Genital Microbiome Research for Transgender Populations

June 28, 2023

Changes in genital microbiota likely have substantial impacts on health.
Changes in genital microbiota likely have substantial impacts on health.
Source: iStock

For most patients, getting to the bottom of bothersome vaginal symptoms, like malodor or itching, is as easy as sending off a vaginal swab for culture. However, many transgender and gender-diverse people recognize the onset of symptoms as the start of numerous clinic appointments, inconclusive culture results and treatment based on research conducted in people with different anatomies, gender identities and hormone levels (i.e., cisgender people). This is because health research—including microbiology research—has historically and systemically excluded transgender and gender-diverse people. Microbiology research that is inclusive of transgender populations is essential to address this health disparity.

Key Terminology

  • Transgender/Gender-Diverse: A person whose gender identity does not align with that associated with their sex assigned at birth. This can include identities such as transmasculine, transfeminine, non-binary, two-spirit, genderqueer, agender and many others.
  • Transmasculine: A term to describe a person assigned female at birth who identifies as male, man/boy, masculine, non-binary and/or an identity other than a woman/girl.
  • Transfeminine: A term to describe a person assigned male at birth who identifies as female, woman/girl, feminine, non-binary and/or an identity other than a man/boy.
  • Cisgender: A person whose gender identity aligns with that associated with their sex assigned at birth.
  • Gender-affirming Medical Care: The process through which individuals alter their primary and/or secondary sex characteristics to align with their sense of gender identity through medical treatment.
  • Vaginoplasty: The surgical construction of a vaginal cavity. Vaginoplasty is a gender-affirming surgery that is undergone by some transfeminine individuals.
  • Neovagina: A term used to refer to the vagina that has been surgically constructed through vaginoplasty.
  • Natal vagina: A term used to refer to the vagina that was not surgically created (i.e., home-grown vagina).

Note: We recognize that individuals use a variety of terms to refer to themselves and their anatomies. In this article, we use the terms listed above for clarity and consistency. We strongly encourage researchers, clinicians and other allies to learn and employ the terms individuals use to identify themselves.

Gender-Affirming Care Is Life-Saving Medical Treatment

Gender-affirming medical care, including, but not limited to, hormone therapy and gender-affirming surgeries, is a medically necessary, life-saving treatment for some transgender and gender-diverse individuals. Among transgender youth, gender-affirming care has been shown to reduce suicidality by over 73% and reduce moderate and severe depression by over 60%.

For some transfeminine people, gender-affirming care may involve the surgical creation of a vulva and/or vaginal canal (neovagina) and may also involve the use of hormone therapy, such as estrogen and/or progestin therapy. Though vaginoplasty and other feminizing surgeries have positive effects on quality of life, with high satisfaction and very low regret rates (1-2%), individuals sometimes experience bothersome neovaginal symptoms. Commonly reported symptoms include discharge and malodor, which are suggestive of microbial dysbiosis. However, for these patients, their unique genital microbiome means that vaginal swabs sent for culture often return inconclusive. This is because tests for vaginal dysbiosis, particularly bacterial vaginosis, rely on Nugent scoring, a process in which a vaginal swab is rolled onto a glass slide, Gram stained and examined under a microscope to identify the specific types of bacteria present. Accuracy of Nugent scoring relies on the understanding that some bacteria (mainly lactobacilli) are health-promoting in the vagina, and others (mainly gram-negative species) are not. However, these assumptions may not hold for the neovagina, where an abundance of lactobacilli is rare, even in seemingly healthy patients. Thus, patients and clinicians are left without evidence-based guidelines for diagnosing and treating neovaginal symptoms.

For many transmasculine individuals, gender-affirming medical care involves testosterone hormone therapy (T-HRT), while genital surgery is relatively uncommon. Individuals receiving T-HRT also commonly experience bothersome symptoms, including vaginal dryness, itching and pain with sexual activity. Currently, topical estrogen is typically prescribed to treat these symptoms. However, the effectiveness of treatment is unknown among this population. Additionally, topical estrogen therapy can potentially cause distressing symptoms of gender dysphoria and individuals may have concerns about potential effects on systemic hormones and T-HRT.

These symptoms experienced by transfeminine and transmasculine people suggest disrupted microenvironments, but a lack of focused research among these populations makes the nature of that disruption unclear.

How Gender-Affirming Medical Care Changes the Genital Microbiome

The genital microbiome is an important determinant of health. In cisgender women, disruptions in the vaginal microbiome are associated with gynecological symptoms and increased rates of preterm birth, pelvic inflammatory disease and STI acquisition, including HIV. Similarly, the composition of the penile microbiome of cisgender men has been shown to impact HIV susceptibility. Hormones and tissue structure shape the genital microbiome, meaning both hormone therapy and gender-affirming surgeries typically cause microbial changes. As in cisgender people, changes in genital microbiota likely have substantial impacts on the health of transgender people.

