Introduction[edit | edit source]
Estrogen, a steroid, is a category of sex hormone. There are three major endogenous estrogens that have estrogenic hormonal activity: estrone, estradiol, and estriol. They are formed from androgen precursors, that are secreted chiefly by the ovaries, placenta, adipose tissue, and testes. They stimulate the development and maintenance of female secondary sex characteristics, exert systemic effects such as the growth and maturation of long bones, promote estrus in many female mammals, and are used as a drug primarily to treat estrogen deficiency.
Types of Estrogen[edit | edit source]
The female body produces three different types of estrogen. During a females lifespan, the amounts of each of these different estrogens changes. The major types are:
- Estradiol: Estradiol is the major estrogen in your body during the childbearing years. In this time the estradiol in the bloodstream is the predominant type of estrogen. Estradiol also has the strongest effect on the estrogen-specific hormone receptors. Estradiol is produced mainly in the ovaries, and the amount they produce varies over the course of the menstrual cycle. Ethinyl estradiol is a synthetic form of estrogen that's commonly used in hormonal contraceptives.
- Estrone: Estrone is the second most common type of estrogen produced by during the childbearing years. Estrone is produced by the adrenal glands and fatty tissue, and is the only type of oestrogen produced after menopause. A small amount of estrone is produced by the ovary.
- Estriol: Typically known as the estrogen of pregnancy. It is present only in a very small amount in females bloodstream when not pregnant.
Effects of Extrogen[edit | edit source]
The effects of estrogen on various systems include:
- Breast: Estrogen is responsible for developing mammary gland changes in breast tissue at puberty in females. Estrogen also causes the development of mammary ducts during puberty and pregnancy and functions to secrete breast milk in postpartum lactation.
- Uterus: In the uterus, estrogen helps rapidly increase the endometrial cells in the follicular phase of the menstrual cycle, thickening the endometrial lining in preparation for pregnancy.
- Vagina: Estrogen supports the health of the vagina and the vulva. In the absence of estrogen, the vaginal and vulvar mucosal epithelium becomes thin and may cause with vulvovaginal atrophy and dryness.
- Cardiovascular: Estrogen affects plasma lipids by increasing high-density lipoproteins (HDL) and triglyceride levels while decreasing low-density lipoproteins (LDL) and total plasma cholesterol and reducing the risk of coronary artery disease with early use in postmenopausal women.
Effects on Musculoskeletal Function[edit | edit source]
Estrogen has a dramatic effect on musculoskeletal function. Estrogen is known for its relationship with bone, however it directly affects the structure and function of other musculoskeletal tissues such as muscle, tendon, and ligament.
- Estrogen is the key regulator of bone metabolism in both men and women. Bone is a complex tissue, consisting of a matrix of proteins and minerals that give it the flexibility and strength to support body movement. Bones specialized cells, help to maintain this matrix. Estrogen protects bones by inactivating osteoclast activity. The dramatic fall in estrogen levels at menopause increases bone loss and can lead to osteoporosis, which puts women at greater risk for a hip fracture.
- Estrogen acts as a regulator of muscle energy metabolism and plays a role in the maintenance of muscle stem cells (i.e., satellite cells) as well promoting self-renewal and differentiation into muscle fibers. Menopause leads to the cessation of ovarian estrogen production concurrent to the deterioration of muscle function. Estradiol deficiency reduces skeletal muscle mass and force generation in women.
- Estrogen increases the collagen content of connective tissues.
- Estrogen in tendons and ligaments decreases stiffness, and this directly affects performance and injury rates. High estrogen levels can make women more prone for catastrophic ligament injury.
Menopausal Hormone Treatment[edit | edit source]
At menopause, a decrease in oestrogen levels can cause symptoms such as hot flushes, vaginal dryness, mood and sleep changes. Menopausal Hormone Treatment (MHT) is an effective way of improving menopausal symptoms. However, there are risks associated with Hormone replacement therapy (HRT). See Menopausal Hormone Treatment
Oestrogen and Breast Cancer[edit | edit source]
The causes of breast cancer involve many factors. However, we know that oestrogen can help breast cancer cells grow. Women who have been exposed to more estrogen, for example women who reach puberty earlier or experience late menopause , are at an increased risk of breast cancer. Women whose bodies are naturally high in estrogen also have an increased risk.
The Female Triad and Estrogen[edit | edit source]
The female athlete triad refers to the coexistence of 3 distinct medical conditions that may occur in athletic girls and women eating. The triad consists of disorders/disordered eating behavior, amenorrhea/oligomenorrhea, and decreased bone mineral density (osteoporosis and osteopenia). When paired with inadequate nutrition, the high caloric expenditure of exercise training causes low energy availability, which is sensed by the hypothalamus, setting in motion a complex neuroendocrine adaptive cascade. This cascade leads to changes in the hypothalamic-pituitary-ovarian axis, resulting in decreased estrogen levels and reproductive dysfunction eg amenorrhea, oligomenorrhea, or anovulation. Low estrogen in otherwise young healthy women is associated with decreased bone mineral density and increased risk of fractures.
Eating Disorders and Estrogen[edit | edit source]
Anorexia nervosa and other eating disorders can have significant short and long term physical consequences. Affected individuals can experience nutritional and hormonal problems that reduce bone density. Low body weight in females causes the body to stop producing estrogen, resulting amenorrhea. Long terms effects of estrogen levels are serious. Estrogen levels help in producing secondary sexual characteristics eg breasts, accelerate the growth of height and metabolism rate in a females body, and help in maintaining blood vessels and skin. Osteoporosis in later life is another consequence of inadequate estrogen levels.
References[edit | edit source]
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- Laakkonen, E.K., Soliymani, R., Karvinen, S., Kaprio, J., Kujala, U.M., Baumann, M., Sipilä, S., Kovanen, V. and Lalowski, M., 2017. Estrogenic regulation of skeletal muscle proteome: a study of premenopausal women and postmenopausal MZ cotwins discordant for hormonal therapy. Aging Cell, 16(6), pp.1276-1287. Available: https://researchportal.helsinki.fi/en/publications/estrogenic-regulation-of-skeletal-muscle-proteome-a-study-of-prem(accessed 25.8.2022)
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- Chidi-Ogbolu N, Baar K. Effect of estrogen on musculoskeletal performance and injury risk. Frontiers in physiology. 2019:1834. Available:https://www.frontiersin.org/articles/10.3389/fphys.2018.01834/full (accessed 25.8.2022)
- Health Direct Estrogen Available:https://www.healthdirect.gov.au/oestrogen (accessed 25.8.2022)
- Papanek PE. The female athlete triad: an emerging role for physical therapy. Journal of Orthopaedic & Sports Physical Therapy. 2003 Oct;33(10):594-614. Available:https://pubmed.ncbi.nlm.nih.gov/14620789/ (accessed 26.8.2022)
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