Roles of Thyroid and adrenal glands in the regulation of gonadotropins secretion during lactation in the rat

研究了大鼠哺乳期甲状腺和肾上腺对黄体生成素和卵泡刺激素分泌的调节作用。在妊娠和哺乳期用ria测定血浆T3和T4浓度的变化。妊娠期血浆T3、T4浓度逐渐下降，在整个哺乳期均维持低水平。在哺乳期第2天（分娩当天=哺乳期第0天）切除卵巢后，血浆中T3和T4水平与假手术动物比较无差异。除窝后血浆T3和T4水平升高。这些结果清楚地表明，哺乳期大鼠伴有甲状腺功能减退。在哺乳期大鼠中，与非哺乳期大鼠相比，固定应激反应中血浆皮质酮水平的升高受到抑制。移除凋落物恢复了对固定应激的降低反应。大鼠哺乳期皮质酮分泌对固定应激的反应降低，并伴有甲状腺功能减退。实验诱导的非哺乳期雌性大鼠甲状腺功能低下状态也抑制了皮质酮分泌对固定应激的反应，甲状腺功能低下大鼠的T4替代恢复了对应激的反应。提示哺乳期大鼠甲状腺功能与肾上腺皮质功能密切相关，甲状腺功能减退和肾上腺功能减退导致性腺功能减退。

The roles of thyroid and adrenal glands in the regulation of LH and FSH secretion were investigated during lactation in rats. Changes in plasma concentrations of T3 and T4 were measured by RIAs throughout pregnancy and lactation. Plasma concentrations of T3 and T4 gradually decreased in the period of pregnancy and the low levels of both hormones were maintained throughout lactation. Ovariectomy on day 2 of lactation (day of parturition = day 0 of lactation) resulted in no difference in levels of T3 and T4 in the plasma as compared with those of sham-operated animals. Plasma levels of T3 and T4 increased after removal of the litter. These results clearly indicated that lactation is accompanied by hypothyroid state in the rat.In the lactating rat, an increase in plasma levels of corticosterone in response to immobilization stress was suppressed as compared with those of non-lactating rats. Removal of the litter restored the reduced response to immobilization stress. The reduced response of secretion of corticosterone to immobilization stress was accompanied by the hypothyroid state during lactation in the rat. Experimentally induced hypothyroid state in non-lactating female rats also suppressed the response of corticosterone secretion to immobilization stress and the replacement of T4 in the hypothyroid rat restored the response to the stress.These findings suggest that thyroid function well correlated with the function of adrenal cortex and hypothyroidal and hypoadrenal state resulted in hypogonadal state in the lactating rat.