Conjugated estrogens

Estrogens
Estrogens
Pregnancy: avoid
Not used in pregnancy.

A mixture of estrogen sulfates (estrone, equilin and others) for menopausal symptoms; with medroxyprogesterone, the regimen of the Women's Health Initiative.

Updated Nov 1, 2026

Quick facts

Group: Estrogens
Target: Estrogen receptors α and β, nuclear receptors
Used for: Hot flushes of menopause
Key effects: Breast pain or tenderness · Nausea · Weight changes
Monitor: Need for continued treatment · Blood pressure
ATC: G03CA57

No doses: the clinician sets them by the current guideline.

Mechanism of action

Estrogen receptors α and β, nuclear receptorsConjugated estrogens

Conjugated estrogens are a mixture; the figure shows estradiol, a related estrogen that occupies the same site, in the ligand-binding domain of human estrogen receptor α.

Target in 3D: Estrogen receptors α and β, nuclear receptors. PDB structure 1ERE (RCSB PDB, public domain). View the structure at RCSB PDB

Conjugated estrogens are mainly sulfate esters of estrone, equilin and other estrogens. Gut enzymes remove the sulfate so the estrogens can be absorbed. They act on estrogen receptors α and β like other estrogens: they relieve hot flushes and vaginal atrophy, slow bone loss and lower LH and FSH by negative feedback. They stimulate the endometrium, so a progestogen is added in women with a uterus.

Gut enzymes remove the sulfate and the estrogens are absorbed
They bind estrogen receptors in target tissues
Hot flushes ease and vaginal epithelium and bone are preserved
The endometrium is stimulated unless a progestogen is added

Indications

Hot flushes of menopause Menopause and climacteric syndrome →
Vaginal atrophy of menopause Genitourinary syndrome of menopause (atrophic vaginitis) →
Prevention of postmenopausal osteoporosis when other drugs are unsuitable Osteoporosis →
Hypoestrogenism in young women with ovarian failure or hypogonadism Primary ovarian insufficiency →

Adverse effects

Common

Breast pain or tenderness
Nausea, stomach upset
Weight changes
Leg cramps
Vaginal discharge or bleeding

Contraindications

Undiagnosed abnormal genital bleeding
Breast cancer or other estrogen-dependent cancer
Active or past venous or arterial thromboembolism
Liver disease

Key interactions

St John's wort and other CYP3A4 inducers: Lower estrogen effect
Grapefruit and other CYP3A4 inhibitors: Higher estrogen levels
Levothyroxine: Estrogen raises thyroid-binding globulin; the thyroid dose may need to rise

What is monitored

Need for continued treatment
Blood pressure
Breast examination and mammography
Abnormal vaginal bleeding
Signs of thrombosis

Administration and safety

Oral tablets at the same time each day
In women with a uterus, given with a progestogen on the schedule ordered
Lowest effective dose for the shortest time; reviewed regularly

Pregnancy and breastfeeding

Not used in pregnancy.

Nursing care

Teach the warning signs of clots and stroke
Teach to report vaginal bleeding and breast lumps
Ask about smoking and past clots
Ask about thyroid medication
Check that a progestogen is prescribed if the uterus is present

Pharmacokinetics

Absorption: Oral tablets; the sulfate is removed in the gut before absorption
Metabolism: In the liver, partly by CYP3A4, with enterohepatic recirculation
Elimination: As conjugated metabolites in urine

Test yourself

Think of the answer, then tap the question to see it.

Which combination was studied in the Women's Health Initiative estrogen-plus-progestin arm?

Conjugated estrogens with medroxyprogesterone acetate.

What did that combination increase compared with placebo?

Venous thromboembolism, stroke, heart attack and invasive breast cancer, and probable dementia in women aged 65 or older.

What are conjugated estrogens made of, and how are they absorbed?

Mainly sulfate esters of estrone, equilin and other estrogens; gut enzymes remove the sulfate so the estrogens can be absorbed.

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Connections

← Back to the class: Estrogens

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Estrogen: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); DailyMed - MEDROXYPROGESTERONE ACETATE tablet (DailyMed (U.S. National Library of Medicine), 2026); DailyMed - ESTRADIOL AND NORETHINDRONE ACETATE tablet (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.