The Science Behind Sexual Health: Research from the Tropini lab
Sophie Cotton and Carolina Tropini wearing lab coats and looking at a sample in their lab.
Aug 31, 2023

World Sexual Health Day is a national day that raises awareness, reduces stigma, and improves access to essential sexual health resources. This year’s theme is “Consent” - a crucial and fundamental element of any healthy sexual encounter.

To acknowledge this day, researchers from the Faculty of Science are sharing their scientific research in relation to sexual health, how scientific knowledge plays an important role in increasing informed consent, and how consent is honoured in collecting research.

In this Q&A from the microbiology perspective of the Department of Microbiology and Immunology and the School of Biomedical Engineering, Professor Carolina Tropini and MSc student Sophie Cotton from the Tropini lab share their research on how the gut microbiota influences levels of sex hormones throughout our bodies. 

Outline your research project: 

Carolina Tropini (CT): Gut health is closely related to our microbiota, a unique consortium of trillions of microbes that live in and on our bodies. Gut bacteria produce compounds that are absorbed into our blood, providing nourishment, and affecting our health. During chronic conditions such as colon cancers or inflammatory bowel disease (IBD), our microbiota and its abilities can be altered, which affects disease progress and treatment. Importantly, the microbiota can affect the levels of sex hormones by producing, degrading, and modifying both estrogen and testosterone in significant quantities, which may affect reproductive health. Excitingly, microbes could be an important way of addressing sexual diseases as the microbiota can be modified through diet and therapeutics. Recently, in an exciting collaboration with the Ciernia lab, we have found that the microbiota correlated with early-life intestinal inflammation may affect puberty timing in an animal model.

Sophie Cotton (SC): I work to understand how the gut microbiota (the bacteria within our gut) influences the levels of sex hormones throughout the rest of our bodies. Bacteria in the gut microbiota are capable of both breaking down testosterone (and reducing the level of it in our systemic circulation) and reactivating estrogens (increasing its level in our systemic circulation) in a clinically significant manner.

Disrupted testosterone levels can cause depression, sexual dysfunction, and disorders such as polycystic ovarian syndrome that affect sexual satisfaction. Similarly, disrupted estrogen levels are associated with vaginal dryness, decreased libido, and diseases such as breast cancer and endometriosis that ultimately have significant impacts on sexual health. By understanding the mechanisms by which gut microbes can influence systemic sex steroid hormone levels we hope to contribute to future work that will eventually enable healthcare providers to take a more personalized approach to sex steroid levels, which ultimately affect sexual health. 


What do you hope to achieve with this research in the future?   

SC: I hope that we can gain enough breadth and depth in our understanding of the microbiota-sex steroid relationship so that it can be taken outside the four walls of the lab and to the bedside of patients. Right now, we are just at the beginning of learning how different bacteria alter sex steroids in vitro (in a test tube) and in animal studies (mice). By understanding how the microbiota affects sex steroid levels in humans, healthcare providers may be able to tailor treatments and interventions in the future based on an individual's unique microbiome composition. Excitingly, this type of personalized medicine could lead to more effective and targeted therapies, reducing the risk of adverse effects and optimizing treatment outcomes. 


What inspired you to research gut microbiota and sex hormones? 

CT: When I started my Ph.D., I didn’t know what research topic my career path would lead me to study, but I was sure of one thing–I would never research microbes. I (erroneously) thought that bacteria were just harmful agents to human health, and being so small, they were too simple to deserve much attention. At Stanford, I took a class with a new Assistant Professor, Dr. KC Huang, who taught a beautiful class on classical experiments in biophysics. Dr. Huang is an excellent speaker, and the way he approached problems captivated my attention. I was looking for a lab to do my doctorate work in, so I looked up his research online and was quite disappointed to find out that he worked on bacteria. However, he encouraged me to work on a project with him, just to try it out. The project investigated how bacteria can grow and sense their environment. The topic was challenging, and delved deep in a world that was incredibly fascinating and largely untapped. As I was learning more about the project, I also realized that the ten trillion bacteria that live on and in us are essential to our health. I soon realized my mistake, joined the Huang lab, fell in love with the world of microbes, and never turned back!

