Genesis of breast cancer in Japanese: a possible relationship between sex hormone binding globulin (SHBG) and serum lipid components.

We investigated changes in the amount of sex hormone binding globulin (SHBG) and the percentage of free estradiol (% FE2) during normal menstrual cycles in the sera of 8 young Japanese controls, and also the relation between the lipid components of serum and the serum level of SHBG in 250 normal Japanese controls aged 18-77 years. The amount of SHBG measured by IRMA was significantly higher in the luteal phase than in the follicular phase, whereas the % FE2 values remained constant throughout the menstrual cycle in 8 healthy young controls. These results suggest that the estrogen status in serum is constantly controlled by SHBG. The amount of SHBG was significantly correlated with the serum level of triglycerides (TG) in 250 normal Japanese controls. From these results, we postulate that the decrease in serum SHBG, probably caused by increased level of serum TG, leads to elevation of % FE2 and later to a status with a high risk of breast cancer.