Oestradiol (E2)

Oestrogens are a group of hormones primarily responsible for the development of female sex organs and secondary sex characteristics. Small amounts are found in men also. In women, follicular stimulating hormone (FSH; produced by the pituitary gland in the brain) stimulates the ovaries to produce oestrogen. There are three main forms of oestrogen: oestrone (E1), oestradiol (E2), and oestriol (E3).
Oestrone (E1) is the major oestrogen produced after the menopause, derived from chemicals released from the adrenal gland and is also made in adipose tissue (fat) – not routinely measured.
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. 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.