Follow-Up Estradiol Levels Based on Regimen Formulation With Guideline-Concordant Gender-Affirming Hormone Therapy

Area of Science:

• Endocrinology
• Gender-affirming care

Background:

• Endocrine Society guidelines for feminizing gender-affirming hormone therapy (GAHT) dosing have not changed since 2009.
• Guidelines recommend maintaining serum estradiol levels between 100-200 pg/mL.
• It remains unclear if current guideline-concordant dosing achieves recommended levels across different estradiol formulations.

Purpose of the Study:

• To determine the frequency of guideline-recommended estradiol levels with guideline-concordant dosing across oral, parenteral, and transdermal estradiol formulations.
• To evaluate the effectiveness of current GAHT dosing recommendations.

Main Methods:

• Retrospective chart review of transgender and nonbinary patients on estradiol-based GAHT from October 2015 to March 2023.
• Analysis of demographics, GAHT regimens, and serum estradiol levels.
• Descriptive statistical analysis of formulation-specific outcomes.

Main Results:

• Oral estradiol (2.8 mg/day) resulted in a mean level of 168 pg/mL, with 32% subtherapeutic and 14% supratherapeutic levels.
• Parenteral estradiol (5.8 mg/week) showed a mean midpoint level of 342 pg/mL, with 91% supratherapeutic levels.
• Transdermal estradiol (0.09 mg/day) yielded a mean level of 81.5 pg/mL, with 70% subtherapeutic levels.

Conclusions:

• Guideline-concordant parenteral estradiol dosing commonly leads to supratherapeutic levels.
• Guideline-concordant transdermal estradiol dosing frequently results in subtherapeutic levels.
• Current dosing guidelines may require revision for parenteral and transdermal estradiol formulations.