What is the Difference Between Estriol and Estradiol?

Estriol and estradiol are two different forms of the female hormone estrogen, which play crucial roles in various bodily functions. Here are the main differences between them:

1. Potency: Estradiol is the stronger and more potent form of estrogen, while estriol is the weakest form of estrogen.
2. Function: Estriol is dominant during pregnancy and helps support both the mother and the fetus, while estradiol is the dominant form of estrogen during reproductive years and plays a role in regulating the menstrual cycle.
3. Side Effects: Estriol is less likely to cause side effects like high blood pressure and blood clots compared to estradiol.
4. Hormone Replacement Therapy (HRT): Estradiol is FDA-approved for hormone replacement therapy, while estriol is not. However, estriol can be used in compounded hormone therapy products.
5. Estrogen Receptors: Estriol has a preferential affinity for estrogen receptor beta (ERβ) and is thought to have a lower estrogenic potential compared to estradiol.

Both estriol and estradiol can be used as part of HRT for women after menopause, but estradiol is considered more effective and potent than estriol. Estriol is sometimes combined with estradiol to offset the risk of uterine cancer associated with estradiol use.

Comparative Table: Estriol vs Estradiol

Estriol and estradiol are both forms of estrogen found in the body, but they have different functions and levels during a woman's reproductive cycle. Here is a table comparing the differences between estriol and estradiol:

Both hormones share some similarities, such as binding to estrogen receptors and being used in hormone replacement therapy. However, their primary functions and levels during different stages of a woman's reproductive life differ.