[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Estrogens](https://durgical.com/en/pharmacology/classes/estrogens/) › Conjugated estrogens

# 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](https://durgical.com/en/pharmacology/classes/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.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Clinical What the labels mean

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## Mechanism of action

◎**Estrogen receptors α and β, nuclear receptors**Conjugated 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](https://www.rcsb.org/structure/1ERE) · Drag to rotate · pinch to zoom

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 →](https://durgical.com/en/conditions/menopause-and-climacteric-syndrome/)
- Vaginal atrophy of menopause [Genitourinary syndrome of menopause (atrophic vaginitis) →](https://durgical.com/en/conditions/genitourinary-syndrome-of-menopause/)
- Prevention of postmenopausal osteoporosis when other drugs are unsuitable [Osteoporosis →](https://durgical.com/en/conditions/osteoporosis/)
- Hypoestrogenism in young women with ovarian failure or hypogonadism [Primary ovarian insufficiency →](https://durgical.com/en/conditions/primary-ovarian-insufficiency/)

## Adverse effects

### Common

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

### Serious (rare, important)

- Endometrial cancer without a progestogen
- With medroxyprogesterone: higher rates of venous thrombosis, stroke, heart attack and invasive breast cancer in the WHI
- Probable dementia in women aged 65 or older
- Gallbladder disease
- Visual loss from retinal thrombosis

## 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

## Memory aid

Conjugated estrogens = «the WHI pill»: with medroxyprogesterone, the trial that taught clots, strokes and breast cancer.

## 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.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/conjugated-estrogens/)

[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## What the labels mean

**Pregnancy: avoid**
Not used in pregnancy.

## Connections

## Related drugs 3

- [Estradiol](https://durgical.com/en/pharmacology/estradiol/)
- [Medroxyprogesterone acetate](https://durgical.com/en/pharmacology/medroxyprogesterone-acetate/)
- [Raloxifene](https://durgical.com/en/pharmacology/raloxifene/)

## Related conditions 4

- [Menopause and climacteric syndrome](https://durgical.com/en/conditions/menopause-and-climacteric-syndrome/)
- [Genitourinary syndrome of menopause (atrophic vaginitis)](https://durgical.com/en/conditions/genitourinary-syndrome-of-menopause/)
- [Osteoporosis](https://durgical.com/en/conditions/osteoporosis/)
- [Primary ovarian insufficiency](https://durgical.com/en/conditions/primary-ovarian-insufficiency/)

[← Back to the class: Estrogens](https://durgical.com/en/pharmacology/classes/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](https://medlineplus.gov/druginfo/meds/a682922.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [DailyMed - MEDROXYPROGESTERONE ACETATE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=9eb200b0-db96-4a51-87ea-04db862978c8) (DailyMed (U.S. National Library of Medicine), 2026); [DailyMed - ESTRADIOL AND NORETHINDRONE ACETATE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=50c786d6-91bd-4eea-9455-ff2abc08372f) (DailyMed (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=G03CA57) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

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