Serum Thyroid Hormone Concentrations During Prolonged Reduction of Dietary Intake T. J. Visser, S. W. J. Lamberts, J. H. P. Wilson, R. Dotter, and G. Hennemann In nine obese but otherwise healthy rubjectr the effect of caloric restriction on the serum concentrations of thyroxine (T,), 3,3’,5triiodothyronine (T,), 3,3’,5’-triiodothyronine (rTs), ureo, uric acid, creotinine, and bilirubin wos studied. Blood wos obtained before and 2, 4, and 6 wk after the subjects hod changed to o chemically defined diet (31 g amino acids, 44 g carbohydrate, and 1.5 g fat; 300 kcol/ day). A decline of body weight to 88% and of serum T, to 70% of the pretreot-

ment values wos observed. Creotinine and bilirubin increased to 115% and 163%, respectively. Uric acid and rT, showed o transient rise to 148% ond 180%, respectively. Serum ureo wos lowest (72%) from the second until the fourth week. There wos o highly significant correlation between serum rT, and uric acid (r = 0.77, p O.l

0.43

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0.12

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>0.5

-0.48

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