Swine, fed with fodder containing 8%-16% rape-seed meal, took 919.42-1416.02 mg of thioglucoside (glucosinolate) daily. After being fed with it for 120 consecutive days, swine's thyroid enlarged and their thyroid follicles and epithelial cells were prominently hyperplastic, lacking secretory granules and lysosome in thyroid cytoplasm, with microvilli condensed in apical cells, and a great number of vacuoles surrounding the colloid in the follicular cavity, with its secretory function vigorous and significantly increased T4 and ratio of T4 to T3, and showing hyperthyroidism. If iodine was supplied in the fodder and the antidotes were administered, the morphology and ultrastructure of the thyroid tissues in swine restored to normal, and their T4 and ratio of T4 to T3 tended to be normal, too.