The test measures the amount of estradiol in the blood. Estradiol is an element of the hormone estrogen. It is usually produced in the ovaries of premenopausal women and in the testicles of men. It is the most potent form of estrogen. A woman’s age and reproductive status can make a big difference in the levels of estradiol. This test can be used to monitor ovarian function in women struggling to get pregnant. This test is usually ordered for women who are experiencing infertility, abnormal menstruation or have evidence of menopause. This test can also be ordered for men who are suffering from testosterone deficiency.