Dietary iodine and risk of breast, endometrial, and ovarian cancer.

Geographic differences in the rates of breast, endometrial, and ovarian cancer appear to be inversely correlated with dietary iodine intake. Endocrinological considerations suggest that a low dietary iodine intake may produce a state of increased effective gonadotrophin stimulation, which in turn may produce a hyperoestrogenic state characterised by relatively high production of oestrone and oestradiol and a relatively low oestriol to oestrone plus oestradiol ratio. This altered endocrine state may increase the risk of breast, endometrial, and ovarian cancer. Increasing dietary iodine intake may reduce the risk of these cancers.