8309 Injectable Estradiol Dosing Regimens; A Retrospective Review of Hormone Therapy for Gender-Diverse Adults Assigned Male at Birth

Abstract

Abstract Disclosure: M. Kanin: None. M. Slack: None. R. Patel: None. K. Chen: None. N. Jackson: None. K. Williams: None. S. Grock: None. Introduction: Many gender incongruent individuals assigned male at birth (AMAB) seek hormone therapy to achieve physical and emotional changes. Hormone therapy typically includes estradiol, with or without an anti-androgen. However, limited data with relatively weak justifications support the currently recommended regimens. In particular, dosing schedules for injectable estradiol can vary considerably. UCSF guidelines recommend initiating estradiol valerate at 5 mg parenterally weekly or estradiol cypionate 2 mg weekly. Endocrine Society Guidelines recommend estradiol valerate or cypionate parenterally 5-30 mg every 2 weeks or 2-10 mg weekly. Our clinical observations led to the concern that current guideline-based dosing of injectable estradiol can result in supratherapeutic estradiol levels. Thus, we designed a retrospective cohort study to evaluate injectable estradiol dosing requirements for gender diverse individuals at our institution. Hypothesis: We hypothesize that low dose estradiol injections can lead to therapeutic estradiol levels (100-200 pg/mL) and suppressed testosterone (<50 ng/dL). Design: We performed a retrospective cohort study of gender diverse individuals AMAB aged 18-89 who were newly prescribed injectable estradiol by a single clinic from January 2017 to March 2023. Exclusion criteria included history of orchiectomy or estradiol use within the previous six months. Patients were identified using structured query language to extract data from our institution’s electronic health record system. A total 33 patients were identified, 29 of whom were eligible for inclusion. Data was collected for 15 months after estradiol initiation. Results: All individuals were prescribed estradiol valerate except for 1 who was prescribed estradiol cypionate. Estradiol dose ranged from 2.5 to 10 mg weekly and an average initial dose of 4.26 mg weekly. Mean initial estradiol level obtained while on treatment for at least 30 days was 349.8 pg/mL, which is supratherapeutic. Mean initial testosterone level was 25.3 ng/dL, which is suppressed. Mean estradiol dose at completion of data collection was 3.68 mg with a mean final estradiol level of 245.2 pg/mL. Testosterone levels reached less than 50 ng/dL for everyone in the sample with a mean final testosterone of 23.3ng/dL despite significant reductions in estradiol dose (change=-0.58 mg per week, p=0.001) Conclusion: Our study demonstrates lower dosages of estradiol can be used to achieve therapeutic estradiol levels in gender incongruent patients seeking estrogen therapy. Using lower dosages can avoid supratherapeutic estradiol levels and the associated risks. Further prospective studies are needed with the aim to reevaluate current guideline dosing recommendations for injectable estradiol. Presentation: 6/2/2024