Main Difference – Estriol and Estradiol
Estrogen is the main female sex hormone that is involved in the development of secondary sexual characteristics in females such as widened hips, enlarged breasts, armpit and pubic hair. Estrone (E1), estradiol (E2), and estriol (E3) are the three forms of estrogens produced by the body. The main difference between estriol and estradiol is that estriol is the strongest form of estrogen whereas estradiol is a weaker form of estrogen. However, estrone is a form of unhealthy estrogen that raises the risk of cancers.
Key Areas Covered
1. What is Estriol/Oestriol
– Definition, Facts, Role
2. What is Estradiol/Oestradiol
– Definition, Facts, Role
3. What are the Similarities Between Estriol and Estradiol
– Outline of Common Features
4. What is the Difference Between Estriol and Estradiol
– Comparison of Key Differences
Key Terms: Estradiol, Estriol, Estrogen, Estrogen Receptors, Female Sex Hormones, Uterine Cancer
What is Estriol/Oestriol
Estriol or oestriol (E3) refers to a form of estrogen, which is a metabolite of estradiol. Hence, it is formed during the estradiol and estrone metabolism. It is produced in the liver and placenta. Estriol is 8% potent as the estradiol. It is 14% potent than the estrone. The binding of estriol with the estrogen receptor blocks the binding of strong estradiol with the receptor. Hence, estriol exhibits both estrogenic as well as the antiestrogenic actions. By this, estriol reduces the cancer-risk of estradiol. The formation of estriol is shown in figure 1.
Figure 1: Formation of Estriol
Estriol is important for healthy skin and mucous membranes. It is given as a drug in hormone replacement therapy. The application of estriol on the skin increases the levels of collagen and hydrates the skin cells. It is given as a supplement for vaginal dryness during menopause. The levels of 16-Hydroxyesterone is a breakdown product of estriol, and it can be elevated in women who receive oral estriol. However, it can increase the risk of both cervical and breast cancers.
What is Estradiol/Oestradiol
Estradiol (E2) or oestradiol refers to the major form of estrogen produced in the ovaries. It is the most potent or the strongest form of estrogen. Hence, even a small quantity of estradiol has a very high effect. Estradiol can be produced during the metabolism of various types of precursors in the adrenal glands. It has the fullest range as it binds to the estrogen receptors throughout the body to produce the effect of estrogen. Hence, estradiol is considered as the active form of estrogen. The estradiol levels during the menstrual cycle are shown in figure 2.
Figure 2: Estradiol Levels during Menstrual Cycle
Estradiol is responsible for the growth of the lining of the uterus and breast tissue. Hence, estradiol increases the risk of the formation of uterine cancers. The enlargement of the breast is also a risk factor. Estradiol is also important in the tenderness of the breast. It is also responsible for the weight gain when estradiol is used as a drug. However, estradiol is important for the maintenance of healthy bones. It eliminates hot flashes as well as the night sweats. As estradiol is neuroprotective, it is good for the health of the brain. It is also good for short-term memory and memory recall.
Similarities Between Estriol and Estradiol
- Both estriol and estradiol are two forms of estrogen.
- Both estriol and estradiol consist of 18 carbon atoms.
- Both estriol and estradiol bind to the estrogen receptors.
- Both estriol and estradiol are involved in the formation and maintenance of secondary, sexual characteristics in females.
Difference Between Estriol and Estradiol
Definition
Estriol: Estriol refers to a form of estrogen, which is a metabolite of estradiol.
Estradiol: Estradiol refers to the major form of estrogen produced in the ovaries.
Designated as
Estriol: Estriol is designated in E3.
Estradiol: Estradiol is designated in E2.
Formation
Estriol: Estriol is formed as waste during both estrone and estradiol metabolism.
Estradiol: Estradiol is produced in the ovaries and in the adrenal gland; it is produced from various metabolites.
Location
Estriol: Estriol is produced in liver and placenta.
Estradiol: Estradiol is produced in ovaries and adrenal gland.
Potency
Estriol: Estriol is 8% as potent as estradiol.
Estradiol: Estradiol is the most potent form of estrogen.
Levels
Estriol: Estriol levels are measurable during the pregnancy as it is produced by the placenta.
Estradiol: Estradiol levels fluctuate throughout the different phases of the menstrual cycle.
Role
Estriol: Estriol binds to the estrogen receptors, making them unavailable for estradiol.
Estradiol: Estradiol is the active form of estrogen that exerts the effect of estrogen hormone by binding to the estrogen receptors throughout the body.
Cancer Formation
Estriol: Estriol has an anti-cancer action.
Estradiol: Estradiol can induce the formation of uterine cancer.
Conclusion
Estriol and estradiol are two forms of estrogen that help in the formation and maintenance of secondary sexual characteristics of females. Estriol is a metabolic waste product of both estrone and estradiol. It blocks estrogen receptors, which are available for the binding with estradiol, reducing the risk of cancers. Estradiol is the strongest form of estrogen that binds to the estrogen receptors of throughout the body, maintaining secondary female sexual characteristics. Therefore, the main difference between estriol and estradiol is their potency and role in the body.
Reference:
1. “The three estrogens: estradiol, estrone, estriol.” A Survivor’s Guide to Surgical Menopause, Available here.
Image Courtesy:
1. “AromataseEnzyme” By Jatlas2 – Own work (Public Domain) via Commons Wikimedia
2. “Estradiol during menstrual cycle” By Häggström, Mikael (2014). “Reference ranges for estradiol, progesterone, luteinizing hormone and follicle-stimulating hormone during the menstrual cycle”. Wikiversity Journal of Medicine 1 (1). DOI:10.15347/wjm/2014.001. ISSN 20018762. – Own work (Public Domain) via Commons Wikimedia
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