SAT404 Achieving Both Target Testosterone And Target Estradiol Levels May Not Be Practical In All Trans Feminine Users Of Estradiol - Which To Prioritize?

Disclosure: D. Slack: None. N. Krishnamurthy: None. F. Contreras-Castro: None. J.D. Safer: None. For feminizing gender affirming hormone therapy (GAHT), the Endocrine Society and WPATH SOC 8 suggest targeting testosterone (T) levels below 50 ng/dL and estradiol (E2) levels in the range of 100-200 pg/mL. However, studies have shown variability in correlation between E2 and T levels. We sought to determine how often medically treated trans feminine individuals on estradiol needed to achieve the E2 goal in order to achieve the T goal. We conducted a chart review of patients actively engaged in GAHT in the Mount Sinai Health System. Included in our analysis were all individuals who had active prescriptions for feminizing GAHT with both T and E2 levels recorded (n = 1,195). We divided the patients between those with T levels at goal < 50 ng/dL (n = 737) and those with T >= 50 ng/dL (n = 458). The mean E2 level was higher in the T < 50 ng/dL group compared to the T >= 50 ng/dL group (292 vs 101 pg/mL; p <.001). We then compared the proportions of individuals with E2 above target > 200 pg/mL (n = 279), at target 100 - 200 pg/mL (n = 296), and below target < 100 pg/mL (n = 620) in the two groups. The T < 50 ng/dL group contained a higher proportion of individuals with E2 > 200 pg/mL (33.5% vs 7%; p < .001) and E2 100 - 200 pg/mL (30% vs 16.4%; p < .001), along with a lower proportion of individuals with E2 < 100 pg/mL (36.5% vs 76.6%; p <.001). Our results indicate that those with E2 > 100 pg/mL were more likely to have a T < 50 ng/dL, but approximately one-third of the T < 50 ng/dL group was made up of individuals with E2 < 100 pg/mL. That is, nearly half (43%) of all individuals with E2 < 100 pg/mL had T levels at goal < 50 ng/dL. Would more exogenous estradiol add benefit for these people or would it simply increase VTE risk for no reason? Also, while the majority of individuals with E2 100 - 200 pg/mL (74.7%) and E2 > 200 pg/mL (88.5%) had a T < 50 ng/dL, there were still many who did not. Our findings suggest that not all trans feminine individuals on feminizing hormone therapy will achieve target levels of both T < 50 ng/dL and E2 100-200 pg/mL. It may be reasonable to expand the target T and E2 ranges to allow for more flexibility or it may be practical to focus on one goal, rather than both. Further stratification by spironolactone (or other adjunct agent) use, estradiol route of administration, and other testing (e.g. LH and FSH levels) may inform the strategy. Presentation: Saturday, June 17, 2023