Estriol

Estriol is one of the three primary forms of estrogen in the body, and it is the weakest of them. It is produced in considerable amounts during pregnancy and is also present at much lower levels in non-pregnant women. Because of its less significant effect, it is sometimes used in compounded hormone preparations, particularly for vaginal symptoms.

Estriol has not been as extensively researched as estradiol (the more potent and more commonly prescribed form of estrogen) has. It has been FDA-approved as a vaginal cream for urinary symptoms that are associated with menopause, but only in some formulations. If a provider recommends estriol for you, it is within reason to ask about the evidence backing that specific recommendation in comparison to other estrogen options.