Low T3syndromeにおける血清遊離甲状腺ホルモン分画への血清遊離脂肪酸の影響

概要

論文の詳細を見る
We studied the role of serum free fatty acid (FFA) in the elevation of serum dializable fraction of T4 (DFT4) and evaluated the serum free T4 (FT4) level in low T3 syndrome. Serum DFT4 and DFT3 were measured by equilibrium dialysis method with phosphate buffer, and serum FFA concentration was obtained by gas chromatography. In patients with nonthyroidal systemic illnesses who showed reduced serum total T3 (TT3) and normal total T4 (TT4) (loW T3 group, TT3 48± 14 ng/dl, n = 10), mean (-± SD) DFT4 value (0.032±0.05%) was significantly higher than that of the group of systemic illnesses with normal TT3 and TT4 (normal T3 group, TT3 79±7 ng/dl, n = 10). Mean TT4 value of low T3 group (6.5± 1.0μg/dl) was lower than that of normal T3 group (8.6±2.4μg/dl, p<0.02). There was no difference in mean absolute FT4 (AFT4) value between the two groups (2.07±0.46 vs 2.19±0.53 ng/dl). On the other hand, there was no significant difference in DFT3 value between the groups (0.274±0.043 vs 0.247±0.035%), and mean AFT3 of low T3 group (1.29±0.39 pg/ml) was low than that of normal T3 group (1.92±0.26 pg/ml, p<0.01). In cases of low and normal T3 groups (n = 20), serum thyroxine binding globulin (TBG) concentration had a negative correlation with DFT3 (r =-0.707, p<0.001), but not with DFT4. Although there were no significant differences in serum albumin and TBG concentrations between the two groups, the mean serum total FFA concentration and molar ratio of FFA to albumin in low T3 group (579± 249 μM and 1.31±0.61) were significantly higher than those in normal T3 group (345±170 μM and 0.75±0.32, p<0.05 and <0.025, respectively). All of FFA concentrations in low T3 group, especially oleate, were higher than those in normal T3 group. Moreover, the higher the total FFA concentration was, the greater was the percent fraction of oleate. DFT4 values were significantly increased by the addition of 1 mM oleate to the sera of low T3 group, and this effect was more marked in the sera of the patients with lower albumin concentration. This effect of oleate on FT4 fraction was also observed by column adsorption chromatography method with Sephadex LH-20. The effect of oleate on DFT4 of subject with TBG deficiency was remarkable, and this was getting less as TBG concen-tration was increased by the addition of the serum containing high TBG to the original serum. In the study of 1-T4 load to the normal serum, this effect of oleate on DFT4 became greater as the amount of 1-T4 loaded was above the maximal binding capacities of TBG and/or thyroxine binding prealbumin (TBPA). And this effect of oleate on DFT4 was not attenuated with barbital buffer which inhibits the binding of T4 to TBPA. We also studied the ability of oleate in displacing 125I-T4 from HSA or purified TBG (Ka for T4 : 1010M-1). One half maximal B/F were obtained at 3.58 × 10-5M oleate and 1.54 × 10-5M HSA (molar ratio : 2.32) or at 1.96 × 10-5 oleate and 7.7 × 10-9M TBG (molar ratio : 2,545). Although oleate was about 3,000 times less potent than T4 in dis-placing 125I-T4 from TBG,
一般社団法人日本内分泌学会の論文

Low T<SUB>3</SUB>syndromeにおける血清遊離甲状腺ホルモン分画への血清遊離脂肪酸の影響

スポンサーリンク

概要

著者

関連論文

スポンサーリンク