Objective: To investigate the effects of fluoride on thyroid structure in chicks.
Methods: 250 one day chicks were randomly divided into 5 groups, 50 for each. Group I was the control, and other four groups, group II, III, IV, V were fed the diets containing 500, 1,000, 1,500, 2,000 mg/kg of fluorine as sodium fluoride, respectively, for 150 days. The contents of serum fluorine were determined, thyroid tissue slices were made, the weight of thyroids was weighed, and the clinical manifestations of experimental chicks were observed.
Results: The animal models of chick fluorosis were successfully established. Compared with the control, the earlier changes of thyroid structure were that the relative weight of thyroid and thyroid follicle colloid in all NaF ingestion groups were less, and the size of thyroid follicles was smaller. During the later stage, the results just reversed to the earlier changes, i.e, both areas and diameters of thyroid follicle were larger and the colloid was over filled, and the follicular epithelia were obviously flatted in the enlarged follicles for being crushed by over filling colloid. Moreover, hyperplastic nodules, consisting of thyroid parafollicular cells appeared in group V.
Conclusions: Fluoride can seriously damage thyroid structure. During the earlier stage, fluoride can induce thyroid atrophia, however, during the later stage, it can induce thyroid enlargement which is nodular and colloid goiter.