Impact of vaginal estriol on serum hormone levels: a systematic review

The genitourinary syndrome of menopause (GSM) affects up to 84% of postmenopausal women and may significantly reduce the quality of life in some. For symptom relief, there are several non-hormonal and hormonal vaginal products available. In Europe, vaginal estriol (E3) is the most frequently chosen estrogen for GSM treatment. The aim of this systematic review was to assess the impact of vaginal E3 on serum sex hormone levels, an outcome that has been previously used to assess safety in similar products. In our review, we did not find any alterations in serum estrone, estradiol, testosterone, progesterone and sex hormone binding globulin levels after vaginal E3 application. In contrast, some studies showed a minimal and transient decrease in serum gonadotropin levels, which however remained within the postmenopausal range. Similarly, only a few studies reported a minimal and transient increase of serum E3 levels, with the rest reporting no changes. The lack of clinically relevant long-term changes in serum sex hormone levels supports the current literature providing evidence about the safety of vaginal E3 products.