Study: Men’s testosterone levels plummet after fatherhood

After a man becomes a parent, his testosterone level plummets. And the more he’s involved with parenting, the lower his male juice flows.

Those are the findings of the first large study comparing the testosterone levels of men when they were 21, single and childless with their levels five years later, after they’d become fathers. The study was published in the Sept. 12 issue of Proceedings of the National Academy of Sciences of the United States of America.

Although testosterone levels naturally decrease with age, the men who became fathers showed declines more than double those of childless men their age. Men who spent more than three hours a day caring for children – playing, feeding, bathing, reading to or dressing them – had the lowest testosterone rates in the study group.

The New York Times interviewed several experts who were not involved in the study about its implications.

 “The real take-home message” is that “male parental care is important,” Peter Ellison, a professor of human evolutionary biology at Harvard, told the Times. “It’s important enough that it’s actually shaped the physiology of men.”

 “My hope would be that this kind of research has an impact on the American male. It would make them realize that we’re meant to be active fathers and participate in the care of our offspring.”

Experts told the Times that the study suggests men’s bodies evolved hormonal systems that helped them commit to their families once children were born. They also said the study suggests that men’s behavior can affect hormonal signals their bodies send, not just that hormones influence behavior.

And, they said, it underscores that mothers were meant to have childcare help.

“This is part of the guy being invested in the marriage,” said Carol Worthman, an anthropologist at Emory University.