Estradiol
Estradiol is the principal natural estrogen in women, used as bioidentical hormone replacement therapy for menopausal symptoms and prevention of osteoporosis. It is available as oral tablets, transdermal patches and gels, vaginal creams, rings and tablets, allowing dose and route to be tailored.
- Chemical formula
- C18H24O2
- CAS number
- 50-28-2
- ATC code
- G03CA03
- Molecular weight
- 272.39 g/mol
- Drug class
- Estrogen / hormone replacement
- Also known as
- Estrace, Vivelle-Dot, Climara, Estraderm, Estrofem
What is it?
Estradiol is the most biologically active form of natural estrogen in premenopausal women, and the most prescribed estrogen for menopausal hormone replacement therapy (HRT) and gender-affirming care. Marketed as Estrace (oral tablets and vaginal cream), Vivelle-Dot, Climara, Estraderm and Minivelle (transdermal patches), Estring and Femring (vaginal rings) and Estrogel/Divigel/EstroGel (transdermal gels). Authorised generic estradiol products are widely available across all formulations.
Mechanism of action
Estradiol binds to estrogen receptors (ERα and ERβ) in target tissues and modulates gene expression for vascular, bone, reproductive, central nervous system and metabolic functions. In menopausal HRT, it relieves vasomotor symptoms (hot flashes, night sweats), urogenital atrophy and reduces bone resorption, slowing post-menopausal osteoporosis. Adequate replacement restores physiological estrogen signalling without supraphysiological exposure.
Pharmacokinetics
Oral estradiol is well absorbed but undergoes extensive first-pass metabolism, producing high estrone levels and increased hepatic protein synthesis (clotting factors, SHBG). Transdermal formulations bypass first pass, give more physiological estradiol/estrone ratios and lower clotting risk. Half-life of free estradiol is ~13 hours; transdermal patches deliver steady release over 3.5–7 days. Hepatic conjugation and CYP3A4 metabolism dominate clearance.
Indications
Estradiol is approved for moderate-to-severe vasomotor menopausal symptoms, urogenital atrophy, prevention of post-menopausal osteoporosis (when other agents are unsuitable), hypogonadism in women, and as part of feminising hormone therapy in transgender women. Women with an intact uterus require concomitant progesterone or progestin to prevent endometrial hyperplasia. According to current menopause guidelines, transdermal routes are preferred when clotting risk is a concern.
Safety profile
Common adverse effects include breast tenderness, nausea, headache, breakthrough bleeding and fluid retention. Class concerns include venous thromboembolism, stroke, gallbladder disease and a small increased risk of breast cancer with long-term combined HRT. Transdermal estradiol carries lower thrombotic risk than oral, making it preferred in patients with elevated clotting risk. According to current evidence, the benefits of HRT outweigh risks for most women under 60 with significant menopausal symptoms.
Products containing this ingredient
Frequently asked questions
Is transdermal estradiol safer than oral? ▾
Transdermal estradiol carries lower venous thromboembolism and stroke risk than oral because it bypasses first-pass hepatic metabolism and produces more physiological estradiol/estrone ratios. According to current menopause guidelines, transdermal routes are preferred for women with elevated clotting risk, migraine, hypertension, hypertriglyceridaemia or gallbladder disease.
Why do I need progesterone with estradiol? ▾
Unopposed estrogen stimulates the endometrium and increases the risk of hyperplasia and endometrial cancer in women with an intact uterus. Concomitant progesterone or progestin protects the endometrium. According to current menopause guidelines, women without a uterus do not require a progestogen, while those with a uterus need either continuous or cyclic progestogen depending on the regimen.
How long can estradiol HRT be continued? ▾
Current guidelines no longer recommend a fixed maximum duration. Treatment is continued for as long as benefits outweigh risks for the individual; many women take HRT for 5–10 years for symptom control. According to current evidence, the safety profile is most favourable for women starting under 60 or within 10 years of menopause.
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.