Estrogens or estrogens are a group of steroids, whose function, naturally, is to be a primary female sex hormone. They are produced primarily by the development of ovarian follicles, corpora lutea (corpus luteum) and the placenta. Some estrogens are also produced in small amounts by other tissues such as liver, adrenal, breast and fat tissue. These secondary sources of estrogen are especially important for women in post-menopausal.
The three naturally occurring estrogens are estradiol, estriol and estrone. In the body, they are all originally produced androgens under the influence of enzymes. Estradiol is produced from testosterone and estrone from androstenedione. Estrone is less potent than estradiol, and among women post-menopause, there are more estrone than estradiol.
While estrogens are present in both sexes, we found a quantity significantly greater among women than among men. It promotes the development of secondary sexual characteristics like breasts, and are also involved in controlling the menstrual cycle, which explains why most of the pills contain.
The use of estrogen, particularly associated with progesterone, is a treatment (hormone replacement therapy) controversial symptoms of menopause.
In addition to their roles in reproduction, but also feminine male, estrogens are involved in the development of central nervous system in homeostasis of the skeleton and cardiovascular system. They also have effects on the liver and adipose tissue.
Cellular estrogen receptors
The main estrogen receptors are intracellular proteins belonging to the family of nuclear receptors encoded by two distinct genes in animals with both types of receptors: these receptors alpha (ERα) and beta (ERβ) of estrogen . The man and woman have these receptors are distributed differently in different organs. A third potential receptor, belonging to another family (receptor coupled to G proteins), encoded by a third gene, called GPR30 has recently been described. The effects of estrogen on their cell / tissue targeted through these receptors can be classified into two categories: the genomic effects, eg on gene expression, and non-genomic effects that directly affect other players in molecular cells, mainly proteins.
Disease and estrogen
Estrogens are involved in diseases with high impact on society by their frequency and / or severity. These are mainly of hormone-dependent cancers in women, breast or uterus. In this case breast cancer is in most cases a hormonal disease linked to the duration and intensity of exposure to estrogen. Men who have estrogen do little or no breast cancer when they have a mammary gland, a rudimentary, but this ...
All factors contributing to increased estrogen exposure are risk factors: an early puberty, lack of breastfeeding, a late menopause.
Obesity is a major risk factor because it exists in the fat of enzymes that convert the hormone estrogen (aromatase). Conversely physical activity by reducing the reserves of fat is protective.
Excessive consumption of alcohol also acts by increasing the level of estrogen by activation of this enzyme.
HRT for menopause and birth control pills containing estrogen are carcinogens.
The late first pregnancy is a major risk factor because it increases the duration of exposure to estrogen while breasts are immature.
Finally, and importantly, estrogen drugs like tamoxifen or raloxifene prevent the occurrence of cancer in a proportion exceeding 50%. These drugs represent the best treatment for preventing recurrence of cancer with estrogen receptor (over 70% of breast cancers).
Estrogens protect against osteoporosis (decrease in the frequency of that when estrogen levels are correct), a disease affecting many women after menopause. However, estrogen effects have neuro-protective proven.
Estrogen secreted naturally by women is one of the reasons advanced on the reduced incidence of cardiovascular disease in the past. The protective role of an artificial treatment is much less clear.
See also Menopause