SEQUENTIAL-CHANGES IN THE PITUITARY-THYROID AXIS DURING PREGNANCY AND LACTATION IN THE RAT
SEQUENTIAL-CHANGES IN THE PITUITARY-THYROID AXIS DURING PREGNANCY AND LACTATION IN THE RAT
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DOI：
10.1210/endo-107-6-1711
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发表时间：
1980-01-01
期刊：
影响因子：
4.8
通讯作者：
GREER, MA
中科院分区：
文献类型：
--
作者：
FUKUDA, H;OHSHIMA, K;GREER, MA
通过测定大鼠血浆中促甲状腺激素、甲状腺素、三碘甲状腺原氨酸和游离甲状腺素（FT 4F）的浓度，研究了妊娠期和哺乳期大鼠垂体-甲状腺轴的动态变化。与人类妊娠相反，血浆T4在妊娠后半期逐渐下降至低至2.6 ±。0.2与6.3 ± μ g/dl相比，0.3μ g/dl（P < 0.01）。血浆T3浓度比血浆T4浓度经历较小比例的降低（66.5 ± 0.01）。6.2第0天ng/dl与44.6 ±。4.9 P < 0.05）。尽管T4急剧下降，但血浆TSH保持在正常水平，直到怀孕第16天，之后出现轻微但显著的增加。在妊娠晚期，FT 4F是未妊娠大鼠的两倍，但游离T4浓度指数显著降低。分娩后，高血浆TSH和低甲状腺激素水平持续整个哺乳期，只有在断奶后才恢复正常。在分娩后不久将幼崽取出的大鼠（非哺乳期）中，激素在几天内恢复到正常范围。泌乳期和非泌乳期大鼠分娩后FT 4F均恢复正常，但前者游离T4浓度指数显著降低。当哺乳期母亲甲状腺切除后，哺乳动物的血浆T4显著降低。在切除甲状腺的母亲补充生理替代剂量的T4的哺乳动物中，血浆T4维持在几乎正常的水平。显然，怀孕期间血浆甲状腺激素浓度的下降至少部分是由于血浆蛋白结合能力下降造成的，而哺乳期间血浆甲状腺激素浓度的下降可能是由于甲状腺激素流失到牛奶中造成的。在大鼠中，妊娠期的相对甲状腺功能减退状态可能是由于与哺乳期不同的机制。
Dynamic changes in the pituitary-thyroid axis were studied during pregnancy and lactation by measuring plasma concentrations of TSH [thyrotropin], T4 [thyroxine] and T3 [triiodothyronine] and the free T4 fraction (FT4F) in the rat. In contrast to human pregnancy, plasma T4 progressively decreased during the 2nd half of pregnancy to as low as 2.6 .+-. 0.2 .mu.g/dl by term compared with 6.3 .+-. 0.3 .mu.g/dl on day 0 of pregnancy (P < 0.01). Plasma T3 concentration underwent a smaller proportional decrease than plasma T4 (66.5 .+-. 6.2 ng/dl at day 0 vs. 44.6 .+-. 4.9 at term; P < 0.05). Despite the dramatic drop in T4, plasma TSH remained at normal levels until the 16th day of pregnancy, after which a slight, but significant, increase was seen. FT4F was twice as high during late pregnancy as in nonpregnant rats, but the free T4 concentration index was significantly lower. After delivery, high plasma TSH and low thyroid hormone levels persisted throughout lactation and returned to normal only after weaning. In rats whose pups were removed shortly after delivery (nonlactating), the hormones returned to the normal ranges within a few days. FT4F became normal in both lactating and nonlactating rats after delivery, but the free T4 concentration index was significantly lower in the former. There was a significant reduction of plasma T4 in sucklings when their nursing mother was thyroidectomized. Nearly nor al levels of plasma T4 were maintained in sucklings whose thyroidectomized mother was supplemented with a physiological replacement dose of T4. Apparently, the decrease in the concentration of plasma thyroid hormones during pregnancy, at least in part, results from a decreased binding capacity of plasma proteins, and the decrease in plasma thyroid hormone concentration during lactation probably results from a loss of thyroid hormones into milk. In rats, the relative hypothyroid state in pregnancy may be due to a different mechanism than that in lactation.