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Estrogen
Estrogen is not one hormone; it is the name of a group of hormones. Estrogens
(also called oestrogens) are a group of steroid compounds that function
as the primary female sex hormone. Primarily developing follicles in the ovaries,
the corpus luteum and the placenta all produce estrogens.
Some estrogens are also produced in the adrenals and the breasts, especially
in post-menopausal women.
There are naturally occurring estrogens in the human body and these are: Estrone,
Estradiol and Estriol (also known as E1, E2 and E3 respectively).
The most common type of estrogen is Estradiol (E2), and is the primary estrogen
produced by the ovaries. Estrone (E1) is formed from Estradiol and is known
as a ‘weak’ estrogen. Estrone (E1) is the most abundant estrogen found in the
body after menopause.
Estriol (E3) is produced in large amounts during pregnancy and is a breakdown
product of Estradiol. Estriol is also a weak estrogen and may have anti-cancer
effects.
Before menopause Estradiol is the main estrogen. After menopause Estradiol
levels drop more than Estrone so that Estrone becomes the predominant estrogen.
While estrogens are present in both men and women, it is found in women in
significantly higher quantities. They promote the development of female secondary
sexual characteristics:
- Enlarged breasts
- Height (on average lower height than men)
- Wider hips than in shoulders
- Less facial hair
- Functional mammary glands
- More subcutaneous fat
- Fat deposits mainly around the buttocks and thighs (pear shape)
- Smoother skin texture
Estrogens are also involved in controlling the menstrual cycle, which is why
most birth control pills contain estrogens.
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