Endocrinology and Reproductive Physiology Laboratory, Department of Physiology, University of Calcutta, Kolkata, West Bengal, India.
Hum Exp Toxicol. 2011 Aug;30(8):884-96. doi: 10.1177/0960327110382563. Epub 2010 Aug 27.
Tea is a rich source of polyphenolic flavonoids including catechins, which are thought to contribute to the health benefits of it. Flavonoids have been reported to have antithyroid and goitrogenic effect. The purpose of this study was to evaluate whether high doses of green and black tea have a harmful effect on thyroid physiology. Un-fractionated green and black tea extracts were administered orally to male rats for 30 days at doses of 1.25 g%, 2.5 g% and 5.0 g%. The results showed that green tea extract at 2.5 g% and 5.0 g% doses and black tea extract only at 5.0 g% dose have the potential to alter the thyroid gland physiology and architecture, that is, enlargement of thyroid gland as well as hypertrophy and/or hyperplasia of the thyroid follicles and inhibition of the activity of thyroid peroxidase and 5(')-deiodinase I with elevated thyroidal Na+, K+-ATPase activity along with significant decrease in serum T3 and T4, and a parallel increase in serum thyroid stimulating hormone (TSH). This study concludes that goitrogenic/antithyroidal potential of un-fractionated green tea extract is much more than black tea extract because of the differences in catechin contents in the tea extracts.
茶是多酚类黄酮的丰富来源，包括儿茶素，被认为对其健康益处有贡献。黄酮类化合物已被报道具有抗甲状腺和致甲状腺肿作用。本研究旨在评估高剂量的绿茶和红茶是否对甲状腺生理有不良影响。将未分级的绿茶和红茶提取物以 1.25 g%、2.5 g%和 5.0 g%的剂量口服给予雄性大鼠 30 天。结果表明，绿茶提取物在 2.5 g%和 5.0 g%剂量下，红茶提取物仅在 5.0 g%剂量下，有可能改变甲状腺的生理学和结构，即甲状腺肿大以及甲状腺滤泡的肥大和/或增生，以及甲状腺过氧化物酶和 5' -脱碘酶 I 的活性抑制，同时甲状腺钠、钾-ATP 酶活性升高，血清 T3 和 T4 显著降低，血清促甲状腺激素（TSH）平行升高。本研究得出结论，由于茶提取物中儿茶素含量的差异，未分级的绿茶提取物的致甲状腺肿/抗甲状腺作用比红茶提取物强得多。
