Estrogen, otherwise known as oestrogen, is a primary female sex hormone that is vital in the development and functioning of females. The name is derived from estrus, the period of fertility for female mammals, and gen, meaning to generate. However, males too contain estrogen in lower quantities.
Production of estrogen occurs primarily in the ovaries, more specifically the theca internal cells. Estrogen secretion is stimulated by another hormone, the luteinizing hormone (LH). Estrogen is also produced, in smaller quantities, in the liver, adrenals glands, fat cells and the breasts.
Types of Estrogen
There are three major naturally occurring estrogens in women: estrone (E1), estradiol (E2), and estriol (E3). Estradiol is the predominant estrogen found in non-pregnant females. Estrone is weaker than estradiol, thus it is the primary estrogen after a woman.
Estradiol is a type of endogenous estrogen hormone, called E2, found in both males and females, and is the most dominant estrogen hormone found in women. The structure contains an aromatic ring and two hydroxyl groups. As a steroid, it is a derivative of cholesterol. The structure is similar to that of testosterone, and with the presence of aromatase, testosterone can be catalyzed into estradiol. Fat cells can also be converted into estradiol. It is produced in the ovaries for women and testes for men, as well as the adrenal cortex, liver, and hair for both sexes.
Estradiol is recognized by either the estrogen receptor ER-alpha or ER-beta, which are found on the surface membrane of cells. After the signal is recognized, estradiol is accepted into the cell and then it penetrates the nucleus, where it gets transcribed. The produced mRNA gets translated and then proteins are synthesized.
Estradiol regulates reproductive, sexual, bone, and various tissue development. In females, it is responsible for the development of secondary sex characteristics, such as breast growth, body hair growth, enlargement of hips, and widening of the uterus. It also helps develop the reproductive organs to prepare the body for a pregnancy. Such induced changes take place in the vaginal and fallopian tube lining and the ovaries. Estradiol affects bone structure and growth, which has been confirmed by observing more cases of osteoporosis in people who are unable to produce any.
Non-steroidal estrogens are either synthetic or naturally occurring substances that possess estrogenic activity. Examples of these are xenoestrogens (synthetic estrogens), phytoestrogens (plant estrogens), mycoestrogens (fungi estrogens).
In males, estrogen helps maintain a healthy libido and aids in the maturation of the sperm. In females, estrogen serves to develop secondary sexual characteristics such as breasts, endometrium, and regulation of menstural cycle. It does this by accelerating burning of body fat, reducing muscle bulk, and decelerating height increase during puberty.
Other functions of estrogen include reducing bone resorption, increasing bone formation, increasing platelet adhesiveness, increasing good cholesterol and triglycerides, improving lung functions, and causing salt and water retention.
Estrogen in Medicine
The most common uses of estrogen in medicine are birth control pills or contraceptives. In birth control pills, either low doses of estrogen combined with progestin is used, or simply progestin. The reason that estrogen is used in such a manner is because estrogen prevents ovulation by reducing secretion of the follicle stimulating hormone and the luteinizing hormone.
Estrogen in Cosmetics
Cosmetics can contain steroidal or non-steroidal hormones. Common products include shampoos, conditioners, moisturizers, body and skin creams, astringents, sunscreens, perfumes, hair sprays, shampoos, conditioners, styling gels, facial creams, foundations, moisturizers, lipsticks, liquid hand soaps, body wash, insect repellants, nail polish, polish remover, aftershave, and shaving creams. These products usually contain estrogen named parabens, placental extracts, and UV screens. It is important to limit the use of such products as long-term exposure may increase the risk of breast cancer.
Mandal, Ananya. "Estrogen - What is Estrogen?." News Medical. Ed. April Cashin-Garbutt. News Medical, n.d. Web. 2 Dec. 2012. <http://www.news-medical.net/health/Estrogen-What-is-Estrogen.aspx>.