Why do women who have more menstrual cycles during their lives have a higher breast cancer risk?
During every monthly menstrual cycle, estrogen peaks just before ovulation. Estrogen is a female hormone and a known carcinogen (an agent that causes cancer). Estrogen stimulates the lobules in the breasts during every menstrual cycle. Estrogen, especially while it is in the presence of the female hormone, progesterone, causes breast tissue to grow and can cause mutations. Estrogen can also initiate cancer by directly damaging the DNA. Overexposure to estrogen is connected with the development of most breast cancers. For these reasons, women who have more menstrual cycles during their lives, especially before the birth of a first child, have a higher breast cancer risk. Women, who start menstruating early before age 12 or go into menopause late after age 55, have more menstrual cycles and a higher breast cancer risk. BACK TO THE TOP 6) Do combined oral contraceptives and combined hormone replacement therapy increase breast cancer risk? If so, is the biological reason for such a link th
