Estradiol is estrogen, which is a hormone produced and synthesized in a woman’s ovaries. Estradiol is also produced in the placenta when a woman is pregnant. It's also produced in the testis in the adrenal glands. Estradiol levels change drastically during menopause.
As a woman enters full menopause, which means the complete cessation of her menstrual period, her estradiol levels will drop substantially, because the ovaries are no longer functioning. However, her adrenal glands will continue to produce some estrogen, even after menopause.
A menopausal woman will have high levels of follicle stimulating hormones (FSH) and luteinizing hormones (LH), but she will have very low levels of estradiol in her bloodstream. Menopause takes place because the ovaries no longer respond to FSH and LH, although the brain keeps releasing it.