| Based on the successful establishment of animal model of endemic goiter caused by iodine deficiency, different doses of KI and KIO3 was administrated for 1 month and 3 months. We have observed the effects of different doses KI and KIOs on the structure and function of thyroid. We hope this study can offer some useful experimental data for the IDD prevention. This study includes two parts.1. The establishment of animal model of endemic goiter induced by iodine deficiencyWistar rats weighting 80-100g, half of male and female, were divided into two groups randomly, normal iodine group (NI) and low iodine group (LI) . All animals were fed with low iodine diet (iodine content is about 40 u g/kg) derived from an endemic goiter area. Rats of NI group drank deionized water containing iodine 0.26 iig/ml; Rats of LI group drank deionized water. 3 months later, 10 rats in each group were sacrificed. The following indicators were measured: urinary iodine, weight of thyroid gland, serum TTj TL}, and morphology of thyroid. The results showed that the urinary iodine excretion and the serum TT4 of LI group were significantly lower than that of NI group. The thyroid weights of LI group were markedly higher than that of NI group. The serum TTs was no significant difference between the two groups. The histological examination of LI group demonstrated a typical goiter of iodine deficiency. The follicles were small and their number increased obviously. The epithelial cells of thyroid follicles were significant hyperplastic. There was a little colloid in the follicular lumen. The results above indicated that the animal model of goiter induced by iodine deficiency had been established successfully.2. The effects of different doses of KI and KlOa on the structure and function of goiter in rats induced by iodine deficiencyThe rats with goiter induced by iodine deficient diet were divided into 7 groups randomly: ?IxKI;?lxKIO3;(D5xKI;?5xKIO3; ?50xKI; ?50xKIO3; ?LI. The 6 administrative groups drank deionized water containing different doses KI and KIOs respectively. The iodine concentrations are 0.26 u g/ml;1.31 n g/ml;13 u g/ml respectively. The NI and LI groups drank water like before as two control groups. 1 month and 3 months later, the rats were sacrificed and some indicators were measured. The results showed that the thyroid weights of all the 6 administrative groups decreased markedly, but no one group in morphology could completely recover to the normal state, although all the groups administrated with iodine showed gradual recovery in the observation on morphology. However, there was a tendency of slowing down in the involution of goiter with increased doses of iodine.The results of urinary iodine and the iodine content per unit weight of thyroidtissue showed that the urinary iodine excretion was paralleled with the iodine intake from the diet. Excessive Iodine ingested from diet can be excreted through urine. The iodine content in thyroid gland of administrative groups with high doses was not higher than that of the NI group. On the contrary, the experiments results showed that the iodine content of all the 6 administrative groups was lower than that of the NI group, and no significant differences of the iodine content in thyroid tissue were found among the 6 administrative groups. This suggested that excessive iodine was not accumulated in thyroid but excreted from urine and the thyroid has strong auto-regulation capability to the intake of excessive iodine. The results of iodine content in thyroid tissue were no obviously differences between 1 month and 3 months. It is indicated that thyroid could keep the iodine content on a relative invariableness as compensation ability to excessive iodine intake.The serum TT4 of the 6 administrative groups was markedly higher than the NI group, but the level of TTj was no significant difference among these groups. The levels of thyroid tissue TT4 in the IxKI, lxKIO3, 5xKI and 5xKIO3 groups were higher than the SOxKI, 50xKIO3 administrative groups and the NI group a...
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