ABSTRACT
Five thousand blood samples were collected from healthy women on the island of Guernsey and stored frozen for several years until a group of these had developed breast cancer. Samples taken earlier from this subgroup of precancer cases were matched with controls from unaffected women and analysed for non-protein-bound oestradiol and sex hormone-binding globulin (SHBG). Precancer cases had a significantly higher proportion of protein-free oestradiol and significantly lower level of SHBG. The data indicate that women who are exposed to higher levels of biologically active oestradiol are at greater risk of breast cancer. It is not possible, however, to conclude that this exposure is directly causative.
