Donda A, Reymond M J, Zürich M G, Lemarchand-Béraud T
Département de Médecine Interne, C.H.U.V., Lausanne, Switzerland.
Mol Cell Endocrinol. 1987 Nov;54(1):29-34. doi: 10.1016/0303-7207(87)90136-5.
A reduced secretion of thyroid hormones with age has been documented in humans and animals with no substantial increase in TSH secretion, which may be indicative of an age-related impairment of the pituitary sensitivity to the negative control exerted by thyroid hormones. We have evaluated in rats the influence of sex and age on pituitary T3 nuclear receptors--known to be determinant in the regulation of TSH secretion--as well as on T3 concentration in the pituitary gland. As regards sex, the density of T3 receptors and the concentration of T3 in pituitary gland and plasma were greater in females than in males whereas pituitary and plasma TSH concentrations were less. As for age, the density of T3 receptors was greater in old male rats than in young ones with no changes in pituitary T3 and plasma TSH concentrations. In old female rats in contrast, there was no significant increase in T3 receptors but pituitary T3 was less and plasma TSH greater than in young female rats. In both sexes plasma thyroid hormones and pituitary TSH were reduced with age whereas TSH response to TRH was not altered. These results illustrate sex and age differences in pituitary T3 receptors and pituitary T3 concentration as well as in TSH secretion. In young animals of both sexes an inverse correlation is observed between the density of pituitary T3 receptors and plasma TSH. In contrast, in old animals the absence of this correlation is suggestive of an age-related impairment of T3 action on the thyrotrophs or of changes pertaining to other factors modulating TSH secretion.
在人类和动物中均有记录表明，随着年龄增长甲状腺激素分泌减少，而促甲状腺激素（TSH）分泌并未大幅增加，这可能表明垂体对甲状腺激素负调控的敏感性出现了与年龄相关的损害。我们在大鼠中评估了性别和年龄对垂体T3核受体（已知其在TSH分泌调节中起决定性作用）以及垂体中T3浓度的影响。关于性别，雌性大鼠垂体中T3受体的密度以及垂体和血浆中T3的浓度均高于雄性，而垂体和血浆中TSH的浓度则较低。至于年龄，老年雄性大鼠垂体T3受体的密度高于年轻雄性大鼠，垂体T3和血浆TSH浓度无变化。相比之下，老年雌性大鼠垂体T3受体无显著增加，但垂体T3低于年轻雌性大鼠，血浆TSH则高于年轻雌性大鼠。在两性中，血浆甲状腺激素和垂体TSH均随年龄降低，而TSH对促甲状腺激素释放激素（TRH）的反应未改变。这些结果说明了垂体T3受体、垂体T3浓度以及TSH分泌在性别和年龄上的差异。在两性的年轻动物中，观察到垂体T3受体密度与血浆TSH之间呈负相关。相反，在老年动物中，这种相关性的缺失表明T3对促甲状腺细胞的作用出现了与年龄相关的损害，或者与调节TSH分泌的其他因素发生了变化。
