Estrogen-induced thyroid follicular cell adenomas in C57BL/6 mice

Diethylstilbestrol (DES) was fed chronically to C57BL/6 mice at concentrations of 0, 5, 10, 20, 40, 160, 320, or 640 ppb in order to define the dose-response curve for neoplastic responses. The incidence of thyroid follicular cell adenomas was higher in control females than in males and was increased at mid-level doses of DES, especially in males. None were found in mice fed 640 ppb DES, probably because these mice died from other causes before follicular cell adenomas had developed. In both sexes, DES fed at 160 or 320 ppb significantly shortened time-to-onset of these tumors, and 40 ppb increased their probability late in life. It is concluded that DES has a causal relationship to thyroid neoplasia in C57BL/6 mice, and similarities between this and the human disease suggest that C57BL/6 mice may be an appropriate model for human thyroid neoplasia.