Schaison G, Thomopoulos P, Leguillouzic D, Thomas G, Moatti M
Acta Endocrinol (Copenh). 1984 Jul;106(3):338-45. doi: 10.1530/acta.0.1060338.
To investigate the respective role of triiodothyronine (T3) and thyroxine (T4) in the regulation of TSH secretion, we studied the action of sodium ipodate and propylthiouracil (PTU) in 11 athyreotic patients. The LT4 replacement dose was adjusted to obtain, in each patient, a normal basal TSH level and a normal TSH response to TRH. In the 5 ipodate-treated patients (single 6 g oral dose), the mean serum T3 level fell by 64% below the baseline value and serum rT3 rose 180% above the baseline. The free T4 index (FT4I) did not change whereas the mean serum TSH concentration increased 280% above baseline values. In the 6 PTU-treated patients (250 mg orally every 6 h for 10 days), serum T3 levels fell 33%, serum rT3 increased up to 82% and the FT4I did not change. The mean serum TSH concentration increased 68% above the baseline value. Thus, the mean percentage increase in serum TSH was less in PTU- than in ipodate-treated patients (68% vs 280%). Statistical analysis of the correlation between the serum T3 decrease (delta T3) and the serum TSH (delta TSH) increase demonstrated that for the same T3 diminution, the ipodate-treated group displayed higher increase of TSH than the PTU-treated patients. In the rat, PTU interferes with the 5'-deiodination of T4 in the liver and kidney but not in the pituitary, while ipodate appears to have the same effect in all tissues. If this holds true for human subjects, our data strongly suggest that circulating T4 (through its intrapituitary conversion to T3) shares with serum T3 the capacity to regulate TSH secretion in man.
为研究三碘甲状腺原氨酸（T3）和甲状腺素（T4）在促甲状腺激素（TSH）分泌调节中的各自作用，我们对11例甲状腺切除患者进行了碘番酸钠和丙硫氧嘧啶（PTU）作用的研究。调整左甲状腺素（LT4）替代剂量，以使每位患者获得正常的基础TSH水平以及对促甲状腺激素释放激素（TRH）的正常TSH反应。在5例接受碘番酸钠治疗的患者中（单次口服6 g剂量），血清T3平均水平比基线值下降了64%，而血清反三碘甲状腺原氨酸（rT3）比基线值升高了180%。游离T4指数（FT4I）未发生变化，而血清TSH平均浓度比基线值升高了280%。在6例接受PTU治疗的患者中（每6小时口服250 mg，共10天），血清T3水平下降了33%，血清rT3升高至82%，且FT4I未发生变化。血清TSH平均浓度比基线值升高了68%。因此，PTU治疗患者血清TSH的平均升高百分比低于碘番酸钠治疗患者（68%对280%）。对血清T3降低量（ΔT3）与血清TSH升高量（ΔTSH）之间的相关性进行统计分析表明，对于相同的T3降低量，碘番酸钠治疗组的TSH升高幅度高于PTU治疗患者。在大鼠中，PTU会干扰肝脏和肾脏中T4的5'-脱碘作用，但不影响垂体，而碘番酸钠似乎在所有组织中都有相同作用。如果这也适用于人类受试者，我们的数据强烈表明，循环中的T4（通过其在垂体内转化为T3）与血清T3一样，具有调节人类TSH分泌的能力。
