Estrogen
From Freepedia
Estrogens (also oestrogens) are a group of steroid compounds that function as the primary female sex hormone.
The three naturally occurring estrogens are estradiol, estriol and estrone. 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.
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Chemistry
Synthesis of oestrogenes starts in theca interna cells in the ovary, by the synthesis of androstenedione from cholesterol. Androstenedione is a substance of moderate androgenic activity. This compound crosses the basal membrane into the surrounding granulosa cells, where it is converted to estrone or estradiol, either immediately or through testosterone. Presence of both cell types is essential for estrogen synthesis.
Sources
Estrogens are produced primarily by developing follicles in the ovaries, the corpus luteum and the placenta. Some estrogens are also produced in smaller amounts by other tissues such as liver, adrenal glands and the breasts. These secondary sources of estrogen are especially important in post-menopausal women.
Effects
While estrogens are present in both men and women, they are found in women in significantly higher quantities. They promote the development of female secondary sexual characteristics, such as breasts, and are also involved in the thickening of the endometrium and other aspects of regulating the menstrual cycle, which is why many oral contraceptives contain estrogens.
Medical applications
The use of estrogen, especially together with a progestin, is a treatment for the symptoms of menopause which is controversially alleged to do as much harm as good because of the Women's Health Initiative and related studies, which have been sensationally reported. Many professional bodies have suggested that the problems may be due only to the particular product(s) (Premarin alone and with Provera as Prempro) and fixed doses used in all the recent studies[1] and extensive research is underway to absolutely confirm the precise processes of such variations.
Estrogen and lung disease
Among people over 70 who have never smoked, women make up 85 percent of those with chronic obstructive pulmonary disease (COPD). Studies with mice (see below) suggest the possibility that COPD incidence may be tied to decreases in estrogen as women age.
Female mice that had their ovaries removed to deprive them of estrogen lost 45 percent of their working alveoli from their lungs. Upon receiving estrogen, the mice recovered full lung function.
Two proteins that are activated by estrogen play distinct roles in breathing. One protein builds new alveoli, the other stimulates the alveoli to expel carbon dioxide. Loss of estrogen hampered both functions in the test mice. (Massaro & Massaro, 2004)
Estrogenic compounds
A range of other synthetic and natural substances have been identified that possess estrogenic activity. These include bisphenol-A, phthalate esters and nonylphenol.
References
- Massaro D, Massaro GD (2004). Estrogen regulates pulmonary alveolar formation, loss, and regeneration in mice. American Journal of Physiology. Lung Cellular and Molecular Physiology 287 (6): L1154-9. PMID 15298854
