TUESDAY, April 21, 2026 (HealthDay News) -- Men with severely impaired fertility may have an increased risk for colorectal and thyroid cancer, according to a study published online Feb. 21 in the European Journal of Epidemiology.Peter Zarén, from Lund University in Sweden, and colleagues compared the risk for developing nonreproductive cancers in men achieving paternity through assisted reproduction to the risk for those conceiving naturally. The analysis included nearly 1.14 million first-time fathers (January 1994 to December 2014) followed from the time of conception until the date of cancer diagnosis, death, or end of follow-up.The researchers found that fathers conceiving by intracytoplasmic sperm injection or donated spermatozoa versus those conceiving spontaneously had an increased risk for nonreproductive cancers (adjusted hazard ratio [aHR], 1.3), particularly colon (aHR, 1.7), rectum (aHR, 1.8), and thyroid (aHR, 3.3) cancer."These findings are important from a public health perspective given that cancers of the colon and rectum, as well as thyroid cancer, are on the rise among younger people," coauthor Angel Elenkov, Ph.D., also from Lund University, said in a statement. "These cancers could be prevented through early screening."Abstract/Full Text.Sign up for our weekly HealthDay newsletter