The ongoing struggle for transgender inclusion in clinical trials

By Alpana Mohta, MD, DNB, FEADV, FIADVL, IFAAD | Fact-checked by Barbara Bekiesz
Published August 28, 2023

Key Takeaways

  • Current clinical research excludes or marginalizes transgender and gender diverse (TGD) individuals due to the gender binary system of patient recruitment in most clinical trials.

  • For TGD patients, barriers to participation in clinical trials include lack of trust, fears of exploitation, and confidentiality concerns.

  • A systematic change in guidelines for clinical trial designs—and the use of gender-neutral language—are needed to foster a more welcoming environment. 

Clinical studies often employ a binary gender system to classify individuals as either male or female. However, this method does not take into account the wide array of gender identities. 

As a result, transgender and gender diverse (TGD) individuals are still excluded from most clinical trials, further increasing the risk of healthcare disparities and negative health outcomes.

The invisible minority

According to a recent national survey, 1.4% of youth between the ages of 13 and 17 years, and 0.5% of adults in the US identify as transgender—equating to roughly 1.6 million individuals.[] Despite being a sizable population, they are seldom taken into account in clinical research that looks at how gender affects various disorders.

Estimates suggest that only a minuscule fraction of clinical trial publications between July 2018 and February 2022—comprising 0.06% of the 116,057 articles—indicated that transgender patients had been included. Most of these trials focused on HIV infection or sexually transmitted diseases, as noted in an article in Clinical Trials Arena.[]

Although the FDA has repeatedly acknowledged the need to include the TGD population in research, the clinical trials sector currently lacks clear guidelines for their participation. Even when transgender participants are welcomed, they may still be subject to a categorization that matches their sex assigned at birth. 

The importance of inclusion

Including TGD individuals in trials is not only important for improving healthcare outcomes and reducing health disparities, but it is also a matter of social justice and equity. Unfortunately, the needs of transgender individuals are often overlooked in the realm of clinical research, as highlighted by the following examples:

  • Cancer screening: Mixed reports exist on the ovarian cancer risk in transgender men taking testosterone, while transgender women have a higher risk of breast cancer than cisgender males. However, this field is under-researched, and no clear screening guidelines are available for cancer in either populations.[]

  • Hormone treatment interactions: Transgender individuals often receive hormone replacement treatment (HRT) to align their physical appearance with their gender identity. More research is needed to understand how drugs in clinical trials interact with HRT.

  • Drug efficacy: According to research published in Clinical Infectious Diseases, transgender women have lower HIV drug pharmacokinetic parameters when compared to non-transgender women.[] 


The common barriers faced by TGD patients when engaging in research include a lack of trust in researchers, a reluctance to feel like a test subject, fears of exploitation, confidentiality concerns, and aversion to research, among others.[] 

The complications that arise from gender dysphoria are frequently disregarded in the planning of therapeutic studies.

Due to gender binary inclusion criteria, rare health issues that affect transgender individuals—such as prostate cancer in transwomen and endometriosis in transmen—are not given due attention. 

At times, clinical trial settings can also be isolating and triggering. TGD participants may find restrooms labeled according to binary genders at a trial site, for example, and informational leaflets may exclude mention of TGD individuals.

Researchers who conducted focus groups with transwomen to explore their attitudes toward participation in HIV vaccine trials uncovered a range of barriers. 

Writing in Prevention Science, the authors reported that clinical studies available to the TGD community predominantly focus on HIV treatments.[] This can dissuade potential enrollees due to the fear of being stigmatized. 

Many transgender women were hesitant to participate in HIV clinical studies due to the potential for further marginalization.

The transgender women also expressed concern that if they enrolled in a clinical study they would not be recognized as their gender, but rather as men having sex with men (MSM). 

Toward inclusive research 

There are some studies that do consider the gender identity of transgender participants, noted Clinical Trials Arena, particularly for those who have undergone HRT for more than 6 months consecutively. However, these types of trials are still uncommon.

Small steps can be taken to make TGD individuals feel more included. 

For example, using gender-neutral language, asking for preferred pronouns during consultations, and including representation in marketing materials can help foster a welcoming environment. Trial sites should have gender-neutral facilities, such as bathrooms and lounge rooms.

Just like other demographic variables, clinical studies should also incorporate gender identity as one of the variables—not just biological sex. 

To achieve long-term change, however, the clinical trials sector must become more educated and informed about the needs of the LGBTQ+ community. By making clinical trials more patient-focused, TGD individuals may be more likely to see a doctor and participate in clinical trials. 

What this means for you

As an HCP, you can actively seek out and invite TGD individuals to participate in clinical studies, or encourage them to take part in one if appropriate. Ensure that your recruitment materials are inclusive and sensitive to the LGBTQ+ community. Provide education and resources to increase understanding of transgender health and issues related to research participation. Lastly, consider partnering with community organizations that serve the TGD population to increase outreach and engagement.

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