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Low Testosterone After Fatherhood

Oct 27, 2011

Men’s testosterone levels decrease once men become fathers, according to researchers from Northwestern University (United States) and the University of San Carlos (Philippines).

The study, published in the September 12, 2011 edition of Proceedings of the National Academy of Sciences also suggests that testosterone levels decline more if a man is more involved with childcare.

During the study, the researchers studied the blood test results of 624 Filipino men between the ages of 21.5 and 26. The men were followed for about 4.5 years. During this time, about a third of the men became fathers. None of the men were fathers at the beginning of the study.

The researchers discovered that after becoming fathers, testosterone levels fell between 26% and 34%, approximately two times the drop for men who did not become fathers.

Men who were more involved with childcare saw their levels decrease the most.

Previous studies were unable to determine whether fatherhood lowered testosterone levels or whether men with low testosterone were more likely to become fathers. However, this study was designed differently, as it started following the men before they became fathers.

In a press release, co-author Lee Gettler remarked, “…the men who started with high testosterone were more likely to become fathers, but once they did, their testosterone went down substantially. Our findings suggest that this is especially true for fathers who become the most involved with childcare.”

“Our assumption is that there’s something about physically interacting with their kids, whether it’s through sight or smell or physical touch, that activates something in the brain of men and has this trickle-down effect,” Gettler told HealthDay.

Gettler is a doctoral candidate in anthropology at Northwestern University.

So why do men’s testosterone levels decrease with fatherhood?

The reasons aren’t clear, but researchers suspect that once men become fathers, they are no longer seeking to attract mates. In other words, they are not competing with other men. Instead, they are creating relationships with their children.