Same Bodies, Different Risks? What Really Drives Health Differences Between Men and Women
A practical FAQ on sex, hormones, genetics, and what it all means for trans healthcare
We hear it all the time.
Men get more heart attacks!
Women get more blood clots!
Men have higher blood counts!
Women live longer!
These statements are often presented as though male and female bodies are fundamentally different machines, built from different parts, running on different fuel. They are not.
Human bodies are remarkably similar, regardless of sex. What differs is the interplay of hormones, genetics, chromosomes, and the body parts you happen to have. Understanding this is not just an interesting bit of biology. It is essential for providing good, safe, and inclusive healthcare to everyone, including transgender people.
I’m going to break it down. Here is everything you need to know about what actually causes health differences between men and women, and what that means if you are transgender and have reassigned your hormone profile.
Are male and female bodies really that different?
Not as different as you might think. At a fundamental level, men and women share the same organs, the same tissues, the same biological systems. We all have hearts, lungs, blood vessels, brains, bones, and immune systems that work in essentially the same way. Both men and women can develop the same diseases, including heart disease, stroke, cancer, diabetes, blood clots, and autoimmune conditions.
The differences that do exist are largely driven by four factors: your chromosomes, your genetics and family history, your hormones, and which body parts you have. None of these factors exist in isolation, and many conditions are influenced by a combination of all four.
What role do chromosomes play?
Your chromosomes (typically XX or XY) determine some aspects of your biology from conception. Certain conditions are linked to genes carried on the X or Y chromosome. For example, haemophilia and Duchenne muscular dystrophy are X-linked conditions that are far more common in people with XY chromosomes, because there is no second X chromosome to compensate if one of them is faulty.
However, chromosomal differences account for a relatively small number of health conditions. Most diseases are not determined by your chromosomes alone. They are shaped by a far more complex web of factors.
What about genetics and family history?
Many conditions run in families regardless of sex. If heart disease, diabetes, breast cancer, or autoimmune conditions are common in your family, your risk will be higher too, whatever your sex or gender.
Genetic risk does not care about your gender identity or your hormones. It is written into your DNA.
This matters for trans people because your family history remains one of the most important predictors of your health, no matter which hormones you are taking. A trans woman with a strong family history of breast cancer should be aware of that risk, just as a cisgender woman would be. A trans man whose family has a history of heart disease should take that seriously, just as a cisgender man would.
How do hormones affect health risks?
This is where it gets really interesting, and really relevant for trans healthcare. Many of the health differences we see between men and women are driven not by some inherent difference in our bodies, but by the hormones circulating in our systems.
Testosterone stimulates the production of red blood cells, which is why people with testosterone-dominant hormone profiles (whether cisgender men or trans men) tend to have higher haemoglobin and haematocrit levels. A large Dutch study following over 1,000 trans men on testosterone found that their red blood cell levels rose to match those of cisgender men. This is not a side effect of testosterone therapy in the way we usually think of side effects. It is testosterone doing what testosterone does. The key is to monitor levels and use the blood reference ranges that match your hormone profile, not your sex assigned at birth.
Oestrogen affects blood clotting, which is why people with oestrogen-dominant profiles (whether cisgender women or trans women) have a somewhat higher risk of venous thromboembolism (blood clots). Research published by the American Society of Hematology in 2024 found that the clotting changes seen in trans women on oestrogen therapy mirror those seen in cisgender women taking hormone replacement therapy. The oestrogen is not creating an abnormal risk. It is bringing the risk profile in line with that of other people who have similar oestrogen levels. Keeping hormone levels within the normal physiological range is the most important thing we can do to keep these risks proportionate.
What about heart disease?
Heart disease is one of the most complex examples because it is multifactorial. Your risk depends on your genetics, your hormones, your lifestyle (smoking, diet, exercise, weight), your blood pressure, your cholesterol, and your family history. It is not simply a case of men getting more heart attacks than women.
Traditionally, cisgender men have had higher rates of heart disease than cisgender women, and this is thought to be related to both genetic and hormonal factors. Research from the Frontiers in Endocrinology journal found that trans men on testosterone had cardiovascular risk profiles that were comparable to those of cisgender men, while trans women on oestrogen showed risk profiles that shifted towards those of cisgender women (Aranda et al., Frontiers in Endocrinology, 2021). A key finding across multiple studies was that trans women had no significant difference in heart attack risk compared to cisgender men, and trans men showed no significant difference compared to cisgender men either.
What this tells us is that hormone profile is one of the drivers, but so are all the usual suspects. If you smoke, carry excess weight, have high blood pressure, or have a family history of heart disease, those risks apply to you regardless of whether you are cis or trans. Good cardiovascular care is about managing all of these factors together.
Do trans women on oestrogen have an increased risk of blood clots?
Trans women on oestrogen therapy do have a somewhat higher risk of venous thromboembolism compared to cisgender men. However, this risk is comparable to that seen in cisgender women, particularly those on hormone replacement therapy. A comprehensive review in the journal Hypertension noted that the thrombotic risk associated with oestrogen use in trans women is broadly similar to that seen in cisgender women using oral oestrogen (Connelly et al., Hypertension, 2019).
The important point here is that oestrogen does not create a new or unusual risk for trans women. It brings their clotting profile closer to that of cisgender women. Using transdermal oestrogen rather than oral preparations, maintaining physiological hormone levels, and managing other risk factors like smoking, weight, and immobility all help to keep this risk at an appropriate level.
What about cancer and body parts?
Cancer risk is closely tied to the body parts you have and the hormones influencing them. A trans man who has a cervix can still develop cervical cancer. A trans woman will not, because she does not have a cervix. Equally, a trans woman who still has a prostate can develop prostate cancer, though the risk appears to be much lower than in cisgender men, likely due to the effect of anti-androgen therapy and oestrogen on prostate tissue (de Nie et al., standardised incidence ratio 0.2 compared with cisgender men).
