This article is Part 5 of our educational series on commonly prescribed compounded BHRT medications. In this installment, we focus on estriol, a gentler estrogen that plays a key role in supporting urogenital and skin health.
BHRT Series Part 1: Estradiol Cream, Troche, Capsules, and More
BHRT Series Part 2: Understanding Compounded DHEA
BHRT Series Part 3: Testosterone
BHRT Series Part 4: Progesterone – The Missing Piece in Many Women’s Hormone Plans
What Is Estriol?
One of three primary estrogens, the human body produces estriol (E3) alongside estradiol (E2) and estrone (E1). While estradiol is dominant during reproductive years, estriol is more prominent during pregnancy and at lower levels in postmenopausal women. Unlike estradiol, it’s considered a weaker estrogen, but this doesn’t diminish its significance in Bioidentical Hormone Replacement Therapy (BHRT).
In clinical settings, estriol is often used for localized estrogen support, particularly for women dealing with vaginal dryness, irritation, or urinary symptoms — common concerns in perimenopause and menopause.
How Estriol Works
Estriol binds primarily to estrogen receptor beta (ERβ) rather than estrogen receptor alpha (ERα), making its activity more selective and tissue-specific. This binding profile allows estriol to support certain tissues (like the vaginal epithelium and urinary tract) without strongly stimulating others, such as the breast or uterus.
This receptor selectivity makes this interesting hormone a favored option for:
- Supporting vaginal lubrication and tissue elasticity
- Managing genitourinary symptoms of menopause (GSM)
- Improving skin tone and hydration
- Reducing urinary urgency and frequency
- Supporting immune-modulatory effects in mucosal tissues
Estriol for Vaginal Health
A study published in Climacteric suggests that even ultra-low-dose estriol, when combined with supportive probiotics, can restore tissue health and reduce symptoms of vaginal atrophy with just two doses per week during maintenance. This makes it an appealing long-term solution for women seeking gentle, localized estrogen therapy with additional microbiome support.
Urinary Tract Support
Frequent urinary tract infections (UTIs) are a frustrating and painful issue for many women after menopause, often linked to low estrogen levels and thinning of the vaginal and urethral tissues.
In a placebo-controlled clinical trial, 93 postmenopausal women with a history of recurrent UTIs were given either vaginal estriol cream or a placebo over an eight-month period.
The results:
- Estriol users had a 91.5% lower rate of UTIs compared to those using placebo (0.5 vs. 5.9 episodes per year)
- Healthy lactobacilli bacteria returned in 61% of women using estriol but in none of the placebo group
- Vaginal pH decreased (from 5.5 to 3.8), creating a more protective environment against infection
- Harmful bacteria (Enterobacteriaceae) dropped from 67% to 31% in the estriol group
- The cream was well tolerated with only minor side effects reported
The research suggests that estriol may be preventing urinary tract infections through vaginal flora.
Raz, R., & Stamm, W. E. (1993). A controlled trial of intravaginal estriol in postmenopausal women with recurrent urinary tract infections. The New England Journal of Medicine, 329(11), 753–756.
Estriol’s Role in Skin and Aging
As estrogen levels decline with age, many women begin to notice changes in their skin, including dryness, thinning, reduced elasticity, and more visible wrinkles. Estriol, the gentlest of the three primary estrogens, has been studied for its ability to support skin integrity and hydration when used topically.
In a study published in the International Journal of Dermatology postmenopausal women used either estriol or estradiol creams for six months. The results were significant:
- Skin became visibly firmer and more elastic
- Wrinkle depth and pore size were reduced by up to 100%
- Skin moisture levels increased
- Under the microscope, researchers saw an increase in Type III collagen, a key component in youthful, supple skin
Importantly, hormone levels in the body remained stable — with only prolactin (PRL) slightly increasing — and no systemic hormone-related side effects were reported.
These findings suggest that a topical form may help improve the texture of aging skin by enhancing collagen production and boosting hydration, without significantly affecting hormone levels elsewhere in the body.
Schmidt, J. B., Binder, M., Demschik, G., Bieglmayer, C., & Reiner, A. (1996). Treatment of skin aging with topical estrogens. International Journal of Dermatology, 35(9), 669–674.
Estriol vs. Estradiol: Why Both May Be Used in BHRT
While estradiol is potent and often used systemically, estriol may be selected for its gentler and localized effects. Some practitioners prescribe Bi-Est (a blend of estriol and estradiol) to combine the benefits of both estrogens. This can offer broader symptom support with a more balanced estrogenic profile.
In clinical compounding, estriol may be customized into:
- Vaginal creams or suppositories
- Oral capsules
- Transdermal creams or troches
- Rectal suppositories (less common, but used in special cases)
Custom Compounded Alternatives from HDRx
- Vaginal Gel (ultra low dose)
- Bi-estrogen (Bi-est) combinations (estradiol and estriol)
- Nasal Drops
- Vaginal Cream
- Custom dosages for urologic or dermatologic protocols
Is Estriol Right for You?
Estriol may be especially appropriate for women who are experiencing:
- Vaginal dryness, itching, or discomfort
- Painful intercourse (dyspareunia)
- Frequent urinary tract infections or urgency
- Skin thinning or dryness
- A desire for milder estrogenic support compared to estradiol
For some women, the hormone may be used alone; others may benefit from it as part of a comprehensive BHRT protocol alongside progesterone or testosterone.
Partnering With HDRx
At HDRx, we work closely with prescribers across Michigan, Florida, Ohio, Illinois, Indiana, Minnesota, and Wisconsin to compound estriol and other BHRT medications.Â
Our PCAB-accredited lab ensures we prepare each formulation with precision, safety, and quality in mind.
If you’re a provider seeking custom estriol options, or a patient exploring BHRT — reach out to HDRx for support. We’re here to help simplify the path toward better hormone balance.
References:
- Donders, G., Neven, P., Moegele, M., Lintermans, A., Bellen, G., Prasauskas, V., Grob, P., Ortmann, O., & Buchholz, S. (2014). Ultra‑low‑dose estriol and Lactobacillus acidophilus vaginal tablets (Gynoflor®) for vaginal atrophy in postmenopausal breast cancer patients on aromatase inhibitors: Pharmacokinetic, safety, and efficacy phase I clinical study. Breast Cancer Research and Treatment, 145(2), 371–379. (Link)
- Jaisamrarn, U., Triratanachat, S., Chaikittisilpa, S., Grob, P., Prasauskas, V., & Taechakraichana, N. (2013). Ultra-low-dose estriol and lactobacilli in the local treatment of postmenopausal vaginal atrophy. Climacteric, 16(3), 356–363. (Link)
- Raz, R., & Stamm, W. E. (1993). A controlled trial of intravaginal estriol in postmenopausal women with recurrent urinary tract infections. New England Journal of Medicine, 329(11), 753–756. (Link)
- Schmidt, J. B., Binder, M., Demschik, G., Bieglmayer, C., & Reiner, A. (1996). Treatment of skin aging with topical estrogens. International Journal of Dermatology, 35(9), 669–674. (Link)
