Sakurai S, Hara Y, Miura S, Urabe M, Inoue K, Tanikawa T, Yanagisawa M, Iitaka M, Ishii J
Fourth Department of Internal Medicine, Saitama Medical School.
Endocrinol Jpn. 1988 Dec;35(6):865-76. doi: 10.1507/endocrj1954.35.865.
To study the factors involved in the low thyroid hormone levels in patients with chronic renal failure (CRF), we investigated thyroid functions just before and after hemodialyses (HD) in 32 such patients who were on maintenance HD. In addition, we measured serum thyroid hormone binding inhibitor activities (THBI) in another set of 37 patients. None of the patients had been suspected of having thyroid diseases. HD duration and aging did not have a significant effect on the results of the thyroid function tests. Before each HD, the serum concentrations of T3, T4, FT3, FT4, rT3, PBI, FT3I, FT4I, FT3/T3, FT4/T4, T4/TBG, T4/TSH and FT4/TSH were lower, and those of TSH, TBG, and thyroglobulin (Tg) were higher in the patients than in normal controls. The thyroid hormone concentrations were negatively correlated with the BUN and creatinine levels. The Tg levels were positively correlated with the BUN levels. After each HD, almost all the thyroid function tests including T4/TBG ratio showed improvements, which indicated that hemodilution and a decrease in the T4-binding affinity of TBG with thyroid hormones were the major factors in the low thyroid hormone levels in CRF patients. However, even after HD, T3, FT3, rT3, T4/TSH and FT4/TSH were still lower and TSH and Tg were still higher in the patients. These data suggested that the CRF patients were in a subclinical hypothyroid state. THBI was high in patients with CRF and did not change following HD. NEFA did not seem to contribute to the high THBI before HD, because they were in the normal range. However, as NEFA became very high after HD and possessed THBI, we calculated the corrected THBI (C-THBI) by subtracting the effect of NEFA from total THBI. C-THBI was high before HD and decreased after HD. Therefore, it was suggested that this C-THBI contributed to the abnormalities in the affinity of TBG with thyroid hormones. From these studies, it is concluded that (1) the patients with CRF may be in a subclinical hypothyroid state, although hemodilution was seen to have a strong effect on the thyroid hormone concentrations, and (2) C-THBI may have an effect on the affinity of TBG with thyroid hormones and play an additional role in low thyroid hormone levels in these patients. The mechanisms of hypothyroidism and the nature of C-THBI remain to be clarified.
为研究慢性肾衰竭（CRF）患者甲状腺激素水平降低的相关因素，我们对32例接受维持性血液透析（HD）的此类患者在血液透析前后的甲状腺功能进行了调查。此外，我们还对另外37例患者测定了血清甲状腺激素结合抑制活性（THBI）。所有患者均未被怀疑患有甲状腺疾病。HD时长和年龄对甲状腺功能测试结果无显著影响。每次HD前，患者血清中T3、T4、FT3、FT4、rT3、PBI、FT3I、FT4I、FT3/T3、FT4/T4、T4/TBG、T4/TSH和FT4/TSH的浓度较低，而TSH、TBG和甲状腺球蛋白（Tg）的浓度高于正常对照组。甲状腺激素浓度与BUN和肌酐水平呈负相关。Tg水平与BUN水平呈正相关。每次HD后，几乎所有甲状腺功能测试（包括T4/TBG比值）均显示改善，这表明血液稀释以及TBG与甲状腺激素结合亲和力降低是CRF患者甲状腺激素水平降低的主要因素。然而，即使在HD后，患者的T3、FT3、rT3、T4/TSH和FT4/TSH仍较低，TSH和Tg仍较高。这些数据表明CRF患者处于亚临床甲状腺功能减退状态。CRF患者的THBI较高，且HD后未发生变化。游离脂肪酸（NEFA）在HD前似乎对高THBI无影响，因为其处于正常范围内。然而，由于HD后NEFA变得非常高且具有THBI，我们通过从总THBI中减去NEFA的影响来计算校正后的THBI（C - THBI）。C - THBI在HD前较高，HD后降低。因此，提示这种C - THBI导致了TBG与甲状腺激素亲和力的异常。从这些研究得出结论：（1）CRF患者可能处于亚临床甲状腺功能减退状态，尽管血液稀释对甲状腺激素浓度有显著影响；（2）C - THBI可能影响TBG与甲状腺激素的亲和力，并在这些患者甲状腺激素水平降低中起额外作用。甲状腺功能减退的机制以及C - THBI的性质仍有待阐明。
