Estriol (medication)

Estriol (E3), sold under the brand name Ovestin among others, is an estrogen medication and naturally occurring steroid hormone which is used in menopausal hormone therapy. It is also used in veterinary medicine as Incurin to treat urinary incontinence due to estrogen deficiency in dogs. The medication is taken by mouth in the form of tablets, as a cream that is applied to the skin, as a cream or pessary that is applied in the vagina, and by injection into muscle.

Estriol is well-tolerated and produces relatively few adverse effects. Side effects may include breast tenderness, vaginal discomfort and discharge, and endometrial hyperplasia. Estriol is a naturally occurring and bioidentical estrogen, or an agonist of the estrogen receptor, the biological target of estrogens like endogenous estradiol. It is an atypical and relatively weak estrogen, with much lower potency than estradiol. When present continuously at adequate concentrations however, estriol produces full estrogenic effects similarly to estradiol.

Estriol was first discovered in 1930, and was introduced for medical use shortly thereafter. Estriol esters such as estriol succinate are also used. Although it is less commonly employed than other estrogens like estradiol and conjugated estrogens, estriol is widely available for medical use in Europe and elsewhere throughout the world.