Test Overview
An estrogen test measures the level of the most important estrogen hormones in a blood or urine sample. It measures estradiol, estriol, and estrone.
- Estradiol is the most common type of estrogen measured for nonpregnant women. The amount of estradiol in a woman's blood varies throughout her menstrual cycle. After menopause, it drops to a very low but constant level.
- Estriol levels are most often measured only during pregnancy. Estriol is produced in large amounts by the placenta. This is the tissue that links the fetus to the mother. Estriol can be found as early as the 9th week of pregnancy. The levels keep rising until delivery. Estriol can also be measured in urine.
- Estrone may be measured in women who have gone through menopause. It's done to find out their estrogen levels. It also may be measured in men or women who might have cancer of the ovaries, testicles, or adrenal glands.
Both men and women make estrogen hormones. Estrogens are responsible for female sexual development and function, such as breast development and the menstrual cycle. In women, estrogens are made mainly in the ovaries and in the placenta during pregnancy. Small amounts are also made by the adrenal glands. In men, small amounts of estrogens are made by the adrenal glands and testicles.
Small amounts of estrone are made throughout the body in most tissues, especially fat and muscle. This is the major source of estrogen in women who have gone through menopause.
For pregnant women, the level of estriol in the blood is used in a serum quad screening test. In most cases, this test is done between 15 and 22 weeks of pregnancy. It checks the levels of four substances in a pregnant woman's blood. They are the hormone inhibin A, alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and a type of estrogen (unconjugated estriol, or uE3). The levels of these substances—along with a woman's age and other factors—help the doctor figure out the chance that the baby may have certain problems or birth defects.
