What causes very heavy menstrual bleeding?
This is not clear. Heavy flow is most common in the teens and in perimenopause—both are times of the lifecycle when estrogen levels tend to be higher and progesterone levels to be lower. Progesterone is made by the ovaries after ovulation. However, even though you may be having regular periods, it doesn’t mean you are ovulating! The lining of the uterus or endometrium sheds during a period. Estrogen’s job is to makes the endometrium thicker (and more likely to shed) and progesterone makes it thinner. Therefore it is likely that heavy flow is caused by too much estrogen and too little progesterone. However, this has not been well shown. The good news is that, in a large study of pre- and perimenopausal women, heavy flow was not caused by endometrial cancer. This means that a diagnostic test for cancer called a D & C (a surgical procedure in which the endometrium is scraped off) is not necessary (3). Heavy flow was most common and occurred in 20% of women ages 40-44 (3). In women ages 40