This phenomenon is evident in transmasculine individuals on T-HRT. Estrogen plays a key role in shaping the vaginal microenvironment by maintaining tissue thickness and promoting glycogen production to support health-promoting lactobacilli bacteria. In cisgender women, these lactobacilli defend against vaginal infections by producing hydrogen peroxide and lactic acid, making the vagina too acidic for colonization by most pathogenic bacteria. When estrogen levels decrease in cisgender women during menopause, the vaginal tissue becomes fragile, and there are less lactobacilli in the vagina. Similar to menopause, T-HRT causes a decrease in estrogen levels, which are likely associated with a similar decrease in lactobacilli in transmasculine individuals on T-HRT, as what is seen among post-menopausal cisgender women. A small-scale study of the testosterone-exposed vaginal microbiome seems to support this theory. However, the effects of testosterone hormone therapy on the vaginal microbiome beyond those associated with estrogen suppression remain unclear. These findings suggest that transmasculine individuals receiving T-HRT rely on different defenses against infection, and further research is needed to understand relationships between microbiome and health in this population.

Gender-affirming surgeries may also create a unique microbiome. Penile inversion vaginoplasty, involving the use of penile and scrotal tissue to create a vulva/vagina, is the gold standard vaginoplasty technique. These skin-like tissues make far less glycogen than the natal vagina, so the bacteria that live in the neovagina are likely different from bacteria commonly found in the natal vagina. Preliminary studies of the neovaginal microbiome suggest that the neovagina hosts a wide variety of bacterial species, but lactobacilli are rarely present. It is not yet known which bacteria are health-promoting, nor which bacteria are associated with symptoms and risk of infection.

The lack of research on how gender-affirming care affects the vaginal microbiome and overall health represents a major health inequity for transgender and gender-diverse people.

Bridging the Gap: TransBiota

TransBiota, a study led by Jessica Prodger, Ph.D., Assistant Professor at Western University.
TransBiota, a study led by Jessica Prodger, Ph.D., Assistant Professor at Western University.

TransBiota, a study led by Jessica Prodger, Ph.D., Assistant Professor at Western University, aims to address this inequity by characterizing the vaginal microenvironments among transmasculine individuals receiving T-HRT and transfeminine individuals who have undergone vaginoplasty. This involves identifying which microbes are beneficial to the microenvironments and which are associated with gynecological symptoms.

TransBiota began recruitment in Canada in late 2020 and has since enrolled over 100 transmasculine individuals who had been receiving T-HRT for at least 1 year, and over 60 transfeminine individuals who underwent vaginoplasty at least 1 year prior to enrollment. To recruit potential participants, the study advertised through social media, collaborated with community groups and organizations, received referrals from health care providers with knowledge of their patients’ identities and recontacted consenting Trans PULSE Canada participants. The study was completely contactless—participants received sample collection materials and returned them via mail. Each participant answered online questionnaires and self-collected vaginal swabs once a week for 3 weeks. Participants were asked details about sociodemographics, gender-affirming care, recent symptoms and recent behaviors and exposures (e.g., douching, sexual activity, medication use). Vaginal swabs were collected for microbial and immunological analyses, and participants used additional swabs to prepare a glass slide for Gram staining and measuring vaginal pH. Data analysis is currently underway.

The community response to TransBiota has been overwhelmingly positive; community members were highly engaged and contributed lots of positive and constructive feedback. Several participants expressed their excitement that this type of research was being done and their hope for more research in the future.

Community investment and partnership in research that directly impact community health are critical. It is this second portion—partnership—that is most difficult to achieve, yet most important, to ensure that research remains community-centered and is positioned to create a positive impact.

Community Members Are the Experts on Their Own Health

Ethical research must be for the target population, not on the population. In other words, research must be centered around its benefits to the community. Transgender and gender-diverse people have historically been mistreated and harmed by researchers with their own agendas. Ethical research grounded in diversity, equity and inclusion among transgender and gender-diverse populations (and marginalized populations in general) therefore requires working with communities and building trust. This will also greatly improve research quality, as community members are the experts on their own health. There are 2 key ethical requirements in this process:

  1. Community members must be compensated for their expertise.
  2. Researchers must listen to and incorporate community input. Community members are too often asked to provide uncompensated input, and the input provided is often ignored.

It is in researchers’ best interest to listen to community experts. For TransBiota, input from community members prompted several important changes and additions to the methodology. Since there are no evidence-based guidelines for neovaginal health, community consultants were extremely helpful in sharing experiences with clinicians and common care practices specific to the neovagina (e.g., douching with solutions other than water). Community members and trusted researchers also helped ensure the language used throughout the study was culturally appropriate. One unique and useful language-related option in the REDCap survey software is the piping function. Certain anatomical terms can cause distress and dysphoria among transgender and gender-diverse individuals, so the piping function was used to let participants specify a term they would like their genitals to be referred to throughout the survey (e.g., “Have you recently applied any products to your [preferred word]?”).

Finally, since the research is for and not on the population, the team must return the results to communities through knowledge translation. The team will be working with community organizations and trusted clinicians to create accessible infographics and other related materials to present and share findings beyond academia.

Transgender and gender-diverse people have the right to evidence, information and informed care regarding their health and well-being. It is time scientists come together as researchers to address these disparities and support the health of this population.

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Author: Ainslie Shouldice

Ainslie Shouldice
Ainslie Shouldice is an M.S. student in the Department of Microbiology and Immunology in the Prodger Lab at Western University.

Author: Jason Hallarn

Jason Hallarn
Jason Hallarn is a Ph.D. candidate in the Department of Epidemiology and Biostatistics at the Schulich School of Medicine & Dentistry at Western University.