Effects of Fluoride on Growth and Thyroid Function in Young Pigs

This study was undertaken to investigate the effects of fluoride on growth and thyroid function in young pigs. Three groups of eight crossbred barrows were exposed to 100, 250, and 400 mg F–/kg (from NaF) in their diets for 50 days. Compared to a control group of eight pigs, the average daily gain in weight was significantly reduced, and serum thyroxine (T4) and free thyroxine (FT4) levels also decreased significantly. On the other hand, the level of serum thyroid-stimulating hormone (TSH) was significantly increased, but no significant differences were observed in serum triiodothyronine (T3) and free triiodothyronine (FT3). The activity of Na/K-ATPase in the thyroid was significantly inhibited as well as thyroid peroxidase (TPO). The results suggest that excessive fluoride in the diet can cause growth depression and hypothyroxinemia in pigs. Accompanying thyroid lesions were attributed to fluoride acting as a TSH analogue in concert with elevated TSH levels.