A Mouse Model to Investigate the Impact of Gender Affirming Hormone Therapy with Estradiol on Reproduction

Abstract Gender‐affirming hormone therapy (GAHT) can help transgender and/or gender diverse (TGD) individuals achieve emobidment goals that align with their transition needs. Clinical evidence from estradiol (E)‐GAHT patients indicate widespread changes in tissues sensitive to E and testosterone (T), particularly in the reproductive system. Notably, E‐GAHTs effects on hormones and reproduction vary greatly between patients. With the goal of informing clinical research and practice for TGD individuals taking E, this study examines intact male mice implanted with capsules containing one of three different E doses (low 1.25 mg; mid 2.5 mg; high 5 mg), or a blank control capsule. All E‐GAHT doses suppress T and follicle stimulating hormone levels while elevating E levels. Only the high E‐GAHT dose significantly supresses luteinizing hormone levels. All E‐GAHT doses affect epididymis tubule size similarly while seminiferous tubule morphology and bladder weight changes are dose‐dependent. E‐GAHT does not alter the presence of mature sperm, though E‐exposed sperm have altered motility. These data represent the first evidence that mouse models offer an effective tool to understand E‐GAHTs impact on reproductive health and the dose‐dependent effects of this model permit examinations of diverse patient outcomes.