The so-called high and low levels of estrogen need to be initially determined depending on the menstrual cycle a woman is in and her different ages. Estrogen is mainly secreted by the granulosa cells inside the follicles. In addition to this, estrogen can also be derived from fat and androgens. Estrogen levels vary during different menstrual periods in women. For example, during the follicular phase, estrogen should not be too high. If it exceeds 80-100 pg/ml, it usually also responds to possible problems with follicular development or incomplete luteal atrophy from the previous menstrual cycle, etc. By the middle of the menstrual cycle, as the follicles develop, the estrogen gradually goes higher. In perimenopausal women, if estrogen levels are high at all periods of menstruation, this should be a cause for concern. This is because high estrogen levels in perimenopausal women may lead to diseases related to excessive endometrial hyperplasia and other metabolic disorders.