What Is HRT?
Hormone Replacement Therapy for Women · Last reviewed by the OPTML clinical team on April 29, 2026
Hormone replacement therapy (HRT) for women is the medical administration of bioidentical estradiol (and micronized progesterone if a uterus is present) to restore hormone levels that have declined during perimenopause and menopause. Modern bioidentical HRT is structurally identical to the hormones the ovaries produce, distinguishing it from older synthetic regimens (conjugated equine estrogens + medroxyprogesterone acetate) used in the original Women's Health Initiative trial.
Indications
HRT is prescribed for women experiencing symptoms of perimenopause, menopause, or post-menopause, typically beginning in the early-to-mid 40s and continuing through the late 50s and beyond. Common symptoms include vasomotor symptoms (hot flashes, night sweats), sleep disruption, mood changes, vaginal dryness, decreased libido, brain fog, joint pain, and accelerated bone loss.
HRT is also used for women with premature ovarian insufficiency (POI) and surgical menopause (oophorectomy), where hormone replacement is generally recommended at least until the average age of natural menopause (~51).
Bioidentical vs. Synthetic Hormones
- Bioidentical estradiol (17β-estradiol): identical molecular structure to ovarian estradiol. Available as oral tablets, transdermal patches, topical cream/gel, vaginal preparations, and pellets.
- Micronized progesterone (Prometrium, compounded): identical molecular structure to ovarian progesterone. Distinct from medroxyprogesterone acetate (Provera), a synthetic progestin used in the original WHI trial.
- Conjugated equine estrogens (Premarin): a mixture of estrogens isolated from pregnant mare urine, not bioidentical to human estradiol. Used in the original WHI trial.
Common Forms and Routes
| Hormone | Form | Route |
|---|---|---|
| Estradiol | Oral tablet (estradiol hemihydrate) | Daily |
| Estradiol | Transdermal patch | Twice weekly |
| Estradiol | Topical cream / gel | Daily |
| Estradiol | Vaginal cream / tablet / ring | For genitourinary symptoms |
| Progesterone (micronized) | Oral capsule | Nightly (often cyclic or continuous) |
Typical Laboratory Monitoring
- Estradiol (E2), target depends on route and goal.
- Progesterone, to confirm absorption with oral micronized.
- FSH (Follicle-Stimulating Hormone), typically elevated in menopause.
- LH (Luteinizing Hormone).
- SHBG, total testosterone (for symptom workup).
- Lipid panel, fasting glucose, HbA1c.
- Bone density (DEXA) at baseline and periodically.
Clinical Trial Evidence
Women's Health Initiative (WHI, 2002), and what its re-analysis showed
The original WHI trial used conjugated equine estrogens + medroxyprogesterone acetate (Premarin + Provera), not bioidentical hormones. It was halted early in 2002 due to a small absolute increase in breast cancer and cardiovascular events. The findings were widely reported, leading to a sharp decline in HRT prescribing.
Subsequent re-analyses by age cohort (Manson JE et al., JAMA 2013, 2017) demonstrated that women who started HRT under age 60 or within 10 years of menopause onset had different, and generally favorable, risk profiles, including reduced all-cause mortality. This is now referred to as the "timing hypothesis."
KEEPS (Kronos Early Estrogen Prevention Study, 2014)
A 4-year RCT in recently menopausal women (median age 52) showed that oral conjugated estrogens and transdermal estradiol were both well tolerated, improved quality-of-life measures (hot flashes, sleep, mood), and showed no progression of carotid atherosclerosis vs. placebo.
ELITE (Early vs. Late Intervention Trial with Estradiol, 2016)
Demonstrated that oral estradiol initiated within 6 years of menopause slowed the progression of subclinical atherosclerosis (carotid intima-media thickness), but the same effect was not seen when estradiol was initiated 10+ years post-menopause.
Side Effects and Risks
- Breast tenderness, breakthrough bleeding (especially in the first 3 months).
- Headache, mood changes.
- Bloating, nausea (typically transient).
- Small absolute increase in venous thromboembolism risk with oral estradiol (transdermal preparations carry lower VTE risk).
- Endometrial hyperplasia / cancer risk if estrogen is given to women with a uterus without opposing progesterone.
- Modestly increased breast cancer risk with combined estrogen + progestin therapy used for >5 years (absolute risk small; magnitude varies by formulation and duration).
HRT vs. TRT (Testosterone Replacement)
HRT for women refers specifically to estradiol ± progesterone. Testosterone replacement for women is a separate (and more controversial) therapy with limited FDA-approved formulations in the U.S.; OPTML does not prescribe injectable testosterone for women. For men, TRT is a distinct therapy targeting hypogonadism.
OPTML for Women: hormones, restored.
Bioidentical estradiol + progesterone, calibrated to your numbers. Free consult. Physician oversight. Labs available as an add-on.
Start your consultation →References
- Rossouw JE, Anderson GL, Prentice RL, et al. Risks and benefits of estrogen plus progestin in healthy postmenopausal women. JAMA. 2002;288(3):321-333. [WHI]
- Manson JE, Aragaki AK, Rossouw JE, et al. Menopausal hormone therapy and long-term all-cause and cause-specific mortality: WHI randomized trials. JAMA. 2017;318(10):927-938.
- Harman SM, Black DM, Naftolin F, et al. Arterial imaging outcomes and cardiovascular risk factors in recently menopausal women: the KEEPS trial. Ann Intern Med. 2014;161(4):249-260.
- Hodis HN, Mack WJ, Henderson VW, et al. Vascular effects of early versus late postmenopausal treatment with estradiol. N Engl J Med. 2016;374(13):1221-1231. [ELITE]
- The 2022 Hormone Therapy Position Statement of The North American Menopause Society. Menopause. 2022;29(7):767-794.