Supplement Forms/Alternate Names :

  • Oestriol
  • Tri-Estrogen


Principal Proposed Uses

Several forms of estrogen occur naturally in a woman's body. The ovary produces a form named estradiol, which is converted into another important estrogen called estrone. Estriol is yet another form of estrogen metabolized from estradiol, weaker than the other two, but still active. The estrogen tablets prescribed for menopausal symptoms usually contain estradiol, estrone, or a combination of the two. Some alternative medicine physicians have popularized the use of estriol as an alternative, and there is no doubt that estriol is also effective for symptoms of menopause. However, despite claims that it is safer than other forms of estrogen, the balance of evidence suggests that, in fact, estriol presents precisely the same risks (see Safety Issues below).


Estriol is manufactured in the body from estrone, estradiol, and androstenedione . When taken as a drug, it is manufactured synthetically, or extracted from animal products.

Therapeutic Dosages

The usual dose of estriol is 2 to 8 mg taken once daily. Estriol is also commonly sold in combination with other forms of estrogen.

Therapeutic Uses

Like more common forms of estrogen, estriol is used for the treatment of menopausal symptoms . Double-blind, placebo-controlled studies and other controlled trials have found oral or vaginal estriol effective for symptoms of menopause, including hot flashes, night sweats, insomnia, vaginal dryness, and recurrent urinary tract infections. Estriol may also help prevent osteoporosis . 1-9 Estriol might cause less vaginal bleeding as a side effect than other forms of estrogen, although this has not been definitively established. 10,11 Some alternative practitioners claim that estriol actually fights cancer, as opposed to estrogen, which increases risk of some cancers. However, this claim is based on exaggerated interpretations of very weak studies. 12,13,14 It is more likely that estriol increases cancer risk in much the same way as other forms of estrogen (see Safety Issues, below).

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