Breast cancer risk in Japanese women with special reference to the growth hormone-insulin-like growth factor axis.

Earlier physical maturity in girls, involving an earlier and more marked growth hormone spurt and also an earlier menarche, is a marker of subsequent higher risk to breast cancer. Based on the results of recent research, it is postulated that interaction between growth hormone, insulin-like growth factor and sex steroids at an earlier age, has a major role in stimulating not only linear growth but also precocious proliferative activity in the breasts of adolescent girls. This may promote carcinogenesis in a susceptible mammary epithelium and could partly account for the rising breast cancer mortality rate among both Japanese and Western women.