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

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.

A synopsis of global frontiers in fertility preservation

Since 2007, the Oncofertility Consortium Annual Conference has brought together a diverse network of individuals from a wide range of backgrounds and professional levels to disseminate emerging basic and clinical research findings in fertility preservation. This network also developed enduring educational materials to accelerate the pace and quality of field-wide scientific communication. Between 2007 and 2019, the Oncofertility Consortium Annual Conference was held as an in-person event in Chicago, IL. The conference attracted approximately 250 attendees each year representing 20 countries around the world. In 2020, however, the COVID-19 pandemic disrupted this paradigm and precluded an in-person meeting. Nevertheless, there remained an undeniable demand for the oncofertility community to convene. To maintain the momentum of the field, the Oncofertility Consortium hosted a day-long virtual meeting on March 5, 2021, with the theme of "Oncofertility Around the Globe" to highlight the diversity of clinical care and translational research that is ongoing around the world in this discipline. This virtual meeting was hosted using the vFairs ® conference platform and allowed over 700 people to participate, many of whom were first-time conference attendees. The agenda featured concurrent sessions from presenters in six continents which provided attendees a complete overview of the field and furthered our mission to create a global community of oncofertility practice. This paper provides a synopsis of talks delivered at this event and highlights the new advances and frontiers in the fields of oncofertility and fertility preservation around the globe from clinical practice and patient-centered efforts to translational research.

A mouse model to investigate the impact of testosterone therapy on reproduction in transgender men

STUDY QUESTION

Can mice serve as a translational model to investigate the reproductive effects of testosterone (T) therapy commonly used by transgender men?

SUMMARY ANSWER

T enanthate subcutaneous injections at 0.45 mg twice weekly can be used in the postpubertal C57BL/6N female mouse to investigate the reproductive effects of T therapy given to transgender men.

WHAT IS KNOWN ALREADY

Most models of T treatment in female mice involve prenatal or prepubertal administration, which are not applicable to transgender men who often begin T therapy after puberty. Studies that have looked at the impact of postpubertal T treatment in female mice have generally not investigated reproductive outcomes.

STUDY DESIGN, SIZE, DURATION

A total of 20 C57BL/6N female mice were used for this study. Study groups (n = 5 mice per group) included sesame oil vehicle controls and three doses of T enanthate (0.225, 0.45 and 0.90 mg). Mice were injected subcutaneously twice weekly for 6 weeks.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Daily vaginal cytology was performed prior to initiation of treatment to confirm that all mice were cycling. At 8-9 weeks of age, therapy with subcutaneous T enanthate (0.225, 0.45 or 0.90 mg) or the vehicle control was begun. T therapy continued for 6 weeks, at which point mice were sacrificed and compared to control mice sacrificed during diestrus/metestrus. Data collected included daily vaginal cytology, weekly and terminal reproductive hormone levels, terminal body/organ weights/measurements, ovarian follicular distribution/morphology and corpora lutea counts.

MAIN RESULTS AND THE ROLE OF CHANCE

Of the mice treated with 0.90 mg T enanthate, two of five mice experienced vaginal prolapse, so this group was excluded from further analysis. T enanthate administration twice weekly at 0.225 or 0.45 mg resulted in cessation of cyclicity and persistent diestrus. One of five mice at the 0.225-mg dose resumed cycling after 2.5 weeks of T therapy. As compared to controls, T-treated mice had sustained elevated T levels and luteinizing hormone (LH) suppression in the terminal blood sample. T-treated mice demonstrated increases in clitoral area and atretic cyst-like late antral follicles (0.45 mg only) as compared to controls. No reduction in primordial, primary, secondary or total antral follicle counts was detected in T-treated mice as compared to controls, and T-treated mice demonstrated an absence of corpora lutea.

LIMITATIONS, REASONS FOR CAUTION

Mouse models can provide us with relevant key findings for further exploration but may not perfectly mirror human reproductive physiology.

WIDER IMPLICATIONS OF THE FINDINGS

To our knowledge, this report describes the first mouse model mimicking T therapy given to transgender men that facilitates analysis of reproductive changes. This model allows for future studies comparing duration and reversibility of T-induced changes, on the reproductive and other systems. It supports a role for T therapy in suppressing the hypothalamic-pituitary-gonadal axis in adult female mice as evidenced by LH suppression, persistent diestrus and absence of corpora lutea. The increase in atretic cyst-like late antral follicles aligns with the increased prevalence of polycystic ovary morphology seen in case series of transgender men treated with T therapy. The results also suggest that T therapy does not deplete the ovarian reserve.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the American Society for Reproductive Medicine/Society of Reproductive Endocrinology and Infertility Grant and NIH R01-HD098233 to M.B.M. and University of Michigan Office of Research funding (U058227). H.M.K. was supported by the Career Training in Reproductive Biology and Medical Scientist Training Program T32 NIH Training Grants (T32-HD079342, T32-GM07863) as well as the Cellular and Molecular Biology Program. The University of Virginia Center for Research in Reproduction Ligand Assay and Analysis Core is supported by the Eunice Kennedy Shriver NICHD/NIH (NCTRI) Grant P50-HD28934. E.E.M. consults for Allergan. No other authors have competing interests.