Estrogen: Test Sample

What is being tested?
Estrogen is a group of hormones primarily responsible for the development of female sex organs and secondary sex characteristics. While estrogen is one of the major female sex hormones, small amounts are found in males. In women, follicular stimulating hormone (FSH; produced by the pituitary gland) stimulates cells (follicles) surrounding the eggs in the ovaries, causing them to produce estrogen. When the estrogen levels reach a certain level, the pituitary produces a surge of luteinizing hormone (LH), which eventually causes the release of the egg, beginning the preparation for fertilization.

There are three main estrogen fractions: estrone (E1), estradiol (E2), and estriol (E3).

Estrone (E1) is the major estrogen after menopause. It is derived from metabolites from the adrenal gland and is often made in adipose tissue (fat).
Estradiol (E2) is produced in women mainly in the ovary. In men, the testes and adrenal glands are the principal source of estradiol. In women, normal levels of estradiol provide for proper ovulation, conception, and pregnancy, in addition to promoting healthy bone structure and regulating cholesterol levels.
Estriol (E3) is the major estrogen in pregnancy, with relatively large amounts produced in the placenta (from precursors produced by the fetal adrenal glands and liver). Estriol levels start to rise in the eighth week of pregnancy and continue to rise until shortly before delivery. Serum 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 the estriol level.