摘要
前言
碘是人体所必需的一种微量元素，是甲状腺激素合成的重要组成物质。碘缺乏病(iodine deficiency disorders，IDD)是一种严重危害人类健康的疾病。为防治IDD，我国政府从1996年起在全国范围内实行全民普遍食盐碘化，IDD得到了有效的控制。但随着我国居民碘摄入量的增加，临床甲状腺疾病的发病率呈现显著增加的趋势。为了解我国实行USI三年后的普通人群甲状腺疾病病谱和患病率的情况，本课题组于1999年4月开始对辽宁省、河北省三个不同碘摄入量农村社区(人群尿碘中位数分别为103μg／L，374μg／L，615μg／L)进行了甲状腺疾病横断面调查，初步调查结果显示：碘摄入量增加主要导致甲状腺功能减退症和乳头状甲状腺癌的发病率增加。
碘致甲状腺功能减退症(iodine induced hypothyroidism，IIH)近年来在国际上倍受学者们的关注。目前认为，碘致甲状腺功能减退症包括两种类型：一是碘加重甲状腺自身免疫破坏；另一是碘致甲状腺非自身免疫损伤。本课题组在调查中共发现121例亚临床甲状腺功能减退症患者甲状腺自身抗体阳性率仅为30％，其余70％的患者甲状腺功能改变可能与碘摄入量增加有关，但是其确切机制尚不清楚。
甲状腺有浓集碘以合成甲状腺激素的功能，碘的转运是甲状腺激素合成的第一个限速步骤，其中碘从细胞间质经基底膜，逆电化学梯度主动进入细胞的过程是碘转运过程中的最关键环节。现已确认，胞外碘进入甲状
腺细胞是由特异性的钠／碘同向转运体（Na、I－symporter，NIS）所介导完
成的。腆摄入量的变化可对NIS的表达产生影响，一定时期的碘摄入量增
加可引起NIS表达的下降，导致映转运异常，并进而影响甲状腺激素的合
成，因而可能参与破致甲状腺功能减退症的发生和发展。
查阅国内外文献，目前尚未见到长期过量碘摄入对甲状腺碘转运过程
影响的研究。本研究选择了三个不同碘摄入量地区的正常人群进行流行病
学对比研究，并模拟其中二个碘摄入量地区的碘摄入水平，进行动物在体
实验研究，观察长期过量碘摄入对甲状腺功能及甲状腺钠／碘同向转运体一
NIS蛋白表达的影响，以初步探讨过量碘摄入对甲状腺腆转运的影响及碘
致甲状腺非自身免疫损伤的机制。
材料 与 方法
一、流行病学调查人群
根据地方病防治部门（辽宁省地方病防治办公室和当地地方病防
治部门）提供的历史流行病学资料及目前不同地区的尿碘中位数水平，
选定辽宁省盘山县、彰武县及河北省黄驿市（县）的三个不同碘摄入
量地区作为研究地区。
二、动物模型：
选取1月龄SD大鼠3 00只，体重160上20克，雌雄各半，随机分
组，各组动物在实验期间均喂以我校动物部提供的普通饲料，分别饲
以不同浓度的碘离子水（均以KI加去离子水配制人
动物分为4组，每组75只：
GI：普通饲料十去离子水喂养（对照组）；
GZ：普通饲料十含碘600 11 g／L的去离子水喂养；
（每天摄碘约 ZIu g，相当于正常大鼠碘摄入量的 3借，下称
3倍高碘组）；
G3：普通饲料十含碘 1200 11 g／L的去离子水喂养；
（每天摄碘约 42 u g，相当于正常大鼠碘摄入量的 6倍，下称
6倍高碘组）；
G。：普通饲料十含碘 2000 u g／L的去离子水喂养；
3
（每天摄碘约 70 u g，相当于正常大鼠碘摄入量的 10倍，下
称10倍高碘组人
三、标本采集和处理
上述各组动物分别于给碘后1大、l周、2周、4周、8周处死，
每次每组处死15只动物。
1．标本采集
1）处死前一晚，每组随机取10只动物（雌雄各半）放人代谢笼中，
留取尿液，次日晨收集尿样：
2）动物以乙醚麻醉，上腹正中切口，游离肋骨，心脏采血，后继续
向上扩大切口至颈部，逐层分离皮肤、皮下组织至完全暴露气管，
迅速沿气管两侧分离甲状腺组织。
2．标本处理
1）尿样置于冻存管中，上0℃冻存，待测尿碘；
2）血标本4OC放置2／J’时后，离心门000fpm）20分钟，取上清，
血清存于eppendorf管中，一70oC冰箱冻存，待测TvTNTSH；
3）甲状腺组织做如下处理：
门）迅速置于液氮中，后于一70℃冰箱冻存；
门）迅速置于4％多聚甲醛溶液中，固定48小时后，转移至30％
蔗糖溶液中浸泡72小时，取出以OCT包埋，一70℃冻存：
u）迅速置于上0 t冻存，后于冷生理盐水中经机械匀浆，制备成
10％的甲状腺组织匀浆，上0 OC保存，待测组织碘。
四、实验方法
1．流行病学调查
每户成年人（＞ 14周岁）进行入户问卷调查及采样检查，检查内
容包括详细填写调查表格、体格检查、甲状腺B超检查、采取血、尿
标本。
空腹血清标本测定TSH、FT卜FT4、甲状腺球蛋白 河G人 甲
Iodine is also a necessary element for human being.Iodine deficiency disease (IDD) is a serious disease and many countries of the world have been take steps to control it including China.Our government has established the law of universal salt iodized (USI) from 1996.In order to acknowledge the situation of thyroid disease in population,we have taken an cross-section study in three different iodine intake areas. The results show the increasing incidence of hypothyroidism and thyroid carcinoma.
