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# Estrogens

Female sex hormones used for menopausal symptoms, to prevent bone loss and to replace missing ovarian hormones, at the lowest dose for the shortest time.

Updated Nov 1, 2026

## What they are

Estradiol, conjugated estrogens and related compounds that act on estrogen receptors. They relieve hot flushes and vaginal atrophy after menopause, prevent postmenopausal osteoporosis when other drugs are unsuitable, and replace hormones in hypogonadism or premature ovarian insufficiency. Ethinylestradiol in contraceptives belongs to the same family. A woman with a uterus also takes a progestogen.

## Mechanism of action

Estrogens cross the cell membrane and bind estrogen receptors α and β, nuclear receptors that switch genes on or off. They maintain the vaginal and urinary epithelium, stabilise temperature control, slow bone resorption, change liver protein synthesis (more clotting factors, SHBG and thyroid-binding globulin) and, through negative feedback, lower LH and FSH. Unopposed, they stimulate endometrial and breast tissue.

Target: Estrogen receptors α and β (ESR1, ESR2), nuclear receptors

## Key points

- Unopposed estrogen causes endometrial hyperplasia and cancer; a woman with a uterus also receives a progestogen.
- The Women's Health Initiative linked menopausal hormones to stroke, venous thromboembolism and probable dementia, and estrogen plus progestin also to breast cancer and heart attack; they are not used to prevent heart disease or dementia.
- Contraindications: undiagnosed genital bleeding, breast or estrogen-dependent cancer, past or present thrombosis, stroke or heart attack, liver disease, thrombophilias.
- Oral estrogen raises thyroid-binding globulin, so women on levothyroxine may need more.
- Lowest effective dose for the shortest time; vaginal products first for isolated vaginal atrophy.

## Drugs in this class

- [**Estradiol** The main human estrogen, given by mouth, skin or vagina for menopausal symptoms and estrogen deficiency, with a… Estrogen receptor α (ERα), a nuclear receptor](https://durgical.com/en/pharmacology/estradiol/)
- [**Conjugated estrogens** A mixture of estrogen sulfates (estrone, equilin and others) for menopausal symptoms; with medroxyprogesterone, the… Estrogen receptors α and β, nuclear receptors](https://durgical.com/en/pharmacology/conjugated-estrogens/)

## Others in the class

- Ethinylestradiol
- Estriol
- Estetrol
- Esterified estrogens

## Test yourself

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

## Which cancer does unopposed estrogen cause, and how is it prevented?

Endometrial cancer (after hyperplasia); adding a progestogen in women with a uterus prevents it.

## Why might a woman on levothyroxine need a higher dose after starting oral estrogen?

Estrogen raises thyroid-binding globulin, so more hormone is bound and less is free.

## What are three contraindications to systemic estrogen therapy?

Any three of: undiagnosed genital bleeding, breast or estrogen-dependent cancer, active or past DVT/PE, stroke or heart attack, liver disease, thrombophilia, pregnancy.

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

Sources: [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); [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).

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Representative model, for educational purposes only.

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