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In women, estrogens are produced mainly in the ovaries (and the placenta during pregnancy). Small amounts are also produced by the adrenal glands. In men, small amounts of estrogens are produced by the adrenal glands and testicles. Small amounts of estrone are made throughout the body in most tissues, especially fat and muscle.
Function; Reasons For Use
Estradiol is the estrogen that is most commonly measured in women who are not pregnant. The amount of estradiol in a woman's blood varies throughout her menstrual cycle. Estriol can be detected as early as the 9th week of pregnancy, and its levels increase until delivery. Usually performed at between 16 and 18 weeks, these tests measure the amounts of three or four substances in a pregnant woman's blood.
It may also be measured in men or women (through a urine sample) as part of a total estrogen value when a tumor of the ovaries, testicles, or adrenal glands may be present. A test for estrogen in the blood is carried out for reasons such as:- Help determine whether a woman's reproductive organs are functioning so she can become pregnant. Because estradiol varies widely during the menstrual cycle, it may be tested only in the third sample of a 3-day series to determine the ovaries' ability to produce eggs.
- Help determine whether menopause has occurred. After menopause, the level of estrogens in the blood decreases to a very low level. This test is sometimes done before hormone replacement therapy is started. Follicle-stimulating hormone (FSH) levels are also commonly measured to determine whether menopause has occurred.
- Help detect fetal birth defects (especially Down syndrome) during pregnancy. When the test for estrogens is combined with alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG), it is called a triple test. Other blood tests and fetal ultrasound may be done also.
- Help detect fetal distress in high-risk pregnancies.
- Evaluate abnormal sexual development. In girls or women, these conditions might include early or delayed puberty, excessive menstrual bleeding, or lack of menstrual bleeding (amenorrhea). Measuring estrogen levels can help evaluate estrogen-producing tumors of the ovaries in girls before menstruation starts and in women after menopause.
- Explain abnormal sexual characteristics in men, such as enlarged breasts (gynecomastia). This test can also help detect the presence of estrogen-producing tumors growing in the testicles.
- Monitor therapy with fertility medications (such as Gonal-F, Follistim, or Repronex). Estradiol levels may be monitored before and during treatment with medications that are given to stimulate ovulation. Estradiol levels may also be monitored with assisted reproductive technology (ART) procedures.
Other factors include women undergoing Hormone Replacement Therapy (HRT); hormonal birth control such as pills or patches; having had a test involving radioactive substances within the previous week; the medication clomiphene (Serophene, Clomid); corticosteroids, such as dexamethasone (Decadron); high levels of sugar in the urine caused by diabetes.
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