The mechanism of iodine-induced hypothyroidism is a hot topic in the world recently.We found 121 cases of subclinical hypothyroidism and 70% thyroid function disorder of them may be related with the increasing iodine intake,but the role is still not known.
Iodine, an essential component of thyroid hormones,is concentrated by the thyroid gland 20-40fold with respect to the iodide concentration in plasma.Active iodide uptake across the basolateral membrane of the thyroid follicular cell is mediated by the sodium/iodide symporter (NIS).TSH regulates every step of thyroid iodide metabolism.Iodine uptake has been demonstrated to be under the control of TSH.
The changes of iodine intake can also have effects on the expression of NIS.A high iodine intake can decrease the level of NIS protein and may cause an abnormal transportation of iodine.So does it take part in the development of hypothyroidism.
In the present study we compared the the relationship between TSH and FT3, FT4 and other factors in normal in three different iodine intake areas.Moreover, we observed the effects of high iodine intake on thyroid function and the expression of NIS in SD rats.We hope to explain the non-autoimmune mechanism of iodine-induced hypothyroidism.
Materials and Methods
1. Epidemical study
In three areas with deficient, moderate, and excess iodine intakes (Panshan, Zhangwu,
and Huanghua respectively), we selected residents randomly, tested their serum TSH (IMMULITE, the third generation assay) , TPOAb, TGAb, TG, FT3, FT4 and urinary iodine, and scan their thyroids with ultrasonic scanning. Those with a history of thyroid diseases, familial thyroid diseases, or with positive TPOAb, TGAb or abnormal levels TG or abnormal thyroid ultrasonic scanning were excluded. Then 650, 728 and 550 subjects from three areas were determined as normal subjects for the further study on the relationship between serum TSH and iodine intakes and its related influencing factors such as sex, age and TG.
2. Animals
Sprague Dawley (SD) rats (160g-220g) were used in the experiments and were maintained on lab diet from the animal department of China Medical University.The rats were divided into 4 groups: control (given distilled water) and three different iodine treatment water (given 600g/L , 1200g/L and 2000g/L iodized distill water respectively).
Thyroid gland from rat were removed immediately,snap frozen and stored at -70 C for measurements.Other thyroid glands were fixed in 4% PFA for 3 days and then removed to 30% sucrose for another 3 days for preparing the ice section.
Blood from rats were collected and the serum was frozen for later measurement of serum TSH, FT3, FT4. Fasting urinary sample from rats were collected before the killed day and stored at -20 C.
3. TSH, FT3, FT4, TPOAb, TGAb, TG of population was all determined by chemiluminescent immunoassay kits (IMMULITE, Diagnostic Products Corporation; USA ) ; Urinary iodine and tissue iodine concentration were determined using the Ce/As method after digestion by alkine ashing.Serum TT3, TT4 of rats were measured by RIA ( DPC,USA ) and TSH was by IRMA ( DPC,USA ) .
4. Immunohistochemical staining
Immunohistochemical staining was performed on frozen tissue section ( 7m ).The expression of NIS protein was studied by SP method of immunohistochemistry in different period of iodine treatments.
5. Western Blot
Total protein from thyroid gland was extracted.Homogenization was perform using a
mechanical device and centrifuged at 15,000 g
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