Osburne R C, Myers E A, Rodbard D, Burman K D, Georges L P, O'Brian J T
Metabolism. 1983 Jan;32(1):9-13. doi: 10.1016/0026-0495(83)90148-8.
We have investigated the physiologic significance of the decline in serum triiodothyronine (T3) occurring during hypocaloric feeding by measurement of changes in cardiovascular function. The QKd interval, the interval between the Q wave of the electrocardiogram and the onset of Korotkoff sounds at diastolic pressure at the brachial artery, is the sum of the preejection period and pulsetransmission time, and has proven to be a sensitive and effective measure of the effect of thyroid hormones on the cardiovascular system. Fifteen euthyroid obese volunteers underwent successive 2 wk periods of hypocaloric feeding (200-400 calories per day) interspersed with periods of at least 2 wk of re-feeding on a weight-maintaining diet (1500 calories). In a later phase subjects received oral supplementation of triiodothyronine (T3) in addition to the diet to prevent the fall in serum T3. In the last study phase, subjects on the diet received supplementation with oral thyroxine (T4), which prevented the fall in serum T3 and resulted in a slight increase in serum T4. During the first 2 wk period of hypocaloric feeding, there was a statistically significant increase in QKd, and a decrease in pulse rate, compatible with a hypothyroid state relative to initial measurements. When oral T3 supplementation was given, the rise in QKd and fall in pulse rate were prevented. Likewise, with oral T4 supplementation, the changes in QKd and pulse were prevented. Thus, the fall in serum T3 occurring during hypocaloric feeding is associated with changes in the cardiovascular system which are qualitatively similar to those observed during hypothyroidism. The present data, taken with other data in the literature, suggest that the decline in serum T3 during hypocaloric feeding may be an adaptive mechanism to conserve energy during caloric deprivation.
我们通过测量心血管功能的变化，研究了低热量饮食期间血清三碘甲状腺原氨酸（T3）下降的生理意义。QKd间期是心电图Q波与肱动脉舒张压时柯氏音开始之间的间期，它是射血前期和脉搏传播时间的总和，已被证明是甲状腺激素对心血管系统作用的一种敏感且有效的测量指标。15名甲状腺功能正常的肥胖志愿者连续进行了2周的低热量饮食（每天200 - 400卡路里），期间穿插至少2周的维持体重饮食（1500卡路里）再喂养期。在后期阶段，受试者除饮食外还接受口服三碘甲状腺原氨酸（T3）补充，以防止血清T3下降。在最后一个研究阶段，接受饮食的受试者接受口服甲状腺素（T4）补充，这防止了血清T3下降并导致血清T4略有升高。在低热量饮食的前2周期间，QKd有统计学意义的增加，脉搏率下降，相对于初始测量结果，这与甲状腺功能减退状态相符。当给予口服T3补充时，QKd的升高和脉搏率的下降得到了预防。同样，给予口服T4补充时，QKd和脉搏的变化也得到了预防。因此，低热量饮食期间血清T3的下降与心血管系统的变化有关，这些变化在性质上与甲状腺功能减退期间观察到的变化相似。结合文献中的其他数据，目前的数据表明，低热量饮食期间血清T3的下降可能是热量缺乏期间保存能量的一种适应性机制。
