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

本文研究了哺乳期大鼠甲状腺和肾上腺在调节LH和FSH分泌中的作用。在整个妊娠期和哺乳期内，通过RIA测定血浆T3和T4浓度的变化。T3和T4的血浆浓度逐渐下降，在怀孕期间和低水平的两种激素维持在整个哺乳期。哺乳期第2天（分娩日=哺乳期第0天）卵巢切除导致血浆中T3和T4水平与假手术动物相比无差异。移除垫料后，T3和T4的血浆水平升高。这些结果清楚地表明，哺乳是伴随着甲状腺功能减退状态的大鼠。在哺乳期大鼠中，血浆皮质酮水平的增加，在响应固定应激被抑制相比，非哺乳期大鼠。去除凋落物恢复了对固定应激的降低反应。皮质酮分泌减少的反应，制动应激伴随着甲状腺功能减退状态在哺乳期大鼠。在非哺乳期雌性大鼠中，实验性甲状腺功能低下也抑制了皮质酮分泌对束缚应激的反应，而甲状腺功能低下大鼠的T4替代恢复了对应激的反应，这些结果表明，甲状腺功能与肾上腺皮质功能密切相关，甲状腺功能低下和肾上腺功能低下导致了哺乳期大鼠性腺功能低下。

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.