Just an excerpt from this article by Dr. Donald Miller. Pdf link embedded.
"In addition to being an essential element in thyroid hormones,iodine has many biological functions. The recommended dietary intake of 100–150 mcg is perhaps 100 times too low. Potential benefits of higher amounts include enhancement of immune function and reducing the incidence of breast cancer. Older studies of therapeutic benefits, particularly with respect to fibrocystic breast disease, need to be updated and expanded."