6480 Variability in Breast Development in Response to Exogenous Estrogen in Girls

Abstract

Abstract Disclosure: T.M. Kurman: None. E.A. Eugster: None. Intro: Adolescents requiring treatment with exogenous estrogen (E2) include girls with primary and secondary hypogonadism and transfeminine youth. While 17B-estradiol is standard of care, the starting dose and escalation schedule are individualized. To what degree the response to E2 as assessed by breast Tanner stage is correlated with the dose is unknown. Similarly, whether the response to E2 varies depending on the underlying diagnosis has not been systematically analyzed. We aimed to investigate relationships between diagnosis, E2 dose, and breast Tanner staging in adolescent girls. Methods: We conducted a chart review of girls treated with E2 followed at our Pediatric Endocrine clinic between 2008-2022. Inclusion criteria included girls who were prepubertal at baseline and on a single increment of a 25 mcg E2 patch changed 2X/week from initiation of treatment to the first follow up visit. Only transgender girls being treated with a GnRH analog were included. Within each group of patients on the same starting dose, a Kruskal-Wallis test was conducted to evaluate differences in Tanner stage between diagnostic groups. Spearman’s correlation was used to evaluate the relationship between starting dose and Tanner stage. Finally, we evaluated differences within the Turner syndrome (TS) group for girls with monosomy X vs a mosaic karyotype. Results: Of 1,899 medical records, 70 eligible patients were identified. Of these, 33 (47.2%) had TS, 17 (24.3%) had primary ovarian insufficiency (POI), 15 (21.4%) had hypogonadotropic hypogonadism (HH), and 5 (7.1%) were transgender (TG). Twenty-three (32.9%) started on 1/4 patch (6.25 mcg), 29 (41.4%) on 1/2 patch (12.5 mcg) and 18 (25.7%) on a full patch (25 mcg). Girls on other regimens (e.g., 1/8 patch worn only at night) were excluded from analysis. The first f/u visit occurred at a median of 6 months (range 3-12 months). All TG girls were started on 25 mcg E2, which was significantly different compared to the other groups (p=0.002, p=0.005, and p=0.005 for TS, POI, and HH respectively). Breast Tanner stage at the first f/u visit ranged from 1-4 with no significant difference within each dose group based on diagnosis. However, a significant correlation between E2 dose and breast Tanner stage at f/u was seen in girls with HH (r=0.601, p=0.018). No effect of karyotype (monosomy X vs mosaic) on response to E2 in girls with TS was seen. Conclusion: There was striking variability in the starting dose of E2 in the vast majority of patients, highlighting the lack of standardization in clinical management. Interestingly, we found significant individual variability in terms of breast development in response to the initial dose of E2, regardless of diagnosis. Factors responsible for the unpredictable nature of the response to exogenous E2 are unexplored. Our findings provide important and novel prognostic information for patients and providers. Presentation: 6/1/2024