Abstract

Understanding the impacts of cross-sex hormone therapy is crucial as gender-affirming hormone therapies are on the rise. However, little research exists on the impact cross sex hormone therapy (HT) may have on other systems of the body, or the general impact of changing the hormonal environment from an individuals gonadal sex. Multiple systems in the body are impacted by hormones or have some sexual dimorphism, including the immune system which has been seen to be impacted by estrogen and testosterone. This research aims to begin filling the gap in cross sex hormone therapy research by investigating the impact of cross sex hormone therapy on the immune system of both males and females. Using Sprague Dawley rats, cross sex hormone therapy, including testosterone in females and 17-β-estradiol plus a tesosterone blocker (cypertone acetate) in males, was administered for five weeks. Neutrophil:lymphocyte ratio (NLR) at baseline and following an acute stressor, and IFN-gamma were both tested to investigate the immune system changes. Additionally, restraint testing was done to investigate how the immune system reacted differently to stress with cross sex hormone therapy. NLR testing revealed that testosterone significantly changed the immune system of female rats receiving hormone therapy in both stress and non-stress conditions (p=< 0.001). No significant changes were seen in NLR of males receiving hormone therapy (p=0.158). IFN-gamma testing did not produce any interoperable results. The NLR testing suggests increased testosterone affects NLR in females, though a combination of decreased testosterone action and increased estrogen in males did not alter NLR. These findings suggest the possibility of testosterone exposure during development leads to an immune system that is less likely to be altered by hormones later in life. Future research is necessary to better understand how cross sex hormone therapy impacts the function of immune cells.

Advisor

Lynn, Sharon

Department

Biology

Disciplines

Biology | Endocrinology | Gender and Sexuality | Hormones, Hormone Substitutes, and Hormone Antagonists | Medical Immunology | Medical Pharmacology | Other Immunology and Infectious Disease

Keywords

testosterone, estrogen, hormone therapy, immunology, endocrinology, transgender, rats, sprague dawley rats

Publication Date

2025

Degree Granted

Bachelor of Arts

Document Type

Senior Independent Study Thesis

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Available for download on Monday, July 22, 2030

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© Copyright 2025 Trystine Chellis