Research On Molecular Pathology Of Thyroid Goiter Induced By Fluoride

Fluoride is the systemic poisonous substance, its negative influence to endocrine glands has changed to be a topic of general interest in the field of fluoride research in recent years worldwide. Some researches showed fluoride could induce thyroid goiter. In this experiment, to clarify the mechanism of fluoride-induced damages and goiter of thyroid from the aspect of fluoride disturbing the structure and function of thyroid in rats, 80 SD rat models of thyroid goiter were created by administering sodium fluoride in drinking water in different levels and some indexes were detected.The experimental thyroid goiter model of SD rats was successfully established. Using the methods followed as pathomorphology, radioimmunoassav(RIA) and so on, a series of indexes reflecting the structure and hormone secreting function of thyroid were determined separately, the result showed that fluoride could disturb the synthesis and secretion of tetraiodothyronine(T4), triiodothyronine(T3)and thyroid control factor of thyroid-stimulating hormone(TSH), which directly interfering with the growth and metabolism of the whole body. The result also confirmed that high level of fluoride can induce thyroid into colloid goiter or nodular, and fluoride injures the ultralstructure of thyroid, especially its cell biological membrane structure. The experiment negated the theory of low iodine is the only factor that induces the local goiter of thyroid, and further clarify the molecular mechanism of fluorosis in rats.Related enzyme and growth factor were determined by RT-PCR and immunofluorescence assay(IFA) method, results were as follows: the indexes such as TG(thyroglobulin),NIS(sodium iodide symporter),TPO(thyroidperoxidase),TSHR (thyroid-stimulating hormone receptor),VEGF(vascular endothelial growth factor) which closely correlated with thyroid function were abnormal. Fluoride disturbed the free radical metabolism, changed the expression of enzyme and growth factor like iNOS(inducible nitric oxide synthase) and VEGF, the capillary vessels proliferated, free radical metabolism and lipid peroxides accumulated, then damaged the structure and function of thyroid follicles, disturbed the colloid catabolism, inhibited the transference and organic proceeding of thyroid iodine, restrained the activity of thyroid enzyme system like TPO andâ… -DI(typeâ… -deiodinase), destroyed every series of synthesis and secretion of thyroid hormone , which resulted in the abnormality of TSH and finally inducing the thyroid goiter in rats.In conclusion: the fluoride can induce the nodular and colloid thyroid goiter in rats, the molecular mechanism of fluorosis in rats and thyroid goiter was clarified systematically. This study provided experimental and theoretical basis for clarifying the molecular mechanism of thyroid goiter induced by fluoride, and promoted new ideas for the study of endemic fluorosis.