Estrogen also œstrogens, Estrogens (AmE), or oestrogens (BE) is derived from Greek, estrus, and gen meaning sexual desire and generate respectively. It is responsible for several functions in the human body especially in females. In its natural form, estrogen occurs as estrone (E1) which is prevalent during menopause, estradiol (E2) found in non-pregnant and non menopausal women and estriol (E3) present during pregnancy.
Estrogen is responsible for many functions
Structural development, development of secondary female sex characteristics, protein synthesis, sodium and water retention, stimulating endometrial growth, increasing vaginal lubrication, fetal development, and mental health, among other functions, are affected by estrogen . Contrary to popular belief, estrogen is not directly tied to sexual desire, but androgen is.
Estrogen biosynthesis in females
In females, ovaries are the basic producers of estrogen through stimulation by the Luteinizing hormone (LH). Estrogen is also produced in the corpus luteum (an endocrine structure that is required for maintaining as well as establishing pregnancy in mammals), and the placenta during pregnancy.
The breasts, liver and adrenal glands also produce estrogen, especially in menopausal women, but in low quantities.
Synthesis begins in the ovary’s Theca interna cells through the synthesis of androstenedione from cholesterol. Androstenedione then passes into the surrounding granulose cells through the basal membrane. It is then changed to estradiol (E2) in non pregnant women, or estrone (E1) in menopausal women instantly or using testosterone. Aromatase enzyme is used for catalyzing testosterone conversion to estradiol (E2,) and conversion of androstenedione to estrone (E1).
It should be noted that estradiol (E2) levels differ in women, and their levels also vary through the menstrual cycle with the peak being during ovulation. This explains low levels during post menopause (no ovulation) and the high levels of estrone (E1,) which is weaker than estradiol (E2.)
Estrogen biosynthesis in males
Although not in high quantities, estrogen, Estradiol specifically, is produced in a man’s testes (Sertoli cells) through conversion of testosterone to 17 beta estradiol used in spermatogenesis. Estradiol is also responsible for preventing apoptosis (programmed cell death) that can lead to male infertility.
Estrogen production in male bones has been associated with proper bone mineralization and osteoporosis prevention. Although estrogen has positive effects in men, when there is a surge it can lead to complications and development of female characteristics. High estrogen in males has also been linked to Klinefelter's syndrome.
Obesity and sterility
It has been discovered that estrogen can also be synthesized in fatty cells and a link made between obesity and sterility. Although estrogen is responsible for establishing pregnancy, when in excess it leads to estrogen overload that acts as birth control.
PubMed.gov [U.S. National Library of Medicine National Institutes of Health] - Estrogen biosynthesis in the human body
Endocrinology.org - Endocrine-Related Cancer - Local estrogen biosynthesis in males
and females (PDF)