Breast cancer is particularly relevant for trans people. Anyone with breast tissue can develop breast cancer. A landmark Dutch study published in the BMJ in 2019, following over 2,200 trans women, found that the risk of breast cancer was 46 times higher in trans women compared to cisgender men, but still more than three times lower than in cisgender women. Most of the breast cancers identified were oestrogen and progesterone receptor positive, suggesting that the hormonal environment plays a role in driving these tumours, just as it does in cisgender women (de Blok et al., BMJ, 2019).
For trans men, the same study found that the risk of breast cancer was lower than in cisgender women, likely reflecting the suppressive effect of testosterone on oestrogen-driven breast tissue. However, trans men who have not had chest surgery still have breast tissue and should be aware of the possibility, particularly if there is a family history of breast cancer.
Should trans men use male or female blood test reference ranges?
This is a really important practical point. If you are a trans man on testosterone, your body is running on a male hormone profile. Your red blood cell count, your haemoglobin, your haematocrit, and your cholesterol patterns will all shift to reflect that. Using female reference ranges will flag results as abnormal when they are actually completely normal for someone with your hormone levels.
The same applies in reverse. Trans women on oestrogen should expect their blood results to shift towards female reference ranges over time. The Endocrine Society guidelines recommend that clinicians interpret laboratory results in the context of the patient’s current hormone profile rather than their sex assigned at birth. This is not a controversial recommendation. It is straightforward good medicine.
Do men and women experience the same symptoms of disease?
Yes, in terms of the physical symptoms. A heart attack causes chest pain, shortness of breath, and arm pain in anyone, regardless of their sex or gender. A stroke causes weakness, speech difficulty, and facial drooping in everyone. Breast lumps feel the same in any chest. The physical manifestations of disease do not discriminate by gender.
Where differences sometimes arise is in how people respond to symptoms emotionally, how quickly they seek help, and how seriously their symptoms are taken by healthcare professionals. These are social and behavioural factors, not biological ones. Trans people may face additional barriers to accessing timely care, which makes awareness of symptoms all the more important.
Is it true that women live longer than men?
On average, yes. In most populations around the world, people with oestrogen-dominant hormone profiles tend to live longer than those with testosterone-dominant profiles. This is thought to be related to the protective cardiovascular effects of oestrogen, as well as differences in risk-taking behaviour and occupational hazards. There is also emerging evidence that genes on the second X chromosome may offer some protective advantage in terms of longevity.
For trans people established on long-term hormone therapy, it is reasonable to expect that their life expectancy patterns may shift to reflect their hormone profile over time. A trans woman on oestrogen may benefit from some of the longevity advantages associated with an oestrogen-dominant system, while a trans man on testosterone may see his risk profile align more closely with that of cisgender men. This is not about hormones causing harm. It is about the normal spectrum of human biology.
So what is the take-home message?
The take-home message is beautifully simple. Men and women have the same bodies. The differences in health risks come from the interplay of chromosomes, genetics, hormones, and body parts. When trans people receive hormone therapy, their risk profiles shift to align with their affirmed gender, and that is exactly what we would expect.
Trans men on testosterone will develop the same cardiovascular risk profile as cisgender men, the same red blood cell levels, and the same patterns of health and disease. Trans women on oestrogen will develop the same clotting profile as cisgender women, the same breast cancer screening needs, and the same longevity patterns. This is not something to be afraid of. It is normal human biology.
Good healthcare for trans people means understanding this, using the right reference ranges, screening for the right conditions, and treating every patient as the whole person they are. It means matching your clinical approach to the person sitting in front of you, not to the sex marker on their birth certificate.
That is where our energy should go. Not debating bathrooms. Not gatekeeping access to care. But understanding the science, following the evidence, and looking after people properly.
Key references
Madsen MC et al. (2021). Erythrocytosis in a large cohort of trans men using testosterone: a long-term follow-up study on prevalence, determinants, and exposure years. Journal of Clinical Endocrinology & Metabolism, 106(6), 1710–1717.
de Blok CJM et al. (2019). Breast cancer risk in transgender people receiving hormone treatment: nationwide cohort study in the Netherlands. BMJ, 365, l1652.
Aranda G et al. (2021). Cardiovascular risk associated with gender affirming hormone therapy in transgender population. Frontiers in Endocrinology, 12, 718200.
Connelly PJ et al. (2019). Gender-affirming hormone therapy, vascular health and cardiovascular disease in transgender adults. Hypertension, 74(6), 1266–1274.
American Society of Hematology (2024). Gender-affirming hormone therapy in the transgender patient: influence on thrombotic risk. Hematology ASH Education Program.
de Nie I et al. (2020). Prostate cancer incidence under androgen deprivation: nationwide cohort study in trans women receiving hormone treatment. Journal of Clinical Endocrinology & Metabolism, 105(9), e3293–e3299.
D’hoore L & T’Sjoen G (2022). Gender-affirming hormone therapy: an updated literature review with an eye on the future. Journal of Internal Medicine, 291(5), 574–592.
Lieve Mees van Zijverden, Abel Thijs, Jeske Joanna Katarina van Diemen, Chantal Maria Wiepjes, Martin den Heijer, Transgender persons receiving gender-affirming hormone therapy: risk of acute cardiovascular events in a Dutch cohort study, European Heart Journal, 2025;, ehaf837, https://doi.org/10.1093/eurheartj/ehaf837
What do you think? Have you had good or bad experiences with healthcare that understood (or didn’t understand) these differences?