SC: Initially I “got lucky” – I was meant to be working on a different microbiota project when a research assistant in my lab, Dr. Kat Ng, did a gut microbiota experiment and found that the reproductive system of the mice was really underdeveloped. We decided to try and understand what was happening, and it ended up becoming my project. Now, I absolutely love having the opportunity to explore something that affects peoples lives in such a personal way, and has the opportunity to help a lot of people. 

Dr. Carolina Tropini (left) and Sophie Cotton (right) examining a sample of their research.

What challenges do you face working within sexual health research? 

CT: Sexual health is very complex and a deeply sensitive topic – we need multidisciplinary researchers to tackle these questions to go beyond the standard science research approach. To really have an impact, we need the support of counselors and social scientists - the implications of our research reach far beyond the laboratory and it’s easy for an academic finding to be misinterpreted.

SC: The gut microbiota is an incredibly complex organ that both influences and is influenced by so many distinct factors. Age, disease, diet, exercise, sleep and other lifestyle habits all constantly influence the type and quantity of bacteria present in the gut microbiota. In our work, we then add in the consideration of hormones, which on their own are complex because they fluctuate according to daily and monthly cycles. Often when we work with microbiome samples (stool samples) we don’t know what time of day they were taken, what part of the menstrual cycle the patient was in, or what their health and lifestyle is like. To really get an accurate picture of the microbiome there are so many factors to consider.

Further, beyond the breadth of the microbiota itself, this area of research relies on board interdisciplinary collaboration. We need clinical biochemists who can understand the intricacies of the hormonal pathways, gynaecologists and urologists who understand patient concerns, microbiologists who understand bacterial mechanisms, bioinformaticians that can translate raw data into meaningful results for the rest of the team, and social scientists who can help contextualize the research and make it available to the public in a healthy and helpful way.  


How does your work help de-stigmatize the importance of sexual health and research? 

CT: We are learning that sexual health is affected by many factors that are not usually considered to be directly relevant to it (e.g., gut inflammation, the microbiota). Similarly, sexual health is tightly linked to the correct function of our body and can be impaired by diseases that originate in non-reproductive body sites. Understanding this interconnectedness normalizes the fact that sexual health is just human health and something we need to embrace and take care of!

SC: Historically, sexual and hormonal health, particularly women's health, have been considered taboo and mysterious. By understanding the complex interactions not just within the endocrine and reproductive system, but also the microbiota, we can begin to demystify it. We can realize that sexual health is not just the result of personal choices and behaviour, but also complex biological factors that sometimes are out of our control. Yes, it is true that there is a lot we can do to preserve and promote sexual health, but it is also true that there are a lot of complex biological factors that affect sexual health that we don’t have complete control over. I think that as the research becomes clearer, it will become more accepted that certain sexual health struggles are common, “normal” and have strong scientific basis. My hope is that this will help normalize conversations around sexual health and decrease shame and stigma that so often surrounds sexual health issues.  


“Consent” is the theme for this year’s World Sexual Health Day. How might “consent” play a role in your research activities or the delivery of health care as a result of these activities?   

CT: In microbiota research, we are realizing that an industrialized lifestyle has led to the disappearance of critical microbial members who helped keep us healthy and protected us against chronic, modern diseases such as asthma, obesity, or diabetes. As these microbes become lost in industrialized countries, many researchers are turning their attention to (uncontacted) Indigenous communities who may still have these microbes within their microbiota. Informed consent is a critical topic for making sure we do right by these communities, who may not be aware of the importance of their microbiota and whether their samples could be used by other countries for financial gain or for research they may not be comfortable with.

SC: Our research shows the complex interconnectedness of factors that are and are not within our control when it comes to our sexual health. I think this knowledge can be really empowering and help individuals make the best decision for them, knowing that their body, and the things influencing how it feels, are unique to them, and therefore their boundaries that they are comfortable with are legitimate not just from a social science standpoint, but also from a biological standpoint. 

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Photography by Leslie Kennah, Michael Smith Laboratories