Experimental Research On The Effect Of Iodine Excess On The Morphology And Thyroid Function

Iodine is an essential element of human body , the primary substrate for the biosynthesis of thyroid hormone and one of the important factors for maintaining the normal morphology and thyroid function. Iodine deficiency can cause iodine deficiency disorders ( IDD) - hypothyroidism and mental impairment. Iodized salt was largely used in IDD - affected countries since 1990. More and more attention is being paid on the side - effect of iodized salt. Epidemiological research indicated that iodine excess can increase the prevalence of iodine - induced hyperthyoridism, autoimmune thyroid diseases, hypothyroidism, goiter and papillary thyroid cancer. Our comparative research on the thyroid function in mild low iodine intake area ( MUI 103ug/L) , moderate iodine intake area (MUI 374ug/L) and high iodine intake area(MUI 614ug/L) show that iodine excess may increase the risk for subclinical hypothyroidism in schoolchildren and increase the prevalence of hypothyroidism and subclinical hypothyoidism in a-dults. Clinical hypothyroidism was caused by autoimmunity while 2/3 subclinical hypothyroidism patients were caused by the suppression of iodine excess. Experimental research on the effect of iodine excess on thyroid function in animal is divided into two aspects: the effect of iodine excess on thyroid function in autoimmune thyroid disease susceptible animal and the effect of iodine excess on thyroid function in common animal. There are more research on the former but fewer research on the latter whose results are mostly contradictary. The dosage of iodine intake in animal experiment was too high. Until now there is no research animal whose were MUI between 300 - 600ug/L. There is no experiment research on monitoring urine iodine and fewer quantitative research on thyroid morphology and fewer experimental research combined with epidemiological research. There are more research on the effect of iodine excess on the thyroid ofautoimmune - thyroid - disease - susceptible animal and fewer research on common animals. The Fas/FasL system has proved to be involved in the induction of apoptosis of thyrocytes in the early stage of involution of goiter induced by low i-odine diet and propylthiouracil(PTU). Until now there are fewer reports on the effect of long - term intake of excessive iodine intake on the expression of Fas and FasL in the thyroid of common animal. At present some disagreement still exists on the application of potassium iodate into salt. And no research reports were seen on the comparison between the effect of potassium iodate and iodine on thyroid function and morphology. Iodine (I2 ) is a commonly - used drinking water disinfectant for traveler. No animal research reports are seen on the effect of iodine (I2) excess on the thyroid function. Therefore, we observed the changes in thyroid function and body weight in Wistar rats whose MUI were between 300 and 600ug/Lo Also we made a quantitative research on the morphological changes of thyroid follicular cells in Wistar rats. Immunohistochemistry and in situ hybridization techniques were used to make in vivo research on the effect of apoptosis and expression of Fas and FasL of thyroid follicular cells of Wistar rats. Research was also made on effect of the different preparations of iodine on the function and morphology of Wistar rats.Methods1. Animal Model and treatment: iodine deficiency animal model: 4 - week - age Wistar rats whose male and female number were equal were fed common diet of our animal center of China Medical University and double distilled water (DDW) containing 1% KCLO4 for 3 weeks and then stop feeding 1% KCLO4. Three groups were randomly divided: DDW,3 times iodine intake than normal and 6 times iodine intake than normal , which were prepared by potassium iodate. The rats were respectively killed 7 days,21 days and 90 days after treatment. Non - iodine - deficiency animal model: 7 - week - age Wistar rats whose male and female number were equal were fed common diet and double distilled water and 1 times N2 timesA3 times V6 times - 1...