Cavalieri R R, Steinberg M, Searle G L
J Clin Invest. 1970 Jun;49(6):1041-50. doi: 10.1172/JCI106320.
The kinetics of distribution of 3,3',5-triiodo-L-thyronine (T(3)) have been studied employing both a single-injection and a continuous infusion of T(3-) (131)I. External monitoring of radioactivity in the liver during the infusion permitted estimation of the hepatic distribution volume (V(H)) and the one-way hepatic clearance (C(H)) of the hormone. Among 10 euthyroid control subjects, V(H) averaged 2.07 liters +/-0.50 (SD), and the mean value for C(H), 231 ml of plasma per min (+/-64). In three euthyroid men whose plasma showed decreased binding capacity by thyroxine-binding globulin (TBG) abnormally high V(H) and C(H) values were found, the increase in C(H) being proportional to the decrease in binding activity by plasma proteins. Among all 13 subjects, there was a high correlation (+ 0.86) between C(H) and the proportion of free hormone in plasma, measured in vitro. In four patients with hyperthyroid Graves' disease V(H) ranged from 3.2 to 4.2 liters and C(H) was elevated in every case, averaging 989 ml/min. The increase in C(H) in this group was out of proportion to the elevation of free hormone fraction in plasma. Seven patients who were either euthyroid or hypothyroid after treatment of Graves' disease showed a slight but significant increase in C(H) compared with the euthyroid controls without Graves' disease. The percentage of free hormone in the plasma of the treated group was normal or low and therefore could not explain the persistent elevation in unidirectional hepatic clearance observed. The rate of accumulation of labeled T(3) in the tissues of the thigh during the interval from 10 to 60 min of the sustaining infusion of tracer was slow compared to the rate of equilibration in the liver and did not differ significantly among the various groups studied. These latter findings suggest that in slowly equilibrating tissues such as the thigh the kinetics of T(3) distribution are relatively insensitive to alterations in hormone-binding activity by plasma proteins.
采用单次注射和连续输注3,3',5-三碘-L-甲状腺原氨酸（T₃）-¹³¹I的方法，研究了T₃的分布动力学。输注过程中对肝脏放射性进行外部监测，从而估算出该激素的肝脏分布容积（V(H)）和肝脏单向清除率（C(H)）。在10名甲状腺功能正常的对照受试者中，V(H)平均为2.07升±0.50（标准差），C(H)的平均值为每分钟231毫升血浆（±64）。在3名甲状腺功能正常的男性中，其血浆甲状腺素结合球蛋白（TBG）的结合能力下降，发现V(H)和C(H)值异常升高，C(H)的增加与血浆蛋白结合活性的降低成正比。在所有13名受试者中，C(H)与体外测量的血浆中游离激素比例之间存在高度相关性（+0.86）。在4例甲状腺功能亢进的格雷夫斯病患者中，V(H)范围为3.2至4.2升，且每例患者的C(H)均升高，平均为989毫升/分钟。该组中C(H)的增加与血浆中游离激素分数的升高不成比例。7例格雷夫斯病治疗后甲状腺功能正常或减退的患者，与无格雷夫斯病的甲状腺功能正常对照相比，C(H)有轻微但显著的增加。治疗组血浆中游离激素的百分比正常或偏低，因此无法解释观察到的单向肝脏清除率持续升高的现象。在持续输注示踪剂10至60分钟期间，大腿组织中标记T₃的积累速率与肝脏中的平衡速率相比缓慢，且在研究的不同组之间没有显著差异。后一项发现表明，在诸如大腿等平衡缓慢的组织中，T₃分布的动力学对血浆蛋白激素结合活性的改变相对不敏感。
