion did not change in any group. In conclusion, in our study low-dose T3 therapy was seen to favour weight loss during low-calorie diet although negative effects on protein metabolism were not excluded, particularly when relatively small amounts of protein were administered.