Estetrol: new perspectives for HRT in menopause and breast cancer patients

Estetrol (E4) is a foetal estrogen, produced by the foetal liver during pregnancy only. It has a selective ERalpha and ERbeta receptor binding with preference for ERalpha, with antagonist action. E4 is present at 9 weeks of gestation, with exponential increase of synthesis and blood levels. At term the foetus produces about 3 mg/day.
Potential applications in women’s life-span include: contraception, hormone replacement therapy (HRT), specifically for vasomotor symptoms, vulvovaginal atrophy and osteoporosis, and therapy of breast cancer.