Estradiol Patch Dosing for Gender Affirming Therapy
For gender affirming therapy, a 100 μg/24 hours transdermal estradiol patch is equivalent to 2 mg of oral estradiol daily. 1
Transdermal vs. Oral Estradiol Administration
Transdermal estradiol offers several advantages over oral administration:
- Avoids first-pass hepatic metabolism
- Provides more physiological estradiol:estrone ratio
- Lower cardiovascular risk profile
- Reduced rates of venous thromboembolism and stroke 1
Pharmacokinetic studies have demonstrated that oral estradiol administration results in significantly higher and more fluctuating serum levels compared to transdermal delivery:
- Oral estradiol (2 mg daily) produces average estradiol concentrations approximately 12 times higher than transdermal delivery (50 μg/24 hours) 2
- Oral administration creates large pulses of estradiol with high fluctuation (fluctuation = 3.68) 2
- Transdermal delivery maintains more constant therapeutic levels (fluctuation = 0.65) 2
Dosing Guidelines for Transdermal Estradiol
When initiating transdermal estradiol for gender affirming therapy:
- Start with 100 μg/24 hours patch (equivalent to 2 mg oral estradiol)
- Apply patches according to manufacturer instructions (typically once or twice weekly)
- Patches are available in different dosages, with standard dosages for transgender women typically ranging from 100-200 μg/24 hours 1
Application Considerations
- Transdermal patches should be applied to clean, dry, hairless skin
- Rotate application sites to prevent skin irritation
- For twice-weekly patches, apply every 3-4 days
- For once-weekly patches, apply every 7 days 3
Monitoring and Dose Adjustments
- Check estradiol levels after 3 months of therapy
- Target estradiol levels in the physiologic female range (typically 100-200 pg/mL)
- Monitor for clinical effects and side effects
- Adjust dosage based on serum levels and clinical response
Important Caveats
- Transdermal estradiol produces lower estrone levels compared to sublingual administration, which may be beneficial for cardiovascular risk profile 4
- Injectable estradiol preparations may result in supraphysiologic levels across the injection cycle and should be started at lower doses than current guidelines suggest 5
- Patients with liver dysfunction may particularly benefit from transdermal administration due to bypass of first-pass metabolism 1
- Contraindications include history of hormonally mediated cancers, active thromboembolic disorders, and arterial thrombotic disease 1
Clinical Application
For most transgender women and transfeminine individuals seeking gender affirming hormone therapy, a 100 μg/24 hours transdermal estradiol patch is an appropriate starting dose when transitioning from 2 mg oral estradiol. This dosage maintains therapeutic hormone levels while potentially reducing cardiovascular risks associated with oral administration.