Kieffer J D, Mover H, Federico P, Maloof F
Endocrinology. 1976 Feb;98(2):295-304. doi: 10.1210/endo-98-2-295.
Systematic comparisons have been made of the development of the pituitary-thyroid axes of male and female rats, by measuring plasma thyrotropin (TSH) and thyroxine (T4) concentrations in neonates and adults. Observations were made in untreated groups as well as in rats treated with various regimens of exogenous T4, thyrotropin-releasing hormone, or TSH. All hormone determinations were by radioimmunoassay (RIA). Salient findings include the following: 1) In early neonatal life, untreated rats showed no significant sex difference in the plasma concentrations of either TSH or T4. 2) In adulthood, the plasma TSH of untreated males attained levels strikingly higher than those of neonates-the differences averaged 5-fold more. For females, the increase in plasma TSH during development was less marked, averaging slightly less than 2-fold more. Thus, untreated adults exhibited a clear sex difference in circulating TSH concentrations; the male TSH levels averaged 2.8-fold higher than those of females. 3) Plasma T4 concentrations also increased markedly during development. For both sexes, adult T4 levels were approximately 3-fold greater than the T4 levels in early neonatal life. Among untreated adults, the female T4 concentrations averaged 28% greater than those of males. 4) Plasma TSH and T4 concentrations exhibited only minor fluctuations, of borderline statistical significance, during the female estrous cycle. 5) A significant reduction in responsiveness to exogenous TRH was observed in adult male rats which had been treated with high doses of T4 in neonatal life, although the effect was not completely consistent. No significant reduction was observed in females which received the same treatment. We have concluded that major changes occur in the circulating hormone levels of the pituitary-thyroid axis of the rat between birth and adulthood, and that such changes are not identical for the two sexes.
通过测量新生大鼠和成年大鼠血浆促甲状腺激素（TSH）和甲状腺素（T4）浓度，对雄性和雌性大鼠垂体 - 甲状腺轴的发育进行了系统比较。在未处理组以及用各种外源性T4、促甲状腺激素释放激素或TSH治疗方案处理的大鼠中进行了观察。所有激素测定均采用放射免疫分析法（RIA）。主要发现如下：1）在新生儿早期，未处理的大鼠血浆TSH或T4浓度无显著性别差异。2）成年期，未处理雄性大鼠的血浆TSH水平显著高于新生大鼠，差异平均为5倍多。对于雌性大鼠，发育过程中血浆TSH的增加不太明显，平均略低于2倍。因此，未处理的成年大鼠循环TSH浓度存在明显的性别差异；雄性TSH水平平均比雌性高2.8倍。3）血浆T4浓度在发育过程中也显著增加。对于两性来说，成年期T4水平约为新生儿早期T4水平的3倍。在未处理的成年大鼠中，雌性T4浓度平均比雄性高28%。4）在雌性发情周期中，血浆TSH和T4浓度仅出现轻微波动，具有临界统计学意义。5）在新生期用高剂量T4处理的成年雄性大鼠中，观察到对外源性TRH的反应性显著降低，尽管效果并不完全一致。接受相同处理的雌性大鼠未观察到显著降低。我们得出结论，大鼠出生至成年期间垂体 - 甲状腺轴的循环激素水平发生了重大变化，且两性的此类变化并不相同。
