A recent study suggests men with severe infertility may face higher risks of colorectal and thyroid cancers.
Around 1 in 6 people will experience infertility, according to the World Health Organization. Prior research has linked male infertility with increased risks of cardiovascular disease, diabetes, and reproductive cancers such as testicular and prostate cancer. A new registry-based study published in the European Journal of Epidemiology examined whether severe male infertility is also associated with non-reproductive cancers.
The researchers analyzed Swedish registry data for more than 1.1 million men who fathered children between 1994 and 2014. Of these, 14,450 became fathers using intracytoplasmic sperm injection (ICSI), an assisted reproduction technique typically used for severe male infertility. Cross-referencing with the national cancer registry revealed a significantly increased risk of thyroid and colorectal cancer among men who became fathers via ICSI.
Experts not involved in the study cautioned that the association likely reflects underlying factors rather than a causal effect of ICSI itself. S. Adam Ramin, MD, noted the findings may reflect genetic mutations that both impair fertility and increase cancer risk. The study authors point to the biological plausibility: more than 2,300 genes influence reproductive function, so shared genetic vulnerabilities could explain concurrent risks for infertility and certain cancers.
Lifestyle factors that raise cancer risk — including smoking, excessive alcohol use, obesity, and physical inactivity — can also be associated with low semen quality. The Swedish analysis adjusted for parental age and educational level but did not include individual lifestyle data, leaving the potential contribution of these factors unresolved.
The researchers emphasized that assisted reproductive techniques are not shown to cause cancer. Instead, the findings suggest men with severe infertility might benefit from targeted follow-up and prevention efforts. Study author Angel Elenkov highlighted that most men undergoing fertility testing are in their early 30s and typically receive no subsequent health follow-up; given rising rates of colorectal and thyroid cancers in younger people, early screening could have public health value. The team recommended considering screening for colorectal, thyroid, and testicular cancers during fertility evaluations and follow-up care.
Clinicians advise maintaining a healthy lifestyle to help reduce cancer risk: avoid processed foods, manage weight and obesity, limit alcohol intake, and quit or avoid smoking. It’s important to remember that an association between two conditions does not prove one causes the other; genetic predisposition increases risk but does not guarantee cancer will develop.