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Estrogen |
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| Estrogens (or oestrogens) are a group of steroid compounds that function as the primary female sex hormone. They are produced primarily by developing follicles in the ovaries, the corpus luteum and the placenta. The major estrogen secreted by the ovary is 17β-estradiol; this is converted to estrone in the blood. Estriol is the principal estrogen formed by the placenta during pregnancy.
These three compounds, 17β-estradiol, estrone, and estriol, account for most of the estrogenic activity in humans. In the body these are all produced from androgens through enzyme action. Estradiol is produced from testosterone and estrone from androstenedione. Estrone is weaker than estradiol, and in post-menopausal women more estrone is present than estradiol.
Estrogen is the female sex hormones produced by the ovaries which are responsible for the development of female sex characteristics. In women, levels of estrogen fluctuate on nature's carefully orchestrated schedule, regulating the development of secondary sex characteristics, including breasts; regulating the monthly cycle of menstruation; and preparing the body for fertilization and reproduction. Estrogens are largely responsible for stimulating the uterine lining to thicken during the first half of the menstrual cycle in preparation for ovulation and possible pregnancy. They are also important for healthy bones and overall health. |
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Functions and health benefits of estrogens |
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| Estrogen stimulates the development of secondary sexual characteristics and induces menstruation in women. Estrogen is important for the maintenance of normal brain function and development of nerve cells. Estrogen is used therapeutically to treat breast and prostate cancer and osteoporosis, and to relieve the discomforts of menopause. Estrogen is also important for healthy bones and overall health. Estrogen is also used with diet, calcium supplements, and exercise to slow the progression of osteoporosis, a disease common in women after menopause resulting in bones that break easily. Estrogen is a hormone that is
essential for the normal growth and development of the breast and tissues important for reproduction. Estrogen is believed to have positive effects on the cardiovascular system by decreasing platelet aggregation and by decreasing low density lipoprotein cholesterol levels in the serum. Estrogen also reduces the risk of colon cancer, diabetes, and Alzheimer's disease. In combination with natural progesterone it may reduce the risk of breast cancer. When estrogen and progesterone are taken together, it is known as hormone replacement therapy or HRT. Estrogen replacement is used for symptoms associated with menopause: hot flashes (feelings of warmth in the face, neck, and chest), sweating, sleep disturbance, vaginal discomfort (dryness and itchiness), poor concentration, and irritability. It also is used in the treatment of breast cancer in postmenopausal women and breast and prostate cancer in men. Estrogen is known to stimulate uterine growth and differentiation while reducing weight gain by decreasing food consumption, and inhibiting cortical bone growth.
Estrogen is crucial to the reproductive success of woman. Estrogen has a major role during pregnancy of building tissue. One role of estrogen during pregnancy is to regulate the production of progesterone over the full term. As estrogen is produced by the placenta, progesterone production is stimulated and regulated. It accomplishes this by either increasing the size or the number of tissues, vessels, and blood cells. It is responsible for the proliferation of the uterine endometrium. This increase in the depth and consistency of the uterine lining prepares it for implantation. Estrogen is a major factor in the increased size of the uterus and thickening of the uterine wall. During the pregnancy, the uterus increases in size to accommodate the developing pregnancy. Estrogen is responsible for an increased blood, lymphatics and nerve supply to the uterus, and throughout the body. The considerable increase in the number and size of vessels in the uterine vascular bed causes a decrease in the uterine vascular resistance. As a result, blood flows to and from the uterus more freely. Estrogen also contributes to the increase in breast size, especially the alveolar ductile tissue. |
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Estrogen replacement therapy |
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Estrogen replacement therapy is the use of the female hormone estrogen to replace that which the body no longer produces naturally after medical or surgical menopause. Estrogen replacement therapy is indicated in menopausal women (either spontaneous or surgical). Aside from reliving hot flashes, preventing osteoporosis, and lowering risk of heart disease, estrogen replacement results in improved clitoral sensitivity, increased libido, and decreased pain during intercourse. Estrogen replacement therapy can help relieve symptoms of the climacteric (menopause), including hot flashes. It has a beneficial effect on bone, and helps prevent and treat osteoporosis. Unopposed estrogen replacement therapy may reduce atherosclerosis and coronary artery disease, but the addition of a progestin may actually increase the risk of coronary artery disease. It includes different amounts of estrogen and progestin, two hormones produced normally by women who have menstrual periods. Preventing these long term problems is the main goal of estrogen replacement therapy, or ERT. Estrogen is given in the form of pills or patches to replace what the body no longer makes. It relieves the hot flashes, reduces the loss of calcium from the bones, and increases the good cholesterol in our blood. Estrogen replacement is the only consistent and satisfactory therapy to sustain systems dependent on ovarian hormone secretion and to relieve hot flushes. Since estrogen nourishes some types of breast cancer, scientists are working on the question of whether estrogen replacement therapy increases breast cancer risk. |
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Estrogen side effects |
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The use of estrogen, especially together with progesterone, is a controversial treatment for the symptoms of menopause which may do as much harm as good. Oral estrogen intake can exacerbate existing liver or gallbladder problems and cause blood clots. Estrogens can also effect blood triglyceride levels and so may increase the risk of cardiovascular problems. Postmenopausal women taking estrogens have a 2 to 3 times greater chance of developing gall-bladder disease. Lifetime exposure to estrogen may affect a woman's risk for breast cancer. Women who begin menstruating early, or who start menopause late, produce more estrogen over their lifetimes and have a higher risk of breast cancer. Since estrogen stimulates cell division, it can increase the chance of making a DNA copying error in a dividing breast cell. If a woman has a budding cluster of estrogen-dependent breast cancer cells, estrogen replacement could promote the tumor's growth. Some breast cancer cells are estrogen sensitive. Estrogen binds to these cells and stimulates their growth and division. After the hormone binds to its receptors in a cell, it turns on hormone-responsive genes that promote DNA synthesis and cell proliferation. If a cell happens to have cancer-causing mutations, those cells will also proliferate and have a chance to grow into tumors. Estrogen can influence the growth of tissue cells of the prostate, especially the breasts. The growth can get so much out of control that the tumors can become cancerous. Unopposed estrogen therapy in women with a uterus may also increase the risk of uterine cancers. Other side effects include enlargement or tenderness of the breasts (both sexes), swelling of the ankles and legs, loss of appetite, weight changes, retention of water, nausea, vomiting, abdominal cramps, and feeling of bloatedness.
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