Institute for Biological Research 'Sinisa Stanković', University of Belgrade, Despot Stefan Blvd 142, 11060 Belgrade.
Exp Biol Med (Maywood). 2010 May;235(5):590-8. doi: 10.1258/ebm.2009.009279.
High intake of soybean phytoestrogens, isoflavones genistein (G) and daidzein (D), has been associated with health benefits. However, isoflavones were reported to affect adversely thyroid function in the presence of other goitrogenic factors. As the thyroid gland becomes functionally impaired with age, we examined whether supplementary doses of G or D would affect morphology and function of pituitary-thyroid axis in middle-aged male rats. Sixteen-month-old orchidectomized Wistar rats were treated with 10 mg/kg of either G or D, while the control sham-operated and orchidectomized group received just the vehicle for three weeks. The animals were fed soy-free diet with increased iodine content, and killed 24 h after the last treatment. Their pituitaries and thyroids were excised and prepared for further immunohistochemical and morphometric investigation. The concentrations of thyroid-stimulating hormone (TSH), total T(4) and T(3), in the serum were determined. In both isoflavone-treated groups, pituitary TSH-immunopositive cells had increased cellular volume and relative volume density (P < 0.05), as well as increased serum TSH levels (P < 0.05) in comparison to the controls; their thyroid tissue was characterized by increased volume of thyroglobulin-immunopositive epithelium (P < 0.05), epithelial height and index of activation rate (P < 0.05), while the volume of luminal colloid, and total serum T(4) and T(3) levels decreased (P < 0.05) in comparison to the controls. In conclusion, this study provides the first direct evidence that both G and D can induce microfollicular changes in the thyroid tissue and reduce the level of thyroid hormones in Orx middle-aged male rats, a model of andropause. This reduction consequently led to a feedback stimulation of pituitary TSH cells. The detected stimulatory effect was higher in the daidzein-treated rats.
大豆植物雌激素、染料木黄酮（G）和大豆苷元（D）的高摄入量与健康益处有关。然而，据报道，在存在其他致甲状腺肿因素的情况下，异黄酮会对甲状腺功能产生不利影响。随着甲状腺随着年龄的增长而功能受损，我们研究了补充 G 或 D 是否会影响中年雄性大鼠的垂体-甲状腺轴的形态和功能。对 16 个月大的去势 Wistar 大鼠给予 10mg/kg 的 G 或 D，而对照组假手术和去势组仅给予载体 3 周。这些动物喂食不含大豆且碘含量增加的饮食，并在最后一次治疗后 24 小时处死。切除它们的垂体和甲状腺，并准备进行进一步的免疫组织化学和形态学研究。测定血清中促甲状腺激素（TSH）、总 T4 和 T3 的浓度。在两种异黄酮处理组中，与对照组相比，垂体 TSH 免疫阳性细胞的细胞体积和相对体积密度增加（P < 0.05），以及血清 TSH 水平升高（P < 0.05）；甲状腺组织的特点是甲状腺球蛋白免疫阳性上皮的体积增加（P < 0.05）、上皮高度和激活率指数增加（P < 0.05），而管腔胶体的体积、总血清 T4 和 T3 水平降低（P < 0.05）与对照组相比。总之，本研究首次直接证明 G 和 D 均可诱导去势中年雄性大鼠甲状腺组织的微滤泡变化，并降低甲状腺激素水平，这种降低导致垂体 TSH 细胞的反馈刺激。在大豆苷元处理的大鼠中，检测到的刺激作用更高。
