孕妇碘营养与子女脑发育

Iodine Nutrition of Pregnant Women and Offspring Brain Development

碘是合成甲状腺激素（TH）的必需元素,在妊娠期TH参与调控与脑神经发育有关的基因,TH的作用一直沿续到婴幼儿出生后3年。胎儿的TH在妊娠早、中期主要来自孕妇的游离甲状腺素（FT4）,而妊娠晚期胎儿TH合成也依赖于母亲提供碘。来自缺碘地区的研究证实缺碘损伤脑神经发育,并因缺碘程度而呈现出从重到轻的脑发育障碍,即地方性克汀病、亚临床地方性克汀病和普遍的智力损伤,即便是隐匿性碘缺乏,也会增加孕妇TH异常和胎儿脑神经发育受损的风险,而有效的补碘能预防脑神经损伤。孕妇面临的碘过量主要发生在高水碘地区,无论是人群调查还是动物研究均显示脑神经对碘过量可能有较强的耐受性,但孕妇仍要避免长期暴露于高碘环境。个体碘营养评价可选用24 h尿碘检测。由于我国多数地区外环境长期处于缺碘状态,建议孕妇首选安全、有效和方便的碘盐,孕妇的适宜碘营养范围为200-500μg/d。

Iodine is an essential element for the thyroid hormone （TH） synthesis. It is well known that TH is involved in the regulation of genes related to fetus brain and neural development during pregnancy. The roles of TH in brain and neural development will even last to 3 years after birth. Fetal TH in the first and second trimesters originally comes from the free thyroxine （FT4） of pregnant women. Fetus in the last trimesters can produce TH which depends on the iodine supplements from pregnant women. The studies from the iodine-deficient areas showed that the iodine deficiency resulted in the brain impairment, and that the severity of brain impairment was related to the severity of iodine deficiency, such as endemic cretinism, subclinical endemic cretinism and intelligence impairments. The risks of TH deficiency and fetus brain impairment were increased even in those pregnant women with the latent iodine deficiency. The iodine replacement therapy in the iodine-deficient areas（iodized salt or iodized oil, etc.） can effectively prevent from offspring intelligence impairments. Excessive iodine intake usually happened in the areas with excessive iodine in drinking water. Studies of human being and animal suggested that the fetus developing brain can tolerate the excessive iodine in a certain extent. However, pregnant women should avoid the exposure to excessive iodine environment for long term. The test of 24 hours urinary iodine is available method for the evaluation of individual iodine nutrition. The iodized salt is a safe, effective and convenient supplement of iodine nutrition for those pregnant women with iodine deficiency. The adviced iodine intake is 200-500 μg/d for pregnant women.