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Pituitary and plasma thyrotropin, thyroxine, and triiodothyronine after hyperthyroidism

机译：甲亢后垂体和血浆促甲状腺激素，甲状腺素和三碘甲状腺素

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During the initial phase of recovery from a chronic overexposure to thyroid hormones, plasma TSH does not increase after the injection of TRH despite normal or low circulating level of T4 and/or T3. To study the possible causes underlying this observation, rats were treated for weeks with very high doses of T4 plus T3, at the end of which age-paired controls and hyperthyroid rats were stimulated with TRH. This test was carried out at different intervals up to 7 days after administration of the last high dose of T4 plus T3. Plasma and pituitary TSH, T4, and T3 were measured by specific RIAs. Chronic treatment with high doses of thyroid hormone resulted in a marked depletion of pituitary TSH stores to less than 1% of the control value. TSH stores did not increase until 4-5 days after withdrawal of the thyroid hormone treatment, though circulating T4 and T3 levels generally had become undetectable by day 3. An increase in circulating TSH and a response to TRH were also not observed until days 4-5 after interruption of the chronic tretment. Present data show that the lack of response to TRH is not due to a persistence of high intrapituitary T4 and/or T3 content. Changes in pituitary T4 and T3 followed a pattern which was similar to, but not identical with, the changes observed in circulating T4 and T3, the concentrations of these iodothyronines decreased very rapidly after interruption of treatment, reaching very low levels on withdrawal days 3 and 4. Levels had not incresed to normal values by the seventh day of the withdrawal period. The phase of low plasma T4 and T3 concentrations which follows interruption of chronic overexposure to thyroid hormones is not due to unresponsiveness of the thyroid to TSH; thyroidal secretion resumes as soon as plasma TSH levels increase to normal. Chronic overexposure appears to have activated excretory and degradative mechanisms which contribute to the ensuing phase of thyroid hormone depletion.
机译：在从长期过度暴露恢复为甲状腺激素的初始阶段，尽管T4和/或T3的循环水平正常或较低，但注射TRH后血浆TSH不会增加。为了研究这一观察结果的可能原因，用非常高剂量的T4和T3治疗大鼠数周，最后用TRH刺激年龄配对的对照和甲状腺功能亢进的大鼠。在最后一次服用高剂量的T4和T3后最多7天，该测试以不同的间隔进行。血浆和垂体TSH，T4和T3通过特定的RIA测量。长期用大剂量甲状腺激素治疗可导致垂体TSH储备显着减少至对照值的1％以下。甲状腺激素治疗停药后4-5天，TSH储存量并未增加，尽管通常在第3天之前无法检测到循环中T4和T3的水平。直到第4天，也未观察到循环中TSH和对TRH的反应。 5．慢性中风中断后。目前的数据表明，对TRH缺乏反应不是由于持续存在高的脑垂体T4和/或T3含量。垂体T4和T3的变化与循环T4和T3的变化相似但不完全相同，这些碘甲状腺素的浓度在治疗中断后迅速下降，在停药第3天和第3天达到极低水平。 4.到提款期的第七天，水平还没有增加到正常值。在长期过度暴露于甲状腺激素之后，血浆T4和T3浓度较低的阶段并不是由于甲状腺对TSH的反应迟钝。一旦血浆TSH水平增加到正常水平，甲状腺分泌就会恢复。慢性过度暴露似乎具有激活的排泄和降解机制，这些机制有助于随后的甲状腺激素消耗期。

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