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Also known as: Estrogen Fractions/fractionated; Estrone (E1); Estradiol (E2); Estriol (E3); Estrogenic Hormones
Formal name: Estrogens; Estrone; Estradiol; Estriol

The Test Sample

What is being tested?

Estrogens are a group of steroids that are responsible for the development and function of reproductive organs and the formation of secondary sex characteristics in women. Along with another hormone, progesterone, they help regulate the menstrual cycle, are involved in the growth of breasts and the uterus, and help maintain a healthy pregnancy. Though considered the main sex hormones for women, they are also found in men and play a role in bone metabolism and growth in both sexes. Estrogen tests measure one of three components: estrone (E1), estradiol (E2), or estriol (E3) in the blood or urine.

  • Estrone (E1) is directly converted from androstenedione (from the adrenal gland) or indirectly from other androgens. E1 can also be produced by the ovaries and placenta, testicles, and adipose (fat) tissues. E2 and E1 can be converted into each other as needed. E1 is the primary estrogen in men and in post-menopausal women.
  • Estradiol (E2) is primarily produced in the ovaries in pre-menopausal women and in the testicles in men. E2 is converted from E1 in post-menopausal women. It is the most potent estrogen and the one that is present in the highest concentration in non-pregnant, pre-menopausal women. E2 levels vary depending on a woman's age and reproductive status. They are a good marker of ovarian function.
  • Estriol (E3) is produced by the placenta, with concentrations rising throughout a woman's pregnancy. Increasing levels are an indication of the health of the pregnancy and developing baby. Estriol is part of the second trimester maternal serum screen, a test performed to evaluate fetal risk due to certain chromosomal abnormalities. Very low levels of E3 are present in non-pregnant women or men.

Estrogen in Girls and Women
The types and amounts of estrogen normally present in a woman's blood will vary throughout her lifetime. Levels vary during each menstrual cycle, during pregnancy, and on a daily basis.

At Birth
Estradiol (E2) and estrone (E1) are high but fall within a few days. Concentration levels are minimal during early childhood.

At Puberty
Concentrations of E2 and E1 begin to rise as puberty approaches. These estrogens are responsible for the development of breasts, uterine growth, and (with other hormones) the onset and regulation of menstruation. A moderate amount of E1 is present from puberty to menopause. This concentration will vary during the day but is otherwise relatively stable.

During Menstruation
The menstrual cycle is approximately 28 days long and consists of two phases, follicular phase and luteal phase. During each cycle, estradiol (E2) and several other hormones normally rise and then fall in a specific sequence.

During Pregnancy
Estriol (E3) is the primary estrogen present during pregnancy. It is produced by the placenta, starts to rise in the eighth week of pregnancy, and continues to rise throughout the pregnancy. A sharp increase of E3 occurs approximately 4 weeks prior to the onset of labor. Estriol circulating in maternal blood is quickly cleared out of the body. Each measurement of estriol is a snapshot of what is happening with the placenta and fetus, but there is also natural daily variation in estriol concentrations.

E1 also rises during pregnancy, increasing as much as 10 fold between weeks 24 and 41. After delivery, E1 falls and E3 again becomes essentially undetectable.

During Menopause
Estrone (E1) is the primary estrogen present during menopause. E2 concentrations significantly decrease as ovarian production wanes and eventually stabilize at a low level.

Estrogen in Boys and Men
The types and amounts of estrogen normally present in a man's blood change, but they vary much less over time than a woman's and they are much lower.

How is the sample collected for testing?

A blood sample is drawn from a vein in the arm or a 24-hour urine sample is collected.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed, but the timing of a woman's sample will be correlated with her menstrual cycle or, if pregnant, with the gestational age of the baby.