Postmenopausal women have low levels of estrogen, and there is not enough estrogen to turn off the brain's production of follicle stimulating hormone, or FSH, explains the University of Pennsylvania Center for Women's Behavioral Wellness. Therefore, high levels of FSH are found in the blood of postmenopausal women.
FSH is a hormone produced by the brain that causes the ovarian follicles to enlarge and produce estrogen, states the University of Pennsylvania Center for Women's Behavioral Wellness. As the woman ages, fewer follicles remain, and less estrogen is produced. Because low estrogen levels cause high FSH levels, the FSH level is used as a marker of whether a woman is perimenopausal or postmenopausal. An FSH level of more than 30 international units per liter is consistent with menopause. However, a high FSH level is not diagnostic of menopause.
Menopause is a natural event that takes place in every woman's life at around the age of 52 years, explains the University of Pennsylvania Center for Women's Behavioral Wellness. During menopause, the low estrogen level may result in symptoms such as night sweats, hot flushes, insomnia, headache, irregular periods and vaginal dryness. In addition, menopausal women may experience moodiness, difficulty concentrating, forgetfulness and distractibility.