Hormonal events during female puberty in relation to breast cancer risk.

The time from puberty to the first pregnancy is particularly important for breast cancer risk, with early menarche increasing the risk of breast cancer. The onset of puberty is elicited by an increase in gonadotropin secretion, that can be modified by metabolic factors. Girls going to have an early menarche, have an earlier and greater increase of follicle stimulating hormone and oestradiol. After menarche, girls having had menarche before 12 years of age have a more rapid onset of ovulatory menstrual cycles, than girls having later menarche. Significantly higher serum oestradiol and lower sex hormone binding globulin concentrations are seen in women having had early menarche, and the differences still remain at 20-30 years of age. Thus, early menarche is associated with increased oestrogen and progesterone secretion, that might induce a higher degree of breast epithelial proliferation. Further research is required concerning the possible role of physical exercise and nutrition in modifying breast cancer risk.