Is breast cancer a result of endocrine targeting? (How women differ from rats or mice)

Parabiosis of female rats with castrate males or oophorectomized females produces carcinoma of the breast in the majority of intact females. When unilateral nephrectomy of each partner is added to the procedure, the incidence is 100 percent. Radioimmunoassays for luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin, estradiol and progesterone have been performed on the sera of these rats. The pathogenesis of the breast carcinomas is discussed in the light of these results. An attempt to weigh various factors thought to be involved in causing human and experimental rat cancer of the breast suggests significant differences of a quantitative nature.