Sean Iwamoto

Research Description

Dr. Iwamoto is an Assistant Professor at the University of Colorado School of Medicine and Rocky Mountain Regional VA Medical Center and co-founder of the UCHealth Integrated Transgender Program. With interests in transgender health, overweight/obesity and aging, Dr. Iwamoto studies the effects of gender-affirming hormones on vascular health and metabolic parameters in older versus younger adult transgender women (on estrogen) and transgender men (on testosterone) compared to age group-matched non-transgender women and men. Dr. Iwamoto’s Ludeman Center-, Colorado Nutrition Obesity Research Center (NORC)-, and VA Geriatrics Research, Education, and Clinical Center (GRECC)-supported research will help answer questions about how estrogen and testosterone impact cardiovascular disease risk among transgender women and men and eventually promote further study of ways to intervene, treat, and prevent cardiovascular disease in these people and the general population.

BIRCWH project title: The effects of orchiectomy and age on vascular and metabolic health in older versus younger transgender women

Current research focus: MY BIRCWH K12 Research Training Project (co-primary mentors: Kerrie Moreau, PhD, and Marc-Andre Cornier, MD) prospectively examines the effects of age and orchiectomy, a type of gender-affirming surgery to remove testes and lower testosterone levels, on vascular and metabolic health in older versus younger transgender women who have been taking estrogen (usually with an antiandrogen). Our previous research has focused on cross-sectional vascular and metabolic outcomes in older versus younger transgender women and transgender men taking chronic gender-affirming hormone therapy. I also study prospective changes to biomarkers of coagulation and thrombosis after transgender women initiate estrogen. Other related research includes identifying and utilizing transgender patients' perspectives of healthcare delivery (both gender-affirming and otherwise) to improve experiences and outcomes. 

How Dr. Iwamoto became interested in this work: During endocrinology fellowship, I did obesity research related to primary care weight loss interventions and appetite regulation in older adults. At the same time, I began seeing an increasing number of transgender patients in clinic and co-founded the UCHealth Integrated Transgender Program. I was also driven to develop and conduct pilot studies that intersect transgender health, obesity, and aging. After joining CUSOM faculty, I had the opportunity through an ACE/AACE travel grant to visit international endocrine leaders in transgender research and medicine (in the Netherlands and Belgium). I learned first-hand about the international collaboration, European Network for the Investigation of Gender Incongruence (ENIGI), a clinical and research cohort from whom data have been used to influence transgender health guidelines. My collaborations with national and international leaders continue to inspire me to focus on this niche research area with broad implications for health in adults across age, sex, and gender identity spectra.

The clinical significance of this research: The research supported by the BIRCWH K12 will hopefully shed light on potential vascular and metabolic mechanisms for the reported increased cardiovascular disease risk in transgender women compared to transgender men and cisgender adults. Ultimately, my studies will inform future research into whether the trajectory of vascular aging and cardiometabolic risk is worse or more impaired in transgender women compared to transgender men, older transgender adults compared to younger transgender adults, and age group-matched transgender adults versus cisgender adults.

Relevance of this work to sex/gender differences research: Better understanding acute and chronic effects of gender-affirming hormone therapy and gender-affirming surgery in older and younger transgender adults will increase our confidence that these life-saving treatments provide maximal physical and mental health benefits and minimal risks, particularly related to cardiovascular disease, through the adult lifespan.