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Estradiol & progesterone (HRT)

Estradiol cypionate / E2, Progesterone · Sex hormones (hormone therapy)

Research reference only. Pepdex does not sell, supply or track this compound, and nothing here is guidance to use it — this page exists so the evidence and the risks are visible.

What it is

Hormone-therapy agents — injectable estradiol esters (the core feminizing agent) and progesterone (whose routine role in feminizing therapy remains optional and debated) — which also circulate outside supervised care.

How it works

This entry covers menopausal hormone therapy — oestradiol, with progesterone added for anyone who still has a uterus. Oestradiol replaces the hormone the ovaries stop producing, which is what addresses hot flushes, night sweats and genitourinary symptoms. Progesterone is not there for symptoms: it protects the uterine lining, because unopposed oestrogen raises the risk of endometrial cancer. That division of labour is the single most important thing to understand about the combination, and it is why the two are not interchangeable components.

What human evidence shows

Large clinical literature in menopausal HRT and transgender medicine, with monitoring frameworks that are indication- and patient-specific — in supervised care. Unsupervised use discards exactly that monitoring.

The studies, one by one

  • STRONG for treating moderate to severe vasomotor symptoms — hot flushes and night sweats — and for genitourinary symptoms of menopause. This is well-established, large-trial evidence.
  • STRONG for preventing postmenopausal osteoporosis, which is an approved indication.
  • The Women's Health Initiative is the study that shaped a generation of practice and was widely misread. Its findings differed substantially by age, by time since menopause, and by whether oestrogen was given alone or with a progestin — and the blanket fear that followed led many women to be denied treatment that would likely have helped them.
  • The risks are real and depend on the specifics: breast cancer risk relates mainly to combined oestrogen-progestin therapy and to duration; venous thromboembolism and stroke risk relate to oral administration in particular, with transdermal routes carrying a lower thrombotic signal.
  • Systemic hormone therapy carries a boxed warning covering endometrial cancer, cardiovascular disorders, breast cancer and probable dementia. Low-dose vaginal products for local symptoms are a different risk proposition from systemic therapy.

Half-life and how long it lasts

Available as oral tablets, transdermal patches and gels, and vaginal preparations. Route matters clinically rather than cosmetically: oral oestrogen passes through the liver first and affects clotting factors, which is the basis of the thrombotic difference from transdermal delivery. Micronised progesterone and synthetic progestins are not equivalent to each other, and the trial evidence differs between them.

Risks

Thromboembolism is the headline estrogen risk (route- and dose-dependent), plus monitoring-dependent items: breast tissue changes, mood effects, fertility impact, and — in unsupervised use — running levels far outside any studied range. Hormone therapy is one of medicine's better-served areas for legitimate clinical access; unsupervised sourcing is all downside here.

Who should never touch it

  • Anyone with undiagnosed abnormal vaginal bleeding, which needs a diagnosis first
  • Anyone with a history of breast cancer, oestrogen-dependent cancer, or a history of stroke or heart attack
  • Anyone with active or prior venous thromboembolism, or a known clotting disorder
  • Anyone with active liver disease, or who may be pregnant
  • Anyone buying compounded or unregulated hormone products outside a prescriber relationship

Interactions worth knowing

  • Anything altering liver enzyme activity, which changes hormone levels in both directions.
  • Thyroid medication, since oestrogen alters thyroid-binding proteins and requirements can change.
  • Anticoagulants and anything raising clot risk, including smoking.
  • Some anticonvulsants and antibiotics, which affect hormone metabolism.

What a clinician would watch

  • This is prescription treatment and the decisions belong with the prescriber managing it — including which formulation, which route and for how long.
  • Any unexpected vaginal bleeding, which needs prompt assessment because of the endometrial risk.
  • Breast changes and adherence to whatever screening schedule applies.
  • Signs of clot — leg swelling and pain, chest pain, breathlessness — as urgent assessment.
  • Blood pressure.

What stopping looks like

Menopausal symptoms commonly return on stopping, sometimes abruptly, and that is not a sign of dependence — it is the underlying hormonal state reasserting itself. Whether to taper or stop outright, and when, is a decision for the prescriber managing the treatment. Bone protection is lost once therapy stops, which matters for anyone taking it for osteoporosis prevention.

Myth vs evidence

“Hormone therapy causes breast cancer, full stop.”

The risk depends on which regimen, for how long, and at what age started. Oestrogen alone and combined therapy have different profiles, and blanket statements in either direction misrepresent what the trials found.

“Bioidentical compounded hormones are safer than pharmaceutical ones.”

FDA-approved products including micronised progesterone and oestradiol are already structurally identical to human hormones. Compounded preparations add variable potency and no approval review — that is added uncertainty, not added safety.

“Progesterone is optional if you feel fine without it.”

For anyone with a uterus it is not a symptom drug. It is there to prevent endometrial cancer from unopposed oestrogen.

“You should stop at a fixed number of years regardless.”

Duration is an individual risk-benefit decision with the prescriber, not a universal rule.

Legal status

US: prescription-only.

Research on this compound

Papers about this compound, not proof of the claims above. A title says what was studied, which is sometimes a negative result or a different question entirely.

  • Endometrial safety and bleeding profile of a 17β-estradiol/progesterone oral softgel capsule (TX-001HR)
    Menopause, 2020
  • Medroxyprogesterone acetate and estradiol cypionate injectable suspension (Cyclofem) monthly contraceptive injection: steady-state pharmacokinetics
    Contraception, 2013

Evidence base

Not auto-graded. This entry covers several different drugs, or a use the published research was never about, so no single letter honestly describes it. The reading below is real literature — read it against what this page says, not as a score.

Research (12)

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Where next

Every compound in the catalogThe full non-peptide index, with evidence grades.→The peptide indexInjectable peptides, half-lives and what trials used.→Spotting a scam vendorRed flags, COA checks and what traceability looks like.→