Thyroid follicular lesions induced by thiazole-Zn feed treatment for one year in Sprague-Dawley rats

Thiazole-Zn is a newly created Chinese systemic fungicide that is a thiadiazole compound. The toxicity of thiazole-Zn was examined in Sprague-Dawley rats fed diets containing 0, 4, 20 and 100 mg/kg thiazole-Zn for one year. Lower body weight gains were noted in both males and females of the 100 mg/kg diet group. Moreover, we show that the toxicity of thiazole-Zn was low, as evidenced by the absence of toxicologically significant changes in the general condition and appearance, hematology and clinical chemistry parameters, organ weights and necropsy findings of the rats. Thyroid follicular cell hyperplasia was the only finding of potential significance. The incidence of thyroid follicular cell hyperplasia significantly increased in high-dose males (4/10) and females (3/10) at the 26-week interim examination; one follicular adenoma in the thyroid was observed in high-dose males. At 52 weeks, the incidence of thyroid follicular cell hyperplasia was significantly higher in high-dose males (4/10) and females (4/10) than in the controls. Two thyroid follicular adenomas were observed in high-dose males. Other treatment-related effects and tumors at other sites were not observed. This study suggests that thiazole-Zn is a thyroid disrupter and likely a rat thyroid carcinogen.