A blood sample taken from a vein in your arm
Oestrogens are a group of hormones primarily responsible for the development of female sex organs and secondary sex characteristics. While oestrogen is one of the major sex hormones, in woman small amounts are found in men. In women, follicular stimulating hormone (FSH; produced by the pituitary gland (a small organ in the head situated at the base of the brain behind the bridge of your nose) stimulates cells (follicles) surrounding the eggs in the ovaries, causing them to produce oestrogen. When the oestrogen concentrations reach a certain level, the hypothalamus (also situated in the head) produces luteinising hormone (LH), which eventually causes the release of the egg, beginning the preparation for fertilisation. Oestrogens also have effects on, for example, blood coagulation, lipid metabolism, bone density and cancer (via hormone sensitive breast cancer).
There are three main forms of oestrogen: oestrone (E1), oestradiol (E2), and oestriol (E3).
- Oestrone (E1) is the major oestrogen produced after the menopause. It is derived from chemicals released from the adrenal gland and is also made in adipose tissue (fat). Sensitive methods for measuring oestrone have recently been developed but the usefulness of these tests is still being established. In the past measurements have been used in women experiencing infertility but this is not routinely available.
- Oestradiol (E2) is mainly produced in the ovary in women and therefore falls at the menopause. In men, the testes and adrenal glands are the principal source of oestradiol. Normal levels of oestradiol are important for ovulation, conception, and pregnancy, in addition to promoting healthy bone structure and regulating cholesterol levels in females.
- Oestriol (E3) is the major oestrogen in pregnancy, with relatively large amounts produced in the placenta (from chemicals produced by the baby's adrenal glands and liver). Oestriol levels start to rise in the eighth week of pregnancy and continue to rise until shortly before delivery. Serum oestriol circulating in maternal blood is quickly removed from of the body by the kidneys. Free oestriol, along with other measurements is used to assess the risk of a woman carrying a foetus with certain abnormalities, such as Down’s syndrome if the woman presents late in the pregnancy (14th-20th week or the second trimester) as part of the quadruple test. In the past urinary oestriol levels were used to examine the function of the placenta and foetus during early stages of pregnancy.
How is the sample collected for testing?
A blood sample will be drawn from a vein in your arm
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed, but the timing of the sample will be correlated with your menstrual cycle or, when you are pregnant, to the gestational age of the baby.
How is it used?
Oestradiol levels are used to evaluate ovarian function and to help diagnose the cause of precocious puberty in girls (signs of puberty before aged 8 years) or delayed puberty (age greater than 13 years in girls or 14 years in boys) and gynaecomastia in men. Its main use has been to help diagnose the reason for amenorrhoea (for example, to determine whether the cause is menopause, pregnancy, or some other problem). In treatment of sub-fertility, repeated measurements are used to follow follicle development in the ovary in the days prior to in-vitro fertilisation. Oestradiol may also be used to monitor hormone replacement therapy in peri/menopausal women, if oestradiol is given by implant, patch or gel. A very raised oestradiol may be associated with excess ovarian oestradiol production for example in ovarian producing tumours.
Free oestriol, along with other measurements is used to assess the risk of a woman carrying a foetus with certain abnormalities, such as Down syndrome if the woman presents in the 14th to the 20th week of pregnancy.
Oestrone may occasionally be measured to aid in the diagnosis of an ovarian tumour, and diagnose precocious puberty. In males, it may help in the diagnosis of gynecomastia or in the detection of oestrogen-producing tumours.
When is it requested?
Your doctor may request oestradiol (along with other tests) if you have abnormal menstrual cycles and/or symptoms, or in women less than 40 years who have hot flushes, night sweats, difficulty sleeping, and/or irregular periods which are symptoms of an early menopause. If you are on hormone replacement therapy, your doctor may use oestradiol levels to monitor your treatment, but only if oestrogen is given in a form that can be measured by the laboratory.
If you are having difficulty becoming pregnant your doctor may use oestradiol measurements over the course of your menstrual cycle to monitor follicle development prior to in vitro fertilisation techniques (timed with a surge in your oestradiol level).
If you are pregnant free oestriol may be measured in the 14th to 20th week of gestation as part of the screening for Down’s syndrome known as the quadruple test. This test is used if a pregnancy present late and the first trimester test is no longer appropriate.
What does the test result mean?
Increased or decreased levels of oestrogen are seen in many metabolic conditions. Care must be used in the interpretation of oestrone, oestradiol, and oestriol levels because their levels will vary on a day-to-day basis and throughout the menstrual cycle. If your doctor is monitoring your hormone levels, s/he may be looking at trends in your result, rising or falling over time, rather than at single values. It must be remembered that a diagnosis cannot be made solely based on one test result.
Is there anything else I should know?
Do all males have female hormones?
What are oestrogen receptors?
What are phytoestrogens and environmental oestrogens?
Phytoestrogens are oestrogen-like compounds from plant sources. The two main classes are isoflavones, found in soy products, and lignans, found in whole grains and some fruits and vegetables. It has been proposed that these products could be used as an alternative to hormone replacement therapy (HRT). Some studies have shown the relief of some menopausal symptoms, such as hot flushes, but there is more research yet to be done.
One of the first environmental oestrogens to be identified was the insecticide DDT which was banned worldwide in 2004. These are also natural chemicals oestrogen from plant sources. These compounds mimic the effect of oestrogen and may cause disorders such as infertility, overgrowth of the vaginal lining, premature breast development, and feminisation in young males. Biphenyl A (BPA) found in plastics since the 1960s is also an alleged endocrine disruptor. The effects,of BPA have been found at extremely low doses where it is reported to affect embryonic and foetal development in the womb.
Where can I find more information on oestrogen?
On This Site
Tests: Follicle stimulating hormone (FSH); Luteinising Hormone (LH); Progesterone; Testosterone; AFP & hCG Maternal Screening; Sex Hormone Binding Globulin
Conditions: Infertility, Menopause, Pregnancy
Elsewhere On The Web
Women’s Health Information site by Obstetrician/Gynaecologist
Frequently Asked Questions on Women's Health
Royal College of Obstetrics and Gynaecology
NHS Breast Cancer Screening Programme
Cancerbackup – UK Cancer Information Service
Cancer Research UK – Breast cancer page
Breast Cancer Care
UK Breast Cancer Awareness Campaign
Oestrogen receptors – comprehensive