Shenkman L, Mitsuma T, Hollander C S
J Clin Invest. 1973 Jan;52(1):205-9. doi: 10.1172/JCI107166.
The relative roles of triiodothyronine (T(3)) and thyroxine (T(4)) in modulating pituitary responsiveness to thyrotropin-releasing hormone (TRH) have been assessed. (a) 10 hyperthyroid patients with elevated serum T(2) and T(4) levels showed no pituitary response to TRH. After 2 wk of propylthiouracil therapy T(4) levels had fallen to normal in only five patients while T(2) levels were normal in all. Pituitary responsiveness to TRH returned in all patients with normal or high T(4) concentrations. (b) Patients with isolated elevations of serum T(3) (T(3) toxicosis) failed to respond to TRH. TRH responsiveness was restored when T(3) levels fell to normal after propylthiouracil therapy. (c) When pituitary responsiveness to TRH was tested 60 min after a single oral dose of 50 mug of T(3), which increased serum T(3) levels to slightly above the normal range, no rise in thyrotropin (TSH) was seen in six subjects. These findings indicate that T(3) elevations alone can rapidly inhibit pituitary responsiveness to TRH.
已评估三碘甲状腺原氨酸（T₃）和甲状腺素（T₄）在调节垂体对促甲状腺激素释放激素（TRH）反应性中的相对作用。（a）10例血清T₃和T₄水平升高的甲状腺功能亢进患者对TRH无垂体反应。丙硫氧嘧啶治疗2周后，仅5例患者的T₄水平降至正常，而所有患者的T₃水平均正常。所有T₄浓度正常或升高的患者垂体对TRH的反应性恢复。（b）血清T₃单独升高（T₃中毒）的患者对TRH无反应。丙硫氧嘧啶治疗后T₃水平降至正常时，TRH反应性恢复。（c）单次口服50μg T₃使血清T₃水平升高至略高于正常范围60分钟后，检测垂体对TRH的反应性，6名受试者的促甲状腺激素（TSH）未见升高。这些发现表明，单独的T₃升高可迅速抑制垂体对TRH的反应性。
