Connors J M, DeVito W J, Hedge G A
Endocrinology. 1985 Sep;117(3):900-6. doi: 10.1210/endo-117-3-900.
We have studied the effects of food deprivation on the plasma concentrations of T4, T3, and TSH, the TSH MCR, the pituitary TSH content, and the pituitary TSH response to TRH in female rats. Two days before the beginning of the experiment all rats were prepared with chronic intraatrial catheters through which TRH (100 ng/100 g BW) or [125I]iodo-TSH was administered, and sequential blood samples were obtained. The plasma concentrations of T4 and T3 in food-deprived rats were significantly (P less than 0.05) reduced compared to those in control rats 6, but not 2, days after food removal. Despite the fall in plasma concentrations of T4 and T3, no compensatory rise in the plasma TSH concentration was observed in the food-deprived rats. Plasma TSH concentrations did not differ between groups at any time. The change in the plasma TSH concentration (delta plasma TSH) was significantly greater 15, 30, and 45 min after iv bolus injection of TRH in food-deprived rats than in control rats. To further evaluate the basal TSH secretion rate (MCR X plasma TSH concentration) and the amount of TSH secreted in response to TRH (MCR X area under delta plasma TSH curve), the MCR of TSH was determined in control and food-deprived rats from the plasma disappearance curves of injected [125I]iodo-TSH. No differences were found in the TSH MCR or the calculated basal plasma TSH secretion rate (micrograms per day/100 g BW) of control or 6-day food-deprived rats. However, the change in the amount of TSH secreted in response to TRH was significantly greater in food-deprived rats than in control rats (17.7 +/- 2.1 vs. 11.0 +/- 1.0 micrograms/100 g BW; P less than 0.05). In addition, pituitary weight was significantly decreased in food-deprived rats (8.3 +/- 0.3 vs. 10.8 +/- 0.5 mg; P less than 0.05), but the pituitary TSH concentration (micrograms per mg tissue) was unchanged. These results are consistent with the development of tertiary hypothyroidism (i.e. decreased TSH stimulatory input to the pituitary by TRH or some other agent) during food deprivation in the rat.
我们研究了食物剥夺对雌性大鼠血浆中甲状腺素（T4）、三碘甲状腺原氨酸（T3）和促甲状腺激素（TSH）浓度、TSH的代谢清除率（MCR）、垂体TSH含量以及垂体TSH对促甲状腺激素释放激素（TRH）反应的影响。在实验开始前两天，所有大鼠均通过慢性心房内导管进行准备，通过该导管给予TRH（100 ng/100 g体重）或[125I]碘-TSH，并采集连续的血样。与对照组大鼠相比，食物剥夺大鼠在食物去除6天后血浆中T4和T3的浓度显著降低（P<0.05），但在2天后未出现这种情况。尽管血浆中T4和T3的浓度下降，但在食物剥夺大鼠中未观察到血浆TSH浓度的代偿性升高。两组在任何时间的血浆TSH浓度均无差异。静脉推注TRH后15、30和45分钟，食物剥夺大鼠血浆TSH浓度的变化（Δ血浆TSH）显著大于对照组大鼠。为了进一步评估基础TSH分泌率（MCR×血浆TSH浓度）以及对TRH反应分泌的TSH量（MCR×Δ血浆TSH曲线下面积），根据注射的[125I]碘-TSH的血浆消失曲线，在对照组和食物剥夺大鼠中测定TSH的MCR。对照组或食物剥夺6天的大鼠在TSH的MCR或计算出的基础血浆TSH分泌率（微克/天/100 g体重）方面未发现差异。然而，食物剥夺大鼠对TRH反应分泌的TSH量的变化显著大于对照组大鼠（17.7±2.1 vs. 11.0±1.0微克/100 g体重；P<0.05）。此外，食物剥夺大鼠的垂体重量显著降低（8.3±0.3 vs. 10.8±0.5 mg；P<0.05），但垂体TSH浓度（微克/毫克组织）未发生变化。这些结果与大鼠在食物剥夺期间发生的三级甲状腺功能减退（即TRH或其他某种因子对垂体的TSH刺激输入减少）的情况一致。
